Method for recording a digital audio signal on a motion picture film

Abstract: There is disclosed a method for recording a digital audio signal on motion picture film (1), a system for reproducing a such recorded digital audio signal and a motion picture film (1) having a such recorded digital audio signal. The digital audio signal is recorded on said motion picture film (1) together with a conventional analog audio track (A) formed in the direcion of film's transfer. The method comprises the steps of: (a) encoding digital audio data to be recorded on said motion picture film (1) into digital audio data having an error correction code; and (b) sequentially arranging said digital audio data having an error correction code in the direction perpendicular to the direction in which said motion picture film (1) is advanced by utilizing two areas or more of an area (D1) in the vicinity of one end of the motion picture film (1) which is in parallel with the direction of the motion picture film's transfer, an area (D2) near the other end of said motion picture film (1) and which is laid between it and one end portion of an analog sound track (A) or an area (D3) near the other end of said analog sound track (A) and recording the same.

Description: The present invention relates to a digital audio signal recording method suitably applied to the case such that an audio signal is recorded on an audio track of a motion picture film in a digital fashion. In motion picture films, an analog audio signal of about two channels is recorded on a so-called sound track which is formed in the vicinity of a video recording portion. According to the recent progress in digital audio technologies, it is known that an audio signal is converted into digital data and then recorded on a recording medium such as a magnetic tape or the like. Also in the motion pictures, it is requested that an audio signal can be recorded on a motion picture film in the form of a digital signal. In the case of the motion picture film, however, the sound track on which the analog audio signal is recorded cannot be substantially removed from such a standpoint as to maintain a compatibility with existing film projection apparatus. Therefore, a new track on which digital audio data can be recorded must be prepared in other portion than the sound track. U.S, Patent US-A-4 600 280 describes a technique in which a digital audio signal is recorded on a motion picture film together with a conventional sound track. Also, U.S. Patent No. US-A-5 101 397 describes a technique in which an audio signal is recorded in the form of digital audio signal. Furthermore, U.S. Patent No. US-A-4 461 552 describes a technique in which an audio signal is encoded according to the pulse-code-modulation (PCM) system and then optically recorded on a film. However, the above-mentioned prior arts all fail to disclose an arrangement in which words forming a digital audio signal are properly arranged on a film or addition and arrangement of an error detection and/or error correction for avoiding data error. US-A-4 600 280 shows a method for recording a digital audio signal on a motion picture film together with a conventional analog audio track. The conventional audio track is splitted in a first track for the right stereo channel and in a second track for the left stereo channel. Furthermore, the digital audio data track is arranged in the vicinity of one end portion of the motion picture film in parallel with the travel direction of the motion picture film. As conventional analog audio tracks are provided in addition on the motion picture film, the motion picture film can be supplied to a conventional film machine which reads both analog audio tracks. As outlined in US-A-4 600 280 the digital data in the digital soundtrack is recorded in the form of black dots and white spaces corresponding to the binary bits of the digital information signal. The dots and spaces are arranged in groups which are representative for a digital binary word. The first binary words are related to the left channel, the second binary words are related to a right channel and third binary words are related to a center channel. A 16-bit quantization is used and thus each data word comprises 16 bits. All these 16 bits of each data word are arranged in a line extending perpendicularly to the travel direction of the motion picture film. From SMPTE Journal vd. 99 (1990) November, No. 11, White Plains, NY, U.S.A., PP 889-908 it is known to produce prototypes capable of recording and playing back a digital soundtrack on 35 mm motion-picture color print stock. The resulting system has sufficient data density for five independent full-bandwidth sound channels with a dynamic range of more than 90 dB. Full backward compatibility with existing analog tracks is maintained. Furthermore, error correction coding is performed in the digital soundtrack of a 35 mm motion picture film. It is the object of the present invention to provide a method for recording a digital audio signal on a motion picture film, whereby a rather small digital audio track can be used for recording the digital audio signal, and further to provide a film suitable for the inventive method. The object is solved by the features of claim 1 as concerns the method for recording and by the features of claim 14 as concerns the motion picture film. The further developments of the invention are defined by claims 2 to 13. A better understanding of the features and advantages of the present invention can be gained from a consideration of the following detailed description of illustrative embodiments thereof, in conjunction with the figures of the accompanying drawings, wherein: FIG. 1 is a format of an audio data track according to an embodiment of the present