Abstract:
A method, apparatus and article of manufacture is provided for processing a previously encoded MPEG video high-resolution (HR) file and corresponding proxy file, for frame accurate timecode repair and synchronization of individual video frames of the HR and proxy files. Each video frame header of the HR and proxy files is modified by a compressed timecode packet having an identifying signature, an absolute timecode of the frame, and a relative timecode of the frame. The timecodes have the SMPTE timecode format HH:MM:SS:FF. The method automatically verifies the timecodes in the HR and proxy files timecode packets. If a repair of the HR file anomalous absolute timecodes is needed, the method automatically corrects the anomalous absolute timecodes in the HR file. If the proxy file starting video frame is offset from the HR file starting video frame, the method automatically synchronizes the proxy and the HR files absolute and relative timecodes.

Description:
RELATED APPLICATIONS 
   The present invention is related to a provisional patent application entitled “Apparatus and Methods For Processing MPEG Streams” by the same inventor, Ser. No. 60/232,893, filed on Sep. 15, 2000, and co-pending applications entitled: “System and Method of Processing MPEG Streams For File Index Insertion” Ser. No. 09/860,700, filed on May 18, 2001, “System and Method of Processing MPEG Streams For Storyboard and Rights Metadata Insertion”, Ser. No. 09/850,522, filed concurrently, and “System and Method of Processing MPEG Streams For Time code Packet Insertion” Ser. No. 09/850,201, filed concurrently, all assigned to the assignee of the present invention and fully incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to the compression, cataloging and viewing of full motion videos and, more particularly, to the processing of compressed video data. 
   2. Description of Related Art 
   The infrastructure and process required to create and operate a video archive in the digital domain are well known in the broadcast video industry. The archiving process generally begins by digitizing and compressing the analog video using MPEG-1 or MPEG-2 compression, then moving the compressed video file to a long term storage. To preserve the contribution quality of the video, broadcasters generally select a high compressed bitrate (i.e., 15–40 Mbps), which allows the original video to be recovered with relatively high fidelity in spite of the lossiness of the MPEG compression scheme. 
   The high bitrate of the compressed video, however, presents considerable problems to the broadcaster&#39;s local area network and computer workstation infrastructure, when the video must be distributed for viewing and post-production work. The high network bandwidth and the amount of time required to transfer the assets throughout the plant places an upper limit on the number of concurrent transfers and severely constrains productivity. In response to this bandwidth problem, broadcasters create an additional copy of the video at a much lower compressed bitrate (i.e., 1.5–4 Mbps). This low bitrate file, referred to as a ‘proxy’ or ‘browse’ file, enables users to quickly download the video or to view it directly on computer monitors by utilizing a streaming video server. To facilitate the viewing of video assets outside the local area network, a second proxy file is often encoded at a very low bitrate (56–1000 Kbps), for streaming over low speed terrestrial lines. 
   After ingestion of the video, the next step in the archiving process is to create an entry for the video in the video library catalog. This entry contains metadata, which is information pertinent to the video. The contents and format of a video catalog record, normally broadcaster unique, facilitate the search and retrieval of video clips within the broadcaster&#39;s video library. Presently, there are commercially available video catalog applications (catalogers) that will automatically extract from an MPEG-1 or MPEG-2 video file metadata, such as closed caption text and the text of the actual audio program, obtained via speech recognition technology. Catalogers further extract metadata from the video by performing scene change analysis and creating a bitmap of the first frame after each cut or major scene transition. These bitmaps, referred to individually as a ‘thumbnail’ or collectively as a storyboard, are considered essential metadata because they enable the end user to determine very quickly the video content. Absent the storyboard, the end user is forced to view the video or, at a minimum, fast forward through a video to find the desired video segment. An additional feature of prior art catalogers is the capability to randomly access and play the proxy video file by double clicking on a storyboard thumbnail. 
   Further productivity gains can be achieved if the proxy file is a replica of the high-resolution video, where both files begin on the same video frame and have equal duration. When the browse file is a true proxy, a video production engineer is able to import several proxy files into a video editor and produce a program, creating an edit decision list (EDL). This EDL is subsequently exported to a high quality video editing suite that downloads the high-resolution version of the videos from the archive and executes the EDL to produce the air-ready material. Ideally, the broadcast editing suite retrieves from the broadcast server or archive only those segments of the high-resolution file that are specified in the EDL. 
   There are two timecodes associated with every video: an absolute and relative timecode. The absolute timecode is the SMPTE timecode recorded as the video is being shot. It usually reflects the actual time of day, but if the camera operator fails to properly set the SMPTE timecode generator on the camera, it may indicate any random clock time. Reporters and producers taking notes will record the SMPTE timecode while filming to enable them to quickly find important footage during post-production. It is for this reason that many archive librarians insist on preserving the absolute timecode as essential metadata when compressing and cataloging video. 
   The relative timecode is a timecode that is relative to the start of the video, and is often referred to as elapsed time. Many producers prefer to use relative timecode instead of absolute timecode during editing sessions, because it can simplify the arithmetic associated with calculating video clip duration. More importantly, it is more dependable than the absolute timecode. 
   The absolute timecode on a source video tape can be anomalous (e.g., missing, discontinuous, jump backwards in time, non-incrementing, non-drop frame mode, etc.). If a dub of the material is used as video source, it may not reflect the original timecode of acquisition. Moreover, regardless of whether longitudinal timecode (LTC) or vertical interval timecode (VITC) is being read as the source of timecode, tape dropout and other media defects can also result in corrupted SMPTE timecodes. 
   Accordingly, it would be advantageous to automatically verify and correct a bad timecode, when ingesting assets for permanent archival. It would be further advantageous for archive librarians to be able to re-stripe or change the timecode of the material, to suite their operational requirements. It would be yet further advantageous to be able to update the timecodes attached to each thumbnail in the storyboard, and any timecodes referenced in any existing description of the video and audio program, whenever the SMPTE timecodes in the high-resolution file have been modified. 
   However, in some instances, librarians may insist on preserving the original source timecode when archiving video. When video is later used to create new program material, the original source timecode facilitates the tracing of the content genealogy to the original source material. However, when the original source timecodes are maintained, the timecodes may contain gaps where shooting was halted and restarted. In the case of a compilation video, the video actually comprises a series of separate video clips. 
