Video camera and remote recording system

A system for recording audio and video comprises at least one video camera device (100), each camera device comprising a subsystem for capturing (112) at least video data, a storage device (107) upon which at least the video data is stored, a wireless interface (108) for communicating with at least one further recording device (200), an internal clock(106) for recording at least a time at which the video data was recorded, and a connecting port (108, 110) enabling connection to a remote-control device (eg. 200). The system also has at least one of the further recording devices (200), each comprising a microphone (215) for capturing audio information and a storage device upon which corresponding audio data is recorded, a wireless interface (208) for communicating with the video camera device, an internal clock (206) for recording at least a time at which the audio data was recorded, and a connection port (208,210) enabling connection to the video camera device.

FIELD OF INVENTION

The present invention relates to the recording of audio with a video camera and, in particular, to the usage and integration of a separated audio source.

BACKGROUND

Integrated microphones are found upon almost all video cameras in the marketplace and are used to record one or more audio tracks in synchronism with video images simultaneously recorded by the camera. Such integrated microphones generally result in poor recorded sound quality, often in spite of the quality of the microphone itself, but primarily because the microphone is not usually positioned close to enough to the sound producing subject. Typically such microphones are omnidirectional and detect much extraneous noise which is recorded along with the subject sound. Existing methods of getting the microphone closer to the desired sound source are unsatisfactory in various ways.

For example, running a cable from the camera to a separate microphone can be inconvenient, potentially dangerous, and is often impractical.

Wireless microphones may be used but are expensive and unreliable. If there is interference between the transmitter and receiver, audio information will often be lost or quality will be reduced. Further, where an increasing number of wireless microphones are used in an area, for example by a number of people making a video recording, it is more likely that there will be interference or lost data.

In professional film and video recording, sound is usually recorded completely separately from the video, and later recombined using such standards as the SMPTE time code system. However, the SMPTE time code system was created with the limitations of tape-based recording media in mind. The SMTPE system requires the recording of an additional audio track containing a special “sync tone”, which contains a simple measure of time. The sync tone repeats every twenty-four hours, however, so it is possible for the system to become confused if recording occurs over a longer period of time. Also, synchronization can be awkward. Devices that wish to be synchronized have to record the sync tone when they do their own recording. If there are several devices recording, they must all connect to the same source producing the sync tone. When the data from separate devices are combined, synchronization is achieved by lining up the sync tones on each device. The inconvenience of recording the same sync tone on each device is too great for most amateur video recording artists.

Video camera remote-controls are typically used when the user of the camera is not nearby the camera. In the instance that the user operates the remote-control to turn the camera on and off, this is usually because the user is in front of the camera and hence is at least part of the subject being recorded.

SUMMARY OF THE INVENTION

It is an object of the present invention to substantially overcome or at least ameliorate one or more deficiencies with existing recording methods.

The present invention addresses this object to allow convenient recording using multiple audio and video sources that can be simply synchronized in a post-recording environment.

In accordance with one aspect of the present invention, there is disclosed a system for recording audio and video, said system comprising:

at least one video camera device, each said camera device comprising a subsystem for capturing at least video data, a storage device upon which at least said video data is stored, a wireless interface for communicating with at least one further recording device, an internal clock for recording at least a time at which said video data was recorded, and a connecting port enabling connection to a remote-control device; and

at least one said further recording device, each said remote recording device comprising at least one microphone for capturing audio information, a storage device upon which corresponding audio data is recorded, a wireless interface for communicating with said video camera device, an internal clock for recording at least a time at which said audio data was recorded, and a connection port enabling connection to said video camera device.

Desirably one said remote recording device is adapted to be physically and detachably coupled to one said video camera device for at least audio recording operations at the video camera device and, when detached, for audio recording operations at a location remote from said video camera device.

In accordance with another aspect of the present invention there is disclosed a system for recording audio and video data, said system comprising:

a video camera device comprising a subsystem for capturing at least video data, a storage device upon which at least said video data is stored, a wireless interface for communicating with at least one remote controller, and an internal clock for recording at least a time at which said video data was recorded; and

at least one said remote controller, each said remote controller comprising at least one microphone for capturing audio data, a storage device upon which said audio data is stored, a wireless interface for communicating with said video camera device, and an internal clock for recording at least a time at which said audio data was recorded, wherein said remote controller transmits reproduced audio data to said video camera device, and makes said video camera device record said reproduced audio data relating to said video data in accordance with each said internal clock of said remote controller and said video camera device.

