JP4197582B2 - Stream synchronization switching device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stream synchronization switching device that synchronizes and selectively switches two or more streams compression-encoded by, for example, the MPEG2 encoding standard.
[0002]
[Prior art]
Conventionally, studio equipment in an analog broadcast transmission facility performs signal processing such as switching, synchronization, and multiplexing of video signals.
[0003]
On the other hand, in a digital broadcast transmission facility, studio equipment that performs signal processing such as switching and synchronization of video streams encoded by the MPEG2 encoding method is indispensable.
[0004]
Here, in the conventional analog broadcasting transmission equipment, the signal is not compressed, so that the shock is not conspicuous when switching the system, the frame is synchronized and then switched at the frame position, and the switching of the contacts It was enough to take measures against noise that sometimes occurred.
[0005]
However, in a digital broadcast transmission facility, a video signal is compressed and encoded by an encoder to form a stream, and the cut is difficult to understand in the compressed and encoded stream. Particularly in video encoding and compression methods such as MPEG2. The stream is formed in a GOP structure including one intra-frame coded picture (I picture) and a plurality of prediction screens (P picture, B picture) created based on this picture. For this reason, in the digital broadcasting transmission facility, it is not possible to simply perform frame synchronization and switch at the frame position as in analog broadcasting in system switching.
[0006]
[Problems to be solved by the invention]
As described above, in the digital broadcast transmission system, when switching between the two systems of encoder output, the analog broadcast technology cannot be applied as it is, and therefore switching can be performed smoothly. In addition, a switching device that can cope with GOP has been strongly desired.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a stream synchronization switching device that can synchronize two streams that have been subjected to compression encoding and can perform switching smoothly without causing disturbance in the transmitted signal. There is.
[0008]
[Means for Solving the Problems]
The stream synchronization switching device according to the present invention is configured to synchronize two standardized streams that are compression-coded with each other and form a specific pattern group with a predetermined block period in accordance with a synchronization trigger signal, and then In the stream synchronous switching device that selectively derives the video stream, the stream is generated by performing compression coding processing on the video signal and controlling the block length of the stream by a signal given from the outside. Possible encoding means, switching means for inputting the output of the encoding means of each system and deriving one stream as a transmission signal, and switching source and switching destination encoding means before a predetermined time of system switching Is generated by each encoding means so that the output of the switching-destination encoding means and the output of the switching-source encoding means are synchronized by giving a synchronization trigger signal to After controlling the block length of the stream, in which as and a timing control means for switching the switching means.
[0009]
In this configuration, the timing control means gives a synchronization trigger signal to the encoding means of each system before a predetermined time of system switching. Then, the encoding means of each system obtains a stream position to be switched after a predetermined time, and variably sets the block length of the stream from the time of receiving the synchronization trigger to the time of switching so as to be switched at this stream position to synchronize with each other. .
[0010]
For this reason, since the timing control at the time of system switching in the switching means can be easily performed, the stream before switching and the stream after switching are neatly connected, thereby preventing the reproduction video from being disturbed.
[0011]
According to the present invention, the encoding means of each system includes a screen group structure (GOP: Group Of Pictures) including at least one intra-frame encoding screen from an input video signal and a plurality of prediction screens created based on this screen. MPEG2 (Moving Picture Experts Group 2) defined stream is generated, and the timing control means provides a synchronization trigger signal to the switching source and switching destination encoding means for a predetermined time before system switching to switch Switching source and switching destination encoding means so that sometimes the last screen of the screen group structure in the output of the switching source encoding means coincides with the last screen of the screen group structure in the output of the switching destination encoding means The switching means is controlled after variably setting the size of the screen group structure in the output. At this time, each encoding unit analyzes the screen group structure of the stream to be output when a synchronization trigger signal is given, and based on the analysis result, the screen group structure at the output of each encoding unit at the time of switching is analyzed. The prediction screen of the screen group structure is replaced with the intra-frame encoding screen so as to coincide with the last screen.
[0012]
In this configuration, the encoding means of each system obtains the stream position to be switched after a predetermined time, and the stream screen from the time of receiving the synchronization trigger to the time of switching so that the last screen of the screen group structure comes at this stream position. By replacing the prediction screen in the group structure with the intra-frame coding screen, the size of the screen group structure is adjusted to forcibly synchronize. Normally, when the pattern of the screen group structure is destroyed, the image quality deteriorates. However, in the stream generated by the encoding means of each system, the period during which the screen group structure size is varied is switched after receiving the synchronization trigger signal. This is a period up to the time, and since this period is not affected by the reproduced video, there is no problem.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a block diagram showing an embodiment of a stream synchronization switching device according to the present invention.
[0015]
In FIG. 1, reference numeral 11 denotes a multiplexer, which inputs a first stream A and a second stream B and outputs one of the streams as a transmission stream C.
[0016]
An encoder 12 is connected to the first system, and an encoder 13 is connected to the second system. Of these, the encoder 12 performs variable-length compression coding based on the MPEG2 coding method on the input program information signal (material A) to generate a stream A. In addition, the encoder 13 performs variable-length compression encoding based on the MPEG2 encoding method on the input program information signal (material B) to generate a stream B.
[0017]
The multiplexer 11 and the encoders 12 and 13 are controlled by the trigger signal generator 14 at the time of system switching.
[0018]
The trigger signal generator 14 gives a synchronization trigger signal to the encoders 12 and 13 to synchronize the output streams before a predetermined time of system switching, and performs switching control of the multiplexer 11.
