PATENT DOCUMENT

Publication Number: US-9240215-B2
Application Number: US-201113250853-A
Country: US
Kind Code: B2

Title: Editing operations facilitated by metadata

Abstract:
Some embodiments provide a media editing application that uses metadata or metadata tags associated with media content to facilitate editing operations. In some embodiments, the editing operations are performed on the media content at various different stages of the editing process in order to create a composite presentation. In creating the composite presentation, one or more effects are associated with a metadata tag. Once the effects are associated, the media editing application applies the effects to different pieces of media content tagged with the metadata tag in order to create the composite presentation.

Claims:
What is claimed is: 
     
       1. A non-transitory machine readable medium storing a program for applying effects to a composite presentation comprising a plurality of media clips, the program for execution by at least one processing unit, the program comprising sets of instructions for:
 associating a set of effects with each tag of a plurality of tags, wherein at least two tags of the plurality of tags are associated with different sets of effects; 
 assigning the plurality of tags to media clips of the plurality of media clips; and 
 in response to a request to output the composite presentation, for each particular tag of the plurality of tags:
 identifying a set of media clips of the plurality of media clips to which the particular tag is assigned; 
 identifying the set of effects associated with the particular tag; and 
 applying the identified set of effects associated with the particular tag to each media clip in the identified set of media clips in order to output the composite presentation, such that a same set of effects is applied to any two media clips that are assigned the same particular tag. 
 
 
     
     
       2. The non-transitory machine readable medium of  claim 1 , wherein the set of instructions for associating a set of effects with each tag comprises a set of instructions for associating an effect chain with at least one tag, the effect chain comprising a series of effects that is applied in sequence to each media clip that is tagged with the associated tag. 
     
     
       3. The non-transitory machine readable medium of  claim 1 , wherein for at least one tag of the plurality of tags, the identified set of media clips comprises audio data, wherein the set of instructions for applying the identified set of effects to each media clip in the identified set of media clips comprises sets of instructions for:
 routing a composite audio signal of one or more media clips in the identified set of media clips over an auxiliary bus using a send operation; 
 applying one or more effects to the composite audio signal; and 
 returning a processed audio signal with the one or more effects. 
 
     
     
       4. The non-transitory machine readable medium of  claim 3 , wherein the set of instructions for applying the identified set of effects to each media clip in the identified set of media clips further comprises a set of instructions for combining the processed audio signal with the audio signal of the one or more media clips in the identified set of media clips. 
     
     
       5. The non-transitory machine readable medium of  claim 3 , wherein the identified set of effects for a first tag comprises a first type of effect and the identified set of effects for a second tag comprises a second type of effect, wherein the set of instructions for applying the identified set of effects to each media clip in the identified set of media clips further comprises a set of instructions for applying the first type of effect using the send operation and applying the second type of effect as an insert effect, wherein the insert effect is applied to an audio signal of an individual media clip instead of a composite audio signal of multiple media clips. 
     
     
       6. The non-transitory machine readable medium of  claim 1 , wherein for at least one tag of the plurality of tags, the identified set of media clips comprises audio data, wherein the set of instructions for applying the identified set of effects to each media clip in the identified set of media clips comprises a set of instructions for applying the identified set of effects as a set of insert effects, wherein each insert effect is applied to an audio signal of the media clip instead of a composite audio signal of multiple clips in the identified set of media clips. 
     
     
       7. The non-transitory machine readable medium of  claim 1 , wherein the program further comprises a set of instructions for specifying properties or settings for one or more effects of the sets of effects. 
     
     
       8. The non-transitory machine readable medium of  claim 1 , wherein one or more effects of the sets of effects are audio effects comprising at least one of a reverb effect, an echo effect, an equalizer, and a compressor. 
     
     
       9. The non-transitory machine readable medium of  claim 1 , wherein one or more effects of the sets of effects are video effects comprising at least one of a color filter, a sharpen filter, a distort filter, a blur filter, and a video transition. 
     
     
       10. The non-transitory machine readable medium of  claim 1 , wherein for at least one tag of the plurality of tags, the identified set of media clips comprises at least one compound clip that contains multiple different inner clips. 
     
     
       11. The non-transitory machine readable medium of  claim 1 , wherein the set of instructions for assigning the plurality of tags to media clips comprises sets of instructions for:
 displaying a list of keywords for the media clips; 
 receiving user input to identify a set of the keywords for the media clips; and 
 assigning a set of tags associated with the identified set of keywords to the media clips. 
 
     
     
       12. The non-transitory machine readable medium of  claim 1 , wherein the set of instructions for assigning the plurality of tags to media clips comprises sets of instructions for automatically assigning a set of tags to a particular media clip based on properties of the particular media clip. 
     
     
       13. A non-transitory machine readable medium storing a program for applying effects to a composite presentation comprising a plurality of media clips, the program for execution by at least one processing unit, the program comprising sets of instructions for:
 associating a plurality of first effects with a first tag and a different plurality of second effects with a second tag; 
 assigning the first tag to each media clip in a first set of media clips of the composite presentation, the first set of media clips comprising at least one compound clip that contains multiple different inner clips; 
 assigning the second tag to each media clip in a second set of media clips of the composite presentation, where the first and second tags associate each media clip of the first and second sets, respectively, with the first and second effects; 
 in response to a request to generate an output of the composite presentation, identifying a set of effects, including the first and second effects, to apply to the media clips of the composite presentation based on different tags associated with the media clips; and 
 based on the identification, applying the plurality of first effects to the first set of media clips and the plurality of second effects to the second set of media clips in order to output the composite presentation based on the association of the pluralities of effects with the different tags, wherein applying the plurality of first effects to the first set of media clips comprises identifying each tag of the compound clip and the compound clip&#39;s inner clips, and determining, based on the identification, whether to apply a particular plurality of effects to the compound clip or one or more of the compound clip&#39;s inner clips. 
 
     
     
       14. A method for applying effects to a composite presentation comprising a plurality of media clips, the method comprising:
 associating a set of effects with each tag of a plurality of tags, wherein at least two tags of the plurality of tags are associated with different sets of effects; 
 assigning the plurality of tags to media clips of the plurality of media clips; and 
 in response to a request to output the composite presentation, for each particular media clip of the plurality of media clips:
 identifying a set of tags of the plurality of tags assigned to the particular media clip; 
 identifying the sets of effects associated with the identified set of tags; and 
 applying the identified sets of effects to the particular media clip in order to output the composite presentation such that a same set of effects is applied to any two media clips that are assigned the same particular tag. 
 
 
     
     
       15. The method of  claim 14 , wherein associating a set of effects with each tag comprises associating an effect chain with at least one tag, the effect chain comprising a series of effects that is applied in sequence to each media clip that is tagged with the associated tag. 
     
     
       16. The method of  claim 14 , wherein a set of media clips of the plurality of media clips comprises audio data, wherein applying the identified sets of effects to media clips of the set of media clips comprises routing a composite audio signal of one or more media clips in the set of media clips over an auxiliary bus using a send operation, applying one or more effects to the composite audio signal, and returning a processed audio signal with the one or more effects. 
     
     
       17. The method of  claim 16 , wherein applying the identified sets of effects to media clips of the set of media clips further comprises combining the processed audio signal with the audio signal of the one or more media clips in the set of media clips. 
     
     
       18. The method of  claim 14 , wherein the identified set of effects for a first tag comprises a first type of effect and the identified set of effects for a second tag comprises a second type of effect, wherein applying the identified sets of effects to the particular media clip comprises applying the first type of effect using a send operation and applying the second type of effect as an insert effect, wherein the insert effect is applied to an audio signal of an individual media clip instead of a composite audio signal of multiple media clips. 
     
     
       19. The method of  claim 14 , wherein a set of media clips of the plurality of media clips comprises audio data, wherein applying the identified sets of effects to the media clips of the set of media clips comprises applying at least one effect of the sets of effects as a set of insert effects, wherein each insert effect is applied to an audio signal of the media clip instead of a composite audio signal of multiple clips in the set of media clips. 
     
     
       20. The method of  claim 14  further comprising specifying properties or settings for one or more effects of the sets of effects.

Description:
CLAIM OF BENEFIT TO PRIOR APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 61/537,041, filed Sep. 20, 2011, and U.S. Provisional Application 61/537,567, filed Sep. 21, 2011. U.S. Provisional Application 61/537,041 and U.S. Provisional Application 61/537,567 are incorporated herein by reference. 
    
