JP4007575B2 - Image / audio bitstream splitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image / audio bitstream dividing apparatus, and in particular, shortens a reception time until reproduction starts by multiplexing a bitstream obtained by compressing and encoding an image / audio and dividing and storing a long content. In addition, the present invention relates to an image / audio bitstream dividing device that enables reproduction from the middle.
[0002]
[Prior art]
A conventional image / audio bitstream divided storage apparatus will be described with reference to FIGS. 6, 7 and 8. FIG. As shown in FIG. 6, the conventional image / audio bitstream divided storage apparatus includes an image encoder 11, an audio encoder 12, an image bitstream buffer 13, an audio bitstream buffer 14, a multiplexing unit 15, and a chunk generation timer. The pulse generator 16, the file generator 17, and the file storage 18 are configured.
[0003]
As shown in FIG. 7, the multiplexing unit 15 includes buffers 21 and 22 that can store several frames, delay means 23 connected to the buffer 22, a buffer 24, and input sides of the buffers 21 and 22. It is comprised from the switching parts 25 and 26 connected to.
[0004]
Now, the bit stream sequentially generated by the image encoder 11 of FIG. 6 is input to the image bit stream buffer 13 simultaneously with the completion of encoding of one image frame. At the same time, the bit stream sequentially generated by the audio encoder 12 is input to the audio bit stream buffer 14 simultaneously with the completion of encoding of one audio frame. The multiplexing unit 15 receives the chunk generation timer pulse Ti from the chunk generation timer pulse generation unit 16 at regular intervals, and alternately multiplexes the image / audio bitstream for each chunk (chunk). Output to the file generation unit 17.
[0005]
That is, when the chunk generation timer pulse Ti is input to the multiplexing unit 15, the switching units 25 and 26 are turned on, encoded so far, and stored in the image bit stream buffer 13 and the audio bit stream buffer 14. The transferred data is transferred to the buffers 21 and 22. Next, the image bit stream transferred to the buffer 21 is sent to the buffer 24, and then the audio bit stream delayed by the delay means 23 is combined in the buffer 24. Then, it is output to the file generation unit 17.
[0006]
The time interval between the image frame and the audio frame input to the multiplexing unit 15 is generally different, and in general, one is not an integer multiple of the other. The file generation unit 17 adds header information to the input multiplexed bit stream and outputs it as one file. At that time, the header information is added and stored separately at regular intervals.
[0007]
FIG. 8 is an explanatory diagram of the chunk generation operation. In the figure, (a) shows an image bit stream, and (b) shows an audio bit stream. Chunk generation timings T1, T2, T3,... Are input to the multiplexing unit 15 at regular time intervals, and the multiplexing unit 15 stores the image / sound frame that has been generated at that time as a buffer. 21 and 22 are input. Therefore, the multiplexing unit 15 configures the image and audio frame-by-frame bitstreams that have been generated when the chunk generation timings T1, T2, T3,... Are input as image chunks and audio chunks, respectively. And output as a file.
[0008]
If the content is long, in order to shorten the reception time or facilitate playback from the middle, if the number of chunks reaches a certain number, it is output separately as a separate file, or within the same file, the split header In general, it is divided and stored.
[0009]
[Problems to be solved by the invention]
As is apparent from FIG. 8, in the conventional method, the frame playback time at the beginning of the chunk does not match between the image bit stream a and the audio bit stream b. There are cases where the playback time (for example, t1) at the beginning of the chunk of the audio bitstream b is earlier or later (for example, t2, t2 ′) than the playback time (for example, t1 ′) of the image bitstream a.
[0010]
When playback is performed from a dividing point in the middle of the content, the playback time must be corrected in order to synchronize the image and audio. However, in a general decoding / playback apparatus, since an audio bitstream is decoded into a continuous audio signal in which one compressed frame is synchronized with a sampling frequency, an image that may be decoded and displayed at discrete time intervals in units of frames. Therefore, there is a problem that time adjustment is very difficult, and further, there is a problem that the synchronization control becomes complicated and difficult when the image is first and the sound is first.
[0011]
An object of the present invention is to solve the above-described problems of the prior art, and an image / audio bitstream that enables chunk generation or division in a format that facilitates image / audio synchronization control as much as possible during decoding and reproduction. It is to provide a dividing device.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention multiplexes an image and an audio bitstream into a single stream by chunking each of a plurality of frames and alternately arranging image and audio chunks. And a chunk generation timing signal generation device for generating a chunk generation timing signal for generating the chunk at regular time intervals in an image / audio bitstream splitting device that divides the data into a plurality of chunks and writes the file to a file , and the chunk Image chunk generation means for waiting until the image bit stream immediately before the image frame immediately after the generation timing signal is read into the multiplexing means and generating the read image bit stream as one image chunk ; Sound that has been read at the time of completion A voice chunk generating means for generating up to bit stream of frames as one audio chunk, there is a first feature in that and means for dividing each of a plurality chunks.