   In case of the noncontinuous absolute timecodes, EDL must be generated using relative timecode. It is for this reason that the relative timecodes of the proxy file must match the relative timecodes of the high-resolution file. This requirement in turn necessitates a method of synchronizing the relative timecodes of the proxy and high-resolution files. 
   Producing a high-resolution video and one or more proxy files with frame accurate synchronized relative timecodes of the proxy and high-resolution files is problematic, because two or more MPEG encoders and the source playout device must be started frame accurately, and the encoders must be capable of extracting SMPTE timecode (VITC) from the vertical blanking interval and storing the timecode in the MPEG Group of Pictures (GOP) header. (Some broadcasters may allow the encoders to encode alternately the locally produced house SMPTE timecode, instead.) Moreover, the encoders must not drop or repeat any frames during the encoding process, and the encoders must stop on the same video frame. 
   Although there are commercially available MPEG encoders that are capable of producing such proxy files, these encoders are prohibitively expensive and are not economical for an archive librarian planning to operate many ingest stations. Moreover, these high-end encoders often store the MPEG data in a vendor proprietary elementary stream format, which makes them uninteroperable with other MPEG decoders. Therefore, video files sent to another broadcast facility must be first remultiplexed into a MPEG compliant format. It is also undesirable from a business perspective to use a nonstandard storage format. Video quality and reliability are the normal criteria for selecting an encoder vendor. However, there is also a need to create proxy files using good-quality, but less capable MPEG encoders. An encoder that fails to store proper SMPTE time in the GOP header, for example, should not be eliminated from consideration, if it meets all other broadcaster requirements. 
   For all but a few high-end MPEG encoders, it is exceedingly difficult for an ingest application to consistently start multiple encoders and video sources with frame accurate timecodes. This can be attributed to the following factors: the inherent latency of MPEG encoders configured to encode at different rates and GOP configurations; operating systems, such as UNIX, AIX, and Windows NT, are not real-time operating systems with low interrupt service latency, consistent thread dispatch and a strict priority enforcement, packet delay when controlling encoders over a TCP/IP network; and inconsistent performance of audio/video equipment. 
   To facilitate the composition of EDL for the production of video programming, it is imperative that both the proxy and high-resolution video files be frame-accurately timestamped. Having to later re-encode proxy files to correct frame inaccuracies significantly increases the cost of operating of video archive. There is a demonstrable need to be able to adjust the timecodes of proxy files, when the starting frame of a proxy MPEG file is offset from the starting frame of its associated high-resolution MPEG file. 
   Presently, there are also problems with Storyboard Timecodes and EDL Composition. Conventional video catalogers capture either the elapsed time or the absolute timecode when creating thumbnails. This is problematic if the video source has anomalous timecodes, because the thumbnail timecode cannot be utilized for either EDL composition or play from offset commands. Storing both relative and absolute timecodes with each thumbnail would provide advantage over prior art. If discontinuous absolute timecodes were encountered, relative timecodes would be used instead, to create EDL and cue the MPEG player. Further advantage would be gained from modifying the EDL builder application to compose EDL statements using either relative or absolute timecode. Automatic switching to relative timecodes would allow librarians to maintain and view the original source timecodes, while generating a frame-accurate EDL. 
   Therefore, a need exists for the post-encoding modification of MPEG file timecodes, to create frame accurate timecodes. It is desirable to be able to adjust the timecodes of proxy files, when the starting frame of a proxy MPEG file is offset from the starting frame of its associated high-resolution MPEG file, to synchronize relative timecodes of the proxy and high-resolution files. It would be further advantageous to automatically verify and correct bad timecode when ingesting assets for permanent archival, and to be able to re-stripe or change the timecode of the material, to suite the operational requirements. It would be further advantageous to be able to update the timecodes attached to each thumbnail in the storyboard, and any timecodes referenced in any existing description of the video and audio program, whenever the SMPTE timecodes in the high-resolution file have been modified. 
   SUMMARY OF THE INVENTION 
   The foregoing and other objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments which makes reference to several drawing figures. 
   One preferred embodiment of the present invention is a method of processing a previously encoded MPEG video high-resolution (HR) file and corresponding proxy file, for frame accurate timecode repair and synchronization of individual video frames of the HR file and proxy file. The method has the following steps:
         (a) for each video frame of the HR file and proxy file, creating a compressed timecode packet having an identifying signature, an absolute timecode of the frame, a relative timecode of the frame, a picture type and a picture reference, wherein the timecodes having the SMPTE timecode format HH:MM:SS:FF;   (b) modifying the HR file and proxy file by inserting in a header of each video frame of the HR file and proxy file the corresponding compressed timecode packet, while maintaining the files&#39; original frame presentation timing;   (c) automatically verifying the timecodes in the HR file and proxy file timecode packets;   (d) if needing a repair of the HR file anomalous absolute timecodes, automatically correcting the anomalous absolute timecodes in the HR file timecode packets; and   (e) if the proxy file starting video frame being offset from the HR file starting video frame, automatically synchronizing the proxy file and the HR file absolute timecodes and relative timecodes in the timecode packets,   thereby preserving the MPEG compliance and compressed audio/video data of the HR file and proxy file.       

   The timecode packet is automatically inserted in a user data packet of the video frame, between a picture start header and a first slice header. The step of inserting the timecode packet preferably includes a step of periodically removing the MPEG video file unused data bytes, equal in number with the inserted timecode packet bytes, for preserving the MPEG video file original size and multiplex bitrate. Alternatively, the step of inserting the timecode packet includes a step of increasing the MPEG video file original multiplex bitrate, to compensate for additional timecode packet bytes inserted into the MPEG video file. Step (d) further has a step for updating the absolute timecodes in the proxy file timecode packets, and a step for updating absolute timecodes and relative timecodes of each storyboard thumbnail, for enabling frame-accurate composition of an edit decision list (EDL). 