[0019]
The processing operation of the above configuration will be described below.
[0020]
First, the encoder 12 and the encoder 13 generate the same streams A and B independently of each other. These streams A and B are formed in a GOP structure consisting of 15 frames, as shown in FIGS. 2 (a) and 2 (b). Here, when the output of the encoder 12 and the output of the encoder 13 are switched by the multiplexer 11, if the GOP boundary is not matched, the GOP collapses as shown in FIG. The later stream B is not connected neatly, and this switching portion causes disturbance in the playback video on the receiver side as shown in FIG.
[0021]
Therefore, in this embodiment, the trigger signal generator 14 gives a synchronous trigger signal to the encoders 12 and 13 before a predetermined time (for example, 3 seconds before) of the system switching instruction notified from the outside, and FIG. ) And (b), the output streams A and B are synchronized. At this time, the encoders 12 and 13 analyze the switching stream position after a predetermined time from the reception of the synchronization trigger signal, and when this position is in the middle of the GOP, from the time when the synchronization trigger signal is received to the time of switching. The GOP size of the stream is variably set to forcibly match the last GOP picture data of the output stream of the encoder 12 and the last GOP picture data of the output stream of the encoder 13 at the time of switching. In the streams A and B generated by the encoders 12 and 13, the period during which the GOP size is varied is a period from when the synchronization trigger signal is received until switching, and this period is a period that does not affect the reproduced video. So there is no problem.
[0022]
Thereafter, the trigger signal generator 14 provides a switching timing signal to the multiplexer 11 and switches from the stream A to the stream B a predetermined time after outputting the synchronization trigger signal. As a result, the stream A before switching and the stream B after switching are clearly connected as shown in FIG. 3C, and the playback video is not disturbed on the receiver side as shown in FIG. 3D. The outgoing stream C is sent out.
[0023]
For reference, FIG. 4 shows a GOP structure in the MPEG2 encoding system. This GOP structure has three types of pictures: an I (Intra) picture by intraframe coding, a P (Predictive) picture by interframe forward prediction coding, and a B (Bidirectionally Predictive) picture by bidirectional prediction coding. The arrangement order is IBBPBBP... And is normally set to 15 frames in one GOP period. If this GOP structure is broken, problems such as a disturbance of the screen during reproduction of the video or interruption of reproduction may occur. For this reason, it is necessary not to destroy the GOP structure pattern when switching streams.
[0024]
In this embodiment, the encoders 12 and 13 sequentially replace at least a P picture or a B picture in a plurality of consecutive GOPs that do not affect the reproduced video from the time of receiving the synchronization trigger signal until the switching with an I picture, Each GOP size is variably set.
[0025]
As described above, in the above embodiment, the trigger signal generator 14 gives a synchronous trigger signal to the encoders 12 and 13 of each system before a predetermined time of system switching, and the encoders 12 and 13 of each system The stream position to be switched after time is analyzed, and the P picture or B picture in the GOP of the stream from the time of receiving the synchronization trigger to the time of switching is set as the I picture so that the last B picture of the GOP comes at the analyzed stream position. By replacing them, the GOP size is adjusted to forcibly synchronize. Normally, when the GOP structure pattern breaks down, the image quality deteriorates. However, in the streams A and B generated by the encoders 12 and 13 of each system, the period during which the GOP size is varied is after receiving the synchronization trigger signal. There is no problem because it is a period that does not affect the playback video until switching.
[0026]
Therefore, since the timing control at the time of system switching in the multiplexer 11 can be easily performed, the stream before the switching and the stream after the switching are cleanly connected, thereby preventing the reproduction video from being disturbed.
[0027]
The present invention is not limited to the above embodiment. For example, in addition to the GOP structure, one stream may be selectively derived after synchronizing two streams constituting a specific pattern group with a predetermined block period in accordance with a synchronization trigger signal. The same can be done.
[0028]
In addition, the device configuration, the type of encoder, the configuration of the trigger signal generator, the type of multiplexer, the synchronization procedure of streams, the switching procedure, and the like can be variously modified and implemented without departing from the gist of the present invention.
[0029]
【The invention's effect】
As described in detail above, according to the present invention, stream synchronization switching can be performed smoothly without causing disturbance in the transmission signal after synchronizing the two streams subjected to compression encoding. An apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a stream synchronization switching device according to the present invention.
FIG. 2 is a timing chart for explaining a processing operation in the apparatus configuration of the embodiment.
FIG. 3 is a timing chart for explaining a processing operation in the apparatus configuration of the embodiment.
FIG. 4 is a diagram for explaining a GOP structure pattern of a stream in the MPEG2 encoding system.
[Explanation of symbols]
11: Multiplexer,
12, 13 ... encoder,
14 ... Trigger signal generator.

Claims (1)

Two streams having a screen group structure (GOP: Group Of Pictures ) that are mutually compressed and encoded, and each frame is composed of at least one intra-frame coded screen and a plurality of predicted screens created based on this screen. In the stream synchronization switching device for selectively deriving one stream after synchronizing according to the synchronization trigger signal,
An encoding unit that is provided in each system and generates the stream by performing compression encoding processing on a video signal, and is capable of controlling the GOP size of the stream by an external signal;
Switching means for inputting the output of the encoding means of each system and deriving one stream as a transmission signal;
Before a predetermined time of system switching, a synchronization trigger signal is given to the switching source and switching destination encoding means, and the last screen of the screen group structure and the switching destination encoding means in the output of the switching source encoding means at the time of switching Timing control means for switching the switching means after variably setting the GOP size in the output of each encoding means so that the last screen of the screen group structure in the output of
The encoding means of each system analyzes the GOP of the stream to be output when the synchronization trigger signal is given, and synchronizes the last screen of the GOP with each other at the time of switching based on the analysis result. A stream synchronization switching device , wherein a GOP prediction screen from the time of receiving a trigger signal until switching is replaced with the intra-frame coding screen .

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