    
     BACKGROUND 
     To date, many media editing applications exist for creating a composite media presentation by compositing several pieces of media content such as video, audio, animation, still image, etc. In some cases, a media editing application combines a composite of two or more clips with one or more other clips to output (e.g., play, export) the composite presentation. 
     There are a number of different problems that can occur when outputting such a composite presentation. For example, some movie studios require a particular content (e.g., dialog content, music content) of a composite presentation to be separate from other content. The content separation allows the movie studios to easily replace the composite presentation&#39;s dialog in one language with a dialog in another language. The problem with providing separate content is that, once several pieces of media content are mixed as one mixed content, the mixed content cannot be un-mixed to provide the separate content. 
     As another example, displaying the audio levels of different media clips during playback of a composite presentation is useful as the audio levels indicate how much audio one or more of the different media clips are contributing to the overall mix. The problem with this is similar to the example described above. That is, a mix of the different media clips cannot be un-mixed during playback to provide metering information for the different media clips. 
     In addition, some media editing applications apply one or more different effects (e.g., reverb effect, echo effect, blur effect, distort effect, etc.) to a set of clips when outputting a composite presentation. Several of these effects are applied using a “send” (i.e., “send and return”) that entails routing audio signals of different clips over an auxiliary (“aux”) bus to an effects unit. For a typical media editing application, a “send” effect is applied with the user manually adding an input aux track, specifying an effect for the aux track, specifying an input bus for the aux track, creating the “send”, and identifying the specified bus to route the audio signals of different clips. In this manner, several audio signals of different clips can be routed over one aux bus in order to apply a same effect (e.g., an echo effect) to a combined audio signal of the different clips. However, the “send” technique becomes increasingly complicated as additional aux buses are added to route audio signals of multiple different clips. 
     Furthermore, several of the media editing applications described above allow users to view metadata associated with media content and/or perform organizing operations using the metadata. However, these media editing applications lack the tools or the functionality to perform different editing operations by using one or more pieces of metadata that is associated with the media content. 
     The concepts described in this section have not necessarily been previously conceived, or implemented in any prior approach. Therefore, unless otherwise indicated, it should not be assumed that any concepts described in this section qualify as prior art merely by virtue of their inclusion in this section. 
     BRIEF SUMMARY 
     Some embodiments provide a media editing application that uses metadata or metadata tags associated with media content to facilitate editing operations. In some embodiments, the editing operations are performed on the media content at various different stages of the editing process in order to create a composite presentation. In creating the composite presentation, one or more effects are associated with a metadata tag. Once the effects are associated, the media editing application applies the effects to different pieces of media content tagged with the metadata tag in order to create the composite presentation. 
     Different embodiments provide different schemes for specifying one or more effects to apply to media content that have been associated with a metadata tag. For instance, in some embodiments, the media editing application allows an effect chain or an effect list to be specified for each type or category of metadata tag. In some embodiments, the media editing application allows its user to specify effect properties for the effects in the effect list. These effect properties define how the corresponding effect is applied to the media content. 
     Based on metadata associated with different clips, the media editing application of some embodiments applies a set of effects (e.g., echo effect, reverb effect) by using a “send” or a “send and return”. In some embodiments, the “send” is performed automatically such that the routing of audio signals of the different clips to an effect module is transparent to the application&#39;s user. That is, the user does not have to add an input auxiliary (“aux”) track, specify an effect for the aux track, specify an input bus for the aux track, create the “send”, and identify the specified bus to route the audio signals of the different clips. Instead, the user can simply specify a particular effect for a metadata tag. The media editing application then applies the particular effect using the “send” to a combined audio signal of each clip tagged with the metadata tag. 
     The media editing application of some embodiments applies one or more effects directly on each clip without using the “send”. One example of such technique is applying an effect as an “insert” effect that processes (e.g., filters, distorts) an incoming audio signal and outputs the processed audio signal. For example, when a metadata tag is associated with a particular effect, the media editing application of some embodiments automatically applies the particular effect to each audio signal of the different clips tagged with the metadata tag. 
     In some embodiments, when playing a composite presentation, the media editing application displays the audio level of a set of one or more clips that has been mixed with other clips. For example, the audio signals of the set of clips can be mixed with other clips in order to play the composite presentation. To indicate the audio level of the set of clips that has been mixed with other clips, the media editing application of some embodiments routes a combined audio signal of the set of clips over a meter bus in order to determine the audio level of the combined audio signal. In some embodiments, the media editing application scales (i.e., reduces or increases) the audio level of one or more clips by processing down a signal chain or sequence of operations and identifying what one or more of the clips are contributing to the overall mix. 
     Alternatively, the media editing application of some embodiments extracts metering information from each clip in a set of clips prior to mixing the clips. The metering information is then used to estimate the audio level of one or more clips in the composite presentation. Similar to sending the audio signal over the meter bus, the media editing application of some embodiments scales the estimated audio level by identifying what one or more of the clips are contributing to the overall mix. 
     In some embodiments, the media editing application allows a composite presentation to be exported to different tracks (e.g., different files). To export the composite presentation, the media editing application of some embodiments performs multiple rendering passes on a sequence of clips while muting one or more of the clips in the sequence. In some such embodiments, the composite presentation is output to different tracks based on metadata associated with the clips. For example, with these metadata tags, a multi-track output can be specified as a first track for each clip tagged as dialog, a second track for each clip tagged as music, etc. In this manner, the editor or a movie studio can easily replace one track with another track. 
     The media editing application of some embodiments uses metadata to provide user interface controls. In some such embodiments, these controls are used to display properties of tagged clips and/or specify parameters that affect the tagged clips. Example of such user interface controls include audio meters, volume controls, different controls for modifying (e.g., distorting, blurring, changing color) images, etc. 
     The preceding Summary is intended to serve as a brief introduction to some embodiments of the invention. It is not meant to be an introduction or overview of all inventive subject matter disclosed in this document. The Detailed Description that follows and the Drawings that are referred to in the Detailed Description will further describe the embodiments described in the Summary as well as other embodiments. Accordingly, to understand all the embodiments described by this document, a full review of the Summary, Detailed Description and the Drawings is needed. Moreover, the claimed subject matters are not to be limited by the illustrative details in the Summary, Detailed Description, and the Drawings, but rather are to be defined by the appended claims, because the claimed subject matters can be embodied in other specific forms without departing from the spirit of the subject matters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth in the appended claims. However, for purpose of explanation, several embodiments of the invention are set forth in the following figures. 
         FIG. 1  conceptually illustrates a process that some embodiments use to apply effects. 
         FIG. 2  shows a signal flow diagram that conceptually illustrates how some embodiments apply the reverb effect. 
         FIG. 3  shows a signal flow diagram of some embodiments that conceptually illustrates application of an effect on multiple clips. 
         FIG. 4  shows a signal flow diagram that conceptually illustrates how some embodiments apply an effect chain with multiple different effects. 
         FIG. 5  shows a signal flow diagram that conceptually illustrates how some embodiments apply a particular effect or a particular filter as an insert effect. 
         FIG. 6  illustrates an example of specifying an effect for a compound clip. 
         FIG. 7  shows a signal flow diagram of some embodiments that conceptually illustrates the application of the reverb effect on the compound clip. 
         FIG. 8  shows a signal flow diagram of some embodiments that conceptually illustrates the application of the reverb effect on an inner clip of a compound clip. 
         FIG. 9  shows a signal flow diagram that conceptually illustrates how some embodiments route a combined audio signal of several clips over a particular aux bus based on the clips&#39; association with a metadata tag. 
         FIG. 10  conceptually illustrates a process that some embodiments use to apply one or more effects to a compound clip and/or the compound clip&#39;s nested clips. 
         FIG. 11  illustrates an example of how some embodiments perform editing operations based a compound clip&#39;s tag. 
         FIG. 12  illustrates example meters that indicate audio levels of several clips that have been mixed with other clips. 
         FIG. 13  shows a signal flow diagram that conceptually illustrates sending an audio signal of a clip over a meter bus in order to display the clip&#39;s audio level during playback of a mixed audio signal of a composite presentation. 
         FIG. 14  shows a signal flow diagram that conceptually illustrates routing a combined audio signal of several clips over a meter bus for the purposes of displaying the clips&#39; audio level. 
         FIG. 15  conceptually illustrates a process that some embodiments use to estimate audio levels of clips that are tagged with metadata tags. 
         FIG. 16  conceptually illustrates a process that some embodiments use to construct user interface controls based on metadata tags. 
         FIG. 17  shows a data flow diagram that conceptually illustrates an example of adjusting parameters of several clips at different levels of a hierarchy, in some embodiments. 
         FIG. 18  illustrates how some embodiments output audio content to different tracks based on metadata that is associated with different clips. 
         FIG. 19  provides an illustrative example of an output tool for the media editing application. 
         FIG. 20A  illustrates the problem with outputting a composite presentation to different tracks. 
         FIG. 20B  illustrates outputting a composite presentation to different audio files, in some embodiments. 
         FIG. 21  conceptually illustrates a process that some embodiments use to output a composite presentation based on metadata tags associated with one or more output tracks. 
         FIG. 22  illustrates a graphical user interface of a media editing application of some embodiments. 
         FIG. 23  conceptually illustrates the software architecture of a media editing application of some embodiments. 
         FIG. 24  conceptually illustrates example data structures for several objects associated with a media editing application of some embodiments. 
         FIG. 25  illustrates an electronic system with which some embodiments of the invention are implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the invention, numerous details, examples, and embodiments of the invention are set forth and described. However, it will be clear and apparent to one skilled in the art that the invention is not limited to the embodiments set forth and that the invention may be practiced without some of the specific details and examples discussed. 
     Some embodiments provide a media editing application that uses metadata or metadata tags associated with media content to facilitate editing operations. In some embodiments, the editing operations are performed on the media content at various different stages of the editing process in order to create a composite presentation. In creating the composite presentation, one or more effects are associated with a metadata tag. Once the effects are associated, the media editing application applies the effects to different pieces of media content tagged with the metadata tag in order to create the composite presentation. 
     Different embodiments provide different schemes for specifying one or more effects to apply to media content that have been associated with a metadata tag. For instance, in some embodiments, the media editing application allows an effect chain or an effect list to be specified for each type or category of metadata tag. In some embodiments, the media editing application allows its user to specify effect properties for the effects in the effect list. These effect properties define how the corresponding effect is applied to the media content. 
     Based on metadata associated with different clips, the media editing application of some embodiments applies a set of effects (e.g., echo effect, reverb effect) by using a “send” or a “send and return”. In some embodiments, the “send” is performed automatically such that the routing of audio signals of the different clips to an effect module is transparent to the application&#39;s user. That is, the user does not have to add an input auxiliary (“aux”) track, specify an effect for the aux track, specify an input bus for the aux track, create the “send”, and identify the specified bus to route the audio signals of the different clips. Instead, the user can simply specify a particular effect for a metadata tag. The media editing application then applies the particular effect using the “send” to a combined audio signal of each clip tagged with the metadata tag. 
     The media editing application of some embodiments applies one or more effects directly on each clip without using the “send”. One example of such technique is applying an effect as an “insert” effect that processes (e.g., filters, distorts) an incoming audio signal and outputs the processed audio signal. For example, when a metadata tag is associated with a particular effect, the media editing application of some embodiments automatically applies the particular effect to each audio signal of the different clips tagged with the metadata tag. 
     In some embodiments, when playing a composite presentation, the media editing application displays the audio level of a set of one or more clips that has been mixed with other clips. For example, the audio signals of the set of clips can be mixed with other clips in order to play the composite presentation. To indicate the audio level of the set of clips that has been mixed with other clips, the media editing application of some embodiments routes a combined audio signal of the set of clips over a meter bus in order to determine the audio level of the combined audio signal. In some embodiments, the media editing application scales (i.e., reduces or increases) the audio level of one or more clips by processing down a signal chain or sequence of operations and identifying what one or more of the clips are contributing to the overall mix. 
     Alternatively, the media editing application of some embodiments extracts metering information from each clip in a set of clips prior to mixing the clips. The metering information is then used to estimate the audio level of one or more clips in the composite presentation. Similar to sending the audio signal over the meter bus, the media editing application of some embodiments scales the estimated audio level by identifying what one or more of the clips are contributing to the overall mix. 
     In some embodiments, the media editing application allows a composite presentation to be exported to different tracks (e.g., different files). To export the composite presentation, the media editing application of some embodiments performs multiple rendering passes on a sequence of clips while muting one or more of the clips in the sequence. In some such embodiments, the composite presentation is output to different tracks based on metadata associated with the clips. For example, with these metadata tags, a multi-track output can be specified as a first track for each clip tagged as dialog, a second track for each clip tagged as music, etc. In this manner, the editor or a movie studio can easily replace one track with another track. 
     The media editing application of some embodiments uses metadata to provide user interface controls. In some such embodiments, these controls are used to display properties of tagged clips and/or specify parameters that affect the tagged clips. Example of such user interface controls include audio meters, volume controls, different controls for modifying (e.g., distorting, blurring, changing color) images, etc. 
     Several more examples editing operations are described below. Section I describes several examples of applying effects to different tagged clips. Section II then introduces compound clips and proves several examples of applying effects to the compound clips. Section III then describes examples of metering clips that has previously been mixed. Section IV then describes constructing user interface controls and propagating parameters specified through the user interface controls. Section V then describes using metadata tags to output a composite presentation to different tracks. Section VI describes an example graphical user interface and software architecture of a media editing application of some embodiments. Section VI also describes several example data structures for the media editing application of some embodiments. Finally, Section VII describes an electronic system which implements some embodiments of the invention. 
     I. Applying Effects to Clips Based on Metadata 