invention; FIG. 2 is an explanatory diagram showing a structure of a track according to the embodiment of the present invention; FIG. 3 is an explanatory diagram showing a structure of one word according to the embodiment of the present invention; FIG. 4 is a diagram showing a data format in a plurality of channels according to the embodiment of the present invention; FIG. 5 is a diagram used to explain the location of respective words according to the embodiment of the present invention; FIG. 6 is a diagram used to explain the location of CRC code according to the embodiment of the present invention; FIG. 7 is a diagram used to explain how to generate P parity words according to the embodiment of the present invention; FIG. 8 is a diagram used to explain how to generate Q parity words according to the embodiment of the present invention; FIG. 9 is a diagram showing an arrangement of a reproducing apparatus according to the embodiment of the present invention; and FIG. 10 is a diagram used to explain how to generate Q parity words according to another embodiment of the present invention. Embodiments of the present invention will hereinafter be described with reference to FIGS. 1 through 10. FIG. 1 of the accompanying drawings shows a track format under which digital audio data is recorded on a motion picture film. As shown in FIG. 1, a video recording portion V is formed on substantially a central portion of a motion picture film 1. An analog audio track A is formed at one end edge of the video recording portion V. An analog audio signal is optically recorded on the analog audio track A. Perforations 1a, 1b are formed on both end edge portions of the motion picture film 1 at a predetermined interval. A first digital audio data recording track D1 is formed on the motion picture film 1 between the perforations 1a and the video recording portion V. A second digital audio data recording track D2 is formed on the motion picture film 1 between the video recording portion V and the analog audio track A. A third digital audio data recording portion D3 is formed on the motion picture film 1 between the analog audio track A and the other perforations 1b. In this embodiment, assuming that the width of the motion picture film 1, for example, is 35 mm, then the width of the first digital audio data recording track D1 is 425 µm, the width of the second digital audio data recording track D2 is 660 µm and the width of the third digital audio data recording track D3 is 410 µm, respectively. Digital audio data of a predetermined number are separately recorded on the respective digital audio date recording tracks D1 to D3. The respective recording tracks D1 to D3 further include tracks corresponding to respective words of digital audio data. White or black patterns are exposed on the respective tracks in response to bits of respective words, thereby data being recorded. FIG. 2 of the accompanying drawings shows the respective recording tracks D1 to D3 that are located close to each other in order to understand more clearly the whole arrangement of audio data separately arranged on the first to third digital audio data recording tracks D1 to D3. In FIG. 2, a square region shows one word forming digital audio data. In this embodiment, each word is composed of 16-bit data of 4 bits x 4 tracks. Accordingly, there are formed tracks corresponding to respective bits. In this embodiment, there are formed 168 tracks in total in the direction perpendicular to the direction in which the motion picture film 1 is transported. FIG. 3 of the accompanying drawings shows a structure of the above-mentioned one word. As shown in FIG. 3, one word comprises 4 bits in the longitudinal direction and 4 bits in the horizontal direction, i.e., 16 bits in total. In one word which constructs digital audio data, b 15 (MSB) to b 0 (LSB) of 16-bit data are arranged as shown in FIG. 3. In FIG. 2, the first digital audio data recording track D1 is composed of 48 tracks (12 words). The second digital audio data recording track D2 is composed of 74 tracks (18.5 words). The third digital audio data recording track D3 is composed of 46 tracks (11.5 words). Accordingly, in the digital audio data recording tracks D1. D2 and D3, data of 48 bits, 74 bits and 46 bits are respectively arranged in the direction (horizontal direction) perpendicular to the direction in which the motion picture film 1 is advanced. According to the above track format, data of one bit occupies a square region one side of which is about 9 µm and one word occupies a square one side of which is about 36 µm. As shown in FIG. 2, on 16 tracks (4 words) from the left end of the first digital audio data recording track D1, there is recorded a first parity (P parity) that is used to detect and/or correct error in digital audio data. Audio data is recorded on the following 28 tracks and synchronizing (sync.) data is recorded on the next 4 tracks (one word). Sync. data is recorded on 4 tracks (one word) from the left end of the second digital audio data recording track D2. Audio data is recorded on the 70 tracks (17.5 words) which follow. On 30 tracks (7.5 words) from the left end of the third digital audio data recording track D3, there is recorded audio data. A second parity (Q parity) that is used to detect and/or correct error in digital audio data is recorded on the remaining 16 tracks (4 words). In this embodiment, as the sync. data recorded on the right end portion of the recording track D1 and the left end portion of the recording track D2, there is utilized sync. data of constant bit pattern which is used to detect the positions of the recording tracks D1 and D2. That is, as shown in FIG. 1, the video signal recording portion V is located between the first and second digital