In accordance with another aspect of the present invention there is disclosed a method for recording audio and video, said method comprising the steps of:

(a) physically connecting an audio device having an internal clock to a video device having a complementary internal clock, thereby synchronizing and associating the two devices;

(c) instructing the audio device to record audio data that contains or is at least associated with a current time presented by the internal clock on the audio device, thereby causing the audio device to commence recording;

(d) instructing the video device to record video data that contains or is at least associated with a current time presented by the internal clock on the video device, thereby causing the video device to commence recording;

(e) instructing the audio device to stop recording;

(f) instructing the video device to stop recording; and

(g) physically connecting the audio device to the video device, thereby causing audio data and associated or embedded time data stored on the audio device to be transferred to the video device.

Preferably the audio device in step (c) sends a wireless instruction to the video device to commence recording, said wireless instruction being received by said video device in step (d) to automatically trigger recording by said video device.

Many other aspects of the invention are also disclosed.

DETAILED DESCRIPTION INCLUDING BEST MODE

FIG. 1shows a video camera device100capable of recording video and optionally audio data into a storage107thereof. The camera device100is preferably a digital video camera having a digital storage. Such affords the ability to non-linearly store metadata associated with recorded content. The camera device100has a lens114and a viewfinder113for viewing a scene to be recorded and a charge-coupled-device112for capturing a video representation of the scene. A central processing unit (CPU)105operates to control the camera device100and specifically to enable recording of video, audio and other information (data) in the storage107. The camera device100also includes other interface features120such as, a record button101, a display control jog dial102for editing control, a port110for wired connection to a remote audio recording device200or to another camera device100, a port111for connecting to a pair of headphones facilitating private audio reproduction, a battery104that powers the video camera device100, and a display103for reproducing the scene presently being viewed.

The camera device100further includes a precision clock106that is desirably kept running as long as possible, even after the power to other components of the camera device100has been shut down. If the precision clock106has to stop and restart, the camera device100is desirably configured via the CPU105to notify the storage107that the clock106has restarted, by incrementing a storage clock-reset counter302, to be described with reference toFIG. 3. The camera device100as illustrated also includes the remote audio recording device200which is detachable and which may be operated via wired or wireless connections. A wireless communications unit108is provided for communicating between the CPU105and the remote recording device200, and an associated-devices toggle switch109for selecting whether to associate single or multiple other camera devices100, and/or remote audio recording devices.

FIG. 2shows the detachable wireless remote audio recording device200which is seen to include a monophonic or stereophonic microphone215configured to enable audio recording operations to be performed. A stereophonic microphone may be formed from a combination of two or more monophonic microphones. A central processing unit (CPU)205is provided to control operation of the remote recording-device200which, like the camera-device100, also includes interface features220including a record button201, a display control jog dial202, an associated-devices toggle switch209for selecting whether to associate single or multiple other devices, a display203, a port210for wired connection to a video camera device100, and a port211for connecting to a pair of headphones. When the recording device200is attached to the camera device100, a wired connection therebetween is preferably formed by a coupling between the ports110and210. The remote recording device200further includes a precision clock206, a storage207for audio data sourced from the microphone215and metadata, a wireless communications unit208for communicating to the camera device100, and a battery204that powers the remote recording device200. Like that in the camera device100, the precision clock206is desirably kept running as long as possible, even after the power to other components of the remote recording device200has been shut down. If the clock206has to stop and restart, the remote recording device200is desirably configured via the CPU205to notify the storage207that the clock206has restarted, by incrementing the corresponding storage clock-reset counter302.

The wireless communications units108and208may be configured to operate according to the IEEE 802.11B or IEEE 802.11G standards for radio frequency communication offering effective communications distances of about 20 metres and 100 metres respectively.

