JPH10322694A - Stream switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stream switching device which does not generate mismatching in a switching position and performs switching control of a stream as it is. SOLUTION: A GOP(group of picture) header information reading means 11 read the number of pictures of a GOP and independence information from GOP header information of 1st and 2nd streams. A timing information generating means 12 performs time calculation of the 1st and 2nd streams based on the number of pictures and generates timing information that is a switching position. A black GOP generating means 13 calculates the size of a black GOP based on the timing information and generates a black GOP. A GOP header information rewriting means 14 rewrites GOP header information based on the independence information and the timing information. A multiplexing stream generating means 15 switches the 1st and 2nd streams and the black GOP and multiplexes them and generates a multiplexing stream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stream switching apparatus, and more particularly to a stream switching apparatus for a stream having a GOP structure.
The present invention relates to a stream switching device that switches a first stream to a second stream.

[0002]

2. Description of the Related Art In recent years, ISDB has been used as a combined use of digital transmission lines including digital transmission of television images.
(Integrated Service Digital Broadcasting) is being considered. In ISDB, all information is handled as digital signals, so that it is excellent in flexibility in programming and expandability of new services.

[0003] As ISDB transmission lines, there are satellite broadcast waves and terrestrial broadcast waves, and cable television networks using coaxial cables, optical fibers, and the like. New services such as digital multi-channel broadcasting and multimedia broadcasting combining audio, video, and data using such various transmission paths are being considered.

FIG. 8 is a diagram showing a configuration of a conventional digital multi-channel broadcast transmission system. Program provider 1
00 supplies the program via a medium such as a satellite, a land line, or tape.

[0005] The baseband processing section 200 receives and processes these programs in the satellite line subsystem 201, terrestrial line subsystem 202, or VTR subsystem 203. Then, the switching is controlled by the master switcher 204 in the baseband state.

[0006] The encode processing unit 300 converts the output from the master switcher 204 into encoders 301a to 301n.
And multiplex with the MUX 302. Modulator 303
Transmits the multiplexed signal after digitally modulating it with QPSK or the like.

[0007] Further, the management system 400 transmits information signals such as accounting, program guide, and encryption key management such as scramble broadcasting to the baseband processing unit 200 and the encoding processing unit 3.
00 to perform service management for the user.

[0008]

However, in a conventional digital multi-channel broadcast transmission system, switching such as program switching is performed in baseband. This is because if a stream having a GOP structure such as MPEG is subjected to switching control as it is, a mismatch occurs at the switching position.

For this reason, the transmission path before the switching control has to be in the baseband band.
There is a problem that the effective use of the transmission path of the entire system is impaired.

The present invention has been made in view of such a point, and an object of the present invention is to provide a stream switching apparatus that performs switching control without changing the switching position without changing the stream.

[0011]

According to the present invention, in order to solve the above-mentioned problems, a stream having a GOP structure is provided.
A stream switching device for switching a first stream to a second stream, a GOP header information reading means for reading GOP picture number and independence information from GOP header information of the first and second streams;
A timing information generating unit configured to perform time calculation of the first and second streams based on the number of pictures and generate timing information that is a switching position; and, based on the timing information, the first and second streams. Black GOP generating means for calculating the size of the black GOP to be inserted at the switching position of the stream and generating the black GOP;
Based on the independence information and the timing information,
GOP header information rewriting means for rewriting the GOP header information, multiplexing for switching and multiplexing the first and second streams having the rewritten GOP header information and the black GOP to generate a multiplexed stream Stream generating means, and a stream switching device.

Here, the GOP header information reading means reads out the number of pictures and the independence information of the GOP from the GOP header information of the first and second streams. The timing information generating means performs time calculation of the first and second streams based on the number of pictures, and generates timing information as a switching position. The black GOP generation means calculates the size of the black GOP to be inserted at the switching position of the first and second streams based on the timing information, and generates a black GOP. The GOP header information rewriting means performs GO based on the independence information and the timing information.
Rewrite P header information. The multiplexed stream generator switches and multiplexes the first and second streams having the rewritten GOP header information and the black GOP to generate a multiplexed stream.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of a stream switching device according to the present invention. GOP (Group Of Picture)
The header information reading means 11 reads the number of pictures of the GOP and the independence information from the GOP header information of the first and second streams.

The timing information generating means 12 performs time calculation of the first and second streams based on the number of pictures, and generates timing information as a switching position.
The black GOP generation means 13 calculates the size of the black GOP to be inserted at the switching position of the first and second streams based on the timing information, and generates a black GOP.

