JP3393907B2 - Video decoding device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture decoding device,
In particular, the present invention relates to a moving picture decoding apparatus which receives a signal in which moving picture coded signals of a plurality of channels are multiplexed in moving picture communication or broadcasting and decodes a moving picture signal of a desired channel.

[0002]

2. Description of the Related Art In the storage and transmission of moving images using digital media, a technique for compressing and coding moving image signals with high efficiency is required. As one of such encoding techniques,
Motion-compensated interframe prediction and DCT (discrete cosine transform)
There is also a hybrid coding method that combines variable length coding. This hybrid coding method is ISO / IEC MPEG which is an international standard of moving picture coding for a wide range of applications from communication to storage media, and a coding method for moving picture communication mainly used for videophone / conference. ITU-T Recommendation H.264. It is used in the H.261.

In these coding methods, usually, intra-frame coded images and inter-frame coded images having different generated code amounts coexist, and variable length coding is also used, so that the coded images are generated every short time. The code amount fluctuates with time. Therefore, usually, a buffer is used to smooth the generated code quantity of the moving picture coding apparatus and send it to the transmission line at a constant rate.
In this case, the buffer has a certain delay.

Further, when interframe prediction is used, when reproduction is performed from an arbitrary time, a correct decoded image cannot be obtained because the reference image used for interframe prediction is not formed correctly at that time. , With significant deterioration in image quality. In order to solve this point, a method is adopted in which intra-frame coded images with good image quality are periodically inserted, for example, at intervals of 0.5 seconds, and the position is used as an entry point for reproduction starting point (for example, Kaisho 63-31029
4 publication). However, in this method, there is a delay between the search for the entry point where the intra-frame coded image exists and the search for the entry point.

The problem of delay due to the various causes described above is
In particular, in the case of multiplexing and transmitting encoded signals of moving image signals of multiple channels, it means that it takes time to obtain a correct decoded image each time the receiving side switches the channels, which is a big problem in practical use. .

[0006]

As described above, according to the conventional technique, a signal in which moving picture coded signals of a plurality of channels are multiplexed is received and a moving picture decoding apparatus decodes a moving picture signal of a desired channel. In that case, there is a problem that it takes time until a correct decoded image is obtained at the time of channel switching. It is an object of the present invention to provide a moving picture decoding device that can effectively reduce the delay until a correct decoded image is obtained when switching channels.

[0007]

In order to achieve the above object, a moving picture decoding apparatus according to the present invention uses an n-channel (n≤m) signal from a multiplexed signal obtained by multiplexing m-channel moving picture coded signals. ), Which separates the moving image coded signal selectively, and the moving image signal of all the images is normally used for one designated channel of the n channel moving image coded signals.
A first decoding means for decoding with quality and the n-channel motion
Of the coded image signals, for the other n-1 channels other than the designated one channel , the moving image signal of only a part of the image necessary as the reference image signal for the subsequent image decoding is decoded. Second decoding means, means for displaying the 1-channel moving image signal decoded by the first decoding means, and n-1 channel moving image signal decoded by the second decoding means. The first decoding means stores in the storage means when a channel switching signal for switching the channel of the moving image signal to be displayed on the display means is input. 1 specified by the channel switching signal by using the reference image signal before the channel switching signal is input.
It is characterized by decoding the moving image signals of all the images of the channel.

[0008]

The decoding means includes at least one of the n-channel moving picture coded signals separated by the separation means.
You may make it decode the moving image signal of all the images about a channel, and decode a moving image signal only about a component with a comparatively low spatial frequency about another channel.

The separating means may update the channel number of the n-channel moving image coded signal to be selectively separated according to the past selection frequency, or may be the n-channel moving image coding to be selectively separated. The channel number of the signal may be determined according to a predetermined priority order.

[0011]

According to the present invention, the n-channel (n≤m) coded signals are selectively separated from the multiplexed m-channel coded video signals, and these are input to the decoder to generate a moving image in real time. Decode the image signal. One or more channels of the decoded n-channel moving image signal are displayed. At this time, if the channel to be switched at the time of channel switching is among the n channels, the display channel can be switched immediately without delay after the channel switching.