   Step (e) preferably has a step for aligning the HR file video frames and proxy file video frames using absolute timecodes, and a step for updating the relative timecodes in the proxy file timecode packets with the relative timecodes of the HR file. In the aligning step of step (e), if the proxy file has accurate absolute timecodes, aligning of the absolute timecodes of the HR file and proxy file is performed. If the absolute timecodes are not accurate, the step uses closed captioning for aligning the proxy file and HR file, and copying the absolute timecodes from the HR file into the proxy file timecode packets. If the HR file and proxy file are not being closed captioned, the closed captioning step further has a step, at the start of the aligning step, for inserting into a predetermined number of video frames of the HR file and proxy file a closed caption data stream for locating and aligning an identical video frame in the HR file and proxy file, and, after the file aligning step, a step for removing the inserted closed caption data stream from the HR file and proxy file. 
   Another preferred embodiment of the present invention is an apparatus implementing the abovementioned method embodiment of the present invention. 
   Yet another preferred embodiment of the present invention is a program storage device readable by a computer tangibly embodying a program of instructions executable by the computer to perform method steps of the above-mentioned method embodiment of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
       FIG. 1  is an illustration of a conventional video ingest/cataloging system, according to a prior art; 
       FIG. 2  depicts the placement of the timecode repair/synchronization application, executing within the video cataloging system, according to the preferred embodiments of the present invention; 
       FIG. 3  illustrates the formatting of an MPEG file as originally encoded, and with timecode packets inserted according to the preferred embodiments of the present invention, while maintaining the same bitrate and file length; 
       FIG. 4  illustrates a data structure of a compressed MPEG user data packet containing encoded timecode and frame information, according to the preferred embodiments of the present invention; 
       FIG. 5  illustrates a data structure of a compressed MPEG user data packet containing encoded introductory timecode and framing information structure, used to mark the first frame of a proxy file, according to the preferred embodiments of the present invention; 
       FIG. 6  illustrates the synchronization of the relative timecodes of a high-resolution video file and its associated proxy file when the proxy file is of longer duration, according to the preferred embodiments of the present invention; 
       FIG. 7  illustrates the synchronization of the relative timecodes of a high-resolution video file and its associated proxy file when the proxy file is of shorter duration, according to the preferred embodiments of the present invention; 
       FIGS. 8A and 8B  represent a logic flow diagram of the video encoding routine of a video ingest application, according to the preferred embodiments of the present invention; 
       FIGS. 9A and 9B  represent a logic flow diagram of the main software routine of the timecode repair/synchronization application, according to the preferred embodiments of the present invention; 
       FIG. 10  is a logic flow diagram of a software routine for detecting and repairing timecode errors in a high-resolution file, according to the preferred embodiments of the present invention; 
       FIG. 11  is a logic flow diagram of a software routine for updating the absolute timecodes of a proxy file, according to the preferred embodiments of the present invention; 
       FIG. 12  is a logic flow diagram of a software routine for synchronizing a proxy file with its associated high-resolution video file, using absolute timecodes to align the two video streams, according to the preferred embodiments of the present invention; 
       FIG. 13  is a logic flow diagram of a software routine for modifying the relative timecodes of a proxy file, according to the preferred embodiments of the present invention; 
       FIG. 14  is a logic flow diagram of a software routine for synchronizing a proxy file with its associated high-resolution video file, using encoded closed caption data to align the two video streams, according to the preferred embodiments of the present invention; 
       FIG. 15A  illustrates the logic flow of a software routine for removing closed caption data from the MPEG files that were inserted by the timecode repair/synchronization application, according to the preferred embodiments of the present invention; 
       FIG. 15B  is a logic flow diagram of a software routine for updating the absolute timecode of each thumbnail in the video storyboard, according to the preferred embodiments of the present invention; 
       FIG. 16  is an illustration of the graphical user interface (GUI)) of the MPEG player and EDL builder, used by a video cataloging application to display streaming video and metadata, according to the preferred embodiments of the present invention; and 
       FIG. 17  is an illustration of the graphical user interface used by a video cataloging application to view both the high-resolution and the proxy videos for the purpose of manual synchronization, according to the preferred embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the following description of the preferred embodiments reference is made to the accompanying drawings which form the part thereof, and in which are shown by way of illustration of specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional changes may be made without departing from the scope of the present invention. 
   The present invention is directed to a method and system for processing an MPEG-1 or MPEG-2 video file, to modify the absolute SMPTE timecodes to fix incorrect or anomalous timecodes. The method and system can further detect inaccurate timecodes in a proxy file and adjust, forward or backward, the relative SMPTE timecodes of the proxy file, when the proxy file is not a replica of its associated high-resolution video file, to enable frame-accurate composition of EDL, and to synchronize the proxy file frames with the corresponding video frames of the high-resolution video file. Furthermore, the present invention stores timecode synchronization metadata in the first frame of the proxy file, to signal a disparity in the durations of the proxy and high-resolution video files. It may also mark frames of the proxy file as unviewable, when there is no corresponding frame in its associated high-resolution video file. 
   Since the generated timecode synchronization metadata flags must be stored on a frame basis, the present invention relies heavily on the technique for inserting timecode packets taught in the co-pending application entitled “System and Method of Processing MPEG Streams For Timecode Packet Insertion”, which inserts timecode packets as user data after the picture header of each frame. Subsequent to the insertion of the timecode packets into the MPEG file and storing of the apposite video metadata into the catalog record, the present invention reprocesses the MPEG video file storing the timecode metadata information in unused fields of the timecode packets. 
   The preferred embodiments of the present invention also stores information in the first video frame, in order to indicate the source of the video timecode and any timecode repair action taken. It also stores both relative and absolute timecodes with each thumbnail in a storyboard. It further allows the EDL builder application to automatically detect anomalous timecodes in the storyboard and proxy file, and to use relative timecodes instead, when generating EDL statements. 
   In order to track the timecode origin and the disparity in video lengths of the proxy and high-resolution files, the following synchronization metadata flags and fields may be defined by the present invention in miscellaneous fields of a timecode data packet of the proxy file: no high-resolution frame match, proxy file start truncated, proxy file end truncated, timecode offset between proxy and high-resolution files expressed as a frame count, and a source of absolute timecode field. These fields create a set of timecode synchronization metadata which are static, that become a permanent part of the proxy file retained for the duration of video playout. 
