AUDIO BLOCK SEQUENCE COMPILER FOR GENERATING PRESCRIBED DURATION AUDIO SEQUENCES

Abstract: An audio block sequence compiler (16) for selecting a plurality of audio blocks to generate a sequence having a duration corresponding to user-prescribed criteria. In a preferred embodiment, a user chooses an audio, e.g., a musical, segment from a predefined audio library (14) and prescribes the duration of an audio sequence. Prior to depositing each musical segment in the library (14), the musical selection is divided into audio blocks that are identified in a corresponding encoding table with characteristics including duration, suitability for being used as beginning or ending of an audio sequence, and musical compatibility with each audio block. Using this characteristic table and the user-prescribed criteria, i.e., duration, the audio block sequence compiler (16) generates a plurality of audio sequences satisfying the user-prescribed criteria which can be reviewed, e.g., played, and/or saved for future use.

Description: TITLE: AUDIO BLOCK SEQUENCE COMPILER FOR GENERATING PRESCRIBED DURATION AUDIO SEQUENCES BACKGROUND OF THE INVENTION The present invention relates generally to hardware/software systems of the type used to generate audio sequences and in particular for generating audio sequences of prescribed durations that are of particular use for creating soundtracks in multimedia systems, e.g., in an audio/video environment. In an exemplary audio/video environment, a visual sequence, e.g., a movie/video clip, is combined with an audio background. However, visual sequences are often repetitively edited before an aesthetically satisfactory sequence is achieved. The audio sequence must then be edited to match the duration of the edited video sequence. With an available orchestra, this process can be repeated as often as necessary but it is very expensive. In a more restricted environment, e.g., a multimedia video game, this procedure is often too costly and cumbersome. SUMMARY OF THE INVENTION The present invention is directed toward an audio block sequence compiler for selecting a plurality of suitable, compatible audio blocks to generate an audio sequence having a duration corresponding to user-prescribed criteria. In a preferred embodiment, a user using a keyboard/mouse interface chooses an audio, e.g., a musical, segment from a predefined audio library and prescribes the duration of an audio sequence. Prior to depositing each musica. segment in the library, the musical selection is divided into audio blocks that are identified in a corresponding encoding table with characteristics including (1) duration, (2) suitability for being used as a beginning or ending of an audio sequence, and (3) musical compatibility with each audio block. Using this characteristic table and user-prescribed criteria, i.e., duration, the audio block sequence compiler, preferably a software program executed by a computer, generates a plurality of audio sequences satisfying the user-prescribed criteria which can be reviewed, e.g., played or displayed, and/or saved for future use. In a further aspect of a preferred embodiment, the characteristic table additionally contains a mood parameter that is user prescribed and used by the audio block sequence compiler to generate an audio sequence of a selected mood. In a still further aspect of a preferred embodiment, the encoding table additionally contains a parameter that identifies blocks that are fadeable. When a fadeable block is selected as an end block, the audio block sequence compiler can truncate the fadeable end block to generate an audio sequence of the prescribed length which might otherwise not be achievable. In a further aspect of a preferred embodiment, the encoding table additionally contains an intensity parameter that, when selected by the operator, is used by the audio block seguence compiler to generate an audio sequence that most closely matches a user-prescribed intensity curve. In a still further aspect of a preferred embodiment, each block can be identified in the encoding table as having a hit point that defines the location (when present) of an intensity burst. When prescribed by the user, the audio block sequence compiler can use the hit point parameter to place an intensity burst at a user-prescribed location in the generated audio sequence. Other features and advantages of the present invention should become apparent from the following description of the presently-preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the present invention. // // // // // // // // // BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 comprises a functional block diagram of an audio block sequence compiler system in accordance with the present invention for generating audio sequences having user- prescribed durations; FIG. 2 is a simplified diagram of an encoding table showing the parameters associated with each audio block; FIG. 3A is a simplified flow chart of the operation of the system of FIG. 1; FIG. 3B is a simplified flow chart depicting the process implemented by the audio block sequence compiler; FIG. 4 is an exemplary encoding table for a fifty second source audio segment; and FIG. 5 shows the iterations performed by the audio block sequence compiler according to the flow chart of FIG. 3B on the data of the encoding table of FIG. 4. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to the drawings, and particularly to FIG. 1, there is shown a block diagram of a preferred embodiment of an audio sequence generator 10 of the present invention. In a preferred embodiment, the audio sequence generator 10 is comprised of a computer-executed software program, generally initially present on a floppy disk, and finally residing on the hard disk of a personal computer (PC) 12, e.g., a Macintosh or IBM compatible PC, controlled by a processor 13. As such the following discussion, relates to this preferred PC environment. However, different computer platforms or hardware only implementations are also considered within the scope of the presently preferred invention. The audio sequence generator 10 is primarily comprised of 1) an audio library 14 and 2) an audio block sequence compiler 16. In operation, a user via a user interface 17, e.g., a keyboard/mouse 18, chooses a source segment from the audio library 14 and prescribes a duration. This information is communicated to the audio block sequence compiler 16 which, under control of a software program executed by the processor 13 in the PC 12, fetches blocks of audio data from the audio library 14 and according to compilation criteria described further below generates a list of potential audio sequences that are preferably temporarily stored within a potential block sequence list depository 19. At that point, the user can select to play via a sound card/speaker 20 or review via a monitor 21 the potential block sequences and/or store selected sequences for future use, e.g., on a hard disk 22. Alternatively, the audio block sequence compiler 16 can compile a single block sequence until prompted by the operator to generate a next audio sequence. The audio library 14 preferably contains library entries 23 pertaining to a plurality of source audio segments. Each library entry 23 is comprised of 1) a source audio segment 24 and 2) an encoding table 26 which describes the partitioning of the source audio segment 24 into blocks and the characteristics of each block. Although, the source audio segment 24 is shown as being located within the library 14, one of ordinary skill in the art will recognize that the source audio segment 24 can alternatively be physically located outside of the library, e.g., on a CD, and referenced, e.g., by pointers, by the encoding table 26. FIG. 2 shows an exemplary structure for the encoding table 26. Each entry 23 in the encoding table 26 contains a definition/pointer 28 which includes identifying information for the library entry, e.g., a title and the physical location of the source audio segment 24, e.g., a CD file. Each encoding table entry 23 is further divided into a plurality of entries that define blocks, i.e., audio blocks, and associated characteristics for the audio from the source audio segment 24. In a simplified example, a source audio segment 24 is divided into five blocks: A, B, C, D, E, F where the sequence ABCDEF corresponds to the source audio segment 24. Although, other combinations of blocks, e.g., FEDCBA, also create audio sequences, not all sequences of blocks will create aesthetically reasonable audio sequences. Thus, it has been determined that information must be derived to determine the musical compatibility according to aesthetic criteria between each block, e.g., A, B, and each potential succeeding block, e.g., while block C may reasonably follow block B, it may not be aesthetically reasonable for it to follow block A. Additionally, while some blocks, e.g., A, are suitable according to aesthetic criteria to reasonably start a musical sequence, other blocks can not. Similarly, only certain blocks, e.g., F, are suitable according to aesthetic criteria to reasonably end a musical sequence. Lastly, not all source audio segments 24 can reasonably be divided into fixed length blocks. In fact, using reasonable aesthetic criteria, blocks will generally be differently sized. Consequently, audio sequences of many different durations can be achieved by combining different combinations of these differently-sized blocks. However, as previously described, the available combinations are limited by the compatibility between potentially adjacent blocks as well as their suitability to begin or end an audio sequence. Corresponding to these criteria, data in the encoding table 26 for each audio block contains parameters pertaining to a l) a duration 30, 2) a type (beginning/end) 32, and 3) a list of compatible blocks 34, i.e., blocks that can aesthetically follow the current block. Additionally, information (not shown) identifying the physical location of each audio block in the source audio segment 24 is retained in the encoding table 26. While data in the encoding table 26 can