audio data recording tracks D1 and D2 and these recording tracks D1, D2 are thereby spaced apart. Therefore, the sync. data are respectively recorded on the first and second recording tracks D1, D2 so as to facilitate the reproduction of data. Incidentally, since a gap between the second and third digital audio data recording tracks D2 and D3 is relatively small, the data recorded on the third digital audio data recording track D3 can be reproduced with ease on the basis of the sync. data recorded on the second digital audio data recording track D2. According to this embodiment, digital audio data of 8 channels can be recorded on the motion picture film 1. A data format for recording 8-channel digital audio data will be described with reference to FIGS. 4 and 5. FIG. 4 of the accompanying drawings shows respective data located on respective channels at the unit of bits (sync. data is not shown). FIG. 5 of the accompanying drawings shows respective data located on respective channels at the unit of words (sync. data is not shown). In this embodiment, as shown in FIGS. 4 and 5, audio data of 8 channels are sequentially recorded on the tracks at every channel in the direction (horizontal direction in FIGS. 4 and 5) perpendicular to the direction in which the motion picture film 1 is advanced. A word sequence in the horizontal direction and shown on the lowermost end of FIG. 5 shows the audio data of the first channel. In this word sequence, from the left end thereof, there are recorded P parity words (P0, P1, P2, P3) of 4 words, in that order. Subsequently, data (W0, W1, ..., W31) of 32 words (32 samples) which construct the first channel (CH1) are recorded which are further followed by Q parity words (Q0, Q1, Q2, Q3) of 4 words. At that time, the data (W0 to W31) of 32 words are recorded in a so-called interleave recording fashion so that data (W0, W2, ..., W30) of even words and data (W1, W3, ..., W31) of odd words are respectively separated. Therefore, from the left end of the audio data recording area, there are recorded data (W0, W2, ..., W30) of even words and data (W1, W3, ..., W31) of odd words, sequentially in that order. In FIG. 5, there are provided the P parity words (P0, P1, P2, P3) which are used to error-detect and/or error-correct data sequence located in the horizontal direction. Also, in FIG. 5, there are provided the Q parity words (Q0, Q1, Q2, Q4) which are used to error-detect and error-correct data sequence located in the oblique direction of data that are arranged in a two-dimensional fashion with respect to the transport direction of the motion picture film 1 and the direction perpendicular to the direction in which the motion picture film 1 is advanced. How to generate the P and Q parity words will be described in detail later on. On the second channel, there are recorded data (W0, W1, ... W1) of 32 words, P parity words (P4 to P7) and Q parity words (Q4 to Q7) similarly to the first channel. Also in this case, the data (W0 to W31) are interleaved to data of even words and data of odd words and then recorded. In a like manner, 32-word data (W0 to W31), P parity words and Q parity words are respectively recorded up to the eighth channel. In the next word sequence of the horizontal direction which follows the word sequence of the eighth channel (CH8), there are recorded data (W32, W33, ..., W63) of 32 words, P parity words (P32 to P35) and Q parity words (Q32 to Q35) constructing the first channel (CH1) thereof. The data (W32 to W63) of 32 words are audio data which are continuous to the word sequence (W0 to W31) of the above first channel CH1. Also in this case, data (W32 to W63) are interleaved to data of even words and data of odd words and then recorded. Similarly, data (W32 to W63) are recorded in 32 words each together with P and Q parity words up to the eighth channel (CH8). Error detection codes formed of CRC (cyclic redundancy check) codes are generated and recorded after two blocks of one data block from the first channel (CH1) to the eighth channel (CH8) located in the horizontal direction. In this case, the CRC codes are generated to and added to the respective tracks which are formed along the travel direction of the motion picture film 1. FIG. 6 of the accompanying drawings shows the condition such that the CRC code is added to respective words located in the direction shown by an arrow a in FIG. 5. As shown in FIG. 6, one word is composed of 4 tracks. The CRC code is generated to and added to 16 words which comprise words W0 of 8 channels from the first channel (CH1) to the eighth channel (CH8) constructing the first data block and words (W32) of 8 channels from the first channel (CH1) to the eighth channel (CH8) constructing the second data block. The first data block, the second data block and the CRC code are repeatedly and sequentially recorded in response to the travel of the motion picture film 1. How to generate and add the P parity words will be described with reference to FIG. 7, FIG. 7 of the accompanying drawings shows one word sequence in the horizontal direction shown in FIG. 5. As shown in FIG. 7, the P parity word P0 is generated from the data W0, W8, W16, W24, W1, W9, W17, W25 arranged at every four words and the Q parity word Q0. Similarly, the P parity word P1 is generated on the basis of data W2, W10-, W18, W26, W11, W19, W27 which are arranged at every four words and the Q parity word Q1. The P parity words P2, P3 are similarly generated on the basis of data of word sequence in which words are arranged at every four words. How to generate the Q parity words (Q0, Q1, Q2, Q3) will be described with reference to FIG. 8. FIG. 8 of the accompanying drawings shows only the word sequences of the horizontal direction in which data of the first channels (CH1) are recorded. As shown in FIG. 8, this word sequence comprises a word sequence in which data W0 to W31 of the first channel (CH1) are recorded, a word sequence in which data W64 to W95 of the first channel are recorded, a word sequence in which data W128 to W159 of the first channel CH1 are recorded, ... Considering a Q parity word 576 within Q parity words 576 to 579 added to the word sequence of the horizontal direction in which data W576 to W607 of the first channel CH1 are recorded, it is seen that the Q parity word 576 is generated on the basis of 9 words which are composed of the P parity word P0, data W64, data W208, ..., data W537 as coupled by a broken line in FIG. 8. Other Q parity words are similarly generated and then interleaved. Equations for generating the P parity words and the Q parity words will be described below. P 4(ℓ-1)+32m +n = W ℓ,32m+2n + W ℓ,32m+2n+1 + W ℓ,32m+2n+8 + W ℓ,32m+2n+9 + W ℓ,32m+2n+16 + W ℓ,32m+2n+17 + W ℓ,32m+2n+24 + W ℓ,32m+2n+25 Q 4(ℓ-1)+32m+n+576 = P 4(ℓ-1)+32m+n + W ℓ,32m+2n+64 + W ℓ,32m+2n+136 + W ℓ,32m+2n+208 + W ℓ,32m+2n+280 + W ℓ,32m+2n+321 + W ℓ,32m+2n+393 + W ℓ,32m+2n+465 + W ℓ,32m+2n+537 where X in PX, QX depict each of parity word numbers, X in WX, Y depicts a channel number at which the word is located, Y depicts the word number, ℓ depict the channel numbers 1 to 8, m depicts the integers from 0 to infinity and n depicts 0, 1, 2 and 3. In this way, digital audio data of 8 channels are divided, arranged and then optically recorded on the digital audio data recording tracks D1, D2 and D3. FIG. 9 of the accompanying drawings shows an arrangement of a reproducing apparatus that reproduces the digital audio data recorded on the recording tracks D1, D2 and D3 of the motion picture film 1. As shown in FIG. 9, first and second CCD (charge-coupled device) line sensors 2 and 3 are disposed in the midst of the transport system of the motion picture film 1. The first CCD line sensor 2 is disposed at the position corresponding to the first digital audio data recording track D1 and the second CCD line sensor 3 is disposed at the position corresponding to the second and third digital audio data recording tracks D2 and D3. That is, since the second digital audio data recording track D2 and the third digital audio data recording track D3 are disposed close to each other, the data thereof can be detected by one CCD line sensor 3. Data of respective tracks detected by the respective CCD line sensors 2 and 3 are supplied to a digital data processor apparatus 4. In this digital data processor apparatus 4, digital audio data, recorded on the motion picture film 1, are reproduced on the basis of sync. data and digital audio data are error-detected and/or error-corrected on the basis of the P parity words, Q parity words and CRC codes, thereby reproducing the digital audio data of 8 channels. In this embodiment, the error detection is carried out mainly by the CRC codes. Since each word formed of 16 bits and relating to the error-detection and error-correction is recorded on the motion picture film 1 in a square configuration of 4 bits each in the longitudinal and horizontal directions, an error rate of erroneous data caused by a scratch in the longitudinal direction of the film is reduced to 1/4 as compared with the case such that each word formed of 16 bits is arrayed on one track in a line. Similarly, as compared with the case such that each word of 16 bits are arranged over the 16 tracks, an error rate of erroneous data caused by a scratch in the width direction of the film can be minimized. Further, since data of even words and data of odd words are interleaved, data can be interpolated with ease. In addition, each track of the P parity words is generated along the horizontal direction of (i.e., width direction of the film) so that, even when an unnecessary portion of the film in the width direction is removed and the films are connected upon edition, the error correction can be carried out on the basis of at least the P parity words and the error correction becomes possible in the vicinity of edit-in. Further, since the Q parity words are interleaved during a long period of time and then generated in the longitudinal direction of the film, a powerful error correction can be made. While the positions (track) of words that are utilized to generate the Q parity words are sequentially displaced toward the right side in accordance with the word sequences of the horizontal direction according to the embodiment shown in FIG. 8, the present invention is not limited thereto and the positions (track) of words that are utilized to generate the Q parity words may be alternately displaced right and left in a zigzag fashion as shown by broken lines in FIG. 10. According to this technique, data can be interleaved in a more complex fashion, thereby making it possible to perform a more powerful error correction. While data constructing each word are arranged in a two-dimensional fashion as in 4 bits x 4 bits and then recorded as described above, data are not always arranged in a square fashion. However, if data are recorded in a two-dimensional fashion substantially similar to the square, then any errors caused by scratches in the longitudinal and horizontal directions can be corrected satisfactorily as described above. Further, while digital audio data of 8 channels are dispersed and recorded on a number of tracks, i.e., 160 tracks (excepting the tracks for sync. data) as described above, the number of tracks and the number of channels are not limited to those in the above embodiments. As described in the above embodiments, the present invention can achieve remarkable effects when data are recorded on tracks whose number is several 10s of times the number of channels.