   In the preferred embodiments of the present invention, the timecode repair and synchronization application (TRSA) software is automatically invoked upon completion of ingest encoding. After the timecode packets have been inserted into the proxy files, the absolute timecodes of the high-resolution (HR) video files are examined and corrected, if the timecode repair feature has been enabled. If the HR timecodes require modification, the absolute timecodes in the proxy files and storyboard are likewise updated. 
   If the automatic synchronization of the HR video files and proxy files feature is enabled, the TRSA proceeds to synchronize the relative timecodes, using either absolute timecode (if the proxy MPEG encoders are frame-accurate) or closed caption data, to precisely align the frames of the HR video files and proxy files. When closed captioning is needed for synchronization and the source material has not been closed captioned, the ingest application injects a short closed caption data stream at the start of encoding. After the files have been synchronized, the injected closed caption characters are removed from the video files. 
   In an alternate preferred embodiment of the present invention, the timecode synchronization of the HR video files and proxy file is performed manually, utilizing a graphical user interface (GUI) of an MPEG player that permits a librarian to simultaneously view the HR and proxy files. Using the VTR controls of the MPEG player, the librarian locates an identical frame in both the proxy and HR player, and clicks a GUI button to command the TRSA application to synchronize the relative timecodes of the two files. 
     FIG. 1  is an illustration of a conventional video ingest/cataloging system, according to a prior art. In  FIG. 1 , a video tape recorder  100  provides a source video for encoding. An ingest/catalog application  125  controls, in parallel, three MPEG encoders  105 ,  115 ,  120 , which produce a high-resolution video file and two proxies. The high resolution MPEG encoder  105  is integrated with a broadcast video server  110 . As the ingest/catalog application  125  creates MPEG files  128  and associated metadata  135 , catalog records in a video library catalog  130  are created or updated using a video library application  140 . The cataloging and indexing of the video files enables subsequent search and retrieval. 
   Upon completion of encoding, the compressed files are moved onto a streaming video server  145  which is capable of file FTP or isochronous streaming to MPEG decoders/players  160 . All video content is copied to a tape library/archive  150  for long term storage, and retrieved as necessary. Catalog records are individually examined using a cataloger/metadata viewer  165 . The full video file or any part thereof may be viewed via the MPEG player  160 . The system also incorporates a broadcast editing suite  155 . 
     FIG. 2  illustrates the system preferred embodiment of the present invention, where an ingest/cataloging application  230  receives a catalog record from a video library catalog file  240 , and updates the metadata in a metadata file  245  of a video library application  255 . The invocation of a timecode repair/synchronization application (TRSA)  265  is automatically triggered by a workflow manager  235 , upon receiving notification from the ingest/cataloging application  230  that encoding has been completed. In  FIG. 2 , there is a video tape recorder  200 , a video line encoder  225 , and an MPEG-2 encoder  215 . Proxy files produced by two low resolution encoders, MPEG-2 encoder  205 , and MPEG-1 encoder  210 , and are stored on a hard drive  260  of a separate server having the TRSA  265 , to be processed by the TRSA. As an ingest/cataloging application  230  signals job completions to the workflow manager  235 , the workflow manager  235  invokes the TRSA  265  to optionally repair and/or synchronize the timecodes of the HR video file and proxy file, and then copy the modified file to a streaming video server  250 . The repair/synchronization process necessitates the retrieval of the HR file from a broadcast video server  220 , for playout to air. The system of  FIG. 2  may also include a high-resolution MPEG player  270 , and a proxy MPEG player  275 . 
   To automate the synchronization of timecodes when using non frame-accurate proxy encoders, the present invention injects a stream of numeric characters into the video stream as closed caption data, which are encoded by the VBI line encoder  225 . Once the TRSA  265  has confirmed that all encoders have begun file encoding, the closed captioning is halted. 
     FIG. 3  illustrates the formatting of an MPEG file as originally encoded, and with timecode packets inserted according to the preferred embodiments of the present invention, while maintaining the same bitrate and file length. Thus,  FIG. 3  provides a high level, non-scaled illustration of the MPEG file format before and after timecode packet insertion, while maintaining the original multiplex bitrate and file size. After a PES  300 , an 18-byte timecode packet, formatted as a user data packet  310 , is placed between a picture header  305  and a first slice header  315  of each video frame. The timecode packet is inserted into other video packets, such as video packets-2  330  and video packets-3  340 . When a first padding packet  360  is encountered, it is reduced in size to balance out the surplus of timecode packet bytes. Thus, the presentation and decoding timestamps do not require recalculation of the video file size. 
     FIG. 4  illustrates a data structure of a compressed MPEG user data packet containing encoded timecode, frame information and metadata, according to the preferred embodiments of the present invention. In  FIG. 4 , each timecode packet compressed data structure begins with a standard user data start code  400 , followed by a unique 13-bit signature  404  (such as 0xAAA8) that disambiguates the timecode packet user data from other user data packets that may be present. Three markers, denoted in  FIG. 4  by ‘X’, are placed throughout the remaining data bytes to prevent start code emulation. These markers are also checked by the decoding MPEG player as part of the signature verification. A relative timecode  410  and absolute timecode  414  are encoded in the next 6 bytes, followed by a picture PTS  420 , and picture type and reference field  424 . The high order bit of the absolute timecode field  414  has been usurped to be used as a ‘No HR match’ (N) flag, to signal the MPEG player that there is no corresponding HR video frame for this proxy frame. An 8-bit checksum  430  enables the decoder to detect packet bit errors. There may also be some optional padding fields  434 .  FIG. 4  also illustrates a legend and the preferable format and hexadecimal value of each byte of the timecode packet. 