     In some embodiments, the media editing application applies one or more effects to clips in a composite presentation based on metadata (i.e., metadata tags) associated with the clips. In creating the composite presentation, one or more effects are associated with a metadata tag. Once the effects are associated, the media editing application applies the effects to different pieces of media content tagged with the metadata tag in order to create the composite presentation. 
     There are many different effects or filters that can be associated with metadata to facilitate editing operations. Although this list is non-exhaustive, several example audio effects include an equalizer for modifying the signal strength of a clip within specified frequency ranges, an echo effect for creating an echo sound, and a reverb effect for creating a reverberation effect that emulates a particular acoustic environment. Several example video effects or image effects include color filters that operate on color values, different filters that sharpen, stylize, distort, or blur an image, and fade-in/fade-out effects for creating transitions between scenes. 
       FIG. 1  conceptually illustrates a process  100  that some embodiments use to apply effects to different clips based on metadata. Specifically, this figure illustrates process  100  that applies effects to the different clips in a composite presentation when outputting the composite presentation. In some embodiments, process  100  is performed by a media editing application. This process  100  will be described by reference to  FIGS. 3-5  that illustrate application of effects on a set of clips based on the association of the effects to metadata and the association of the metadata to the set of clips. 
     As shown, process  100  identifies (at  105 ) each clip tagged with a particular metadata tag having an associated effect.  FIG. 2  shows a signal flow diagram  200  that conceptually illustrates application of an effect. Specifically, the signal flow diagram  200  illustrates an example of how the audio signal of a clip  215  is routed to output a mixed audio signal with a specified reverb effect. As shown, the figure includes the clip  215 , a master  210 , and a reverb effect (“FX”) module  205 . The reverb FX module  205  receives an audio signal of one or more clips, applies the reverb effect to the received audio signal, and outputs an audio signal containing the reverb effect. The master  210  defines the output audio level of a composite presentation. 
     In example illustrated in  FIG. 2 , process  100  identifies the clip  215  as a clip tagged with a “Dialog” tag having an associated effect. In some embodiments, the identification is initiated based on user input to output a composite presentation based on a sequence of clips that define the composite presentation. Alternatively, in some embodiments, the media editing application performs rendering and/or mixing operations in the background in order to output the composite presentation (e.g., to play a preview of the composite presentation in real-time). 
     Process  100  then identifies (at  110 ) the effect that is associated with the particular metadata tag. As shown  FIG. 2 , the clip  215  is associated with a “Dialog” tag. This piece of metadata is associated with a reverb effect. Process  100  then determines (at  115 ) whether the effect requires data of one or more clips to be routed to one effect creation unit (e.g., by using send and return). 
     When the effect does not requires data of one or clips to be routed, process  100  proceeds to  120  which is described below. Otherwise, process  100  process  100  defines (at  135 ) a bus for the particular metadata tag. In some embodiments, the process creates this bus to send a combined audio signal of each clip tagged with the particular metadata tag. In the example illustrated in  FIG. 2 , an aux send bus is defined to send an audio signal of each clip tagged with the “Dialog tag”. 
     Process  100  then sends (at  140 ) an audio signal of each identified clip over the aux send bus. Process  100  identifies (at  145 ) parameters of the identified effect. Different effects can be associated with different parameters. For example, a reverb effect can have one set of parameters including the output audio level of the reverberation effect, the type of reverberation (e.g., room, hall, space), etc. Different from the reverb effect, an image distortion effect can have a different set of settings or parameters for distorting images. 
     The process  100  then applies (at  150 ) the effect to each identified clip based on the identified parameters. As shown in  FIG. 2 , the clip  215  is tagged with a “Dialog” tag. This “Dialog” tag is associated with a reverb effect. Based on the association, the reverb effect is applied to the clip  205  using the send and return. Specifically, the audio signal of the clip  215  is routed to the reverb FX module  205 . The audio signal of is directly routed to the master  210 . The reverb FX module  205  then applies the reverb effect to the received audio signal and returns an audio signal containing the reverb effect to the master  210 . The “+” symbol in this and other figures indicates that audio signals are being combined (i.e., mixed, summed). Hence, the master  210  receives the mixed audio signal and outputs a resulting mixed audio signal for the composite presentation. 
     In the example illustrated in  FIG. 2 , the audio signal of the clip  215  and the audio signal containing the reverb effect are mixed because a reverb effect represents one type of effect that typically mixes back in the original audio signal. An echo effect is another example of such type of effect. For example, the output of the reverb FX module  205  for a clip with dialog is the reverberation of that dialog (e.g., in a theatre, in a hallway). Therefore, the audio signal of the clip is mixed back in such that the audience can hear the dialog and not just the reverberation of that dialog. 
     In the example illustrated in  FIG. 2 , the routing of the audio signal to the reverb effect module  205  is transparent to the application&#39;s user. The user does not have to add an auxiliary track, insert the reverb effect to the auxiliary track, specify a bus for the auxiliary track, etc. The user can simply associate the clip&#39;s metadata tag with the reverb effect. The media editing application then automatically applies the reverb effect to the clip  215  using the “send and return”. 
     One reason for utilizing the “send” technique is that it allows a combined audio signal of multiple clips to be processed through the same effects unit. In most cases, the “send” operation is used to efficiently process multiple audio signals as one composite audio signal. In other words, as multiple audio signals are mixed and processed together, the “send” technique can be less computationally expensive than applying an effect to each individual audio signal. 
       FIG. 3  shows a signal flow diagram  300  that conceptually illustrates an example of applying an effect to multiple different clips. Specifically, this figure illustrates an example of how audio signals of clips  305 - 315  are routed to output a mixed audio signal for a composite presentation. As shown, the figure includes clips  305 - 315 , an echo FX module  305 , and the master  210 . The master  210  is the same as the one described above by reference to  FIG. 2 . The echo FX module  305  receives an audio signal of one or more audio clips, applies the echo effect to the received audio signal, and output an audio signal containing the echo effect. 
     As shown in  FIG. 3 , the audio signals of clips  305 - 310  are sent to the echo FX module  305 . The audio signals of clips  305 - 315  are sent to the master  210 . The echo FX module  305  receives a mixed audio signal of clips  305 - 310 , processes the received audio signal, and returns an audio signal containing the echo effect to the master  210 . The master  210  receives a mixed audio signal of clips  305 - 315  and the audio signal containing echo effect from the echo FX module  305 . The master  210  then outputs a resulting mixed audio signal for the sequence of clips  305 - 315 . Here, the resulting mixed audio signal is a composite audio signal of clips  305 - 315  and includes the echo effect applied to clips  305  and  310 . In some embodiments, the duration of this composite audio signal is the duration of the composite presentation. 
     In the examples described above, one effect is applied to one or more clips.  FIG. 4  shows a signal flow diagram  400  that conceptually illustrates applying an effect chain with multiple different effects. In some embodiments, the effect chain represents an ordered sequence or series of effects that is specified for a particular metadata tag and applied to one or more clips tagged with the particular metadata tag. 
     As show in  FIG. 4 , the clip  215  is tagged with the “Dialog” tag, and a chain of effect has been specified for this tag. The chain of effects includes a reverb effect and an echo effect. As the echo effect is being applied to the clip  215 , the signal flow diagram  400  includes an echo FX module  305 . 
     In the example illustrated in  FIG. 4 , the clip&#39;s audio signal is first routed to the reverb FX module  205 . This is because the reverb effect is the first effect in the chain of effects. Here, the reverb FX module  205  applies the reverb effect to the incoming audio signal and outputs an audio signal containing the reverb effect. To continue the chain of effects, the audio signal containing the reverb effect is received at the echo FX module  305 . The echo FX module  305  processes the incoming audio signal and outputs a processed audio signal. As indicated by the “+” symbol, the audio signal from the echo FX module  410  is then mixed with the audio signal of the clip  215 . The master  210  receives the mixed audio signal and outputs a resulting mixed audio signal. 
     Referring back to  FIG. 1 , when the effect does not require data of one or more clips to be routed, process  100  identifies (at  120 ) properties of the identified effect. As mentioned, different effects can have different properties. For example, an image distortion effect can have one set of parameters for distorting an image, while an echo effect can have another set of parameters for adding the echo to an audio signal. 
     The process  100  then applies (at  125 ) the effect to each identified clip. Specifically, each particular effect is applied to the clip based on the properties of the particular effect. The media editing application of some embodiments applies one or more effects directly on each clip without using the “send”. One example of such technique is applying effects as “insert” effects. Different from the “send” effect, an “insert” effect simply processes the incoming audio signal and outputs a processed audio signal. In using this technique, the audio signals of different clips are not routed over an auxiliary bus to an effect module to be processed as one combined audio signal. Also, the output of an effect module is not mixed back in with one or more original audio signals. For example, the output audio data of a filter or an effect that compresses or distorts input audio data does not need to be mixed back in with the original uncompressed or undistorted audio data. Similarly, the output of an equalizer that reduces the bass of a clip does not need be mixed back in with the original clip as it will defeat the purpose of reducing the bass in the first place. Many different audio effects or audio filters (e.g., equalizers, compressors, band-pass filters) are applied as “insert” effects, in some embodiments. 
       FIG. 5  shows a signal flow diagram  500  that conceptually illustrates compressing audio signals of clips  305 - 310  based on the clips&#39; association with a “Music” tag. Specifically, this figure illustrates how the media editing application of some embodiments compresses the audio signals of clips  305 - 310  as insert effects instead of routing the audio signals using the “send and return”. As shown, the figure includes a set of compression modules  505 . In some embodiments, the set of compression modules  505  represents separate instances of the same compression module that are linked parametrically. For example, the output of these instances can be based on the same set of compression parameters or settings. 
     As shown in  FIG. 5 , the audio signals of clips  305 - 310  are individually compressed by the set of compression modules  505 . The compressed audio signals of clips  305 - 310  are then output to the master  210 . As indicated by the “+” symbol, the compressed audio signals of the clips  305  and  310 , and the audio signal of clip  315  are then mixed. This mixed audio signal is received at the master  210  that defines the output audio signal for the composite presentation. 
     Referring back to  FIG. 1 , process  100  determines (at  130 ) whether any other clip is tagged with a different tag having an associated effect. When no other clip is tagged with a different tag, process  1500  proceeds to  1520 . Otherwise, the process outputs (at  155 ) the composite presentation. For example, the media editing application may output the composite presentation by playing a real-time preview. Alternatively, the media editing application renders and/or mixes the composite presentation to storage (e.g., for playback at another time). The process then ends. 
     Some embodiments perform variations on process  100 . For instance, process  100  of some embodiments identifies each effect in an effect chain. Specifically, before identifying a next tag with an effect, process  100  applies each effect in the chain to a set of tagged clips. Also, some embodiments might take into account that a clip can be a compound clip (described below). In some such embodiments, process  100  identifies each outer metadata tag of the compound clip and each inner tag of the compound clip&#39;s nested clips. Process  100  then applies one or more effects to the compound clip and/or the inner clips according to this identification. Several examples applying effects to compound clips are described below by reference to  FIGS. 6-10 . 
     In the examples described above, different effects are applied using different techniques. In some embodiments, the media editing application automatically determines whether to apply an effect by using an “insert” or by using the “send and return”. For instance, the media editing application of some embodiments automatically applies a first type of effect (e.g., reverb, echo) using the “send and return”, while applying a second type of effect (e.g., compressor, equalizer) as an “insert” effect. In conjunction with this automatic determination, or instead of it, the media editing application of some embodiments provides one or more user-selectable items for specifying whether to apply an effect as a “send” effect or an “insert” effect. 
     II. Applying Effects to Compound Clips 
     The media editing application of some embodiments allow users to create compound clips from multiple different clips. In some embodiments, a compound clip is any combination of clips (e.g., in a composite display area or in a clip browser as described below by reference to  FIG. 22 ) and nests clips within other clips. Compound clips, in some embodiments, contain video and audio clips as well as other compound clips. As such, each compound clip can be considered a mini project or a mini composite presentation, with its own distinct project settings. In some embodiments, compound clips function just like any other clips. That is, the application&#39;s user can add the compound clips to a project or composite display area, trim them, tag them, retime them, and add effects and transitions. 
       FIG. 6  illustrates an example of specifying an effect for a compound clip. Specifically, this figure illustrates (1) creating a compound clip from multiple different clips, (2) tagging the compound clip with a metadata tag, and (3) specifying an effect for the metadata tag. Five operational stages  605 - 625  of the GUI are shown in this figure. 
     As shown, the figure includes a composite display area  660  and a tag display area  665 . The composite display area  660  provides a visual representation of the composite presentation (or project) being created with the media editing application. Specifically, it displays one or more geometric shapes that represent one or more media clips that are part of the composite presentation. In some embodiments, the tag display area  665  displays one or more pieces of metadata associated with different media clips. 
     The first stage  605  shows the tag display area  665  and the composite display area  660 . The tag display area  665  includes a metadata tag  655  that is associated with an add effect control  660 . The composite display area  660  displays representations of three clips  630 - 640  that are not tagged with the metadata tag  655 . In this first stage, the user selects the clip  630  by selecting a corresponding representation in the composite display area  660 . 
     The second stage  610  shows the creation of a compound clip from clips  630  and  635 . Specifically, after selecting these two clips, the user selects a selectable option  640  (e.g., context menu item) to create the compound clip  650  as illustrated in the third stage  615 . In some embodiments, the media editing application provides several different controls (not shown) for creating the compound clip. Several examples of such controls include (1) a text field for inputting a name for the compound clip, (2) a first set of control for specifying video properties (e.g., automatically based on the properties of the first video clip, custom), and a second set of controls for specifying audio properties (e.g., default settings, custom). 
     The third stage  615  illustrates tagging the compound clip  650  with the first metadata tag  655 . Here, a tagging option  645  is used to tag the compound clip  650 . However, different embodiments provide different ways for tagging a compound clip. The fourth stage  620  illustrates the selection of an add effect control  660 . The selection causes an add effect window  665  with a list of effects to appear as illustrated in the fifth stage  625 . As shown in the fifth stage  625 , the add effect window  665  displays several different effects from which the user can choose from to associate with the first metadata tag  655 . The user then selects the reverb effect to associate it with the first metadata tag  655 . 
     Once the effect is set, the media editing application applies the reverb effect to the compound clip  650  in order to produce a resulting composite presentation. For example, the media editing application of some embodiments applies the reverb effects to the compound clip  650  to play a real-time preview of the presentation. Alternatively, the media editing application renders or outputs the sequence in the composite display area  660  to storage for playback at another time. 
       FIG. 7  shows a signal flow diagram  700  that conceptually illustrates the application of the reverb effect on the compound clip  650 , in some embodiments. Specifically, this figure illustrates an example of how audio signals of clips  630 - 640  (in the composite display area  660  of  FIG. 6 ) are routed to output a mixed audio signal with the reverb effect. As shown, the figure includes the clips  630 - 640 , the master  210 , and the reverb FX module  205 . 
