Abstract:
Automatic detection of errors among different formatted sound tracks of the same language on a motion picture film stock can be achieved by first acquiring successive audio segments from each of the sound tracks. During a time window of prescribed duration, the audio of each different formatted track undergoes analysis to yield a numeric value. The successive analysis of the audio continues until no further audio exists for analysis. The resultant collection of numeric values undergoes formatting into a numeric file for comparison against a reference file representing audio obtained from a particular source, such as originally recorded material, a sound print, or a duplicated copy of a sound film. If the difference between a formatted numerical file and the reference file exceeds a threshold value, then an error exists in that formatted sound track, and an operator can take appropriate action.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to checking the contents of multiple sound channels, and in particular, to checking soundtracks on a motion picture film stock.  
       BACKGROUND OF THE INVENTION  
       [0002]     Typically, motion picture films released for public exhibition include four soundtracks each recorded in a different format. The four different format soundtracks collectively comprise a “quad” format optical soundtrack. The quad format advantageously allows reproduction by equipment compatible with any one of the four-recorded formats. The four separate audio tracks have different locations on the film. For example, the sound track for a Digital Theater System Corp. or DTS® formatted sound file lies between the edge of the film frame and the SMPTE standardized location for a variable area audio track. (DTS® is a registered mark of the Digital Theater System Corp.) The DTS® code track provides a synchronization signal for an external DTS® CD player which can provide six audio channels. A Dolby SR® encoded track lies in the variable area audio track position and this signal provides backwards compatibility for cinema sound processors incapable of signal decoding. (Dolby SR® is a registered mark of Dolby Laboratories Inc.) The Dolby SR® track offers the simplest reproducing system, namely a stereo formatted audio signal, or stereo plus two additional channels. A Dolby Digital® (SR.D) track lies in the area between film perforations and supports six channels of audio and is typically known as 5.1. A fourth recording format developed by Sony and known as Sony Dynamic Digital Sound® or SDDS® offers eight channels of audio with data recorded at the edges of the film. (Sony Dynamic Digital Sound® and SDDS® are registered marks of Sony Corp.) In this way, the quad format optical soundtrack offers enhanced playback capability that is backwardly compatible with stereo variable area (SVA) cinema sound processors.  
         [0003]     To appreciate the composition of the quad format soundtrack, a consideration of the original sound assembly procedures will be helpful. A typical mixing operation to create a quad format sound track combines various separate sources, including dialogue, sound effects, ambiance, and music, with each originating from mono or multi-track sources. The mixing operation yields a six channel discrete sound format known as the original master mix. The term discrete sound format typically means that no relationship exists among different channels. The original master mix includes dialogue that represents about 95% of the normal sound content and is usually located in the center channel, sometimes 5% can be located or combined on left and/or right or surround channels and manipulated for effect, for example emanating from a radio, TV or telephone. If required, an operator can add reverberation on the center channel alone, or occasionally on the lateral or surround channel. Sound effects related to the dialogue, such as foot steps, etc exist with the dialogue in the center channel. Other effects can be located on the lateral or surround channels to increase the sound perspective. Special effects normally exist on all channels depending to the required result. Action ambiance is normally located in the lateral or surround channels. However, sometimes an operator will place the ambience in the center channel if such ambience exists as part of the original sound track. If an original music recording exists in a multi-channel format, the center channel will typically contain any solo instrument or vocalist. The lateral, surround and subwoofer channels provide the main support for the sound contents.  
         [0004]     During mixing of various signals, audio processors can provide reverberation and can add perspective by the use of delay or special filter functions, simulation on music or ambiance. These acoustic enhancements, while fully permissible, nonetheless can introduce unexpected and undesired phase shifts, during encoding, such as by as Dolby SR® encoding, and subsequently reproduced in a monaural or a two-track stereo format.  
         [0005]     In the digital film domain, the discrete tracks can very faithfully deliver to the listener the original sound perspective of the master mix. However, the various coding algorithms employed by the three digital systems can introduce differences into the sound. For example, one encoding system includes the subwoofer channel sound content in the surround channels, thus using just five tracks instead of six.  