   The present invention generates other metadata associated with timecode synchronization and identification, that must be permanently stored within the proxy file. This is accomplished by creating a second type of timecode packet, referred to as an introductory timecode packet, that utilizes the last two padding bytes of the standard timecode packet of  FIG. 4 , and gets inserted into the first video frame of the proxy file. When the packet is decoded by the MPEG player, the timecode metadata are extracted and retained for the duration of video playout. Referring now to  FIG. 5 , the introductory timecode packet starts with a standard user data start code  500 , and contains its own unique signature  505  (0xBBB8), to distinguish it from the standard timecode packet. A relative  510  and absolute  515  timecodes are encoded in the next 6 bytes, followed by a picture PTS  520 , and picture reference and type field  525 . An 8-bit checksum  530  enables the decoder to detect packet bit errors, 
     FIG. 5  also illustrates a legend and the preferable format and hexadecimal value of each byte of the timecode packet. As can be seen in the legend of  FIG. 5 , a timecode repair information field  535  contains two flags (U,V) to signal a truncated proxy file start and end flags, a timecode type field (Y), and a proxy offset field (Z), which encodes the starting timecode differential as a frame count. The proxy offset field is 9 bits in length, with a tenth bit that signs the value. The range of +/−511 frames provides the ingest application with a window of 34 seconds for starting the proxy encoder. Lastly, the timecode type identifies the source of the absolute timecode as original source timecode, repaired timecode, elapsed timecode or house timecode. 
     FIG. 6  illustrates an HR  600  and proxy file  605 , where the proxy file  605  has extra frames at the beginning and end that are not present in the HR file  600 , so that the proxy file is of longer duration than the HR file. Further shown are relative timecodes of the proxy file: a relative timecode  610  before the timecode synchronization has occurred, and a relative timecode  615  after timecode synchronization has occurred. The proxy relative timecodes  615  have been adjusted to match relative timecodes of the HR file  625 . The extraneous leading and trailing proxy frames are each marked with a ‘No HR Match’ flag, that will cause the MPEG player to suppress rendering so that they are never viewed by the end user. 
   Similarly,  FIG. 7  illustrates the synchronizing of a HR video file  700  and proxy file  705 , where the proxy file is of shorter duration than the HR file. To synchronize the proxy file with the HR file, the relative timecodes  710  of the proxy file  705  are adjusted to commence at the same relative timecode  715 ,  725  of the corresponding HR video frame, and ‘truncated’ flags are set accordingly. Although the truncated proxy prevents the end user from viewing the extremities of the HR file, in practice, the loss of a few leading and trailing frames is usually of little consequence. However, if the missing proxy frames are considered problematic, the ingest application can be configured to start proxy encoders earlier, to ensure the proxy file is always longer than the HR file. 
   After synchronization, the TRSA calculates and stores the original difference between the HR and proxy relative timecodes. This proxy timecode offset may be a positive or negative value. Since the absolute timecodes  720  are used to synchronize the relative timecodes, they are synchronized at an earlier stage in the process, but absolute timecode synchronization is only required when the proxy encoder does not provide reliable timecodes. 
   MPEG File Encoding 
     FIGS. 8A and 8B  represent a logic flow diagram of the video encoding routine of a video ingest application, that encodes the HR and proxy files according to the preferred embodiments of the present invention. In  FIGS. 5A and 5B , the VTR containing the source video material is commanded to start in step  800 , and the AutomaticSync input parameter is tested in step  810  for the set condition. Automatic synchronization is the default application behavior, which must be overridden by the AutomaticSync input parameter in order to suppress it. 
   In order to automate the synchronization process, the TRSA requires either frame-accurate absolute timecodes in the proxy files, or closed captioning in the source material. If the proxy encoder does not provide frame accurate timecodes, and the source material is not closed captioned, then the ingest application must generate its own character stream and enable the VBI line encoders to insert the characters as NTSC line  21 , field  1  closed caption data, in a predetermined number of frames at the beginning of the video file. Since line  21  is limited to two characters, the application generates a stream of unique alphanumeric character pairs, such as AA, AB, AC, AD, . . . ending with 97, 98, 99. This pattern generates 1296 unique character pairs, which is sufficient for 43 seconds of closed captioning. 
   Continuing in  FIGS. 8A and 8B , if automatic synchronization is enabled in step  810 , it is tested in step  815  whether the input video is not flagged as closed captioned material in the catalog record, and in step  820  whether the proxy encoder does not provide reliable absolute timecode. If the yes condition of step  820  is reached, the ingest application enables the VBI line encoder and starts the closed caption character stream in step  825 , and a flag is set in step  830  to signal the start of character generation. If, in step  815 , the source video is found to be closed captioned, or the proxy encoder is found in step  820  to provide dependable timecode, the need to insert close caption data is precluded, and the code falls through to step  834  to start the HR encoder, and to step  838  to start proxy encoder. 
   After commanding the encoders to start, if the CCStreamStarted flag is set in step  842 , the code enters a loop in step  846  where the proxy encoders are continuously queried, to verify that encoders have begun streaming MPEG data to be saved on a disk. While a delay of up to 200 milliseconds is common, some encoders may greatly exceed this value. Once the data streams have been verified, the application disables the VBI encoders and terminates the closed caption character stream in step  850 . 
   The application then enters another loop in step  854 , for monitoring the VTR for the end of material timecode. When the video out-point has been detected, the yes condition in step  854 , in step  858  the HR encoder is commanded to stop, in step  862  the proxy encoders are commanded to stop, and in step  866  the VTR is commanded to stop. The video is then run through a video cataloger in step  870 , using the proxy file as input. In an alternate embodiment, the video cataloging may have occurred concurrently as the file was encoded. After the cataloging has been completed, the generated storyboard is retrieved in step  874 , and processed to add the absolute timecodes to the already captured relative timecodes. In step  878 , a loop starts for each thumbnail, and the relative timecode is read in step  882  and used to locate the captured frame timecode packet in the proxy file in step  886 . The absolute timecode is then read in step  890  and copied to the thumbnail in step  894 . When all thumbnails are processed the loops exits, the modified storyboard is stored in the library in step  896 . The encoding routine then posts a message to the workflow manager to signal ingest completion in step  898 , and the routine returns to the caller in step  899 . 