be manually generated, automated procedures are also possible. FIG. 3B shows a simplified flow chart of the iterative process implemented by the audio block sequence compiler 16 after being provided the user-prescribed data (as shown in FIG. 3A) . As previously described, after the user has determined a selection 36 from the library 14 and a duration 38, the audio block sequence compiler 16 operates on the data in the encoding table 26 according to the flow chart of FIG. 3B. Accordingly, a list of potential audio sequences is compiled and stored in the potential block sequence list 20. FIG. 4 shows an exemplary encoding table for a fifty second source audio segment 24. In this example, the source audio segment is partitioned into ten blocks, each being five seconds long. (However, while fixed length blocks exist in this example, this is often not the case) . In this example, Blocks A and C have been marked as potential beginnings and blocks E and J have been marked as potential endings. In the example shown in FIG. 5, the user has selected a duration of thirty-five seconds for this source audio segment 24. Accordingly, FIG. 5 shows the iterations performed by the audio block sequence compiler on the encoding table of FIG. 4 according to the flow chart of FIG. 3B. FIG. 5 shows that the original audio sequence has now been rearranged into three potential sequences that each have the prescribed duration, begin with a beginning block and end with an ending block. In an exemplary embodiment, the audio sequence generator 10 allows users to quickly and easily create movie or record quality music soundtracks for any application or document that can import sound. The audio sequence generator 10 is able to accomplish this by using the encoded music and input from the user. The user selects a musical style and sub-style from a list, then specifies the length (in minutes, seconds and tenths) . A piece of music is selected from their library that meets the users needs and a custom version of that music is created that is exactly (within user-prescribed criteria) the specified length. If the user doesn't like the selected music, they can hear a different version of the same music or a different piece music - all of the versions presented will fit the specifications of the user. By using music and its corresponding encoding table 26, and input from the user, the compiler 16 can customize the following aspects of the music: • The length of the music can be customized in tenths of second increments from seconds to hours. • Different versions of the same piece of music (sometimes hundreds of thousands of options) can be generated. • In an alternative embodiment, the compiler 16 can customize the intensity of the music. The user can define a graph of the intensity which they request on a timeline. This will allow them to have the program make a piece of music that begins softly (perhaps while an announcer speaks) and builds to a climax (perhaps when the narration has ended) . In this embodiment, an intensity parameter is added to the encoding table 26 for each block and the audio block sequence compiler 16 selects blocks that most closely correspond to the prescribed intensity graph. • In an alternative embodiment, the user can specify and modify the mood of the music without changing any other characteristics. In this embodiment, a mood parameter is added to encoding table 14. Additionally, multiple renditions of the source audio segment 24 are prerecorded corresponding to different moods. The audio block sequence compiler 16 will then select renditions that correspond to the prescribed mood parameter. • In another alternative embodiment, a user can specify 20 seconds of background music followed by 12 seconds of introductory music. The program will be able to locate two different pieces of music and make a smooth, musical, transition between them. • In an additional alternative embodiment, blocks can be identified as fadeable blocks in the encoding table 26. When a block is fadeable, its duration can be truncated to become a satisfactory end block, even if its duration would normally be too long. The audio block sequence compiler 16 will then truncate the fadeable block to achieve the user-prescribed duration. Additionally, the intensity of the end of the fadeable block will fade at a prescribed rate to reduce the effects of the truncation. • In still another embodiment, each block can be identified in the encoding table 26 as having a hit point that defines the location (when present) of an intensity burst. When prescribed by the user, the audio block sequence compiler 16 can use the hit point parameter to place an intensity burst at a user-prescribed location in the generated audio sequence. // // // The following defines the data structure for each block of the encoding table in an exemplary embodiment: filelnfo a pointer to which sound file this block is associated with blockStart the sample number within the sound file at which this block begins blockLength the number of samples that this block contains