         [0006]     Mixing the original six channel master mix into a four track master mix yields an analog format audio signal comprising left, right, center and surround channels. These four channels are processed, for example using a Dolby SR® 4:2 spatial encoder, to form a two-track encoded audio signal which enables stereo reproduction and, in addition, also enables decoding to restore the four tracks of the master mix with substantially similar quality. The encoder output produces two encoded channels identified as Left total and Right total or Lt-Rt. These two encoded tracks pass through two Dolby SR® noise reduction processors for recording on the optical negative film. During film exhibition, these two encoded tracks are reproduced and coupled, for example, via and appropriate Dolby SR® equipped reader followed by a 2:4 decoder which transforms the encoded channels Lt-Rt to recreate the original four discrete channels, Left, Right, Center and Surround.  
         [0007]     Ideally, the four soundtrack formats should be substantially similar in contents, if not identical, within the constraints of each individual system parameters. However, manipulation of various acoustic parameters in the digitally formatted tracks can produce unwanted and unexpected consequences, especially when using Dolby Surround encoding and decoding. Thus, a need exists need for a technique for rapidly identifying the occurrence of such unwanted acoustic consequences.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     Briefly, in accordance with a preferred embodiment of the present principles, there is provided a method for automatically detecting errors among different formatted soundtracks of the same language version without the need for a check by human listening. The method commences by acquiring contemporarily successive audio segments from each of a plurality of different formatted sound tracks. During a time window of preset duration, the audio of each different formatted track undergoes analysis to yield a numeric value. The successive analysis of the audio continues until no further audio exists for analysis. The resultant collection of numeric values undergoes formatting into a numeric file for comparison against a file representing audio obtained from a particular source, such as originally recorded material, a sound print, or a duplicated copy of a sound film. If the difference between a formatted numerical file and the comparison file exceeds a threshold value, then an error exists in that formatted sound track, and an operator can take appropriate action. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  shows a prior art dubbing and transfer system, which produces a quad-formatted, recorded sound track for reproduction on a motion picture film stock;  
         [0010]      FIG. 2  shows a typical arrangement for soundtrack reproduction from a motion picture film stock;  
         [0011]      FIG. 3  is a block diagram showing a monitoring system in accordance with a preferred embodiment of the present principles;  
         [0012]      FIG. 4  depicts in flow chart form the steps of a program executed by the monitoring system of  FIG. 3  to automatically check sound formats; and  
         [0013]      FIG. 5  depicts in flow chart form the steps of an analysis procedure executed during the program of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION  
       [0014]      FIG. 1  depicts a prior art dubbing and transfer system employed for transferring (i.e., dubbing) audio information onto a 35 millimeter motion picture film stock  14 . The system of  FIG. 1  includes a Dubbing Studio  10 , a Digital Theater Sound Transfer Center  11  and an Optical Transfer Center  12 . The Dubbing Studio  10  receives separate audio files from at least one source  16 . The source  16  comprises a plurality of different audio files, including: (a) the original dialogue, (b) the original music performances, (c) the original sound effects, and (d) the original environmental sounds, all formatted in each of the Dolby SR® digital (SR.D), DTS® and SDDS® formats, with or without Surround EX. Within the dubbing studio  10 , a mixer  18  serves to mix selected audio files from the source  16 . Effectively, the mixer  18  includes a six track digital mixer  20  for mixing six tracks of SR.D files and for providing two tracks of analog audio in a SR format. When dubbing of foreign languages is necessary, the dubbing studio  11  can include a separate mixer (not shown) ahead of the mixer  18  for mixing the local dialogues. A magneto-optical (MO) disk  24  serves to store the audio mixed by the mixers  20  and  22 , to maintain a Dolby SR.D formatted audio file and an analog Dolby SR file.  
         [0015]     Within the DTS transfer center  11 , a mixer  26  provides a mix of audio files received from the mixer  18  in the dubbing studio  10 . The mixed files from the mixer  26  are recorded by a DTS® master recorder  28 . From the recording made by the DTS® recorder  28 , a DTS® CD master machine  30  makes a CD master for duplication by a DTS® duplicator  32 . The DTS® CD which can provide six audio channels synchronized to the DTS sound track on the film.  