Claims: A method for recording a digital audio signal on a motion picture film (1) together with a conventional analog audio track (A) formed in the travel direction of the picture film (1) comprising the steps of; sequentially arranging said digital audio data in the direction perpendicular to the travel direction of the motion picture film (1) in at least one digital audio data recording track (D1, D2, D3) in the vicinity of the end portions of the motion picture film (1) and in parallel with the travel direction of the motion picture film (1), characterized by the steps of encoding said digital audio data to be recorded on said motion picture film (1) into digital audio data having an error-correction code; arranging the m x n bits of each word comprised in said encoded digital audio data in the form of a two-dimensional m x n structure (Fig. 3); recording m bits of said structure sequentially in the direction perpendicular to the travel direction of the motion picture film (1); and repeating said recording of m bits n times in the travel direction of the motion picture film (1) to record all m x n bits of said word. The method according to claim 1, wherein the error-correction code is produced by adding first parity words with said digital audio data. The method according to claim 2, wherein said first parity words are generated on the basis of words sequentially arranged and recorded in the direction perpendicular to the travel direction of the motion picture film (1). The method according to claim 1, wherein the error-correction code is produced by adding first and second parity words with said digital audio data. The method according to any one of claims 1 to 4, wherein said digital audio data is separated into, arranged and then recorded as two groups composed of data of even words and odd words. The method according to any one of claims 1 to 5, wherein synchronizing data, which is used to reproduce said digital audio data, is added to and recorded on one end portion of said motion picture film (1) or on an area near the other end of said motion picture film (1), each of them being in parallel with the direction of the motion picture film's transfer. The method according to claim 1, wherein one word is formed of 16 bits, m is 4 and n is 4, whereby one word is arranged in 4 rows and 4 columns and then recorded on said motion picture film (1). The method according to any one of claims 1 to 7, wherein said digital audio data is composed of signals of a plurality of channels and signals of respective channels are sequentially arranged and recorded in the direction perpendicular to the travel direction of said motion picture film (1), thereby cyclically recording signals of respective channels in the travel direction of said motion picture film (1). The method according to claim 8, wherein error-detection parity words are generated for the signals of a predetermined number of channels arranged and recorded on the travelling direction of said motion picture film (1) so as to detect errors of said signals and said error-detection parity words are sequentially arranged and recorded in the direction perpendicular to said travelling direction of said motion picture film (1). The method according to claim 9, wherein said words for error detection are generated on the basis of a CRC (cyclic redundancy check) code. The method according to claim 4 and to any one of claims 5 to 10 if related to claim 4, wherein said first parity words are generated on the basis of digital audio data which are sequentially arranged and recorded on the direction perpendicular to the travelling direction of said motion picture film (1) and said second parity words are generated on the basis of words of a predetermined number located in the oblique direction of two-dimensionally-arranged data which are formed by digital audio data sequentially arranged and recorded in the direction perpendicular to the travelling direction of said motion picture film (1) in response to the travel of said motion picture film (1). The method according to claim 11, wherein said second parity words are generated so as to include said first parity words. The method according to claim 11, wherein said first parity words are generated so as to include said second parity words. A motion picture film (1) with digital audio tracks and at least one conventional audio track, comprising: (a) an area (V) in which a motion picture is recorded; (b) a conventional audio track (A) in which an analog audio signal is recorded; and (c) digital audio data recording tracks (D1, D2, D3) in the vicinity of one end of the motion picture film (1) and in parallel with the travel direction of the motion picture film (1), in which a digital audio signal is recorded by the method of any of claims 1 to 13.

Inventors: ODAKA KENTARO, ODAKA, KENTARO, ODAKA, KENTARO, C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1992
Main classification: H04N5
IPC codes: G11B7, G03B31, H04N9, G11B20, H04N5