JPH08161827A - Optical disk and optical disk reproducing device - Google Patents

Abstract

PURPOSE: To synchronize a dynamic image coded at a variable bit rate with a sound coded at a fixed bit rate by a simple means by setting the ratio of the dynamic image to the sound in each block in their respective compressed amts. corresponding to the ratio of their respective coding bit rates. CONSTITUTION: Compressed data read out of an optical disk D by a read means 11 is switched by a switching means 15 in a block unit to the side of a dynamic image decoder 33 or the side of a sound decoder 43. Moving picture compressed data coded at the variable bit rate and sound compressed data coded at the fixed bit rate are recorded on the optical disk D. Then, each block has recording areas for these compressed data respectively, and a ratio of their compressed data amts. in each block is correspondent with a ratio of bit rates for coding the corresponding moving picture and sound respectively, and distribution information is recorded in each block for the purpose of indentifying the recording area of each compressed data in each block.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc on which a moving image coded at a variable bit rate and a voice coded at a fixed bit rate are recorded, and a reproducing apparatus therefor.

[0002]

2. Description of the Related Art As a method for compressing and encoding digital moving images and audio, for example, MPEG standardized by ISO is used.
And H.264 recommended by CCITT. There is 261. In these methods, the intra-image unit compression and the inter-image unit compression are interwoven and used to encode a moving image at a high compression rate while maintaining high image quality. Here, the intra-image unit compression is a compression form that can be decoded only by the compressed data, and the inter-image unit compression is a compression form that is encoded by utilizing the correlation with other image data.

In the intra-image compression, all macroblocks in the image are directly subjected to two-dimensional discrete cosine transform (DCT) to obtain a spatial frequency component, which is subjected to matrix division called quantization. This is to divide a frequency component by a matrix having a predetermined value, and by multiplying this matrix and the quantized data by a decoder, the frequency component can be obtained. In addition, it is possible to reduce the accuracy below the matrix value. In addition, taking advantage of the fact that human visual characteristics are insensitive to high frequencies,
More codes are assigned to the low frequency side than to the high frequency side.

In the inter-image compression, the motion vector from the referenced image is obtained for each macroblock, and the region closest to the macroblock is detected. Further, two-dimensional discrete cosine transform (DCT) and quantization are performed on the difference between the region and the macroblock data, and the difference data and the motion vector are encoded.

Therefore, the amount of bits generated in a moving image coding system such as MPEG greatly varies depending on the complexity of the image and the size of the motion. For this reason, a method is used in which the amount of generated bits is adjusted by adjusting a multiplier for a quantization matrix called a quantization width at the time of quantization.
However, this method has a problem that the image quality deteriorates in a complicated image or a scene with large motion, and conversely, the image quality becomes unnecessarily high in a simple image or a scene with small motion.

For this reason, a variable bit rate method is being adopted which suppresses the fluctuation of the image quality by allowing the fluctuation of the generated bit amount. In this system, a buffer memory is provided in the preceding stage of the decoder on the reproducing device side to absorb the fluctuation of the generated bit amount. Japanese Unexamined Patent Publication No. 4-326687 discloses a device that encodes a moving image at a variable bit rate in accordance with the MPEG standard to limit the maximum bit rate.

[0007]

FIG. 4 shows a conventional apparatus for reproducing an optical disc d on which moving image compressed data (= variable bit rate) and audio compressed data (= fixed bit rate) are recorded. In this apparatus, the moving image decoder switches the compressed data read from the optical disk d by the reading means 11 by the switching means 15 in units of sectors (blocks).
It is sent to the 33 side or the audio decoder 43 side. Further, this switching is performed according to the discrimination information of the header of each sector. In other words, in the conventional optical disc d, only one of the moving image compressed data and the audio compressed data is recorded in one sector. Therefore, in order to synchronize the reproduced moving image and the sound, it is necessary to adjust the appearance frequency of the sector of each compressed data. However, this process is complicated, and there is a problem that the circuit configuration also becomes complicated. Further, there is also a problem that a means for detecting the bit rate of the moving image compressed data is required for this processing.

Also, in this apparatus, the buffer memory 31 in the preceding stage of the moving picture decoder 33 is full or empty.
y) and whether the buffer memory 41 in the preceding stage of the audio decoder 43 is full or empty, the intermittent reading by the reading means 11 is controlled. ing. However, since the encoding bit rate of the moving image compressed data varies as described above, there is a problem that it is impossible to accurately predict the amount of data to be read next from the optical disc. There is also a problem that the data amount of any of the buffer memories may be insufficient. In addition, the buffer memory in the previous stage of the video decoder 33
Although it is possible to thin out moving images when the data amount of 31 is insufficient, the buffer memory 41 in the previous stage of the audio decoder 43
There is also a problem that it is impossible to thin out the audio when the data amount of is insufficient.