     As shown in  FIG. 7 , the audio signals of clips  630  and  635  are mixed for the compound clip  650 . The mixed audio signal of the compound clip  650  is sent to the reverb FX module  205 . The reverb FX module  205  processes the received audio signal and returns the audio signal containing the reverb effect to the master  210 . The master  210  receives a mixed audio signal containing the audio signal of the compound clip  650 , the audio signal of clip  640 , and the audio signal containing reverb effect. The master  210  then outputs a resulting mixed audio signal. 
     In the example illustrated in  FIG. 7 , the “send” is performed on the audio signal of the compound clip  650 . Alternatively, the media editing application of some embodiments allows its users to add “insert” effects for compound clips tagged with a metadata tag. Several examples of such “insert” effects are described above by reference to  FIG. 5 . 
     In the previous example, a compound clip is tagged with a metadata tag that is associated with an effect. Also, the nested clips of the compound clip are not tagged with this metadata tag. Accordingly, the effect associated with the compound clip&#39;s tag is applied to the audio signal of the compound clip. In some cases, one or more inner clips of the compound clip are tagged with a metadata tag. In order to simply the discussion below, a compound clip&#39;s tag will be referred to as an outer tag, while the tag of the inner clip of the compound clip will be referred to as an inner tag. Also, in several examples below, the outermost tag refers to the tag of the compound clip that is not contained by another compound clip. 
       FIG. 8  shows a signal flow diagram  800  that conceptually illustrates the application of the reverb effect on an inner clip  805  of a compound clip  820 . Specifically, this figure illustrates an example of how audio signals of clips  805 ,  815 , and  810  (e.g., in the composite display area  660  of  FIG. 6 ) are routed to output a mixed audio signal with the reverb effect. In this example, the inner clip  805  has been tagged with a “Dialog” tag with a reverb effect, while the compound clip  820  is not tagged with any tag. 
     As shown, the audio signal of clip  805  is routed to the reverb FX module  205 . This is because the clip  805  is tagged with the “Dialog” tag that is associated with a reverb effect. In other words, even though the clip  805  is a nested clip of the compound clip  820 , the media editing application of some embodiments identifies each inner tag of the compound clip&#39;s nested clips to apply one or more effects. Here, the reverb FX module  205  applies the reverb effect to the received audio signal and returns an audio signal containing the reverb effect to the master  210 . As indicated by the “+” symbol, the audio signals of clip  805  and  810  are combined for the compound clip  820 . The audio signal of the compound clip  820 , the audio signal containing the reverb effect for clip  805 , and the audio signal of clip  805  are then mixed. The master  210  receives the mixed audio signal and outputs a resulting mixed audio signal. 
     In the example described above, the output of the reverb FX module  205  is sent to the master  210  instead of being mixed in as part of the compound clip  820 . This is because the media editing application of some embodiments defines a separate auxiliary (“aux”) bus or virtual pathway for one or more effects associated with a metadata tag. In some embodiments, this aux bus always outputs to the master. 
       FIG. 9  shows a signal flow diagram  900  that conceptually illustrates how audio signals of several clips are routed to a particular aux bus based on the clips&#39; association with a metadata tag. This example is similar to  FIG. 8 . However, the “Dialog” tag is associated with a chain of effects that includes a reverb effect and an echo effect. Also, the clips  805  and  815  are both tagged with the “Dialog” tag. 
     As shown in  FIG. 9 , the audio signal of each clip that is tagged with the “Dialog” tag is routed to the “Dialog” aux bus. Specifically, the audio signals of clips  805  and  815  are both routed to this aux bus. The audio signals are routed to the aux bus regardless of whether the clip is a nested clip (as in clip  805 ) or a non-nested clip (as in clip  815 ). The audio signals of clips  805  and  815  are then combined and sent over the aux bus in order to apply the chain of effects to the clips  805  and  805 . 
     In the example illustrated in  FIG. 9 , the combined audio signal is first routed to the reverb FX module  205 . To continue the chain of effects, the audio signal containing the reverb effect is received at the echo FX module  305 . The echo FX module  305  processes the incoming audio signal and outputs a processed audio signal. The output of the echo FX module  305  is returned to the master  210 . As indicated by the “+” symbol, the audio signals of clip  805  and  810  are combined for the compound clip  820 . The audio signal of the compound clip  820 , the audio signal from the echo FX module  305 , and the audio signal of clip  805  are then mixed. The master  210  receives the mixed audio signal and outputs a resulting mixed audio signal. 
     In some cases, a compound clip is tagged with the same tag as one or more of the compound clip&#39;s inner clips. In some embodiments, the media editing application identifies an appropriate level of a compound clip to apply the effect such that the effect is not reapplied at another level. For example, when the inner clip&#39;s tag is the same as the compound clip&#39;s outer tag, the media editing application of some embodiments identifies the compound clip&#39;s outer tag and performs the editing operations based on the compound clip&#39;s outer tag. This prevents the same effect being applied to the compound and one or more of the compound clip&#39;s nested clips. 
       FIG. 10  conceptually illustrates a process  1000  that some embodiments use to apply one or more effects to a compound clip and/or the compound clip&#39;s nested clips. In some embodiments, process  1000  is performed by a media editing application. Process  1000  may be a performed in conjunction with several other processes (e.g., including  FIGS. 15 ,  16 , and  20  described below). Process  1000  will be described by reference to  FIG. 11  that illustrates applying an effect to a compound clip based on the compound clip&#39;s outer tag. 
     As shown, process  1000  identifies (at  1005 ) a clip tagged with a particular metadata tag in a composite presentation. Process  1000  then determines (at  1010 ) whether the clip tagged the particular metadata tag is a compound clip. In the example illustrated in  FIG. 11 , the clip  820  is a compound clip tagged with a particular metadata tag. Specifically, the compound clip  820  is associated with a “Dialog” tag having a reverb effect. 
     When the clip is not a compound clip, process  1000  proceeds to  1035 , which is described below. Otherwise, process  1000  identifies (at  1015 ) the particular metadata tag of the compound clip and each inner tag of the compound clip&#39;s nested clips. Process  1000  then determines (at  1020 ) whether any inner tag of the compound clip&#39;s nested clips is different from the outer tag of the compound clip. 
     When no inner tag is different than the outer tag or no nested clip is tagged with a tag associated with an effect, process  1000  performs (at  1025 ) one or more operations based on the outer tag. In the example illustrated in  FIG. 11 , as the compound clip&#39;s outer tag takes precedence over the inner tag, the effect associated with the inner tag of inner clip  805  is not applied to this inner clip. Instead, the effect is applied to the mixed audio signal of the compound clip  820 . Specifically, the audio signals of clips  810  and  805  are mixed as a mixed audio signal for the compound clip  820 . As the compound clip is tagged with the “Dialog” tag, the mixed audio signal of the compound clip is then sent to the reverb FX module  205 . Although the clip  805  is also tagged with the “Dialog” tag, the clip&#39;s audio signal is not sent to the reverb FX module. This is because the media editing application identified that the compound clip&#39;s outer tag is the same as the inner tag of the nested clip  805 . 
     The reverb FX module  205  applies the reverb effect to the received audio signal and returns an audio signal containing the reverb effect to the master  210 . The mixed audio signal of the compound clip  820 , the audio signal containing the reverb effect from the reverb FX module  205 , and the audio signal of clip  815  are then mixed. The master  210  then receives the mixed audio signal and outputs a resulting audio signal. 
     Referring back to  FIG. 10 , when one or more inner tags of the compound clip&#39;s nested clips are different, process  1000  performs (at  1030 ) one or more operations based on each different inner tag. Process  1000  also performs (at  1030 ) one or more operations based on the compound clip&#39;s outer tag. In some embodiments, process  1000  applies the different effects following a sequence of operations (e.g., as represented in a signal chain or render graph). For example, when a reverb effect is associated with a first metadata tag of a compound clip&#39;s nested clip, process  1000  of some embodiments first applies the reverb effect to the compound clip&#39;s nested clip. Once the effect is applied to the nested clip, process  1000  combines the nested clip with one or more other clips in order to apply a second effect associated with a second metadata tag of the compound clip. 
     Process  1000  then determines (at  1035 ) whether there is any other tagged clip in the composite presentation. When there is another tagged clip, process  1000  returns to  1005  which was described above. Otherwise, process  1000  ends. 
     Some embodiments perform variations on process  1000 . For example, the specific operations of process  1000  may not be performed in the exact order shown and described. The specific operations may not be performed in one continuous series of operations, and different specific operations may be performed in different embodiments. 
     III. Audio Meters 
     In many of the example described above, the audio signals of several clips are mixed and output as one combined audio signal for a composite presentation. In some cases, the mixed audio signal of a compound clip is again combined with an audio signal of another clip to output a composite presentation. In some embodiments, the media editing application displays the audio level of a set of one or more clips even though the set of clips has been mixed with other clips. 
     A. Displaying Audio Levels 
       FIG. 12  illustrates an example of displaying the audio levels of several mixed clips. Specifically, this figure illustrates meters that indicate the audio levels of the clips even though the clips have been mixed with other clips. Three operational stages  1205 - 1215  are shown in this figure. The composite display area  660  is the same as the one described above by reference to  FIG. 6 . The figure also includes an audio mixer  1220 . 
     In some embodiments, the media editing application provides audio meters and/or audio controls for metadata tags associated with different clips. An example of this is illustrated in  FIG. 12 . Specifically, the audio mixer  1220  includes a corresponding audio meter ( 1245  or  1255 ) and a level control ( 1240  or  1250 ) for each of a first metadata tag specified as “Dialog” and a second metadata tag specified as “SFX”. Several other examples of providing different controls (e.g., audio meters, audio controls) for different metadata tags are described below by reference to  FIG. 16 . 
     The first stage  1205  shows the composite display area  660  and the audio mixer  1220  prior to playing the composite presentation. As shown, clip  1225  is tagged with the “Dialog” tag. Compound clip  1235  includes several nested clips  1260  and  1265 . The compound clip  1235  is tagged with the “SFX” tag. The nested clips  1260  and  1265 , and clip  1230  are not tagged with the “Dialog” tag or the “SFX” tag. 
     The second stage  1210  shows the playback of the composite presentation represented in the composite display area  660  at a first instance in time. To output the composite presentation&#39;s mixed audio signal, the audio signals of the nested clips  1260  and  1265  has been mixed for the compound clip  1235 . In addition, the audio signals of the clips  1225  and  1230  have been mixed with the audio signal of the compound clip  1235 . In this second stage  1210 , the audio meter  1245  displays the audio level of the clip  1225  even though the clips in the composite display area  660  has been mixed to play the composite presentation. 
     The third stage  1215  shows the playback of the composite presentation at a second instance in time. Similar to the previous stage, the audio meter  1255  displays the audio level of the compound clip  1225  even though the compound clip has been mixed with the clips  1225  and  1230 . 
     B. Sending an Audio Signal Over a Meter Bus 
     In the example illustrated in  FIG. 12 , the media editing application provides meters that indicate the audio levels of clips that have been mixed with other clips. To display audio levels of these clips, the media editing application of some embodiments creates one or more meter buses and routes audio signals of the clips over the meter buses. 
       FIG. 13  shows a signal flow diagram  1300  that conceptually illustrates sending an audio signal of a clip over a meter bus  1305  in order to display the clip&#39;s audio level during playback of a mixed audio signal of a composite presentation. As shown, the figure includes clips  1310  and  1315  that are mixed as a compound clip  1320 . The figure also includes the meter bus  1305  and the master  210 . The master  210  is the same as the one described above by reference to  FIG. 2 . 
     As shown  FIG. 13 , the signal flow  1300  includes a chain or a sequence of operations that is performed on the clips  1310  and  1315 . However, this signal chain does not include a place to determine the audio level of clip  1310  once it has been summed with clip  1315 . Specifically, in the signal chain, the clips  1310  and  1315  are mixed as the compound clip  1320 . The mixed audio signal of clips  1310  and  1315  is then output through the master  210 . Also, the mixed audio signal cannot be used to determine how much the clip  1310  contributed to the overall mix. 
     As the audio level of clip  1310  cannot be determined using the mixed audio signal, the clip&#39;s audio signal is sent over the meter bus  1305 . This meter bus  1305  is not for playing sound but for metering. Specifically, in the example illustrate in  FIG. 13 , the meter bus  1305  is for displaying the audio level of each clip tagged with the “Dialog” tag. In some embodiments, the clips audio is routed over the meter bus  1305  to a component (not shown) that translates the audio signal to one or more meters. For example, the media editing application of some embodiments determines a set of decibel (dB) values. The set of dB values is then used to meter the audio level of the clip  1310 . 
       FIG. 14  shows a signal flow diagram  1400  that conceptually illustrates routing a combined audio signal of several clips over the meter bus  1305  for the purposes of displaying the clips&#39; audio level. This example is similar to  FIG. 13 . However, in addition to the clip  1310 , the figure includes a clip  1405  that is tagged with the “Dialog” tag. 
     As shown in  FIG. 13 , the clips  1310  and  1315  are mixed as the compound clip  1320 . The mixed audio signal of the clips  1310  and  1315  is then combined with the audio signal of the clip  1405 . The composite audio signal of the clips  1310 , Q 15 , and Q 15  is then output through the master  210 . To display the audio level of the “Dialog” clips  1310  and  1410 , the audio signals of these clips are combined and sent over the meter bus  1305 . Similar to the example of  FIG. 14 , the combined audio signal is then translated into a set of decibel values by the media editing application. 
     In some embodiments, the media editing application takes into account other factors when displaying the audio level of clips that has been with other clips. The media editing application of some embodiments scales (i.e., reduces or increases) the audio level of one or more clips by processing later down the signal chain. For example, in the example illustrated in  FIG. 14 , the audio meter for the “Dialog” clips  1310  and  1405  should reflect the audio level of the entire mix (e.g., as defined by the master  210 ). That is, when the master&#39;s volume is set at a particular dB, the combined audio signal of clips  1310  and  1405  should be scaled or synchronized such that audio meter does not indicate an audio level that is higher than the particular dB. 
     C. Estimating the Volume 
     In the previous example, a combined audio signal of several clips is sent over a meter bus to display the audio level of several clips. Alternatively, the media editing application of some embodiments estimates the audio level of the one or more clips. That is, instead of routing the audio signal over the meter bus, the media editing application numerically estimates the audio level by extracting metering information from the clips prior to mixing the clips. 
       FIG. 15  conceptually illustrates a process  1500  that some embodiments use to estimate audio levels of clips that are tagged with metadata tags. In some embodiments, process  1500  is performed by a media editing application. As shown, process  1500  identifies (at  1505 ) each clip, in a composite presentation, that is tagged with a particular metadata tag. Process  1500  then extracts (at  1510 ) metering information (e.g., audio level) from each clip tagged with the particular metadata tag. 
     Process  1500  then determines (at  1515 ) whether any other clip is tagged with a different tag. When no other clip is tagged with a different tag, process  1500  proceeds to  1520 . Otherwise, process  1500  returns to  1505  which was described above. 
     At  1520 , process  1500  determines the audio level of one or more clips based on the metering information. In the example described above in  FIG. 14 , the audio level of several clips is determined by summing the clips&#39; audio signals and sending the summed audio signal over the meter bus. Here, as the audio signals are being mixed later in the signal chain, process  1500  estimates the audio level based on the metering information (e.g., audio signal data) extracted from each of the clips. In other words, process  1500  estimates what the audio level would be when two or more audio signals of different clips are added together. 
     In some embodiments, process  1500  estimates the audio level by adding the power contribution of each clip. One example of such addition is adding about 3 dB for every doubling of equal input sources. For example, if the audio signals of two clips have an identical volume of −10 dB, then the sum of the two signals is estimated to be about 3 dB higher. As such, the estimated sum of the two signals is about −7 dB. If there are four audio signals that have the identical volume, then the sum of these signals will be estimated to be about 6 dB higher, and so on. One example formula for adding sound pressure levels of multiple sound sources is shown below: 
     