[0013]
According to this feature, the playback time of the audio frame at the beginning of the chunk can always be the same as or earlier than the playback time of the image frame.
[0014]
In addition, the present invention provides a chunk generation timing signal generation device that generates a chunk generation timing signal for generating the chunk at regular time intervals, and a chunk of the image frame immediately after the chunk generation timing signal only for the chunk that becomes a division point. Wait until the previous image bitstream is completely read by the multiplexing means, and the image chunk generating means for generating the image bitstream that has been read as a single image chunk , and the reading is completed at the time of completion. There is a second feature in that audio chunk generating means for generating up to a bit stream of an audio frame as one audio chunk and means for dividing the chunk into a plurality of chunks and outputting the signal at the division point are provided. .
[0015]
According to this feature, in the chunk that becomes the division point, the playback time of the audio frame at the beginning of the chunk can always be the same as or earlier than the playback time of the image frame.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of the main part. Note that the same reference numerals as those in FIG. 6 in FIG.
[0017]
When receiving one frame of the encoded bit stream from the image encoder 11, the image bit stream buffer 13 outputs a frame unit notification signal q. The frame unit notification signal q is input to one input terminal of the AND circuit 22. Further, the chunk generation timer pulse generator 16 generates a chunk generation timer pulse Ti at regular intervals. The chunk generation timer pulse Ti is input to the hold circuit 21 and held. As a result, the output of the hold circuit 21 is as indicated by r in FIG.
[0018]
When the chunk generation timer pulse Ti is input to the hold circuit 21, the output r of the hold circuit 21 becomes H (high) level and is input to the other terminal of the AND circuit 22, as shown in FIG. . Thereafter, when the frame unit notification signal q1 is input, the signal q1 passes through the AND circuit 22 and is input to the multiplexing unit 15 as the chunk generation signal s1. Then, the multiplexing unit 15 generates a chunk using the chunk generation signal s1 as a trigger signal. The hold circuit 21 is reset by the chunk generation signal s1.
[0019]
That is, as illustrated in FIG. 2, the multiplexing unit 15 divides the image bit stream a and the audio bit stream b at the timing of the chunk generation signal s1. As can be seen, the frame boundary of the image bitstream a coincides with the chunk generation signal s1, and is thus divided at the frame boundary (for example, a1, a2). However, the audio bitstream b does not always coincide with the audio frame boundary. If they do not match, the frame of the voice that has been generated at that time is set as a boundary (for example, b1, b2).
[0020]
As a result, according to this embodiment, the playback time of the audio frame at the beginning of the chunk can be the same as or earlier than the playback time of the image frame. In other words, the playback time of the audio frame at the beginning of the chunk will never be later than the playback time of the image frame. Therefore, when playing back from a division point in the middle of a file, if the image frame is delayed by a time difference from the audio frame, the image and the audio can be synchronized, which is a problem in the conventional method. It becomes possible to prevent the image / sound synchronization control from becoming complicated. As a result, the reproduction terminal can be reduced in size and price.
[0021]
The hold circuit 21 and the AND circuit 22 are specific examples of means for waiting until the image bit stream immediately before the image frame immediately after the chunk generation timing signal for generating the chunk is read into the multiplexing means. be able to.
[0022]
Next, a second embodiment of the present invention will be described with reference to FIGS. In general, as shown in FIG. 4, for example, as shown in FIG. 4, a single header is attached to a plurality of chunks, and a portion to which the header is attached is a division point. In this embodiment, only at the division point, the playback time of the audio frame at the beginning of the chunk is the same as or earlier than the playback time of the image frame. 3 that are the same as or equivalent to those in FIG.
[0023]
As shown in FIG. 3, in this embodiment, a circuit in parallel with the hold circuit 21 and the AND circuit 22 in which the switching means 23 is connected between the chunk generation timer pulse 16 and the output of the AND circuit 22. Is connected. The switching means 23 is turned off by the file division point signal m from the file generation unit 17, and is turned on otherwise. Therefore, only at the file division point, the playback time of the audio frame at the beginning of the chunk is the same as or earlier than the playback time of the image frame.