The present invention eliminates the need for means for detecting the bit rate of moving image compressed data in the reproducing apparatus,
An object of the present invention is to enable synchronous reproduction of a moving image and audio with a simple process and circuit configuration.

[0010]

DISCLOSURE OF THE INVENTION The present invention is an optical disc in which moving image compressed data encoded at a variable bit rate and audio compressed data encoded at a fixed bit rate are recorded, and the optical disc is recorded in each block. There is a recording area for each compressed data of moving image and audio, and the ratio of each compressed data amount of moving image and audio in each block is the bit rate of each encoding of moving image and audio corresponding to the block. The optical disc is configured so as to correspond to the ratio, and distribution information for identifying the recording areas of the compressed data of the moving image and the audio in each block is recorded in the block.

Further, according to the present invention, the recording information of the optical disc on which the compressed moving image data and the compressed audio data are recorded is read out, the moving image decoding means decodes the moving image data from the compressed moving image data, and the decoded audio data from the compressed audio data. An optical disk reproducing apparatus for decoding audio data by means, and extracting from each block read from the optical disk, distribution information for identifying a recording area of each compressed data of moving image and audio in the block; Switching means for sending moving image compressed data to the moving image decoding means based on the distribution information, and for sending compressed audio data to the audio decoding means,
It is an optical disk reproducing apparatus having. In the above, a control means for controlling reading of recorded information from the optical disk may be further provided so that the transfer rate of the compressed audio data sent to the audio decoding means becomes constant.

[0012]

The distribution information of each block is extracted from the recording information read from the optical disk by the extraction means, and the switching means is controlled based on the distribution information. As a result, the moving image compressed data in the block is sent to the moving image decoding means, and the audio compressed data is sent to the audio decoding means. Since each compressed data amount of the moving image and audio in each block is set so as to correspond to the bit rate ratio of each encoding of the moving image and audio corresponding to the block, the decoded moving image It becomes easy to obtain synchronization between data and voice data.

[0013]

Embodiments of the present invention will be described below.

* Optical Disc of Embodiment FIG. 1 shows a block structure of an optical disc D of an embodiment reproduced by a first and a second embodiment device described later. In the figure, (a) shows the case where the ratio of the bit rate of the moving image compressed data and the bit rate of the audio compressed data is 3, (b) shows the case of 7, and (c) shows the case of 15. Here, the bit rate of the moving image compressed data is variable, the bit rate of the audio compressed data is fixed, and the respective ratios of (a) to (c) above are in a certain short period (eg, 1 second, 2 Seconds, 1 GOP of MPEG standard, etc.).

As shown in the figure, in the optical disc D of the present embodiment, the data area of each block delimited by the header is distributed according to the above bit rate ratio. For example, when the ratio is 3 (a), the block is configured such that the moving image compressed data and the audio compressed data have a data amount ratio of “3: 1” in the data area. There is. Similarly, in the case of (b) where the ratio is 7, "7:
The data area of each block is distributed such that the data area becomes "1" and the data area becomes "15: 1" when the ratio is 15 (c).

In the above description, the header includes the recording mode of the block (recording data amount in the block, presence / absence of subheader, presence / absence of error correction, etc.) and block address (minutes, seconds, block) of the block. ) And the like, the ratio of the data amount of the moving image compressed data and the audio compressed data is recorded. Instead of this ratio, the data amount of each of the compressed moving image data and the compressed audio data may be recorded, or the data indicating the boundary between the compressed compressed image data and the compressed audio data may be recorded. Further, the distribution information may be recorded in the data in a multiplexed manner.

FIG. 1 shows an example of a block structure, and the present invention naturally includes a block structure having a subheader and an error correction code. Also, the type of disc is not limited to the CD-ROM, and it may be a CD or a CD-M.
As a matter of course, various discs having a block structure such as O and LD are included.

First Embodiment Device FIG. 2 shows the configuration of the first embodiment device. The parts having the same configurations as those of the conventional device shown in FIG. In the apparatus of the first embodiment, the compressed data read from the optical disk D by the reading means 11 is converted into the data of the CD-ROM format by the CD-ROM decoder 13 having a built-in CD decoder, and then the switching means 15 is used. It is switched to the moving picture decoder 33 side or the audio decoder 43.
Sent to the side.

Here, the switching operation by the switching means 15 is controlled according to the distribution information (the ratio of the data amount of the moving image compressed data and the audio compressed data, or each data amount itself, or the data regarding the boundary). . That is, in the optical disc D of the embodiment, moving image compressed data and audio compressed data are recorded in each block as described above, and each data amount and recording position are recorded in the block as the distribution information. There is. This distribution information is extracted by the ratio extraction means 21, and the ratio extraction means 21 is performed based on the result.
The switching operation of the switching means 15 is controlled by the command from. For example, in the case of the block of FIG.
After the beginning 3/4 of the data area of the block is sent to the moving picture decoder 33 side, the remaining 1/4 is sent to the audio decoder 43 side. Similarly, in the case of (b), 7/8 is sent to the moving picture decoder 33 side, then the remaining 1/8 is sent to the sound decoder 43 side, and in the case of (c) 15/16 is the moving picture decoder. After being sent to the 33 side, the remaining 1/16 is sent to the audio decoder 43 side.