FIG. 3shows the layout of data storage300as implemented in each of the storage107of the video camera device100and the storage207of the remote recording device200. Each storage107,207keeps the data intact even in the absence of power. Each device100,200has an unchanging globally unique identity (GUID) string301permanently retained to identify the respective storage107,207. A Clock-reset Counter (CRC)302is provided to store an incrementing integer, also permanently retained to maintain track of those instances where the corresponding precision clock106,206has been restarted. Also provided is a message counter307adapted to maintain a unique count for each message produced by the storage300. Each storage107,207further includes a detachable storage component303that stores corresponding audio or visual data304, a list of device associations305, a list of device synchronization messages306, and a message log308. The message counter307initially stores the number 0, and is incremented every time a message is sent from the corresponding device100,200. The clock-reset counter302initially stores the number 0. Every time the internal clock106or206has to be restarted, the CRC302is incremented by one, and the message counter307reset to zero.

FIG. 4shows the format of a message400that might be sent from either device100,200, hereafter referred to as the “sender”, either wirelessly using the wireless communications108or208, or wired, using the connection port110or210of the corresponding device100,200. The message400comprises the sender's GUID401obtained from the sending device's GUID storage301, the sender's CRC402obtained from the sending device's CRC storage302, and optionally the recipient device's GUID403, a message ID404obtained from the sending device's message counter307, an indication of the message type405, and the message contents406.

FIG. 5shows the format of a device association list305as present in each storage300. The device association list305includes zero or more device association elements502, each of which comprise an associated GUID503, being the GUID of the device200,100being associated with, the associated CRC504being the CRC of the device200,100being associated with, and wireless connection details505, being whatever information is required to reconnect to the associated device200,100via the wireless connection108or208.

FIG. 6shows the format of a device synchronization list306as present in each storage106,206. The device synchronization list306comprises zero or more device synchronization elements602, each of which include an associated GUlD603, being the GUID301of the device200,100being associated with, the associated CRC604being the CRC302of the device200,100being associated with, a Local GUID608, being the GUID of the local device100,200, a local CRC604being the CRC302of the local device100,200, a local clock value605, being a value of the internal clock106,206of the local device100,200, an associated clock value606, being a value of the internal clock206,106of the associated device200,100, and a clock tolerance607, being a measure of the accuracy of the synchronization between the local clock value605and the associated clock value606.

FIG. 7shows structures used to determine synchronization between devices, such as the camera device100and the remote recording device200. Synchronisation is required when a recording operation, undertaken with either one or both of the devices100,200produces what is termed in the art a “clip”, defined as data continuously recorded between a start time and an end time. A clip may be for any duration however, in amateur video productions, clips may typically have a duration of between about 10 seconds and 2 minutes. Some clips can be very short, occupying only a small number of video frames, or quite long, for example if an entire event (eg. a concert or football match) is recorded. As seen inFIG. 7, a Time-Line Segment (TLS)701includes a GUID301and a CRC302. Further all AudioNideo Clips704, as the case may be, that have those included GUID and CRC are listed in the Time-Line Segment701, alongside the Start and End Times705of each clip704. In addition, all Device Synchronization Elements706that relate to the GUID301and CRC302are listed in the Time-Line Segment701. InFIG. 8, an Overall Time-Line (OTL)710is seen to have a structure formed of any number of Time-Line Segments (TLSs)701, along with a Time-offset711and a Clock Tolerance value712, whose determinations are discussed later in this document.

In a preferred implementation, a user has two devices, which may be both video camera devices100, both audio remote recording devices200, or one each of the video camera device100and the remote recording device200device.

Each device100,200is capable of sending messages400, either directed towards other devices or omnidirectionally broadcast, using the corresponding wireless communications108or208. Whenever a device100,200sends a message400(the circumstances in which messages are sent being stated below), the device100,200puts the message into the Message format400as indicated inFIG. 4. The device100,200includes in the content at least its GUID301in the Sender GUID401, the value of its Clock-Reset Counter302in the Sender's Clock-Reset Counter402, the value of the Message Counter307in the Message ID404, and an indication of the type of the message in the Message Type405. The device100,200then increments the Message counter307.