         [0016]     Within the optical transfer center  12 , a MO disk  34  stores the Dolby SR.D and analog Dolby SR sound files received from the MO disk  24 . The MO disk  34  simultaneously provides audio files to a Dolby® digital optical recorder  36 , an analog optical recorder  38  and to a DTS® optical recorder  40 , each recording respective formatted soundtracks on the film stock  14 . In the illustrated embodiment, the dubbing center  10  and the optical transfer center  12  have separate MO disks  24  and  34 , respectively. Rather provide a separate MO disk  34  within the optical transfer center  12 ; each of the recorders  36 ,  38  and  40  could directly access the MO disk  24  for files. With the optical transfer center  12 , a mixer  42  receives the mixed files from the mixer  18  for further mixing. A SDDS® recorder  44  optically records mixed files from the mixer  44  onto the film stock  14 .  
         [0017]     In practice, the DTS® recorder  40  records a time code track on the film stock  14  in the region between the variable area audio track or tracks and the edge of the film frame. The recorder  38  writes a Dolby SR® track in the standardized sound track location, while the recorder  36  writes a Dolby SR Digital® track in the area between the perforations. At both film edges, the recorder  44  records SDDS® tracks. The four tracks recorded in this fashion, referred to as a quad format, provide an enhanced playback capability that is backward compatible with a conventional variable area analog sound system.  
         [0018]      FIG. 2  depicts a block diagram of a typical prior art audio reproduction system  46  for use in a movie theater (cinema) for reproducing each of the different audio formats recorded on the film stock  14 . The reproduction system  46  of  FIG. 3  includes readers  48 ,  50 ,  52 , and  54 , for reading the Dolby SR.D®, Dolby SR®, Sony SDDS® audio tracks, plus DTS® time code track, respectively, from the film stock  14 . Each of decoders  56 ,  58  and  60  decodes its proprietary audio format received from its respective reader  48 ,  52  and  54 . An analog equalizer  62  serves to equalize the analog Dolby SR® signal received from the reader  50 .  
         [0019]     A sound processor  64  processes receives the output signals from the decoders  56 ,  58  and  62  and the analog equalizer  52  prior to amplification by an amplifier  66  that drives a set of speakers  68 . In this way, the sound processor  64  drives reproduction of the digitally formatted tracks in compliance with an ISO standard 2969/87 for the B-chain. The soundtrack signals originating from the optical analog reader  38  are read in accordance with the ISO standard 7831/86 for the A-chain. A sound level meter  70  measures the audio level of the sound output by the speakers  68  to provide feedback to the sound processor  64 . Noise reduction and decoding processors (not shown) can reside between the equalizer  62  and the sound processor  62  to transform the encoded Dolby SR® tracks back into four channels and to provide the listening audience with a similar sound perspective to that produced by an original 5.1 recording format reproduced from Dolby Digital® encoded tracks. However, the expansion of the two encoded tracks to yield four tracks cannot provide the full channel separation that is achievable from the six discrete channels reproduced from the Dolby Digital® track and consequently can cause ambiguities when identifying certain defects.  
         [0020]     Despite careful efforts, the sound recording process described with respect to  FIG. 1  can introduce sound content loss as well as synchronicity and/or phase errors in the sound tracks recorded on the film stock  14 .  FIG. 3  depicts a system  100 , in accordance with a preferred embodiment of the present principles for automatically detecting errors and audible defects in a multiple format movie sound track, such as the sound track on the film stock  14  of  FIGS. 1 and 2 . The system  100  of  FIG. 3  includes an audio acquisition processor  102 , typically a personal computer with an audio sound card, for executing a program  104  denominated as “PC SynchroCheck” in  FIG. 3  for the purpose of examining the sound tracks on film stock  14 .  