       
         
           
             
               L 
               Σ 
             
             = 
             
               
                 10 
                 · 
                 
                   
                     log 
                     10 
                   
                   ⁡ 
                   
                     ( 
                     
                       
                         10 
                         
                           
                             L 
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                           10 
                         
                       
                       + 
                       
                         10 
                         
                           
                             L 
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                           10 
                         
                       
                       + 
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                       + 
                       
                         10 
                         
                           
                             L 
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     Here, L Σ  equals total level, and L 1 , L 2 , . . . L n  equal sound pressure level (spl) of the separate sources in dBspl. This formula above translates to about 3 dB per doubling of equal sources. One of ordinary skill in the art would realize that other formulas can be used to differently sum two or more audio signals in order to estimate the audio level. 
     Returning to  FIG. 15 , process  1500  displays (at  1525 ) the audio level of one or more tagged clips based on each estimated audio level. Specifically, process  1500  displays the audio level when playing the mixed audio signal of the composite presentation. Process  1500  then ends. 
     In some embodiments, process  1500  takes into account other factors when displaying the audio level of clips that has been previously mixed. For example, process  1500  of some embodiments scales (i.e., reduces or increases) the audio level of one or more clips by processing later down the signal chain. In some embodiments, the process estimates the audio level of the mixed clips by identifying what each clip is contributing to the overall mix and numerically estimating the audio level based on the identification and the extracted metering information. For example, when a compound clip is muted, the media editing application should not display audio level of the compound&#39;s nested clip as the nested clip is also muted. 
     In some cases, estimating the audio level has several advantages over routing audio signals over meter buses. For example, this technique can be less computationally expensive than using meter buses. This is because the meter buses do not have to be created and the audio signals of different clips do not have to be routed over these meter buses. 
     IV. Parameter Controls and Propagation 
     The media editing application of some embodiments uses metadata to provide user interface controls. In some embodiments, these controls are used to display properties of tagged clips and/or specify parameters that affect the tagged clips. Example of such user interface controls include audio meters, volume controls, different controls for modifying images (e.g., distorting, blurring, changing color), etc. 
       FIG. 16  conceptually illustrates a process  1600  that some embodiments use to construct user interface controls based on metadata tags. In some embodiments, process  1600  is performed by a media editing application. As shown, process  1600  identifies (at  1605 ) each clip tagged with a particular metadata tag. In some embodiments, one or more clips are categorized with a particular role or category. For example, several clips may be assigned one audio role of “Dialog”, “Music”, or “SFX”. Process  1600  then provides one or more user interface controls. Here, the user interface controls are also associated with the tagged clips. That is, the user interface controls are associated so that these controls can be used to display or modify properties of the tagged clips. 
     Process  1600  then determines (at  1615 ) whether any other clip is tagged with a different tag. When no other clip is tagged with a different tag, process  1600  proceeds to  1620 . Otherwise, process  1600  returns to  1605  which was described above. Process  1600  then receives (at  1620 ) adjustment of parameters through one or more corresponding user interface controls. Process  1600  then outputs (at  1625 ) the sequence of clips in the composite presentation by propagating the adjusted parameter to one or more of corresponding tagged clips. Process  1600  then ends. 
     Some embodiments allow a compound clip to be tagged with the same tag as one or more of the compound clip&#39;s inner clips. In some embodiments, the media editing application identifies an appropriate level in a render graph or signal chain to adjust parameters such that the parameters are not readjusted at another level. For example, when the inner clip&#39;s tag is the same as the compound clip&#39;s outer tag, the media editing application of some embodiments identifies the compound clip&#39;s outer tag and performs the adjustment based on the compound clip&#39;s outer tag. This prevents the same adjustment being applied at multiple different levels. 
       FIG. 17  shows a data flow diagram  1700  that conceptually illustrates an example of adjusting parameters of several clips at different levels of a hierarchy, in some embodiments. As shown in  FIG. 17 , clips  1705  and  1710  are combined for the compound clip  1715 . The nested clips  1705  and  1710  are tagged with the “Dialog” tag, while the compound clip  1715  is not tagged with this tag. As the compound clip  1715  is not tagged with the same tag as its nested clips  1705  and  1710 , the parameter adjustment occurs for this compound clip at the level of the nested clips. Similarly, the adjustment for compound clip  1740  occurs at the level of the nested clips  1735  and  1730 . 
     In the example illustrated in  FIG. 17 , the clips  1720  and  1725  are combined for the compound clip  1730 . Here, the nested clip  1720  and the compound clip  1730  are tagged with the “Dialog” tag, while the nested clip  1725  is not tagged this tag. As the compound clip  1730  includes the same tag as one of its nested clips (i.e., the clip  1720 ), the adjustment occurs for this compound clip at the level of the compound clip. Similarly, the adjustment for compound clip  1755  occurs at the level of the compound clip. This is because the nested clips  1745  and  1755  are tagged with the same “Dialog” tag as the compound clip  1755 . 
     In some cases, the compound clip&#39;s outer tag can be different from one or more tags of its inner clips. When the compound clip&#39;s outer tag is different from the inner clip&#39;s tag, the media editing of some embodiments adjusts one set of parameter associated with the inner clip based on the inner clip&#39;s tag. Also, the media editing application adjusts another set of parameters associated with the compound clip based on the compound clip&#39;s tag. 
     In some embodiments, the media editing application does not support tagging compound clips. In some such embodiments, the adjustment is only made at the nested clip level. For example, when several nested clips of a compound clip are tagged with a “Dialog” tag, an adjustment to a control relating to the “Dialog” tag will adjust parameters associated with these nested clips and not the combined clip of the compound clip. 
     V. Outputting Content to Different Tracks 
     The media editing application of some embodiments allows a composite presentation to be output to different tracks (e.g., different files) based on metadata associated with media content. Outputting content to different tracks is particularly useful because one track can easily be replaced with another track. For example, when audio content is mixed, a movie studio cannot replace a dialog track in one language with another dialog track in another language. With audio content output to different tracks (e.g., audio files), the movie studio can easily replace one dialog track with another such that the dialog is in a different language. 
     A. Specifying Output Tracks 
       FIG. 18  illustrates specifying output tracks for clips based on metadata that is associated the clips. Six operational stages  1805 - 1830  of the GUI are shown in this figure. In this example, the tag display area  665  includes an output control ( 1835 ,  1840 , or  1845 ) for each metadata tag ( 1850 ,  1855 , or  1860 ). The output control allows the application&#39;s user to specify an output track or stem for each clip associated with a metadata tag. 
     The first stage  1805  shows the tag display area  665  and the composite display area  660 . The tag display area  665  includes a list of metadata tags. This list includes a first metadata tag  1850  specified as “Dialog”, a second metadata tag  1855  specified as “Music”, and a third metadata tag  1860  specified as “SFX”. The first metadata tag  1850  is associated with a first output control  1835 , the second metadata tag  1855  with a second output control  1840 , and the third metadata tag  1860  with a third output control  1845 . 
     The composite display area  660  displays representations of five clips  1865 - 1885 . The clips  1865  and  1885  are tagged with the first metadata tag  1850 , the clip  1870  is tagged with the second metadata tag  1855 , and the clips  1875  and  1880  are tagged with the third metadata tag  1860 . To specify an output track for the clips  1865  and  1885  that are tagged with the first metadata tag  1850 , the user selects the output control  1835 . The selection causes a track control  1890  to appear as illustrated in the second stage  1810 . 
     The second stage  1810  illustrates specifying an output track for the clips  1865  and  1885  tagged with the first metadata tag  1850 . Specifically, the user specifies the output track to be “Track  1 ” by using the track control  1890 . In some embodiments, the media editing application provides various different options for outputting content. Several example output options include compression type and settings, bit rate, bit size, mono or stereo, name of file, etc. For instance, when outputting an audio containing dialog to a separate file, the media editing application of some embodiments displays different user interface items that allow the application&#39;s user to define the output audio clip such as the type of audio file, compression settings, etc. 
     The third and fourth stages  1815  and  1820  illustrate specifying an output track for the clip  1870  that is tagged with the second metadata tag  1855 . To specify the output track, the user selects the output control  1840  that is associated with the second metadata tag  1855 . The selection causes the track control  1890  to appear, as illustrated in the fourth stage  1820 . In the fourth stage  1820 , the application&#39;s user specifies the output track to be “Track  2 ” by using the track control  1890 . 
     The fifth and sixth stages  1825  and  1830  are similar to the previous stages. However, in these stages  1825  and  1830 , an output track is specified for the clips  1875  and  1880  that are tagged with the third metadata tag  1860 . To specify the output track, the user selects the output control  1845  that is associated with the third metadata tag  1860 . The selection causes the track control  1890  to appear, as illustrated in the sixth stage  1830 . In the sixth stage  1830 , the user specifies the output track to be “Track  3 ” by using the track control  1890 . Once the output tracks are specified for the metadata tags, the user can select an output or export option (not shown) to start the output of clips based on the clip&#39;s association with a particular metadata tag. 
     In the example described above, several output tracks are associated with metadata tags. In some embodiments, the media editing application allows a user to associate metadata tags with output tracks.  FIG. 19  provides an illustrative example of an output tool  1900  for the media editing application. As shown, the figure includes several user-selectable items (e.g., drop-down lists)  1905 - 1920 . Each selectable item represents a particular output track for a composite presentation. The user can use any one of these items  1905 - 1920  to associate one or more roles with a particular track. For instance, two different roles have been specified with the selectable item  1920 . This is different from  FIG. 18  where a particular output track is associated with one particular metadata tag (e.g., a role). 
     As shown in  FIG. 19 , several of these selectable items  1905 - 1920  are associated with other user interface items  1925 - 1935 . A user of the application select any one of these items  1925 - 1935  to associate a particular output setting (e.g., mono, stereo, surround) with a corresponding output track. The user can then select a button  1940  to specify a multi-track output for the composite presentation. 
     B. Performing Multiple Passes 
     In some embodiments, the media editing application performs multiples passes on a render graph or signal chain to output a composite presentation to different tracks.  FIG. 20A  shows a signal flow diagram  2000  that conceptually illustrates the problem of outputting the composite presentation to different tracks in a single pass. To simplify the discussion, this signal flow diagram  2000  represents a scenario where only one compound clip  2010  that nests clips  2005  and  2010  is in the composite presentation. 
     As shown in  FIG. 20A , the inner clip  2005  is tagged with a first metadata tag, and inner clip  2010  is tagged with a second metadata tag. The output track for the first metadata tag has been specified as “Track  1 ”, and the output track for the second metadata tag has been specified as “Track  2 ”. Here, the audio signals of clips  2005  and  2010  are mixed as one mixed audio signal for the compound clip  2010 . This prevents the audio signal of clip  2005  to be played through one channel, while the audio signal of clip  2010  is being played through another channel. As such, the mixed audio signal cannot be unmixed to output the audio signal of clip  2005  to the first track and the audio signal of clip  2010  to the second track. 
     Although the composite presentation cannot be unmixed during playback, the media editing application allows the composite presentation to be output to different audio files by performing multiple passes on a render graph or signal chain.  FIG. 20B  illustrates outputting the composite presentation different audio files. Two example stages  20 B 05  and  20 B 10  of the media editing application are illustrated in this figure. Specifically, these stages illustrate performing multiple rendering passes to output the composite presentation to different files. 
     The first stage  20 B 05  illustrates a first pass that is performed to output the audio content of clip  2005  to “Track  1 ”. The audio signals of clips  2005  and  2010  are mixed for the compound clip  2020 . However, in this first pass, the audio signal of clip  2010  is disabled (e.g., muted or silenced). As the audio clip  2010  is muted, the mixed audio signal includes only the audio signal of the clip  2005 . 
     The second stage  20 B 10  illustrates a second pass that is performed to output the audio content of clip  2010  to “Track  2 ”. Similar to the first stage  20 B 05 , the audio signals of clips  2005  and  2010  are mixed for the compound clip  2020 . However, in this second pass, the audio signal of clip  2005  is disabled (e.g., muted). As the audio clip  2005  is disabled, the mixed audio signal includes only the audio signal of the clip  2010 . In some embodiment, the output files include a same duration as the composite presentation. For example, if the duration of the composite presentation (e.g., represented in the composite display area) is one hour and each of the clips  2005  and  2010  includes thirty minutes of sound, then each output file will be one hour in duration with thirty minutes of sound. 
     In the example described above, multiple rendering passes are performed to output the audio content to different tracks. The media editing application of some embodiments performs these multiple passes simultaneously. In some such embodiments, the media editing application generates multiple copies of one or more render objects (e.g., render graphs, render files) for rendering the sequence of clips in the composite display area. The media editing application then performs the multiple passes such that these passes occur at least partially at the same time. By simultaneous performing these passes, the media editing application saves time in that it does not need to wait for one pass to end to start another. This also saves time as files (e.g., source clips) are read out of disk or loaded in memory once instead of multiple times. 
     The preceding section described and illustrated various ways to use metadata to facilitate output operations.  FIG. 21  conceptually illustrates a process  2100  that some embodiments use to output a composite presentation to different tracks. In some embodiments, process  2100  is performed by a media editing application. As shown, process  2100  receives (at  2105 ) input to output a composite presentation (e.g., a sequence of clips in the composite display area). Process  2100  then identifies (at  2110 ) a track to process. 
     At  2115 , process  2100  identifies each clip tagged with a tag (e.g., role) that is associated with the identified track. An example of associating one or more roles to a particular output track is described above by reference to  FIG. 19 . 