When the channel to be switched is not included in the above n channels, the timing of switching the channel is delayed, or the channel is switched immediately.
Immediately after switching, an incomplete reproduced image is displayed.

Here, when selecting and separating the coded signal of the n channel from the coded signal of the m channel, the frequency is selected in the past of each channel and its history, or it is predetermined. By selecting according to the priority order, it is possible to further effectively reduce the delay until a correct decoded image is obtained at the time of channel switching.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing the arrangement of a moving picture decoding apparatus according to the first embodiment. The moving picture decoding apparatus of this embodiment includes a separation circuit 12 and n decoders 13-1.
13-n, a selection circuit 14, a channel control circuit 15, a data memory 16, a channel changeover switch 17 and a display device 18.

A multiplexed signal 11 obtained by multiplexing moving image coded signals of m channels (for example, several tens of channels) is input to the moving image decoding apparatus. The multiplexed signal 11 is input to the demultiplexing circuit 12, and the moving image coded signals of n (n ≦ m) channels (for example, several channels) designated by the channel control circuit 15 are selectively demultiplexed. The n-channel moving image coded signals separated by the separation circuit 12 are n decoders 1.
3-1 to 13-n, respectively, and the moving image signals of n channels are decoded in parallel. Decoder 13-1 to 13-
The n-channel moving image signal obtained from n is selected by the selection circuit 14
And one or a plurality of channels of moving image signals designated by the channel control circuit 15 are selected. The moving image signal of the channel selected by the selection circuit 14 is a CRT.
It is sent to the display device 18 such as a display or a liquid crystal display and displayed.

The data memory 16 stores k fixed channels (k <n) and nk non-fixed channels, and information about the frequency of each channel selected in the past and its history. The channel changeover switch 17 is used by the user to specify a channel that the user actually wants to display. The channel control circuit 15 includes a channel changeover switch 1
When the channel switching signal is input from the decoder 7, the moving image signal of the channel designated by the channel switching signal is input to the decoder 1
If it is decoded by any of 3-1 to 13-n, the selection circuit 14 is controlled to display the moving image of the channel on the display device 1.
The display channel (referred to as the channel displayed on the display device 18) is switched so as to be displayed at 8, and the channel selection frequency and the history information in the data memory 16 are updated.

Further, the channel control circuit 15 includes a decoder 1
When a channel that has not been decoded by any of 3-1 to 13-n is designated by the channel changeover switch 17, of the currently fixed non-fixed channels, the channel selection frequency stored in the data memory 16 and its At the same time as stopping the decoding operation of the decoder (referred to as 13-i) which is decoding the moving image signal of the channel having the lowest priority obtained from the history, it controls the separation circuit 12 to the decoder 13-i. The moving image coded signal of the new channel designated by the channel changeover switch 17 is transmitted. As a result, the decoder 1 that has received the moving image coded signal of the new channel
3-i searches the frame of the intra-coded image, that is, the entry point, and starts decoding from that.

When the decoder 13-i correctly resumes the decoding, the channel control circuit 15 controls the selection circuit 14 to switch the channel to switch the display channel and the channel in the data memory 16. Update selection frequency and history information.

(Second Embodiment) FIG. 2 shows a block diagram of a moving picture decoding apparatus according to the second embodiment. The moving picture decoding apparatus according to this embodiment includes a separation circuit 22 and two decoders 23-
1, 23-2, a frame memory 24, a channel control circuit 25, a data memory 26, a channel changeover switch 27 and a display device 28.

The demultiplexing circuit 22 is controlled by the channel control circuit 25, and among the n-channel moving picture coded signals selectively separated from the multiplexed signal 21 in which the m-channel moving picture coded signals are multiplexed, The decoder 23-decodes the moving image coded signal of the display channel designated by the control circuit 25.
1 and sends the remaining n-1 channel moving image coded signals to the decoder 23-2.

The decoder 23-1 is a normal decoder, in other words, a full-spec decoder capable of obtaining a decoded image of desired image quality guaranteed by the encoding / decoding method, The moving image signal decoded by the decoder 23-1 is sent to the display device 28 and displayed. On the other hand, the decoder 23-2 is a decoder that performs n-1 channel decoding in a time division manner, and for the input n-1 channel moving image coded signals, a reference image for decoding the subsequent images. decoding in a time division moving image signal of only some of the necessary images as a signal. The moving image signals decoded by the decoders 23-1 and 23-2 are stored in the frame memory 24 for each channel.