The end sample number is derived by adding blockStart and blockLength blockName the name to display on this block (no longer than 15 characters blockDesc the long text description of this block (up to 63 characters) compatibility an array of bits specifying this block's compatibility with all other blocks in this file (described below) usageFlags bit flags indicating properties of this block (described below) nextBlock the block number of the best block to followin: this block quickEnd the block number of the best next block to end the music quickly blockSection a section number of this block assigned for use in grouping sub-blocks into grouped blocks for display blockPriority a priority number of this block assigned for use in displaying blocks at different detail levels blockType a set of bits specifying if this block should be displayed, if the block is in-use, and other status flags. USER_BLOCK_TYPE, INVISIBLE_BLOCK_TYPE, AVAILABLE_BLOCK_TYPE selected a True/False flag indicating if the block is currently selected intensity each block is assigned an intensity index in relation to the other blocks in the file. The higher the intensity number, the more intense the audio in the block is in relation to the other blocks. hitPoint the sample number, if any, of a musical "Hit" within the block. (0 for no significant hit) moodlndex a number grouping this blocks mood with other blocks mood. All blocks with the same moodlndex will have the same mood. next a pointer to the next block Compatibility Each block has an array of unsigned longs which are used as an array of bits. Each bit corresponds to a block from the soundfile. Bit 0 corresponds to block 0, etc. Bit 15 should be set if the block is compatible with block 15. Compatible blocks are blocks which sound musically correct when they are played one after the other. For example, "Block A" should be flagged as compatible with "Block B" when it sound musically correct to listen to "Block A" followed by "Block B". If "Block B" was the 24th block from the soundfile, then bit 24 of "Block A"s compatibility array should be set. USAGEFLAGS DEAD END FLAG Set if this block will lead you directly toward an ending. Set this bit if this block is a bad choice to build a long cue (1L<<0) NEXT CONTIGUOUS FLAG Set this bit if the next block doesn't need a crossfade to make a good sounding transition (1L<<1) FADEABLE BLOCK Set this bit to signal that this block can be effectively faded (in volume) to any length. (1L<<2) BEGINING BLOCK Set this bit if the block is a good choice (sounds musically correct) to begin a selection (1L<<30) // 0x40000000 ENDING BLOCK Set this bit if the block is a good choice to end a selection (1L<<31) // 0x80000000 While some of the above functions can be applied to existing music (through an encoding process) and some are dependent on a custom music library in which music is composed and performed in a specific format. struct BlockStruct { SoundFilelnfoPtr filelnfo,* // pointer to file struct for this block unsigned long blockStart;// sample number unsigned long blockLength,*// number of samples Strl5 blockName,* Str63 blockDesc,* unsigned long compatibility[COMPAT_SIZE] ; unsigned long usageFlags,* short nextBlock,* short quickEnd; unsigned char blockSec ion,* unsigned char blockPriority,* BlockTypes blockType,* Boolean selected; BlockStructPtr next; },* HINTING/WARNING Using the encoded information in the blocks, the user is assisted by visually displaying information about the blocks. Block attributes including beginnings, endings and compatibility are all displayed. Beginning- displayed by a stair-step pattern on the left edge of the block Ending- displayed by a stair-step pattern on the right edge of the block Compatibility- the rightmost end cap of a selection in the sequence window is colored and all of the compatible blocks in the block window will have their left end caps colored. Warning- when two non-compatible blocks are next to each other, we display a red edge at their junction. THE ENCODING PROCESS The process of encoding of music and sound is both musical and technical . The encoding is used to provide as much information as possible about each piece of music or sound so that the program can make informed, musical decisions, when it manipulates the music according to requests from users . The encoding process includes the following: 1. Block Start and End: The beginning and ending of each discrete music section (block) is determined. This necessarily determines the length of each block. Listen to the piece of music and divide it into segments based on musical phrases and musical uses called blocks . On average there are fifteen blocks per minute of music . 2. Block Name: Code each block with a name and description. 3. Beginning Blocks: For each block a determination is made as to whether it would make a good way to start a musical section or phrase. 4. Ending Blocks : Same concept as that described for Beginning Blocks. 5. Block Compatibility: Each block is tested for its specific compatibility to each and every other block which comprise the source audio segment. 6. Intensity: Code each block's musical intensity relative to other blocks. 7. Fadeable Block: Each block has a determination made as to whether it sounds musically viable to fade or not. Although the present invention has been described in detail with reference only to the presently-preferred embodiments, those of ordinary skill in the art will appreciate that various modifications can be made without departing from the invention. Accordingly, the invention is defined by the following claims. // // // // // // // // // // // // // // // // //