     Process  2100  then adds (at  2120 ) each identified clip to a render list for that track. Process  2100  then determines (at  2125 ) whether there are any more tracks. When there is another track, process  2100  returns to  2110  that was described above. Otherwise, process  2100  renders the composite presentation based on one or more render lists. For example, process  2100  of some embodiments renders the composite presentation by identifying clips in a render list, combining any two or more clips in the list, and outputting the combined clip to a particular track. Process  2100  then ends. 
     Some embodiments perform variations on process  2100 . For example, the operations of process  2100  might be performed by two or more separate processes. Also, the specific operations of the process may not be performed in the exact order shown and described. 
     VI. Software Architecture 
     A. Example Media Editing Application 
     Having described several example editing operations above, an example media editing application that implements several editing features will now be described.  FIG. 22  illustrates a graphical user interface (GUI)  2200  of a media editing application of some embodiments. One of ordinary skill will recognize that the GUI  2200  is only one of many possible GUIs for such a media editing application. In fact, the GUI  2200  includes several display areas which may be adjusted in size, opened or closed, replaced with other display areas, etc. As shown, the GUI  2200  includes a clip library  2205  (also referred to as an event library), a clip browser  2210  (also referred to as a clip browser), a composite display area  2215 , a preview display area  2220 , an inspector display area  2225 , and a toolbar  2235 . 
     The clip library  2205  includes a set of folder-like or bin-line representations through which a user accesses media clips that have been imported into the media editing application. Some embodiments organize the media clips according to the device (e.g., physical storage device such as an internal or external hard drive, virtual storage device such as a hard drive partition, etc.) on which the media represented by the clips are stored. Some embodiments also enable the user to organize the media clips based on the date the media represented by the clips was created (e.g., recorded by a camera). 
     Within the clip library  2205 , users can group the media clips into “events” or organized folders of media clips. For instance, a user might give the events descriptive names that indicate what kind of media is stored in the event (e.g., the “New Event 2-5-11” event shown in clip library  2205  might be renamed “European Vacation” as a descriptor of the content). In some embodiments, the media files corresponding to these clips are stored in a file storage structure that mirrors the folders shown in the clip library. 
     In some embodiments, the clip library  2205  enables users to perform various clip management actions. These clip management actions include moving clips between bins (e.g., events), creating new bins, merging two bins together, duplicating bins (which, in some embodiments, create a duplicate copy of the media to which the clips in the bin correspond), deleting bin, etc. 
     As shown in  FIG. 22 , the clip library  2205  displays several keywords  2202  and  2204 . To categorize a clip or associate the clip with a particular keyword, the application&#39;s user can drag and drop the clip onto the particular keyword. The same technique used in some embodiments to associate multiple clips with the particular keyword by simultaneously dragging and dropping the clips onto the keyword. In some embodiments, the keywords  2202  and  2204  are represented as keyword collections (e.g., keyword bin or keyword folder) in the clip library  2205 . That is, the keyword collection acts a virtual bin or virtual folder that the user can drag and drop items onto in order to create keyword associations. In some embodiments, upon selection of a keyword collection, the media editing application filters the clip browser  2210  to only display those clips associated with a particular keyword of the keyword collection. 
     The clip browser  2210  allows the user to view clips from a selected folder or collection (e.g., an event, a sub-folder, etc.) of the clip library  2205 . In the example illustrated in  FIG. 22 , the collection “New Event 2-5-11” is selected in the clip library  2205 , and the clips belonging to that folder are displayed in the clip browser  2210 . Some embodiments display the clips as thumbnail filmstrips (i.e., filmstrip representations). These thumbnail filmstrips are similar to the representations in the composite display area  2215 . 
     By moving a position indicator (e.g., through a cursor, through the application&#39;s user touching a touch screen) over one of the thumbnails, the user can skim through the clip. For example, when the user places the position indicator at a particular horizontal location within the thumbnail filmstrip, the media editing application associates that horizontal location with a time in the associated media file, and displays the image from the media file for that time. In addition, the user can command the application to play back the media file in the thumbnail filmstrip. In some embodiments, the selection and movement is received through a user selection input such as input received from a cursor controller (e.g., a mouse, touchpad, trackpad, etc.), from a touchscreen (e.g., a user touching a user interface (UI) item on a touchscreen), from the keyboard, etc. In some embodiments, one example of such a user selection input is the position indicator that indicates the user&#39;s interaction (e.g., with the cursor, the touchscreen, etc.). The term user selection input is used throughout this specification to refer to at least one of the preceding ways of making a selection, moving a control, or pressing a button through a user interface. 
     In the example illustrated in  FIG. 22 , the thumbnails for the clips in the clip browser  2210  display an audio waveform underneath the clip that represents the audio of the media file. In some embodiments, as a user skims through or plays back the thumbnail filmstrip, the audio portion plays as well. Many of the features of the clip browser are user-modifiable. For instance, the user can modify one or more of the thumbnail size, the percentage of the thumbnail occupied by the audio waveform, whether audio plays back when the user skims through the media files, etc. In addition, some embodiments enable the user to view the clips in the clip browser  2210  in a list view. In this view, the clips are presented as a list (e.g., with clip name, duration, metadata, etc.). Some embodiments also display a selected clip from the list in a filmstrip view at the top of the clip browser  2210  so that the user can skim through or playback the selected clip. The clip browser in some embodiments allows users to select different ranges of a media clip and/or navigate to different sections of the media clip. 
     In some embodiments, the media editing application displays content differently based on their association with one or more metadata tags (e.g., keywords). This allows users to quickly assess a large group of media clips and see which ones are associated or not associated with any metadata tags. For example, in  FIG. 22 , a horizontal bar is displayed across each of the clips  2240 - 2250 . This indicates to the application&#39;s user that these clips are tagged with one or more metadata tags. 
     In some embodiments, the media editing application allows the user to tag a portion of a clip with a metadata tag. To associate a metadata tag with a portion of a clip, the user can select the portion of the clip (e.g., using a range selector on a clip&#39;s filmstrip representation in the clip browser  2210 ), and drag and drop the selected portion onto the metadata tag (e.g.,  2202  or  2204 ). For example, a user can specify that an audio clip includes crowd noise starting at one point in time and ending at another point, and then tag that range as “crowd noise”. When a portion of a clip is associated with a metadata tag, the media editing application of some embodiments indicates this by marking a portion of the clip&#39;s representation in the clip browser  2210 . For example, a horizontal bar is displayed across only the portion the clip&#39;s filmstrip representation associated with a particular metadata tag, in some embodiments. 
     The composite display area  2215  provides a visual representation of a composite presentation (or project) being created by the user of the media editing application. As mentioned above, the composite display area  2215  displays one or more geometric shapes that represent one or more media clips that are part of the composite presentation. In some embodiments, the composite display area  2215  spans a displayed timeline  2226  which displays time (e.g., the elapsed time of clips displayed on the composite display area). The composite display area  2215  of some embodiments includes a primary lane  2216  (also called a “spine”, “primary compositing lane”, or “central compositing lane”) as well as one or more secondary lanes (also called “anchor lanes”). The spine represents a primary sequence of media which, in some embodiments, does not have any gaps. The clips in the anchor lanes are anchored to a particular position along the spine (or along a different anchor lane). Anchor lanes (e.g., the anchor lane  2218 ) may be used for compositing (e.g., removing portions of one video and showing a different video in those portions), B-roll cuts (i.e., cutting away from the primary video to a different video whose clip is in the anchor lane), audio clips, or other composite presentation techniques. 
     The user can select different media clips from the clip browser  2210 , and drag and drop them into the composite display area  2215  in order to add the clips to a composite presentation represented in the composite display area  2215 . Alternatively, the user can select the different media clips and select a shortcut key, a tool bar button, or a menu item to add them to the composite display area  2215 . Within the composite display area  2215 , the user can perform further edits to the media clips (e.g., move the clips around, split the clips, trim the clips, apply effects to the clips, etc.). The length (i.e., horizontal expanse) of a clip in the composite display area is a function of the length of the media represented by the clip. As the timeline  2226  is broken into increments of time, a media clip occupies a particular length of time in the composite display area. As shown, in some embodiments, the clips within the composite display area are shown as a series of images or filmstrip representations. The number of images displayed for a clip varies depending on the length of the clip (e.g., in relation to the timeline  2226 ), as well as the size of the clips (as the aspect ratio of each image will stay constant). As with the clips in the clip browser, the user can skim through the composite presentation or play back the composite presentation. In some embodiments, the playback (or skimming) is not shown in the composite display area&#39;s clips, but rather in the preview display area  2220 . 
     The preview display area  2220  (also referred to as a “viewer”) displays images from media files which the user is skimming through, playing back, or editing. These images may be from a composite presentation in the composite display area  2215  or from a media clip in the clip browser  2210 . In the example of  FIG. 22 , the user is playing the composite presentation in the composite display area  2215 . Hence, an image from the start of the composite presentation is displayed in the preview display area  2220 . As shown, some embodiments will display the images as large as possible within the display area while maintaining the aspect ratio of the image. 
     The inspector display area  2225  displays detailed properties about a selected item and allows a user to modify some or all of these properties. The selected item might be a clip, a composite presentation, an effect, etc. As shown in  FIG. 22 , the inspector display area  2225  displays information about the audio clip  2250 . To display the information, the application&#39;s user might have selected the audio clip  2250  from the clip browser  2210 . In this case, the information about the selected media clip  2250  includes name, notes, codec, audio channel count, and sample rate. However, depending on the type of media clip, the inspector display area  2225  can display other information such as file format, file location, frame rate, date created, etc. In some embodiments, the inspector display area  2225  displays different metadata tags associated with a clip. For example, the inspector display area  2225  includes a text box  2206  for displaying and/or modifying one or more metadata tags. 
     The toolbar  2235  includes various selectable items for editing, modifying items that are displayed in one or more display areas, etc. The illustrated toolbar  2235  includes items for video effects, visual transitions between media clips, photos, titles, generators and backgrounds, etc. The toolbar  2235  also includes selectable items for media management and editing. Selectable items are provided for adding clips from the clip browser  2210  to the composite display area  2215 . In some embodiments, different selectable items may be used to add a clip to the end of the spine, add a clip at a selected point in the spine (e.g., at the location of a playhead), add an anchored clip at the selected point, perform various trim operations on the media clips in the composite display area, etc. The media management tools of some embodiments allow a user to mark selected clips as favorites, among other options. 
     The audio mixer  2255  provides different audio mixing tools that the application&#39;s user can use to define the output audio of the composite presentation represented in the composite display area  2215 . The audio mixer  2255  includes several level controls ( 2260 ,  2270 , and  2280 ) and several audio meters ( 2265 ,  2275 , and  2285 ). The level control  2280  and the audio meters  2285  are related to the master that represents the output audio. Specifically, the master&#39;s level control  2280  raises or lowers the combined output level of all sequence of clips in the composite display area at the same time. That is, the control  2280  affects output levels during playback, export to a file, etc. Hence, the level control  2280  adjusts the level of the output audio, and the meters  2285  display that audio level. In the example illustrated in  FIG. 22 , the audio meters  2285  include a first meter that represents the left channel of the output audio, and a second meter that represents the right channel of the output audio. In some embodiments, the master includes an audio meter for each output track (e.g., channel, file) specified for the sequence. For example, when the sequence of the clips has four output tracks, there are four corresponding audio meters for the master in the audio mixer  2255 . Several examples of specifying different output tracks by using metadata tags are described above in Section V. 
     As shown in  FIG. 22 , the audio meters  2285  provide visual representations of the level of the output audio. Specifically, each meter displays a fluctuating or moving bar in accord with the audio level. In some embodiments, the fluctuating bar changes color when the audio level exceeds a particular threshold. For example, the color of the bar may change from one color to another color when the volume goes over a predetermined threshold decibel value. 
     The level control  2260  and the audio meter  2265  are related to the keyword  2202 . The level control  2270  and the audio meter are related to the keyword  2204 . In some embodiments, the audio meters  2265  and  2275  display the audio levels of the clips associated with the corresponding keywords. For example, when a clip tagged with “Dialog” is being output, the audio meter  2265  fluctuates to indicate the level of the clip&#39;s audio. Similarly, the audio level control  2260  controls the audio level of each clip that is tagged with the keyword  2202 , and the audio level control  2270  controls the audio level of each clip tagged with the keyword  2204 . 
     As shown in  FIG. 22 , the level controls  2260 ,  2270 , and  2280  are represented as channel faders, while the audio meters  2265 ,  2275 , and  2285  are represented as fluctuating bars. Alternatively, the media editing application of some embodiments provides different types of controls. For example, any one of the level controls can be provided as a dial knob that is rotated to adjust the gain or volume of each clip that is tagged with a particular keyword. Also, in different embodiments, the audio levels at different instances in time are represented as a graph, numerically by displaying different decibels, etc. In some embodiment, the audio controls (e.g., audio level controls  2260  and  2270 ) are not used to control absolute audio levels but are used to make relative adjustments. In some such embodiments, the media editing application provides a wheel or a knob that can be turned infinitely to add or subtract gain to all clips tagged with a particular metadata tag. 
     In the example illustrated in  FIG. 22 , the audio mixer  2255  includes other controls associated with the master and the keywords  2202  and  2204 . For example, the keyword  2204  includes (1) a mute button  2208  for muting all clips associated with the keyword, (2) a solo button  2212  for muting all other clips except those associated with the keyword, and (3) a pan control  2214  for controlling the spread of audio. The same set of controls is provided for the keyword  2202 . In addition, the master includes a mute button  2222  for muting all channels and a downmix button  2224  for mixing down all output channels to a single stereo output. In some embodiments, when the downmix is activated, all audio outputs in the composite display area&#39;s sequence are mixed down to stereo during playback, export to one or more files, etc. Instead of, or in conjunction with these controls, the media editing application of some embodiments provides other controls such as two separate controls for controlling the gain and the volume, two separate faders or knobs for individually controlling the audio levels of left and right channels, a record button for recording the audio, etc. 