   MPEG File Processing 
     FIGS. 9A and 9B  represent a logic flow diagram of the main software routine of the timecode repair/synchronization application, according to the preferred embodiments of the present invention. In the preferred embodiments, the application is automatically scheduled and invoked by the workflow manager. There are two primary input parameters that control application processing, Repair HR Timecode and AutomaticSync, both of which are enabled by default. The Repair HR Timecode parameter triggers the automatic detection and correction of anomalous timecodes. The AutomaticSync parameter enables the TRSA to automatically synchronize the proxy&#39;s relative timecodes with the relative timecodes of the HR file. A third parameter, No Proxy Absolute TC, is specified if the proxy encoders do not timestamp the proxy MPEG files with accurate, trustworthy SMPTE timecodes, that mirror the timestamping of the HR encoder. When this parameter is set to 1, the TRSA extracts the absolute timecodes from the HR file and inserts them into the proxy timecode packets. Furthermore, when this parameter is set, the TRSA uses closed captioning to align and synchronize the proxy and HR files, since the accuracy of the absolute timecodes is suspect. If none of the three input parameters are specified, the processing of the TRSA is limited to the insertion of the timecode packets into the proxy files. Finally, when the Repair HR Timecode parameter is set, there is a secondary input parameter that dictates how the bad timecode is to be corrected. The parameter value may be set to Repair Original Source, Use House Timecode or Use Elapsed Timecode. 
   In  FIGS. 9A and 9B  the application processing commences in step  900  by inserting the introductory timecode packet into the first video frame, and in step  905  by inserting the standard timecode packet into the remaining video frames If none of the three input parameters, AutomaticSync, No Proxy Absolute TC or Repair HR TC is found set in step  910 , the applications ends in step  999 . Otherwise, the HR MPEG file is retrieved from the broadcast video server in step  915 , to read the absolute timecodes. The Repair HR TC parameter is tested in step  920 , to determine if the HR timecodes should be examined and repaired. If the HR timecode repair parameter is enabled, the Check and Repair HR Timecode routine of  FIG. 10  is called in step  925 . 
   HR Timecode Repair 
     FIG. 10  is a logic flow diagram of a software routine for detecting and repairing timecode errors in a high-resolution file, according to the preferred embodiments of the present invention. In  FIG. 10 , in steps  1000  and  1010  the starting timecode and the drop-frame mode of the HR video are compared to the start-of-material (SOM) timecode and the drop-frame mode, respectively, as specified in the catalog record. If the HR file is compliant, a yes condition in both operations, the logic falls into a loop in step  1015 , and each frame is tested for properly incrementing timecode in step  1020 . The correct timecode results in the no condition in step  1020 , and when the final frame has been tested, the loop exits in step  1015 , and the routine returns in step  1090 . A disruption of timecode detected in step  1020  causes a breakout of the loop and a timecode repair type parameter has to be tested to determine how to repair the discontinuous HR timecode. 
   If, in step  1025 , it is found that the original timecode is to be repaired, the timecode of the previous frame is incremented by one frame in step  1030 , and the code continues on to initiate the repair. If, in step  1035 , it is found that the house timecode is to be used, the current house timecode is read in step  1040 , and the file pointer is reset to the first frame (0) in step  1055 , because the entire file needs to be restriped with timecode. If the use of the house timecode is not detected in step  1035 , the code defaults to use elapsed timecode, the current timecode is reset to the first frame (0) in step  1050 , and the file pointer is reset to the beginning of the first frame of the file in step  1055 . Returning to the tests of steps  1000  and  1010 , a failure of either test results in step  1005  for the correct timecode to be loaded from the catalog record, and in step  1012  for the drop-frame mode to be loaded from the catalog record. 
   The operation of  FIG. 10  continues in step  1060  with restriping the HR absolute timecodes. Since the file pointer is currently set at the first frame of video, there is no need to reset it. The code paths for all corrective actions converge at step  1060 , where the HR Modified global flag is set to 1. The setting of this flag will eventually result in the updating of both the proxy file and storyboard. The timecode type is then updated in the catalog record in step  1065 , and the routine falls into a loop in step  1070 , where the timecode of each remaining frame in the file is updated in step  1075 , as the timecode is incremented in step  1080 . When the end-of-file is detected in step  1070 , the loop exits and the routine returns in step  1090 . 
   Returning to  FIGS. 9A and 9B , the processing advances to step  930 , to test whether the absolute timecodes in the proxy file require updating. The proxy file is only updated if the proxy file has a reliable absolute timecode, and the HR file has had its absolute timecodes modified. Proxy files with unreliable absolute timecode will have its timecode aligned using closed caption data. If the proxy file requires timecode update, in steps  935 ,  940  the absolute timecodes of HR and proxy files are loaded, respectively, and passed in step  945  to the Update Proxy Absolute Timecodes routine of  FIG. 11 . 
   Updating Proxy Absolute Timecode 
     FIG. 11  is a logic flow diagram of a software routine for updating the absolute timecodes of a proxy file, according to the preferred embodiments of the present invention. Before the timecodes are copied from the HR file to the proxy file, the file pointers of the two files are set to point at the same video frame. In step  1100  of  FIG. 11 , the two input timecodes are compared to determine which file has the later timecode. If the proxy file has the later timecode, the HR timecode is subtracted from the proxy timecode in step  1120 , and the result itself is used as a relative timecode with which to index into the proxy file in step  1125 . Then, the HR file pointer is positioned at the first frame of video, in step  1130 . 
   If the HR file timecode was found in step  1100  to be the larger of the two, the same process is conducted on the HR file timecode in steps  1105  and  1110 , and the proxy file is set to the first frame of video, in step  1115 . Then, the absolute timecode type flag is read from the catalog record and written into the proxy&#39;s introductory timecode packet in step  1135 . In the subsequent processing loop, starting in step  1140 , for each remaining frame of the proxy file, the absolute timecode is read from the corresponding HR frame in step  1145 , and written into the proxy file timecode packet in step  1150 , as absolute timecode. The routine returns in step  1155 , when the loop of step  1140  exits on a no condition. 
   Returning to the application&#39;s main routine of  FIGS. 9A and 9B , the AutomaticSync input parameter is tested in step  950 . If set, a further test is conducted to determine whether to synchronize absolute timecode by using proxy file absolute timecodes or closed caption characters. If the proxy file has trustworthy absolute timecodes, the no condition in test of step  955 , the Synchronize Relative Timecodes routine of  FIG. 12  is called in step  960 . Otherwise, the Synchronize Absolute Timecode Using CC Data routine is invoked in step  965 , to first synchronize the absolutes timecodes before processing the relative timecodes of the proxy file, according to  FIG. 14 . 