The ratio extracting means 21 may be any one capable of extracting the distribution information from each block, and its configuration is a recording method of the distribution information (a method of recording in the header, a method of multiplexing in the data, etc.). Each is different. Further, the distribution information may be detected before the configuration of FIG. 2, and the reading speed from the optical disk may be controlled as described above based on the detection.

Further, in the first embodiment, the amount of data in the buffer memory 41 for relaxation in the preceding stage of the audio decoder 43 is monitored, and the data concerning the full state of the buffer memory 41 and the empty state are monitored. Data regarding the (empty) state is sent to the control means 23. Based on this, the control means 23,
The reading operation from the optical disc D by the reading means 11 is controlled. That is, an optical disc is used so that the supply bit rate of audio compression data encoded at a fixed bit rate becomes constant.
The read operation from D and the transfer operation to the audio decoder 43 are controlled. For example, if the moving image is a block coded at a bit rate n times as high as the audio, the audio decoder 43
The read operation from the optical disc D is performed at a speed (n + 1) times the transfer rate to the audio decoder 43, and the transfer operation to the moving image decoder 33 is performed at a speed n times the transfer rate to the audio decoder 43. Therefore, it is possible to always read the record information of the optical disc D at an optimum speed without causing a shortage of the data amount of the buffer memories 31 and 41.

* Second Embodiment Device FIG. 3 shows the configuration of the second embodiment device. It should be noted that parts having the same configurations as those of the conventional device shown in FIG. 4 and the device of the first embodiment shown in FIG. The device of the second embodiment is substantially the same as the device of the first embodiment. Therefore, mainly different points will be described, and description of the same points will be omitted.

In the apparatus of the second embodiment, the data read from the optical disc D is temporarily stored in the buffer memory 12. The buffer memory 12 relaxes the reading speed from the optical disc D and the processing speed on the decoder side. Further, the control means 23 is an optical disc by the reading means 11.
The read speed from the buffer memory 12, not the read speed from D, is controlled as described above. With this configuration, the same effect as that of the first embodiment can be achieved. The buffer memory 12 is replaced by a CD-ROM decoder 13
The same effect can be achieved by the configuration provided in the latter stage.

[0024]

As described above, the optical disc of the present invention is distributed and recorded in each block so that the ratio of each compressed data amount of moving image and audio corresponds to the ratio of encoding bit rate, and Distribution information for identifying the recording areas of both compressed data is recorded in the block. Therefore, when the optical disc of the present invention is reproduced by the reproducing device of the present invention, the compressed data of the moving image and the audio in each block is sent to the moving image decoding means or the audio decoding means according to the distribution information and is decoded respectively. Therefore, the synchronization of the moving image data and the audio data can be obtained with a simple configuration. Further, in the configuration in which the reading of the recorded information from the optical disc is controlled so that the transfer rate of the compressed audio data sent to the audio decoding means becomes constant, the data amount in the buffer memory in the preceding stage of each decoding means does not become insufficient, It is possible to read from the optical disc at an optimum speed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration inside a block of an optical disc according to an embodiment.

FIG. 2 is a block diagram showing the configuration of the first embodiment device.

FIG. 3 is a block diagram showing the configuration of a second embodiment device.

FIG. 4 is a block diagram showing a configuration of a conventional optical disc reproducing apparatus.

Claims (3)

[Claims] 1. An optical disc on which moving image compressed data encoded at a variable bit rate and audio compressed data encoded at a fixed bit rate are recorded, wherein each compressed image data of moving image and audio is contained in each block. , And the ratio of the compressed data amount of each moving image and audio in each block is set to correspond to the bit rate ratio of each encoding of the moving image and audio corresponding to the block. An optical disc in which distribution information for identifying a recording area of each compressed data of moving image and audio in each block is recorded in the block. 2. The recording information of the optical disc on which the compressed moving image data and the compressed audio data are recorded is read, the moving image data is decoded from the compressed moving image data by the moving image decoding means, and the audio is decoded from the compressed audio data by the audio decoding means. An optical disk reproducing apparatus for decoding data, which comprises: extracting means for extracting, from each block read from the optical disk, distribution information for identifying a recording area of each compressed data of moving image and audio in the block; And a switching means for sending the compressed video data to the moving picture decoding means and the compressed audio data to the sound decoding means. 3. The optical disc according to claim 2, further comprising control means for controlling the reading of recorded information from the optical disc so that the transfer rate of the compressed audio data sent to the audio decoding means becomes constant. Playback device.