     One or ordinary skill will also recognize that different display areas shown in the GUI  2200  is one of many possible configurations for the GUI of some embodiments. For instance, in some embodiments, the presence or absence of many of the display areas can be toggled through the GUI (e.g., the inspector display area  2225 , clip library  2205 , etc.). In addition, some embodiments allow the user to modify the size of the various display areas within the GUI. For instance, when the mixer  2255  is removed, the composite display area  2215  can increase in size to include that area. Similarly, the preview display area  2220  increases in size when the inspector display area  2225  is removed. 
     B. Example Software Architecture 
     In some embodiments, the processes described above are implemented as software running on a particular machine, such as a computer or a handheld device, or stored in a machine readable medium.  FIG. 23  conceptually illustrates the software architecture of a media editing application  2300  of some embodiments. In some embodiments, the media editing application is a stand-alone application or is integrated into another application, while in other embodiments the application is implemented within an operating system. Furthermore, in some embodiments, the application is provided as part of a server-based solution. In some such embodiments, the application is provided via a thin client. That is, the application runs on a server while a user interacts with the application via a separate machine remote from the server. In other such embodiments, the application is provided via a thick client. That is, the application is distributed from the server to the client machine and runs on the client machine. 
     The media editing application  2300  includes a user interface (UI) interaction and generation module  2305 , a media ingest module  2310 , editing modules  2315 , effects modules  2340 , output components  2308 , a playback module  2325 , a metadata association module  2335 , and an effects association module  2330 . 
     The figure also illustrates stored data associated with the media editing application: source files  2350 , event data  2355 , project data  2360 , and other data  2365 . In some embodiments, the source files  2350  store media files (e.g., video files, audio files, combined video and audio files, etc.) imported into the application. The source files  2350  of some embodiments also store transcoded versions of the imported files as well as analysis data (e.g., people detection data, shake detection data, color balance data, etc.). The event data  2355  stores the events information used by some embodiments to populate the thumbnails view (e.g., in a clip browser). The event data  2355  may be a set of clip object data structures stored as one or more SQLite database (or other format) files in some embodiments. The project data  2360  stores the project information used by some embodiments to specify a composite presentation in the composite display area  2345 . The project data  2360  may also be a set of clip object data structures stored as one or more SQLite database (or other format) files in some embodiments. 
     In some embodiments, the four sets of data  2350 - 2365  are stored in a single physical storage (e.g., an internal hard drive, external hard drive, etc.). In some embodiments, the data may be split between multiple physical storages. For instance, the source files might be stored on an external hard drive with the event data, project data, and other data on an internal drive. Some embodiments store event data with their associated source files and render files in one set of folders, and the project data with associated render files in a separate set of folders. 
       FIG. 23  also illustrates an operating system  2370  that includes input device driver(s)  2375 , display module  2380 , and media import module  2385 . In some embodiments, as illustrated, the input device drivers  2375 , display module  2380 , and media import module  2385  are part of the operating system  2370  even when the media editing application  2300  is an application separate from the operating system  2370 . 
     The input device drivers  2375  may include drivers for translating signals from a keyboard, mouse, touchpad, tablet, touchscreen, etc. A user interacts with one or more of these input devices, each of which send signals to its corresponding device driver. The device driver then translates the signals into user input data that is provided to the UI interaction and generation module  2305 . 
     The present application describes a graphical user interface that provides users with numerous ways to perform different sets of operations and functionalities. In some embodiments, these operations and functionalities are performed based on different commands that are received from users through different input devices (e.g., keyboard, trackpad, touchpad, mouse, etc.). For example, the present application illustrates the use of a cursor in the graphical user interface to control (e.g., select, move) objects in the graphical user interface. However, in some embodiments, objects in the graphical user interface can also be controlled or manipulated through other controls, such as touch control. In some embodiments, touch control is implemented through an input device that can detect the presence and location of touch on a display of the input device. An example of a device such functionality is a touch screen device (e.g., as incorporated into a smart phone, a tablet computer, etc.). In some embodiments, with touch control, a user directly manipulates objects by interacting with the graphical user interface that is displayed on the display of the touch screen device. For instance, a user can select a particular object in the graphical user interface by simply touching that particular object on the display of the touch screen device. As such, when touch control is utilized, a cursor may not even be provided for enabling selection of an object of a graphical user interface in some embodiments. However, when a cursor is provided in a graphical user interface, touch control can be used to control the cursor in some embodiments. 
     The display module  2380  translates the output of a user interface for a display device. That is, the display module  2380  receives signals (e.g., from the UI interaction and generation module  2305 ) describing what should be displayed and translates these signals into pixel information that is sent to the display device. The display device may be an LCD, plasma screen, CRT monitor, touchscreen, etc. 
     The media import module  2385  receives media files (e.g., audio files, video files, etc.) from storage devices (e.g., external drives, recording devices, etc.) through one or more ports (e.g., a USB port, Firewire port, etc.) of the device on which the application  2300  operates and translates this media data for the media editing application or stores the data directly onto a storage of the device. 
     The UI interaction and generation module  2305  of the media editing application  2300  interprets the user input data received from the input device drivers  2375  and passes it to various modules, including the editing modules  2315 , the rendering engine  2320 , the playback module  2325 , the metadata association modules  2335 , and the effects association module  2330 . The UI interaction and generation module  2305  also manages the display of the UI, and outputs this display information to the display module  2380 . This UI display information may be based on information from the editing modules  2315 , the playback module  2325 , and the data  2350 - 2365 . In some embodiments, the UI interaction and generation module  2305  generates a basic GUI and populates the GUI with information from the other modules and stored data. 
     As shown, the UI interaction and generation module  2305  of some embodiments provides a number of different UI elements. In some embodiments, these elements include a tag display area  2306 , a composite display area  2345 , an effects association tool  2304 , an audio mixing tool  2318 , and a preview display area  2312 . All of these UI elements are described in detail above by reference to  FIG. 22 . 
     The media ingest module  2310  manages the import of source media into the media editing application  2300 . Some embodiments, as shown, receive source media from the media import module  2385  of the operating system  2370 . The media ingest module  2310  receives instructions through the UI interaction and generation module  2305  as to which files should be imported, then instructs the media import module  2385  to enable this import (e.g., from an external drive, from a camera, etc.). The media ingest module  2310  stores these source files  2350  in specific file folders associated with the application. In some embodiments, the media ingest module  2310  also manages the creation of event data structures upon import of source files and the creation of the clip and asset data structures contained in the events. In some embodiments, the media ingest module  2310  tags the imported media clip with one or more metadata tags. For example, when a media clip is imported from a music library, the media ingest module  2310  might tag the clip with a “Music” tag. Alternatively, when the media clip is imported from a folder named “Dialog”, the media ingest module  2310  might tag the clip with a “Dialog” tag. 
     The editing modules  2315  include a variety of modules for editing media in the clip browser as well as in the composite display area. The editing modules  2315  handle the creation of projects, addition and subtraction of clips from projects, trimming or other editing processes within the composite display area, or other editing processes. In some embodiments, the editing modules  2315  create and modify project and clip data structures in both the event data  2355  and the project data  2360 . 
     The effects association module  2330  of some embodiments associates an effect with a metadata tag. In some embodiments, the effect association module  2330  defines an effect chain with one or more effects for the metadata tag. The effect modules  2340  represent the various different effects, filters, transitions, etc. As mentioned above, there are many different effects or filters that can be associated with metadata to facilitate editing operations. Although this list is non-exhaustive, several example audio effects include different equalizers for modifying the signal strength of a clip within specified frequency ranges, a compressor/limiter for reducing the clip&#39;s dynamic range by attenuating parts of the audio signal above a particular threshold, an echo effect for creating an echo sound, and a reverb effect for creating a reverberation effect that emulates a particular acoustic environment. Several example video effects or image effects include color filters that operate on color values, different filters that sharpen, stylize, distort, or blur an image, and fade-in/fade-out effects for creating transitions between scenes. Several of these effect modules are associated with one or more settings or properties that the application&#39;s user can specify to edit media content. 
     In some embodiments, the output components  2308  generate the resulting output composite presentation based on one or more clips in the composite display area  2345 . As shown, the output components  2308  include a rendering engine  2320  and a mixer  2314 . However, depending on the type of output, the media editing application of some embodiments includes other component (e.g., encoders, decoders, etc). The rendering engine  2320  handles the rendering of images for the media editing application. In some embodiments, the rendering engine  2320  manages the creation of images for the media editing application. When an image is requested by a destination within the application (e.g., the playback module  2325 ) the rendering engine  2320  outputs the requested image according to the project or event data. The rendering engine  2320  retrieves the project data or event data that identifies how to create the requested image and generates a render graph that is a series of nodes indicating either images to retrieve from the source files or operations to perform on the source files. In some embodiments, the rendering engine  2320  schedules the retrieval of the necessary images through disk read operations and the decoding of those images. 
     In some embodiments, the rendering engine  2320  performs various operations to generate an output image. In some embodiments, these operations include blend operations, effects (e.g., blur or other pixel value modification operations), color space conversions, resolution transforms, etc. In some embodiments, one or more of these processing operations are actually part of the operating system and are performed by a GPU or CPU of the device on which the application  2300  operates. The output of the rendering engine (a rendered image) may be stored as render files in storage  2365  or sent to a destination for additional processing or output (e.g., playback). 
     In some embodiments, the mixer  2314  receives several audio signals of different clips and outputs a mixed audio signal. The mixer  2314  of some embodiments is utilized in number of different instances during the non-linear editing process. For example, the mixer may be utilized in generating a composite presentation from multiple different clips. The mixer can also act as the master to output a mixed audio signal, as described in many of the examples above. In some embodiments, the media editing application includes different types of mixers for mixing audio. For example, the media editing application can include a first mixer for mixing one type of audio file and a second mixer for mixing another type of audio file. 
     The playback module  2325  handles the playback of images (e.g., in a preview display area  2312  of the user interface). Some embodiments do not include a playback module and the rendering engine directly outputs its images for integration into the GUI, or directly to the display module  2380  for display at a particular portion of the display device. 
     In some embodiments, the metadata association module  2335  associates clips with metadata tags. Different embodiments provide different ways of associating media clips with metadata tags. In some embodiments, the metadata tags indicate pre-defined categories (e.g., dialog, music) that an editor can select to categorize different clips. Instead of, or in conjunction with, these categories, some embodiments allow the editor to specify one or more keywords to associate with the media clips. For instance, in some such embodiments, the media editing application provides a keyword association tool that displays different keywords for tagging the media content. To tag a clip, the application&#39;s user drags and drops the clip onto a particular keyword in the keyword association tool. The same technique is used in some embodiments to associate multiple clips by simultaneously dragging and dropping the clips onto the particular keyword. 
     In addition, some embodiments automatically associate one or more metadata tags with a media clip. In some such embodiments, this automatic association is based on a number of different factors including the source of the media clip (e.g., based on the library or camera from which the clip was imported), based on an analysis of the media clip (e.g., based on color balance analysis, image stabilization analysis, audio channel analysis, etc.). For example, the media editing application might tag one set of clips from a music library as “Music” and tag another set of clips from a sound effects library as “SFX”. Alternatively, the automatic association can be based on an analysis of the media content (e.g., based on color balance analysis, image stabilization analysis, audio channel analysis, people analysis, etc.). As mentioned above, in some embodiments, the media ingest module  2310  can also perform at least some of the metadata association task when importing media content into the media editing application  2300 . In some embodiments, the media editing application includes one or more analysis modules for analyzing the number of people (e.g., one person, two persons, group, etc.) in a clip and/or a type of shot (e.g., a close-up, medium, or wide shot). Other types of analysis modules can include image stabilization analysis modules (e.g., for camera movements), color balance analysis modules, audio analysis modules (e.g., for mono, stereo, silent channels), metadata analysis, etc. In some embodiments, metadata tags represent metadata that are embedded in media content. For example, some video cameras embed frame rate, creation date, and encoding info into video clips that they capture. In addition some devices embed other metadata such as location data, audio channel count, sample rate, file type, camera type, exposure info, etc. 
     While many of the features of the media editing application  2300  have been described as being performed by one module (e.g., the UI interaction and generation module  2305 , the media ingest module  2310 , etc.), one of ordinary skill in the art will recognize that the functions described herein might be split up into multiple modules. Similarly, functions described as being performed by multiple different modules might be performed by a single module in some embodiments (e.g., the playback module  2325  might be part of the UI interaction and generation module  2305 ). 