         [0021]     The audio acquisition processor  102  receives the different formatted sound tracks for inspection from either the MO disk  34  within the optical transfer center  12  of  FIG. 1  or from an storage device  106  that stores the soundtracks read from a positive print film check (not shown). The soundtracks stored in the MO  34  and those played by cinema sound systems are buffered by each one of buffers  107   1  and  107   2  respectively. A switch  108  selects the output of one of the buffers  107   1  and  107   2  for input to a summing device (preamplifier)  110  connected to the audio acquisition processor  102 . In this way, the audio acquisition processor  102  receives the formatted soundtracks stored in a selected one of the MO disk  34  and the storage device  106 .  
         [0022]     Typically, the system  100  also includes a pair of audio monitors 112 1  and 112 2 , each driven by the audio acquisition processor  102  to provide sound monitoring within an audio facility  113   1  associated with the Optical Transfer Center  12  of  FIG. 1 , and within a theater room  113   2  associated with the screening of a check positive print film, respectively. The audio room  113   1  and the theater room  113   2  can also include remote control units  114   1  and  114   2 , respectively, for controlling the execution of the PC SynchroCheck program  104  by the audio acquisition processor  102 . Each remote control unit typically includes a display as well as a mouse or other type of user-actuated input device.  
         [0023]      FIG. 4  depicts in flow form the steps performed by the PC SynchroCheck program  104  for automatically detecting errors among different formatted film sound tracks of the same language without the need for human hearing. The PC SynchroCheck program  104  commences upon execution of step  200  of  FIG. 4 . During step  200 , the audio acquisition process processor  102  of  FIG. 3  acquires audio files from one of the MO disk  34  of  FIG. 1  or from storage device  106 . The audio acquired during step  200  undergoes storage in a disk  202  accessible by the audio acquisition process processor  102  of  FIG. 4 .  
         [0024]     Following step  200 , an operator initiates a manual launch of an integration analysis routine during step  204 , whereupon audio information stored on the disk  202  undergoes integration during successive intervals, as indicated by box  206 . The details of the integration analysis routine performed during step  204  will become better understood with respect to  FIG. 5 .  
         [0000]     The integration analysis routine performed during step  204  (including the integration process of step  205 ) yields a set of numerical files exported to a document (i.e., a file) during step  208 .  
         [0025]     During step  210 , an operator initiates an analysis of the data exported during step  208 . Such data analysis occurs during execution of the PC SynchroCheck program  104  of  FIG. 3  by processing a comparison of sound tracks during step  212  and by processing a comparison of files during step  214 . As it will be better explained hereinafter, audio tracks comparison performed during step  212  is conducted between audio levels of paired tracks (according to the sound formats) integrated during successive time windows, typically with a duration of 20 ms each. The file comparisons involve comparison with values in a reference file, such those coming from the acquisition of a master audio source (MO-Disk and/or DTRS). Following processing of the sound track and file comparisons, a display of the results occurs during step  216 . Based on such results, a decision is made during step  218  whether the soundtracks have an error. If an error exists (i.e., one or more of the sound tracks is no good), then the audio acquisition processor  102  of  FIG. 3  outputs a report during step  220 , for output on one or both of the remote control devices  114   1  and  114   2,  or a similar output device, such as a display monitor or a printer (not shown). Otherwise, if no errors exist, program execution ends during step  222 .  
         [0026]     The basis for the decision made during step  218  can be found either in the comparison conducted between numerical levels of adequately paired tracks in the same acquisition file, or in the comparison (always in a track-to-track basis) against a reference acquisition file representing audio obtained from a master (i.e., the contents stored on the MO  34  of  FIGS. 1 and 3 ) as well as the audio obtained from a positive check print film. Indeed, the same decision could involve a comparison to both the formatted file of another track, and a reference file. If either comparison shows a difference in value greater than a preset threshold, then a “No-Good” decision would result.  