The user may further connect the two devices using the ports (110and/or210) for connection either directly or via a connecting cable (not illustrated but functionally known in the art). The connection between the two devices serves as a trigger for the following, labelled A-E:

A. Each (specific) device100,200stores a Device Synchronization Element602in its Device Synchronization List306in its storage300(107or207), including the following data:AA. The Local Clock value605, being the time at which the devices were connected, according to the internal clock (106or206) of the specific device. The time may be expressed as a real-time (ie. year, month, date, hour, second, etc) and desirably has a resolution of milliseconds thereby enabling sufficient scope for resolving time differences between recorded image frames over a range of popular recording formats which may have frame rates of 24-30 frames per second (ie. 42-33 ms) or interlace rates of 100 Hz (ie. 10 ms). The internal clock may merely be a counter having, say, 36 bit accuracy to give at least 2 years of usable time. However since the described arrangements operate according to time differences, shorter periods of time may be suitable for some productions. In some implementations, resources may be better expended upon minimizing drift in the clocks106and206rather than extending their respective absolute times of operation.AB. The Associated GUID603being the GUID301of the device to which the specific device is connected, and the Associated CRC value302of the device to which the specific device is connected.AC. The Local GUID608being the GUID301of the specific device, and the Local CRC value609being the CRC302of the specific device.AD. The Associated Clock value606, being the time at which the devices were connected, according to the internal clock (106or206) of the device to which the specific device is connected.AE. A Clock Tolerance value607, indicating the level of accuracy of the synchronization between the Local clock value605and the Associated Clock value606.

B. If either device100,200has its associated-devices toggle switch109or209set to “single device”, that device deletes all the Device Association Elements502from the Device Association List305in its storage300(107or207).

C. Each specific device100,200creates a Device Association Element502comprising the Associated GUID503taken from the GUID301of the connected device, and the Associated CRC504taken from the Clock-reset counter302of the connected device, along with any other information the specific device needs to wirelessly communicate with the connected device at some later stage505. The specific device puts this Device Association Element502into its Device Association List305, in its storage (107or207).

D. If one device is an audio device200and the other device is a video device100, and the audio device200has audio data in its storage304or in its device synchronization list306, and if the video device100has sufficient space in its storage, the audio device200may transfer all its audio/video data into the video device100, either automatically, or by indicating to the user on either or both displays103and203that there is data that may be transferred, and requesting the devices100and200choose whether to do so using the display control jog dial102or202. The transfer of the data between the devices100and200is done in such a way that detaching the two devices100and200at any point in the procedure does not cause any data to be lost.

E. If the two devices100,200have audio/video data304that overlap in time, each specific device may make copies of the data that overlaps from the other connected device, depending on the space available in the storage of that specific device300. This may either be done automatically, or by indicating to the user on either or both displays103and203that there is data that may be exchanged and requesting the user to choose whether to do so using the display control jog dial102or202. Similarly, the devices100,200may choose to copy each others' Device Synchronization List306, either manually or automatically, and may base this decision on whether elements of the other connected device's Device Synchronization List306refer to devices that are in its Device Association List305or are referred to in the connected device's AudioNideo Data304.

The connection between the ports110and210may also be used to supply electrical energy from the battery104of the camera device100to the battery204of the remote recording device200to effect a recharging operation.

The user may then separate the two devices100,200by unplugging the connector between them from the connection ports (110and/or210).

The user may subsequently connect other devices100,200to these devices100,200. The same process is carried out whenever two such devices are connected.

In respect of general operation of the devices100,200a number of events, in no particular order, may occur at any time:

(i) If the user presses the record button (101or201) on a specific device that is not currently recording, the specific device100,200starts recording video or audio data respectively into its storage304, and also records the GUID301and CRC302and the start time of the data as read from the internal clock106or206with the audio and/or video data. The specific device indicates that it has started recording on the display103or203, and sends a message400with a message type405“Start Recording”, to each recipient one of the devices100,200in its associated devices list305and stores a copy of each message that it sends in the Message Log308. The specific device100,200may also indicate on its display103or203for each associated device that the associated device has not started recording yet. While the devices are recording, a user may listen to the sound level of the audio being recorded on that device via the headphone port111or211. Where a camera device100has an integrated microphone (not illustrated but well known in the art), the camera device100can be enable top record both audio and video data to the storage107according to the protocols described herein. Similarly, and where appropriate it may be possible to transfer recorded video data to the storage207in the remote recording device200.

(ii) If a specific device100,200receives a message with Message Type405“Start Recording”, the specific device100,200checks that the associated device100,200that sent the message is in the Device Association List305. This is done by the specific device100,200examining the Sender GUID401received with the message and checking each Associated GUID503of the various Device Association Elements502retained in the Device Association List305of the specific device100,200. If the Sender GUID is found, the specific device100,200acknowledges this by starting recording, consistent with the received Message Type405. The specific device100,200further indicates on its display103,203that recording has been started in response to the request of an associated device. Additionally, the specific device100,200sends a reply message with Message Type405“Acknowledge Start Recording” to the associated device. The reply message includes information on whether the specific device100,200started recording or not, and a reference to the message ID404of the original message in the message contents406of the reply message.