The GOP header information rewriting means 14 rewrites the GOP header information based on the independence information and the timing information. The multiplexed stream generation means 15
The first and second streams having the rewritten GOP header information and the black GOP are switched and multiplexed to generate a multiplexed stream.

Next, the operation will be described. FIG. 2 is a flowchart showing a schematic operation procedure of the stream switching device of the present invention. [S1] The GOP header information reading means 11 reads the number of pictures of the GOP and the independence information from the GOP header information of the first and second streams. [S2] The timing information generating means 12 calculates the time of the first and second streams based on the number of pictures, and generates timing information as a switching position. [S3] The black GOP generating means 13 calculates the size of the black GOP to be inserted at the switching position of the first and second streams based on the timing information, and generates a black GOP. [S4] The GOP header information rewriting means 14 rewrites the GOP header information based on the independence information and the timing information. [S5] The multiplexed stream generating means 15 switches and multiplexes the first and second streams having the rewritten GOP header information and the black GOP to generate a multiplexed stream.

Next, the stream switching of the present invention will be described in detail. However, in the following description, the first stream is stream A, the second stream is stream B,
The multiplexed stream is called stream C.

FIG. 3 is a diagram showing an image of switching from stream A to stream B. Stream A GO
It is assumed that the middle of P-A3 and the middle of GOP-B3 of stream B are switching positions.

In such a case, the GOP-
The size of the black GOP is calculated so as not to break A2 and GOP-B4 of stream B. And GOP-A
2 and GOP-B4, a stream G is generated by inserting a black GOP.

Here, when the last picture in the original screen reproduction order of one GOP is an I or P picture as in MPEG, GOP-A2 is not disturbed. However, in the case of GOP-B4, the GOP itself is not broken, but may depend on GOP-B3 instead of being independent.

That is, a stream having a GOP structure having a bidirectional predictive coded image (B picture) such as MPEG,
GOPs may not be completely independent. This is because the first few B pictures in a GOP are
This is because prediction from the last intra-coded image (I-picture) of the OP or the inter-forward predictive-coded image (P-picture) is used.

Therefore, a closed GOP flag and a broken link flag are prepared in the MPEG GOP header in order to consider the independence and editability of the GOP.
The closed GOP flag is a flag that is set at the time of encoding.
Does not depend on Editability is enhanced by placing importance on the independence of GOPs over image quality.

The broken link flag is a flag that is set when a stream that is not a closed GOP is cut by editing and connected. At this time, the normal decoder reproduces some B pictures at the head of the GOP only by backward prediction from the immediately following I picture.

Therefore, GOP-B4 becomes GOP-B3
Is read from the GOP header, and if not, the broken link flag is set to G.
The header information is rewritten using the GOP header of OP-B4.

Next, the detailed configuration of the stream switching device of the present invention will be described. FIG. 4 is a diagram showing a detailed configuration of the stream switching device. The GOP header information reading units 11a and 11b
From the P header, the number of pictures N of each GOP and independence information on the independence of the GOP are read.

The timing information generating means 12 determines whether each GOP
Stream A and stream B
Always calculate the time relationship of Also, a switching control signal for notifying a stream switching instruction is input from outside.

The black GOP generating means 13 generates a black GOP to be inserted at the stream switching position based on the timing information.
Calculate the magnitude of P to generate a black GOP. The GOP header information rewriting units 14a and 14b rewrite GOP header information based on the independence information and the timing information. For example, in the case of FIG. 3, if GOP-B4 and GOP-B3 are not independent, the broken link flag is set to GO.
Set in the GOP header of P-B4.

The multiplexed stream generating means 15 generates a stream C by switching between a stream A and a stream B, which have undergone GOP header rewrite control based on timing information, and a black GOP.

Timing adjustment memories 16a and 16b
Adjusts the timing of switching between the streams A and B and the black GOP. That is,
This is to read the header information from the GOP headers of the stream A and the stream B, generate a black GOP, and adjust the time for rewriting the GOP header.

Next, the black GOP generating means 13 will be described. FIG. 5 and FIG. 6 are diagrams showing the structure of the black GOP. FIG.
Is a black still image of an I picture, and the number of pictures N in a GOP is N = 1. FIG. 6 is a P picture,
This is a case where the number N of pictures in a GOP is N ≧ 2.