   Relative Timecode Synchronization 
     FIG. 12  is a logic flow diagram of a software routine for synchronizing relative timecode of a proxy file with its associated high-resolution video file, using relative timecodes to align the two video streams, according to the preferred embodiments of the present invention. In  FIG. 12 , synchronization from relative timecode begins by subtracting the starting HR timecode from the start proxy timecode in step  1200 . This result, referred to as the proxy timecode offset, is then stored in the proxy&#39;s introductory timecode packet in step  1205 . If, in step  1210 , it is found that the starting proxy timecode is earlier than the starting HR timecode, the proxy encoder began encoding before the HR encoder and, in step  1215 , the ‘No HR Match’ flag is set in the timecode packet of each extraneous proxy frame. The logic then continues to compare the end of the files. If the first proxy timecode was not found to be earlier than the first HR, in step  1210 , the starting proxy timecode is retested in step  1220  to determine if it starts after the HR file timecode. If so, the ‘Truncated Proxy Start’ flag is set in the introductory timecode packet in step  1225 . Otherwise, the proxy and HR files have equal starting times indicating synchronized timecodes. 
   In step  1235 , the ending timecodes of the proxy and HR files are compared in a similar fashion. If the proxy ending timecode is greater than the HR, the ‘No HR Match’ flag is set in step  1240  in the trailing proxy frames. If, in step  1245 , the proxy timecode is less than the HR timecode, the Truncated Proxy End is flagged in the introductory timecode packet in step  1250 . Again, if both ending timecode comparisons fail, it indicates that both the proxy and HR encoders halted encoding on the same frame. After marking the extraneous trailing proxy frames, the proxy timecode offset value is tested for a value zero in step  1255 , to determine if the proxy&#39;s relative timecode requires adjustment. If the offset equals zero, both files started on the same frame and the relative timecodes are in sync. Otherwise, the Restripe Proxy Relative Timecodes routine of  FIG. 13  is called in step  1260  to adjust the proxy&#39;s relative timecodes accordingly, and the routine returns in step  1265 . 
   Adjusting the Proxy&#39;s Relative Timecodes 
     FIG. 13  is a logic flow diagram of a software routine for modifying and adjusting the relative timecodes of a proxy file, according to the preferred embodiments of the present invention. In  FIG. 13 , if the proxy timecode offset is found to be positive in step  1300 , the proxy encoder started before the HR thus creating a timecode mismatch, as illustrated in  FIG. 6 . This is corrected by starting the first relative timecode at zero in step  1310 , and advancing the file pointer to the offset of the proxy file frame, that will be designated as the first viewable frame, in step  1315 . If the proxy timecode offset was not found to be positive in step  1300 , it is converted to a positive integer and used as the first relative timecode in step  1305 . With the value of the first relative timecode established, the routine enters a loop in step  1320 , to process each frame in the proxy file. Ignoring the leading frames that have been found in step  1325  to be No HR Match, each of the subsequent video frames is assigned a new relative timecode in step  1330 , and the timecode is incremented in SMPTE fashion in step  1335 . When the last frame has been updated, the routine returns in step  1340 . 
   Absolute Timecode Synchronization Using Closed Caption Data 
     FIG. 14  is a logic flow diagram of a software routine for synchronizing a proxy file with its associated high-resolution video file, using encoded closed caption data to align the two video streams, according to the preferred embodiments of the present invention. In  FIG. 14 , the TRSA uses the encoded closed caption characters inserted into each frame to locate identical frames in the proxy and HR files for precise alignment, so that the absolute timecodes of the HR file may be copied over to the proxy file. Once the two files have identical absolute timecodes, the Synchronize Relative Timecodes routine is called to mark up the proxy file and synchronize the relative timecodes. 
   The routine of  FIG. 14  begins by looping through the HR file in step  1400 , extracting the closed caption data. When, in step  1405 , a frame is found with two alphanumeric characters (this test specifically excludes the closed captioning control characters), the timecode and the found characters are recorded in step  1410 . To ensure uniqueness, the loop iterates until a second frame with two alphanumeric characters is located in step  1415 . The code then falls into an identical loop starting in step  1425 , that processes the proxy file to locate two frames, each having a pair of alphanumeric closed caption characters, in steps  1430 ,  1435  and  1440 . If the end-of-file is found in step  1400  or  1425  before two qualifying frames are found, and error code is set in step  1485 , the routine exists in step  1499 , and the files will have to be manually synchronized by an archive librarian. 
   After the two frames are found in each file, in step  1450  the two sets of characters extracted from each file are compared, to determine the amount of frame separation between the two samples. If the comparison test shows equal frame separation in both files, a yes condition, identical frames have been located in the two MPEG files, HR and proxy file, allowing the files to be synchronized. If the comparison fails, the logic returns to the top of the routine, step  1400 , to resume the search from where it left off. Proceeding with a known frame offset, the first found relative HR timecode and proxy timecode, in step  1455  and  1460 , respectively, are loaded and passed to the Update Proxy Absolute Timecodes routine of  FIG. 11 , in step  1465 . This routine copies the absolute timecodes from the HR file frames to the corresponding proxy frames. The Synchronize Relative Timecodes routine is then invoked in  1470  to complete the synchronization. Upon return, if, in step  1475 , it is found that close captioning was inserted by the ingest application, the Remove Injected Closed Caption Data routine is called in step  1480 , to expunge the injected alphanumeric characters. The routine returns in step  1499 . 
   Removing the Injected Close Caption Data 
     FIG. 15A  illustrates the logic flow of a software routine for removing closed caption data from the MPEG files, that were inserted by the timecode repair/synchronization application, according to the preferred embodiments of the present invention. To remove the injected closed caption data from each MPEG file, in  FIG. 15A  the routine initiates an outer loop starting in step  1500  to process each encoded MPEG file. An inner loop is started in step  1505 , which examines each frame of the chosen file for a closed caption user data packet. If a closed caption packet is discovered in step  1510 , it is overwritten with zeros in step  1525 , to prevent it from being decoded by the player. If no such packet was found, a ‘no CC packet found’ counter is incremented in step  1515 , and the counter is compared in step  1520  to the file GOP size. Once an entire GOP is found to be free of closed caption packets in step  1520 , it is safe to assume that all injected closed caption packet have been found and cleared, and the outer loop iterates to step  1500 , to the next file. 