(iii) If a specific device100,200receives a message with Message Type405“Acknowledgement Start Recording” that corresponds to a “Start Recording” message in the Message Log308of the specific device100,200, the display103, is altered to show that the associated device is recording.

(iv) If the user presses the record button (101,201) on a specific device100,200that is currently recording, the specific device100,200stops recording audio and/or video data into the corresponding storage304, and also records the stop time of the data as read from the internal clock106,206with the audio and/or video data. The specific device100,200indicates on the display103,203that recording has been stopped, and sends a message400with a message type405“Stop Recording”, to each associated device100,200in the associated devices list305of the specific device100,200whilst storing a copy of each message that the specific device100,200sends in the corresponding Message Log308.

(v) If a specific device100,200receives a message with Message Type405“Stop Recording”, the specific device100,200checks that the other device100,200that sent the message is identified in the Device Association List305. This is done by examining the Message Sender GUID401in each of the Associated GUIDs503retained in each Device Association Element502of the specific device100,200. If the appropriate Message Sender GUID401is located, and the specific device100,200is currently recording, the specific device100,200stops recording, and indicates on the corresponding display103,203that recording has been stopped in response to a request received from an associated device100,200. Additionally, the specific device100,200sends a reply message with Message Type405“Acknowledge Stop Recording” to the associated other device100,200that sent the original message. The reply message includes information on whether the specific device100,200stopped recording or not, and a reference to the message ID404of the original message in the message contents406of the reply message.

(vi) If a specific device100,200receives a message with Message Type405“Acknowledgement Stop Recording” that corresponds to a “Stop Recording” message in the Message Log308of the specific device100,200, the corresponding display103,203is changed to show that the associated device100,200is no longer recording.

(vii) If a specific device100,200is running low on battery power, such may be indicated on the corresponding display103,203. The specific device100,200may additionally send a message with Message Type405“Low Battery” to all the other devices100,200identified in the corresponding device association list305. The message may optionally contain in its Message contents406an indication of the battery time remaining by virtue of the stored energy capacity thereof.

(viii) If a specific device100,200receives a message with Message Type405“Low Battery”, it may indicate on the corresponding display103,203that the associated device has low battery.

(ix) If a specific device100,200is running low on memory, particularly as used for the data304, such may also be indicated on the corresponding display103,203. The specific device100,200may additionally send a message with Message Type405“Low Memory” to all the other devices in the corresponding device association list305, optionally containing in the Message contents406thereof an indication of the memory remaining.

(x) If a specific device100,200receives a message with Message Type405“Low Memory”, an indication that an associated device100,200has low memory may be made on the display10,203of the specific device100,200.

(xi) A specific remote recording device200may periodically send a message with Message Type405“Recording Levels” to each of the associated devices100,200identified in the device association list305of the specific remote recording device200. These audio recording levels are contained in the message contents406of the sent message.

(xii) If a specific device100,200receives a message with message type405“Recording Levels”, the specific device100,200may indicate recording levels of the associated device on the display103,203of the specific device100,200.

(xiii) The user may further alter the recording levels of a device100,200that has audio recording levels represented on the display103,203of a specific device100,200using the display control jog dial102,202of the specific device. The deice100,200having audio recording levels adjusted may therefore by the specific device100,200or an associated device100,200. When the recording levels of an associated device are requested to be changed by the user, the specific device100,200sends to the associated device100,200a message with message type405“Change Recording Levels”, with the message contents406thereof being an indication of the desired level to which the recording level is to be changed. If the specific device100,200does not receive a message with Message Type405“Acknowledgement Change Recording Levels” in a timely fashion, being an acknowledgment by the associated device100,200, an error may be indicated on the display103,203of the specific device100,200.