Claims: CLAIMS We claim: 1. A compiler for generating an audio sequence having a prescribed duration, comprising: an encoding table referencing at least one predefined audio segment wherein said encoding table contains entries to partition each said predefined audio segment into blocks,* said encoding table entries including data corresponding to the duration of each said block, the suitability for each said block to begin or end an audio sequence, and the compatibility of each said block to sequentially follow each other said block; a user interface for prescribing an audio segment and an audio sequence duration; an audio block sequence compiler for iteratively compiling a list of said blocks comprising at least one audio sequence according to said user interface such that each said audio sequence conforms with said encoding table entries,* and means for displaying said list. 2. The compiler of claim 1, additionally comprising means to store at least one entry from said list. 3. The compiler of claim 1, additionally comprising means to play a selected entry from said list. 4. The compiler of claim 1, wherein said encoding table additionally comprises a mood parameter for each said block and said audio block sequence compiler can select blocks according to said mood parameter when requested by a user. 5. The compiler of claim 1, wherein said encoding table additionally comprises a fadeable parameter for each said block and said audio block sequence compiler can select a fadeable block as an ending block and wherein said fadeable blocks can be truncated to achieve audio sequences of said prescribed duration. 6. The compiler of claim 1, wherein said encoding table additionally comprises an intensity parameter for each said block and said audio block sequence compiler can select blocks according to a user-definable intensity curve. 7. The compiler of claim 1, wherein said encoding table additionally comprises a hit point parameter for each said block for specifying an intensity burst when present within said block and said audio block sequence compiler can select the sequence of said blocks according to said intensity burst at a user-prescribed location. // // // // // 8. A compiler for generating an audio sequence having a prescribed duration, comprising: an encoding table referencing at least one predefined audio segment wherein said encoding table contains entries to partition each said predefined audio segment into blocks; said encoding table entries including data corresponding to the duration of each said block, the suitability for each said block to begin or end an audio sequence, and the compatibility of each said block to sequentially follow each other said block; means for a user to select an audio segment and an audio sequence duration,* means for iteratively compiling a list of at least one audio sequence from said blocks according to said user interface; and means for displaying said list. 9. The compiler of claim 8, additionally comprising means to store at least one entry from said list. 10. The compiler of claim 8, additionally comprising means to play a selected entry from said list. 11. The compiler of claim 8, wherein said encoding table additionally comprises a mood parameter for each said block and said compiling means can select blocks according to said mood parameter when requested by a user. 12. The compiler of claim 8, wherein said encoding table additionally comprises a fadeable parameter for each said block and said compiling means can select a fadeable block as an ending block and wherein said fadeable blocks can be truncated to achieve audio sequences of said prescribed duration. 13. The compiler of claim 8, wherein said encoding table additionally comprises an intensity parameter for each said block and said compiling means can select blocks according to a user-definable intensity curve. 14. The compiler of claim 8, wherein said encoding table additionally comprises a hit point parameter for each said block for specifying an intensity burst when present within said block and said compiling means can select the sequence of said blocks according to said intensity burst at a user-prescribed location. // // // // // // // // // // //

Inventors: HUFFORD CHRISTOPHER P, HUFFORD GEOFFREY CALVIN, KLINGLER KEVIN C, HUFFORD, CHRISTOPHER, P., HUFFORD, GEOFFREY, CALVIN, KLINGLER, KEVIN, C.
Applicants: SONIC DESKTOP SOFTWARE
Application year: 1996
Main classification: G10H1
IPC codes: G06F17, G10H1