         [0027]      FIG. 5  depicts the steps of integration analysis routine executed by the audio acquisition processor  102  of  FIG. 3  during step  204  of  FIG. 4 . The integration analysis routine of  FIG. 5  commences upon execution of a start instruction  300  during which initialization occurs. Thereafter, the audio acquisition processor  102  of  FIG. 4  inputs the audio signals stored on the disk  202  during step  304 . Next, simultaneous processing occurs for each channel (audio track), including as many as twelve channels at once. For each channel, the audio acquisition processor  102  of  FIG. 4  integrates the level of the audio within a time window of prescribed duration, typically 20 ms, during step  306 . The integration occurs in accordance with the relationship:  
         L     eq   .   T       =       10   ⁢   log     ❘     (       1     20   ⁢           ⁢   ms       ⁢       ∫   0   20     ⁢           Vm   2     ⁡     (   t   )         Vo   2       ⁢     ⅆ   t           )             
         [0028]     Following the integration performed during step  306 , the results are stored during step  308  yielding in a formatted text file  310 , an example of which is found in Table I. The top row of the table provides channel identification, with the remaining values used for comparison purposes.  
                                                                                                                     TABLE 1                       Identification   1   2   3   4   5   6   7   8   9   10   11   12                                Nb Elements   3880   3800   3888   3000   3880   3080   3800   3008   3088   3000   3888   3000       Integration Value   87.2   45.1   83.1   85.7   84.1   83.3   85.7   84.8   90.4   89.9   92.1   92.4           85.5   53.4   83.2   86.1   84.3   83.7   86.3   85.0   98.7   89.7   92.4   92.2           86.8   69.9   82.7   85.1   83.4   83.6   86.4   84.9   98.8   90.1   92.3   92.1           85.4   78.0   83.8   86.4   84.8   83.6   85.8   84.6   98.4   89.3   92.3   91.8           86.4   86.4   83.2   86.3   84.3   83.3   85.7   85.1   90.6   98.0   92.4   92.3           86.7   89.5   83.3   85.8   83.9   83.1   86.3   84.5   90.3   98.8   92.0   92.2           85.8   86.8   83.3   86.1   84.1   83.4   86.0   85.3   90.8   89.7   92.3   92.3           85.1   85.6   83.4   85.2   83.7   83.4   86.2   85.4   90.5   98.8   92.1   92.1           86.8   45.0   83.8   86.4   84.6   83.0   85.8   84.3   90.7   98.8   92.5   92.1           85.8   47.0   83.3   86.1   83.8   52.9   5.30   84.1   89.6   90.1   91.9   92.8           86.3   68.1   83.0   86.2   84.3   53.6   86.3   85.1   90.6   98.0   92.5   92.2           87.1   72.0   82.9   85.6   84.8   53.6   86.3   85.3   98.8   90.2   91.9   92.0           84.1   81.6   82.3   85.6   83.5   83.4   86.0   85.0   90.7   09.8   92.6   92.2           85.2   83.1   83.1   85.8   83.3   83.4   85.6   84.1   90.4   90.0   92.2   91.7                  
 
         [0029]     As can now be appreciated, with a standard arrangement of channels in the multi-format movie soundtrack film stock  14  and with signals suitably assembled and routed by the audio acquisition processor  102  of  FIG. 3 , the PC SyncroCHECK software  104  can compare data of correspondent columns in the Table I to find differences caused by errors. In detail, the PC SyncroCHECK software reads each row and calculates differences between correspondent data. If a differences greater than predefined tolerance is found, the software signals and records relevant data of the error condition for subsequent presentation on the screen and generation of the NG Report during step  220  of  FIG. 4 . Each row of data is corresponds to a 20 ms widow during which the sound track audio undergoes integration. Thus, by knowing which integration step yielded bad data, it becomes possible to identify the exact footage of the film stock  14  in which the error occurred.  
         [0030]     Once an operator launches each of the Integration Analysis and SynchroCheck procedures, each procedure occurs automatically, without any further intervention. In particular, each procedure operates without the need for any decision making. Thus, no need exists for the operator to listen to any of the sound tracks. In this way, the sound track synchronization detection process of the present principles remains free of any subjective influence.  
         [0031]     The foregoing describes a technique for monitoring multiple sound channels, and in particular, for monitoring sound tracks on a motion picture film stock, to detect errors without the need for human analysis.