     C. Example Data Structure 
       FIG. 24  conceptually illustrates example data structures for several objects associated with the media editing application of some embodiments. Specifically, this figure illustrates a sequence  2435  that references a primary collection data structure  2440 . Here, the primary collection data structure  2440  is in itself a group of one or more clip objects or collection objects. As shown, the figure illustrates (1) a clip object  2405 , (2) a component object  2410 , (3) a tag object  2420 , (4) an effect object  2430 , (5) the sequence object  2435 , (6) the primary collection object  2440 , and (7) an asset object  2445 . 
     As shown in  FIG. 24 , the sequence  2435  includes a sequence ID and sequence attributes. The sequence ID identifies the sequence  2435 . In some embodiments, the application&#39;s user sets the sequence attributes for the project represented in the composite display area. For example, the user might have specified several settings that correspond to these sequence attributes when creating the project. The sequence  2435  also includes a pointer to a primary collection  2440 . 
     The primary collection  2440  includes the collection ID and the array of clips. The collection ID identifies the primary collection. The array references several clips (i.e., clip  1  to clip N). These represent clips or collections that have been added to the composite display area. In some embodiments, the array is ordered based on the locations of media clips in the composite display area and only references clips in the primary lane of the primary collection. An example of one or more clips in the primary lane of the composite display area is described above by reference to  FIG. 22 . 
     The clip object  2405  or collection object, in some embodiments, is an ordered array of clip objects. The clip object  2405  references one or more component clips (e.g., the component object  2410 ) in the array. In addition, the clip object  2405  stores a clip ID that is a unique identifier for the clip object. In some embodiments, the clip object  2405  is a collection object that can reference component clip objects as well as additional collection objects. An example of such collection object is a compound clip that references multiple different clips. In some embodiments, the clip object  2405  or collection object only references the video component clip in the array, and any additional components (generally one or more audio components) are then anchored to that video component. 
     As shown in  FIG. 24 , the clip object  2405  is associated with one more metadata tags (i.e., tags  1 -N). In some embodiments, these tags represent those that are associated by the application&#39;s user. Alternatively, one or more of these tags can be tags specified by the media editing application. For example, when a media clip is imported from a music library, the media editing application might tag the clip with a “Music” tag. Alternatively, when the media clip is imported from a folder named “Dialog”, the media editing application might tag the clip with a “Dialog” tag. 
     The component object  2410  includes a component ID, an asset reference, and anchored components. The component ID identifies the component. The asset reference of some embodiments uniquely identifies a particular asset object. In some embodiments, the asset reference is not a direct reference to the asset but rather is used to locate the asset when needed. For example, when the media editing application needs to identify a particular asset, the application uses an event ID to locate an event object (not shown) that contains the asset, and then the asset ID to locate the particular desired asset. Several examples of clips associated with an event or an event folder are described above by reference to  FIG. 22 . 
     In some embodiments, the clip object  2405  only stores the video component clip in its array, and any additional components (generally one or more audio components) are then anchored to that video component. This is illustrated in  FIG. 24  as the component object  2410  includes a set of one or more anchored components  2415  (e.g., audio components). In some embodiments, each component that is anchored to another clip or collection stores an anchor offset that indicates a particular instance in time along the range of the other clip or collection. That is, the anchor offset may indicate that the component is anchored x number of seconds and/or frames into the other clip or collection. In some embodiments, the offset refers to the trimmed ranges of the clips. 
     As shown, the asset object  2445  includes an asset ID, reference to a source file, and a set of source file metadata. The asset ID identifies the asset, while the source file reference is a pointer to the original media file. The set of source file metadata is different for different media clips. Examples of source file metadata include the file type (e.g., audio, video, movie, still image, etc.), the file format (e.g., “.mov”, “.avi”, etc), different video properties, audio properties, etc. 
     In the example illustrated in  FIG. 24 , the tag object  2420  includes a tag ID that identifies the tag, a tag name that represents the metadata tag, and an effect list  2425  that represents the one or more effects associated with the metadata tag. In some embodiments, the tag object  2425  includes an output track that represents the output track associated with the metadata tag. Several examples of such output track are described above by reference to  FIGS. 18-20 . 
     As shown in  FIG. 24 , the effects object  2430  includes an effect ID and effect properties. The effect ID identifies the effect. In some embodiments, the effect properties are based on parameters specified using an effect properties tool. The properties tool can include different user interface items to specify different parameters or settings for the effect. 
     One of ordinary skill will also recognize that the data structures shown in  FIG. 24  are just a few of the many different possible configurations for implementing the editing features described above. For instance, in some embodiments, instead of multiple tags per clip, only one tag (e.g., role, category) is assigned to the clip. For example, several clips may be assigned one audio role of “Dialog”, “Music”, or “SFX”. When multiple tags per clip are supported, the media editing application applies different sets of effects in parallel. For example, if a clip is tagged with both first and second tags, the media editing application applies a first set of effects associated with the first tag, and applies a second set of effects in parallel with the first set of effect. Also, in the example illustrated in  FIG. 24 , the tag object  2420  can be associated with the component object  2410  or the asset object  2445  instead of the clip object  2405 . 
     VII. Electronic System 
     Many of the above-described features and applications are implemented as software processes that are specified as a set of instructions recorded on a computer readable storage medium (also referred to as computer readable medium). When these instructions are executed by one or more processing unit(s) (e.g., one or more processors, cores of processors, or other processing units), they cause the processing unit(s) to perform the actions indicated in the instructions. Examples of computer readable media include, but are not limited to, CD-ROMs, flash drives, random access memory (RAM) chips, hard drives, erasable programmable read only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), etc. The computer readable media does not include carrier waves and electronic signals passing wirelessly or over wired connections. 
     In this specification, the term “software” is meant to include firmware residing in read-only memory or applications stored in magnetic storage, which can be read into memory for processing by a processor. Also, in some embodiments, multiple software inventions can be implemented as sub-parts of a larger program while remaining distinct software inventions. In some embodiments, multiple software inventions can also be implemented as separate programs. Finally, any combination of separate programs that together implement a software invention described here is within the scope of the invention. In some embodiments, the software programs, when installed to operate on one or more electronic systems, define one or more specific machine implementations that execute and perform the operations of the software programs. 
       FIG. 25  conceptually illustrates an electronic system  2500  with which some embodiments of the invention are implemented. The electronic system  2500  may be a computer (e.g., a desktop computer, personal computer, tablet computer, etc.), phone (e.g., smart phone), PDA, or any other sort of electronic device. Such an electronic system includes various types of computer readable media and interfaces for various other types of computer readable media. Electronic system  2500  includes a bus  2505 , processing unit(s)  2510 , a graphics processing unit (GPU)  2515 , a system memory  2520 , a network  2525 , a read-only memory  2530 , a permanent storage device  2535 , input devices  2540 , and output devices  2545 . 
     The bus  2505  collectively represents all system, peripheral, and chipset buses that communicatively connect the numerous internal devices of the electronic system  2500 . For instance, the bus  2505  communicatively connects the processing unit(s)  2510  with the read-only memory  2530 , the GPU  2515 , the system memory  2520 , and the permanent storage device  2535 . 
     From these various memory units, the processing unit(s)  2510  retrieves instructions to execute and data to process in order to execute the processes of the invention. The processing unit(s) may be a single processor or a multi-core processor in different embodiments. Some instructions are passed to and executed by the GPU  2515 . The GPU  2515  can offload various computations or complement the image processing provided by the processing unit(s)  2510 . 
     The read-only-memory (ROM)  2530  stores static data and instructions that are needed by the processing unit(s)  2510  and other modules of the electronic system. The permanent storage device  2535 , on the other hand, is a read-and-write memory device. This device is a non-volatile memory unit that stores instructions and data even when the electronic system  2500  is off. Some embodiments of the invention use a mass-storage device (such as a magnetic or optical disk and its corresponding disk drive) as the permanent storage device  2535 . 
     Other embodiments use a removable storage device (such as a floppy disk, flash memory device, its corresponding disk drive, etc.) as the permanent storage device. Like the permanent storage device  2535 , the system memory  2520  is a read-and-write memory device. However, unlike storage device  2535 , the system memory  2520  is a volatile read-and-write memory, such as a random access memory. The system memory  2520  stores some of the instructions and data that the processor needs at runtime. In some embodiments, the invention&#39;s processes are stored in the system memory  2520 , the permanent storage device  2535 , and/or the read-only memory  2530 . For example, the various memory units include instructions for processing multimedia clips in accordance with some embodiments. From these various memory units, the processing unit(s)  2510  retrieves instructions to execute and data to process in order to execute the processes of some embodiments. 
     The bus  2505  also connects to the input and output devices  2540  and  2545 . The input devices  2540  enable the user to communicate information and select commands to the electronic system. The input devices  2540  include alphanumeric keyboards and pointing devices (also called “cursor control devices”), cameras (e.g., webcams), microphones or similar devices for receiving voice commands, etc. The output devices  2545  display images generated by the electronic system or otherwise output data. The output devices  2545  include printers and display devices, such as cathode ray tubes (CRT) or liquid crystal displays (LCD), as well as speakers or similar audio output devices. Some embodiments include devices such as a touchscreen that function as both input and output devices. 
     Finally, as shown in  FIG. 25 , bus  2505  also couples electronic system  2500  to a network  2525  through a network adapter (not shown). In this manner, the computer can be a part of a network of computers (such as a local area network (“LAN”), a wide area network (“WAN”), or an Intranet, or a network of networks, such as the Internet. Any or all components of electronic system  2500  may be used in conjunction with the invention. 
     Some embodiments include electronic components, such as microprocessors, storage and memory that store computer program instructions in a machine-readable or computer-readable medium (alternatively referred to as computer-readable storage media, machine-readable media, or machine-readable storage media). Some examples of such computer-readable media include RAM, ROM, read-only compact discs (CD-ROM), recordable compact discs (CD-R), rewritable compact discs (CD-RW), read-only digital versatile discs (e.g., DVD-ROM, dual-layer DVD-ROM), a variety of recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SD cards, mini-SD cards, micro-SD cards, etc.), magnetic and/or solid state hard drives, read-only and recordable Blu-Ray® discs, ultra density optical discs, any other optical or magnetic media, and floppy disks. The computer-readable media may store a computer program that is executable by at least one processing unit and includes sets of instructions for performing various operations. Examples of computer programs or computer code include machine code, such as is produced by a compiler, and files including higher-level code that are executed by a computer, an electronic component, or a microprocessor using an interpreter. 
     While the above discussion primarily refers to microprocessor or multi-core processors that execute software, some embodiments are performed by one or more integrated circuits, such as application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). In some embodiments, such integrated circuits execute instructions that are stored on the circuit itself. 
     As used in this specification and any claims of this application, the terms “computer”, “server”, “processor”, and “memory” all refer to electronic or other technological devices. These terms exclude people or groups of people. For the purposes of the specification, the terms display or displaying means displaying on an electronic device. As used in this specification and any claims of this application, the terms “computer readable medium,” “computer readable media,” and “machine readable medium” are entirely restricted to tangible, physical objects that store information in a form that is readable by a computer. These terms exclude any wireless signals, wired download signals, and any other ephemeral signals. 
     While the invention has been described with reference to numerous specific details, one of ordinary skill in the art will recognize that the invention can be embodied in other specific forms without departing from the spirit of the invention. In addition, a number of the figures (including  FIGS. 1 ,  10 ,  15 ,  16 , and  21 ) conceptually illustrate processes. The specific operations of these processes may not be performed in the exact order shown and described. The specific operations may not be performed in one continuous series of operations, and different specific operations may be performed in different embodiments. Furthermore, the process could be implemented using several sub-processes, or as part of a larger macro process. In addition, some embodiments execute software stored in programmable logic devices (PLDs), ROM, or RAM devices. 
     In addition, many of the user interface controls described above relates to controlling audio. However, one of ordinary skill in the art would recognize that similar controls can be provided for image effect or filters. For example, one or more user interface controls (e.g., sliders, knobs, buttons) can be provided for each metadata tag to control the effect settings (e.g., brightness, sharpness, amount of distortion, fade-in effect, fade-out effect, etc.). 
     In many of the examples described herein, a media editing application uses metadata to facilitate editing operations. However, one of ordinary skill in the art would recognize that the metadata features can be provided for different types of applications or programs (e.g., an image organizing application, a server-side web application, an operating system framework). For instance, the metadata features can be provided in an image application that allows the application&#39;s user to associate different items with keywords, and apply one or more effects to those items based on the association of the keywords, and/or output those items to different tracks (e.g., files, channels) based on the association of the keywords. Thus, one of ordinary skill in the art would understand that the invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the appended claims.

Metadata:
Filing Date: 20110930
Publication Date: 20160119
Grant Date: 20160119
Priority Date: 20110920
Inventors: EPPOLITO AARON M.
MEANEY BRIAN
PENDERGAST COLLEEN
STIKICH MICHAELLE
Assignee: APPLE INC
CPC Classifications: [{"code": "G11B27/034", "inventive": true, "first": true, "tree": "[]"}, {"code": "G11B27/322", "inventive": true, "first": false, "tree": "[]"}, {"code": "G11B27/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G11B27/034", "inventive": true, "first": true, "tree": "[]"}, {"code": "G11B27/322", "inventive": true, "first": false, "tree": "[]"}, {"code": "G11B27/34", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 47881820