Here, the decoder 23-2 is used for creating a reference image signal, and when the reference image is actually used after channel switching, it has a normal quality corresponding to the image to be displayed on the display device 28. (Resolution, quantization accuracy, etc.)
However, considering the reduction of the hardware scale and the frequency of channel switching, the spatial frequency component of the input video coded signal is relatively low, at the expense of some quality compared to normal quality. It is also possible to simply perform decoding using only the part. This way, with limited processing power,
In other words, a multi-channel (n-1 channel) moving image signal can be decoded as a reference image without significantly increasing the hardware cost.

When the channel switching signal is input by the channel switching switch 27, the channel control circuit 25 decodes if the moving image signal of the channel designated by the channel switching signal has been decoded by the decoder 23-2. Bowl 23-1
The separation circuit 22 is controlled so that the moving image signal of that channel is input to the input terminal, and the reference image address in the frame memory 24 is changed. As a result, the video signal of the channel designated by the channel switching signal is the decoder 23-
1 decodes with a desired image quality. The channel control circuit 25 also updates the channel selection frequency and history information in the data memory 26.

On the other hand, when the channel change-over switch 27 requests switching to a channel which has not been decoded by the decoder 23-2, the channel control circuit 25 selects the selected frequency among the currently decoded channels and the selected frequency. Decoding of the moving image signal of the channel with the lowest priority obtained from the history and control for stopping the transmission of the moving image encoded signal to the decoder 23-2 are performed.

Next, the channel control circuit 25 uses the separation circuit 2
2 is controlled to send the moving image coded signal of the designated channel to the decoder 23-2, where the entry point is searched and decoding is started. Then, when the decoding of the reference image signal for correctly restarting the decoding is completed, the decoder 2
The decoding operation of 3-1, that is, the decoding operation of the moving image signal of the display channel that has been selected so far is stopped, and the moving image encoded signal of the channel newly designated by the channel changeover switch 27 is decoded by the decoder 23-1. Separation circuit 22 to send to
And the reference image address in the frame memory 24 is changed to start the normal decoding operation by the decoder 23-1. Further, the channel control circuit 25 also updates the channel selection frequency and history information in the data memory 26. Regarding the moving image signal of the channel which has been decoded by the decoder 23-1 immediately before switching the channel, the decoder 2
Switch to 3-2 and continue decoding.

In the display device 28, the decoder 23-
It is also possible to use it as a menu screen for channel selection by reducing the moving image signals of the n-1 channel decoded by 2 and displaying them simultaneously by dividing one screen as shown in FIG. It is possible.

(Third Embodiment) FIG. 3 shows a block diagram of a moving picture decoding apparatus according to the third embodiment. The moving picture decoding apparatus according to this embodiment includes a separation circuit 32, a decoder 33, a frame memory 34, a channel control circuit 35, and a data memory 3.
6, a channel changeover switch 37 and a display device 38.

The separation circuit 32 is controlled by the channel control circuit 35 and selectively separates and decodes only the n-channel moving image coded signal from the multiplexed signal 31 obtained by multiplexing the m-channel moving image coded signal. Send to vessel 33. Decoder 33
Then, the moving image signal is time-decoded from the input n-channel moving image encoded signal. Of these n-channel moving image signals, the display channel moving image signal is the display device 3
7, the remaining n-1 channel moving image signals are stored as the reference image signals in the frame memory 34, only the image signals necessary for decoding the subsequent images.

When the channel changeover switch 37 inputs the channel changeover signal, the channel control circuit 35 determines whether the moving picture signal of the channel designated by the channel changeover signal has been decoded by the decoder 33. The decoder 33 is controlled so that the moving image coded signal is sent to the display device 38 as the signal of the display channel, and the channel selection frequency and the history information in the data memory 36 are updated.

On the other hand, when the channel changeover switch 37 requests switching to a channel that has not been decoded by the decoder 33, it is first obtained from the selection frequency and the history of the channels currently decoded by the decoder 33. The decoding operation of the moving picture signal of the channel having the lowest priority and the control for stopping the transmission of the moving picture coded signal of the channel to the decoder 33 are performed.