(xiv) If a specific device100,200receives a message with Message Type405“Change Recording Levels”, the Device Association List305of the specific device100,200is checked to determine that the other device100,200making the request is identified by looking for the Sender GUID401conveyed with the message in each of the Associated GUIDs503of the Device Association Element502. If the other device is indeed associated, the specific device100,200then changes the recording levels as requested, show such on the corresponding display103,203, send a reply message with Message Type405“Acknowledgement Change Recording Levels” to the other associated device100,200, and include in the message content406of the reply message that the specific device100,200has changed the microphone recording levels in response to the request from the other associated device100,200.

(xv) A specific device100,200may periodically broadcast a message400with a Message Type405“Synchronization Message”, containing the current internal clock value106,206in the message contents406.

(xvi) If a specific device100,200receives a message400with Message Type405“Synchronization Message”, the message is stored in the Message Log308and the specific device100,200sends a reply message with Message Type405“Acknowledgement for Synchronization Message” and containing the current internal clock value106,206of the specific device100,200in the Message Contents406, to the original device100,200that broadcast the received message. The acknowledgement reply message contains the time at which the specific device100,200received the original message containing the internal clock value106,206, in the message contents406thereof. The acknowledgement message may additionally contain a request for a further acknowledgement message in response.

(xvii) If a specific device100,200receives a message400with Message Type405“Acknowledgement for Synchronization Message”, and there is a record of a corresponding synchronization message in the Message Log308, the specific device100,200creates a Device Synchronization Element602having an Associated GUID603and Associated CRC604taken respectively from the sender GUID401and sender CRC402from the message400, and the Local GUID608and Local CRC609taken from the specific device100,200. The Device Synchronization Element602also has formed a Local Clock value605equal to an average of the time at which the original synchronization message was sent from the specific device100,200and the time at which the acknowledgement was received by the specific device100,200. An Associated Clock value606is set equal to the clock value in the Message Contents406, and the Clock Tolerance607is determined to be equal to half the difference between the time at which the original synchronization message was sent and the time at which the acknowledgement was received, both by the specific device100,200. The specific device100,200then adds the newly created Device Synchronization Element602to the Device synchronization list306. The specific device100,200may also send a further message400of Message Type405“Acknowledgement for Synchronization Message”, containing the current internal clock value106,206in the Message Contents406. In this way, a series of synchronization messages may be sent back and forth until both devices are satisfied that they have a sufficiently accurate estimate of the difference between the clock values of the two devices.

(xviii) A remote recording device200may attempt to transfer sections of data retained in the storage207to another device100,200using the wireless communications module208. Such transfer may take the form of a message400with a Message Type405“Data transferral”, and a Message Contents406including a section of the Audio/Video Data304or of the Device Synchronization List306both taken from the storage207of the remote recording device200. The recipient device100,200of the transfer message will be the first member that was added to the Device Association List305. In addition, the recipient device100,200stores a copy of the message minus the Message Contents406in the Message Log308thereof, the transferred Message Contents being stored in the corresponding audio/video data storage304and Device Synchronization List306, as the case may be.

(xix) If a specific device100,200receives a message400with a Message Type405“Data transferral”, the specific device100,200first checks if there is enough space in the corresponding storage300to add the content. If there is sufficient capacity, the content is then added to the corresponding Audio/Video Data304or Device Synchronization List306as appropriate. The specific device100,200then sends a reply message with Message Type405“Acknowledgement for Data transferral”, stating in the Message contents406thereof whether or not the data transferral was successful.

(xx) If a specific device100,200receives a message400with a Message Type405“Acknowledgement for Data transferral”, the specific device100,200confirms that it had sent the data transferral message in question by checking for a record thereof in the Message Log308. If such a message exists and the Message Contents406indicate that the transferral was successful, the specific device100,200then deletes the section of data that had been successfully transferred.

(xxi) A user may detach the detachable storage303from a first device100,200and attach the storage303to another device200,100. If a device100,200has no detachable storage303currently attached, such information is displayed via the display103,203. Such a device100,206does not allow recording, and does not send or receive messages until such time as a detachable storage303is re-attached.

(xxii) If a device100,200had detachable storage303attached, and the detachable storage303has memory space available, the device100,200can resume recording and sending/receiving messages. Such is useful for re-attachment of the detachable storage303.