Since the I picture of the black GOP is a still picture with a black screen, it can be easily prepared in advance, and its data amount is significantly smaller than that of a normal screen. Further, since the difference between the P picture of the black GOP and the I picture is 0, the data amount is extremely small. As described above, the I and P pictures of the black GOP can be prepared in a small memory area in the black GOP generating means 13 in advance.

Next, a system configuration when the stream switching device of the present invention is applied to a digital multi-channel broadcast transmission system will be described. FIG. 7 is a diagram showing a configuration example of a digital multi-channel broadcast transmission system to which the present invention is applied.

[0033] The program provider 20 is the MPEG server 2
2 is encoded by the encoders 21a to 21n and supplied through a satellite, a ground line, or the like. Transmission control unit 3
0, these programs are received and processed by the satellite line subsystem 31, the terrestrial line subsystem 32, or the MPEG server 33. Then, the MPEG switch 34 controls the switching of the encoded stream.

The MUX 35 multiplexes the switched streams. Modulator 36 converts the multiplexed signal to Q
Digitally modulated by PSK or the like and transmitted. It should be noted that the stream switching device of the present invention uses the MPEG switch 34 and M
Although included in the UX 35, other configurations may be adopted as long as the above-described operation of the device of the present invention is performed similarly.

The management system 400 transmits information signals such as accounting, program guide, and encryption key management for scrambled broadcasting to the transmission control unit 30 to manage services for users.

As described above, the stream switching apparatus of the present invention has a configuration in which a black GOP is inserted at a switching position when a stream is switched. This makes it possible to perform switching control without changing the switching position and without changing the stream.

In the digital multi-channel broadcast transmission system, there is no problem even when a black image is inserted at a switching position in switching of a program or insertion of a CM.

Therefore, if the present invention is applied to a digital multi-channel broadcast transmission system, the program provider 2
The encoding may be performed once on the 0 side, and the stream can be entirely passed through the subsequent transmission path. Therefore, it is possible to effectively use the bandwidth of the transmission path.

[0039]

As described above, the stream switching apparatus of the present invention has a configuration in which a black GOP is inserted at a switching position when a stream is switched. This makes it possible to perform switching control without changing the switching position and without changing the stream.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a stream switching device according to the present invention.

FIG. 2 is a flowchart showing a schematic operation procedure of the stream switching device of the present invention.

FIG. 3 is a diagram showing an image of switching from stream A to stream B.

FIG. 4 is a diagram showing a detailed configuration of a stream switching device.

FIG. 5 is a diagram showing a structure of a black GOP.

FIG. 6 is a diagram showing a structure of a black GOP.

FIG. 7 is a diagram illustrating a configuration example of a digital multi-channel broadcast transmission system to which the present invention has been applied.

FIG. 8 is a diagram showing a configuration of a conventional digital multi-channel broadcast transmission system.

[Explanation of symbols]

11: GOP header information reading means, 12: timing information generating means, 13: black GOP generating means, 14
... GOP header information rewriting means, 15 ... multiplexed stream generation means.

Claims (5)

[Claims] 1. A stream having a GOP structure,
A stream switching device for switching a first stream to a second stream; a GOP header information reading means for reading the number of pictures and the independence information of the GOP from the GOP header information of the first and second streams; A timing information generating unit configured to calculate a time of the first and second streams based on the timing information, and to generate timing information that is a switching position; based on the timing information, the timing information of the first and second streams; Black GOP generation means for calculating the size of the black GOP to be inserted at the switching position and generating the black GOP; based on the independence information and the timing information,
GOP header information rewriting means for rewriting the GOP header information; multiplexing for switching and multiplexing the first and second streams having the rewritten GOP header information and the black GOP to generate a multiplexed stream A stream switching device, comprising: stream generation means. 2. The GOP header information reading means,
A GOP corresponding to the switching position of the second stream
2. The stream switching apparatus according to claim 1, wherein the independence information such as whether or not the GOP immediately after the switching position is encoded independently of each other is read. 3. The black GOP generating unit according to claim 1, wherein the black GOP generating means calculates the size of the black GOP so as not to break the GOP before and after the switching position of the first and second streams. Stream switching device. 4. The GOP header information rewriting means, wherein a GOP corresponding to the switching position of the second stream is
If the GOP and the GOP immediately after the switching are coded depending on each other, a flag is set to make the GOP
2. The stream switching device according to claim 1, wherein the header information is rewritten. 5. The stream switching device according to claim 1, wherein
2. The stream switching apparatus according to claim 1, further comprising a timing adjustment memory for adjusting timing when switching between the second stream and the black GOP.