[0024]
Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a division point (header) can be entered in a file having no division point, for example, a file having a header only at the beginning and no header after that.
[0025]
The file storage unit 31 stores files without the division points. The file reading unit 32 reads the file from the file storage unit 31 and sends it to the image / sound demultiplexing unit 33. The image / audio demultiplexing unit 33 separates image data and audio data from the file, and sends them to the image bit stream buffer 13 and the audio bit stream buffer 14 in FIG. Subsequent operations are the same as those in FIG. Note that 34 in FIG. 5 may be replaced with the corresponding configuration in FIG.
[0026]
The file generator 17 can output a file containing division points. Therefore, according to this embodiment, a file without division points can be converted into a file with division points.
[0027]
When playing back a file formed in the present invention and stored in the file storage unit, the header is first decoded and the index is extracted. In the case of playing from the nth (n is a positive integer) division point, the reproduction time of the audio and image at the nth division point is acquired from the index, and then (audio reproduction time-image reproduction time) The image reproduction is delayed by the amount, and thereafter the image and the sound are reproduced in order. Thereby, the reproduction of the image and the sound can be matched.
[0028]
According to the present invention, there is no need to time delay an audio bitstream that is very difficult to adjust in time.
[0029]
【The invention's effect】
As is apparent from the above description, according to the first to fourth aspects of the invention, the playback time of the audio frame at the beginning of the chunk can always be the same as or earlier than the playback time of the image frame. Therefore, when playing back from a division point in the middle of a file, if the image frame is delayed by a time difference from the audio frame, the image and the audio can be synchronized, which is a problem in the conventional method. It becomes possible to prevent the image / sound synchronization control from becoming complicated.
[0030]
According to the invention of claim 2, the playback time of the audio frame at the beginning of the chunk is always the same as or ahead of the playback time of the image frame only at the division point where the header is added. be able to. According to the invention of claim 4, a file having no division point can be converted into a file having division points.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a timing chart of signal and chunk generation of the main part of the first embodiment.
FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 4 is an explanatory diagram of a file configuration.
FIG. 5 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.
FIG. 6 is a block diagram showing a configuration of a conventional image / audio bitstream dividing apparatus.
FIG. 7 is a block diagram illustrating a specific example of a multiplexing unit.
FIG. 8 is a timing chart of conventional chunk generation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Image encoder, 12 ... Audio encoder, 13 ... Image bit stream buffer, 14 ... Audio bit stream buffer, 15 ... Multiplexer, 16 ... Chunk generation timer pulse generator , 17 ... file generation unit, 18 ... file storage unit, 21 ... hold circuit, 22 ... AND circuit, 23 ... switching unit.

Claims (4)

An image and an audio bitstream are each chunked into a plurality of frames, multiplexed as a single stream by alternately arranging image chunks and audio chunks, and divided into a plurality of chunks and written to a file. In the audio bitstream splitting device,
A chunk generation timing signal generating device for generating a chunk generation timing signal for generating the chunk at regular time intervals;
Image chunk generating means image bit stream immediately before the image frame immediately after the chunk generation timing signal wait until the completion of reading to the multiplexing means, for generating a video bit stream that completion of the loading as one image chunk When,
Audio chunk generation means for generating up to a bit stream of an audio frame that has been read at the time of completion as one audio chunk;
Video and audio bit stream dividing device is characterized in that and means for dividing each of a plurality chunks. An image and an audio bitstream are each chunked into a plurality of frames, multiplexed as a single stream by alternately arranging image chunks and audio chunks, and divided into a plurality of chunks and written to a file. In the audio bitstream splitting device,
A chunk generation timing signal generating device for generating a chunk generation timing signal for generating the chunk at regular time intervals;
Only for chunks that are division points, wait until the image bitstream immediately before the image frame immediately after the chunk generation timing signal is read into the multiplexing means, and the read image bitstream is read into one image chunk. Image chunk generation means to generate as
Audio chunk generation means for generating up to a bit stream of an audio frame that has been read at the time of completion as one audio chunk;
An image / audio bitstream dividing apparatus comprising: means for dividing a plurality of chunks and outputting a signal at the division point .   The image / audio bit according to claim 1 or 2, further comprising image encoding means for generating the image bitstream and audio encoding means for generating the audio bitstream. Stream split device. Means for reading a bitstream file in which undivided image and audio bitstreams are multiplexed;
Means for demultiplexing the read image and audio bitstreams;
3. The image / audio bitstream dividing apparatus according to claim 1, wherein the demultiplexed image and audio bitstream are input to means for generating the image chunk and audio chunk , respectively .

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