At some point, the user may wish to play back data that they have recorded, either on a video camera device100or a dedicated playback device of some description, such as a digital video player. To do so, the user is presented with the audio and video clips that are stored in the storage304of the device100. Those clips may have been obtained from a number of possible devices100,200, each having different clocks106,206. In order to find the relationships between the clips, it is necessary to use the Device Synchronization List306. The following rules may be used to determine the order of the clips in time:

(a) A Time-Line Segment (TLS)701is created to group all Audio/video clips704that have the same GUID301and CRC302. Each Audio/video clip704has corresponding Start and End Times705of that clip.

(b) If, when examining the Device Synchronization List306, in a Device Synchronization Element602, there is a first TLS701having a GUID301corresponding to the Associated GUID603, a CRC302corresponding to the Associated CRC604and a second TLS701having a GUID301corresponding to the Local GUID608and CRC302corresponding to the Local CRC609, the device100adds that Device Synchronization Element602to each of the first and second TLSs706.

(c) One or more Overall Time-Lines (OTL)710are constructed from the individual TLSs701. The function of an OTL710is to show TLSs701in time-sequence and is formed using a list of TLSs701. Each TLS701has a Time-Offset711and a Clock Tolerance712. The OTL710is constructed in the following manner:(ca) Select an initial TLS701. The user may perform this selection by manipulating the user inputs120. Otherwise the TLS710corresponding to the current Device GUID301and the most recent CRC302is chosen, otherwise the TLS701that contains the most data is chosen. The chosen TLS701has a time-offset711of 0 and a Clock Tolerance712of 0.(cb) With the initial TLS701, the Device Synchronization Elements602thereof are reviewed from the highest to lowest time-stamps, being the local clock value605. If the Associated GUID603and Associated CRC604are the values of the initial TLS701, then add the TLS701referred to by the Local GUID608and Local CRC609of the Device Synchronization Element602to the OTL710, if such has not already been added. The associated time-offset711of the OTL710is then determined to be equal to (Associated Clock Value606−Local Clock Value605+Initial TLS time-offset711). If instead, the Local GUID608and Local CRC609are the values of the initial TLS701, then add the TLS701referred to by the Associated GUID603and Associated CRC604to the OTL710, if such has not already been added. The associated time-offset711in this case is then determined to be equal to (Local Clock Value605−Associated Clock Value606+Initial TLS time-offset711). In either case, the Clock Tolerance712of the OTL710is determined to be equal to (Clock Tolerance607+Initial TLS Clock Tolerance712).(cc) For each newly included TLS701in the OTL710, step (cb) is repeated, treating each newly included TLS701in turn as the initial TLS701. This step is repeated until no new TLSs701are added to the OTL710.

(d) The user may then view the entire OTL710or play segments of the OTL710. If the user requests to play from a particular time-stamp local clock value605of an OTL710, it is necessary to then determine which audio and/or video clip data704are active at that time-stamp, and at what point the data704should be played, by going through each TLS in turn and checking whether it has data at that time-stamp705, taking into account the time-offset711attached to the TLS710. The appropriate video and audio segments may be simultaneously reproduced, or the user may choose which video and/or audio segments to reproduce.

In some cases, there will be more than one Device Synchronization Element602shared between TLSs701. Such may occur more than one DSE links to the same two TLSs. This may occur for example if a remote audio device200were connected to a camera device100twice, which would produce two DSE between those two devices, assuming the CRC is the same. Where more than one DSE is shared, information about relative clock-speeds from the time-stamps may be derived and used to compress or expand audio and/or visual data to better synchronize the two with other data. It is also possible to choose which Device Synchronization Elements602of the TLS701to use depending on the Clock Tolerance607of the DSE602, and to make corrections to the Time-offset711of each TLS701accordingly.

The arrangements described are preferably implemented using digital recording devices for each of the storages107,207. Typically the camera device will be a digital video camera and the storage107may be implemented using a hard disk drive or non-volatile semiconductor memory. However, because of size constraints, convenience and the smaller volume of data, the storage207, which operates for audio recording, is typically formed of non-volatile semiconductor memory. In alternative implementations, either one or both of the storages107,207may be performed using a writable optical disk. Any one or more of a number of image and audio compression schemes may be implemented within the system to achieve compression of captured information prior to storage thereof, thereby optimizing storage capacity. Suitable compression formats include MPEG for combined audio and video, MPEG for video only, and MP3 or Ogg Vorbis for audio only.

INDUSTRIAL APPLICABILITY

The arrangements described are applicable to the video recording and production industries.