   Returning again to the main application routine of  FIGS. 9A and 9B , after synchronization has been completed, the HR Modified global flag is tested in step  970  to determine if the HR absolute timecodes were modified. If so, the storyboard timecodes also need to be updated in Update Absolute Timecodes in Storyboard routine of  FIG. 15B , to keep in synch with the actual high-resolution content. 
   Updating Storyboard Timecodes 
     FIG. 15B  is a logic flow diagram of a software routine for updating the absolute timecode of each thumbnail in the video storyboard, according to the preferred embodiments of the present invention. In  FIG. 15B , after retrieving the storyboard from the library in step  1550 , the routine enters a loop in step  1555  to process each thumbnail in the storyboard. For each thumbnail found in step  1555 , the thumbnail&#39;s relative timecode is loaded in step  1560 , and used in step  1565  to index into the proxy file to locate the timecode packet. The proxy&#39;s absolute timecode is loaded in step  1570 , and used to update the thumbnail&#39;s absolute timecode in step  1575 . When the last thumbnail has been processed, the no condition in step  1555 , the updated storyboard is saved in the library in step  1580  and the routine returns in step  1585 . 
   Upon return, the main routine of  FIGS. 9A and 9B  copies the modified HR file to the broadcast server in step  985 , the local copy of the HR file is deleted in step  995 , and the application ends in step  999 . If the test of step  950  for automatic synchronization resulted in the no condition, the HR Modified flag is checked in step  980 , in case that the HR file underwent a timecode repair. If the HR file was updated, it is copied to the broadcast server in step  990 , the local copy is purged in step  995  and the application ends in step  999 . 
   Library Administrator&#39;s MPEG Decoder/Player/EDL Builder 
   The introductory and standard timecode packets are extracted, decompressed and stored into global memory by the MPEG Decoder/Player/Metadata Viewer/EDL Builder, as the file is decoded, to assist in composing EDL statements. The timecode information and synchronization metadata can be referenced by any application via an API interface. 
     FIG. 16  is an illustration of the graphical user interface (GUI) of the MPEG player, metadata viewer and the EDL builder  1600 , used by a video cataloging application to display streaming video and synchronization metadata, according to the preferred embodiments of the present invention. In  FIG. 16  VCR controls  1602  are provided, and a video display area  1605  reflects a stopped video with a current position of 00:02:22:27. Relative timecode  1615 , absolute timecode  1620 , and duration  1625  of the current frame are displayed. These timecodes are captured by the application in response to the end user clicking a mark-in  1680  and mark-out  1685  buttons, to define the starting and ending frames of a video clip. A jump to button  1630  and a timecode selected field  1635  are also provided. The lower portion of the window provides a display area for the catalog record  1675 , and a compiled EDL display area  1670 . 
   A storyboard display area  1640  contains  16  thumbnails  1645 ,  1650 , each annotated with a relative and absolute timecode. An absolute timecode type field  1628  indicates that the timecode is an original source timecode in this example, and fields  1695 ,  1696 ,  1697  and  1698  indicate synchronization status as a no HR match  1695 , a proxy start truncated  1696 , a proxy end truncated  1697 , or a discontiguous timecode  1698 . The checked fields  1696  and  1697  inform the end user that both the beginning and end of the proxy video are truncated with respect to the high-resolution video file. A Proxy TC Offset field  1699  shows that the first frame of the proxy video starts 4 frames into the high-resolution video. 
   No HR match field  1695  is reset on this display. The fact that the discontiguous timecode field  1698  is reset, indicates that the absolute timecode is continuous for the duration of the video. Thus, it causes the EDL builder to automatically select an absolute timecode on an absolute timecode button  1682 , when composing EDL statements. The end user however may override this setting and select a relative timecode on a relative timecode button  1687 , if anomalous timecodes in the storyboard and proxy file are detected, and to use relative timecodes when generating EDL statements. 
   Manually Synchronizing the Proxy and High-resolution Files 
   In another preferred embodiment of the present invention the synchronization of the HR file and proxy file is performed manually, by a librarian.  FIG. 17  is an illustration of the graphical user interface used by a video cataloging application to view both the high-resolution and the proxy videos for the purpose of manual synchronization, according to the preferred embodiments of the present invention. Preferably, the HR file is decoded with a hardware MPEG decoder which is capable of displaying the video on either a computer monitor  1780  (as shown) or on a separate video monitor. The proxy video is decoded with a software MPEG decoder/player  1700 . 
   The MPEG decoder/player  1700  has a relative timecode  1708 , absolute timecode  1710 , and duration  1712  of the current frame display areas. A jump to button  1736  and a timecode select button  1740  are also provided. The lower portion of the window provides a display area for a catalog record  1760 . A discontiguous TC indicator  1756  is also shown. A storyboard display area  1768  contains  16  thumbnails  1764 , each annotated with a relative and absolute timecode. The computer monitor  1780  has a relative timecode  1788 , absolute timecode  1792 , and duration  1796  of the current frame display fields. A jump to button  1703  and a timecode select button  1706  are also provided. 
   The librarian displays and freezes the first frame of a high-resolution video  1784 , and then steps through the proxy video frames  1704 , one frame at a time, until the corresponding frame is found. After selecting one of four timecode repair modes using an original source timecode button  1720 , a repair source timecode button  1724 , an elapsed timecode button  1728 , or a house timecode button  1732 , the user presses a synchronize files button  1744  to record the beginning timecode of the proxy file, and the TRSA synchronizes the proxy file with the HR file, accordingly. When synchronizing a video that fades out of black over several frames, the HR file must be frozen on a non-black frame, at some offset into the file. In this case, the user must enter the frame offset into an additional offset timecode field  1748 , before clicking the synchronize files button  1744 . This procedure synchronizes files when the proxy file begins before the HR file, as depicted in  FIG. 6 . 
   To fix up a proxy file that started encoding after the HR file, as seen in  FIG. 7 , the librarian must display the first frame of the proxy file and find the corresponding frame in the HR file. When found, the high-resolution timecode must be entered in a high-resolution timecode field  1752 , before commanding synchronization by pressing the synchronize files button  1744 . 
   The foregoing description of the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.