Next, the channel control circuit 35 operates as the separation circuit 3
2 is controlled to send the moving picture coded signal of the channel to be switched to the decoder 33, where the entry point is searched and decoding is started. Then, the channel control circuit 35
Controls the decoder 33 so that the video signal of the channel selected by the channel changeover switch 37 is output from the decoder 33 to the display device 38 when the decoding is correctly restarted by the decoder 33. The channel selection frequency and history information in the data memory 36 are updated.

Next, the channel control circuit 40 (15 in FIG. 1, 25 in FIG. 2, 35 in FIG. 3) used in the above embodiments.
(Corresponding to) is shown. Further, FIG. 6 shows an example of data in the data memory 46 (corresponding to 16 in FIG. 1, 26 in FIG. 2, and 36 in FIG. 3) in FIG. The channel control circuit 40 shown in FIG. 5 includes a viewing time counting circuit 41 and a selection frequency counting circuit 4.
2. Priority calculation circuit 43 and control signal generation circuit 44
Consists of.

In the channel control circuit 40, the viewing time of the display channel is counted by the viewing time counting circuit 41, and the channel changeover switch 45 (17 in FIG. 1, FIG. 2) is used.
27, corresponding to 37 in FIG. 3), each data shown in FIG. 6 in the data memory 46 is updated, and the priority calculation circuit 43 recalculates the priority of each channel. To do. In the control signal generation circuit 44,
The decoding channel control signal 47 and the display channel control signal 48 are generated in accordance with this priority order, and control for selecting a channel to be decoded and a display channel is performed. In addition,
The decoded channel control signal 47 is the separation circuit 1 in the case of FIG.
2, the separation circuit 22 and the decoder 23-2 and the frame memory 24 in the case of FIG. 2, and the separation circuit 3 in the case of FIG.
2, the decoder 33 and the frame memory 34, respectively.

Here, the priority control circuit 43 determines the priority according to the long-term cumulative viewing time and the short-term cumulative viewing time of each channel, the channel selection frequency and the selection history. However, high priority is given to the preset reserved channel and the channel displayed immediately before, regardless of the past viewing data. In accordance with these priorities, a plurality (n) of channels for decoding the moving image signal are determined, and in the case of FIG. 1, for each of the channels, the decoders 23-1 to 23-23 used for decoding are determined.
The number of -n, in the case of FIGS. 2 and 3, the timing (time slot) of the time division decoding in the decoder 23-2 and the decoder 33 is set.

The flow chart shown in FIG. 7 shows the flow of a series of processing when the processing of the channel control circuit 40 is realized by software. That is, when a channel switch request is made to the X channel by the channel switch (step S2), it is checked whether or not the moving image signal of the X channel is being decoded (step S2).
3). If the moving picture signal of the X channel is not being decoded here, the decoding of the moving picture signal of the channel having the lowest priority among the decoding channels is stopped and the decoding of the moving picture signal of the X channel is started. (Steps S4 to S
5). Next, when the moving image signal of the X channel starts to be correctly decoded, the display channel is switched to the X channel (steps S6 to S7), and the viewing data (cumulative viewing time, channel selection frequency, channel selection history) in the data memory is further changed. Etc.) is updated (step S8), and the priority order is recalculated (step S9). Then, n decoding channels are switched based on the recalculated priority order (step S10), and the process returns to step S1. If it is determined in step S1 that the channel switching request has not been made for a certain period of time, the series of processes ends.

As the channel changeover switch, there are a type having a channel selection key for each channel, and a serial type switch for performing channel selection by sequentially scanning each channel with the up / down keys. Although FIG. 7 described above shows the former case, the latter case may be performed as follows.
That is, in the mode in which the channels are sequentially scanned, since the channel to be displayed next is known in advance, the channel switching control circuit stops the decoding of the two channels having the lower priority and the channel to be displayed next. Reserve a decoder for decoding. If the channel to be displayed next is not being decoded, these two decoders are sequentially switched to start decoding in advance, so that smooth channel scanning becomes possible.

[0037]

As described above, according to the present invention, when a moving picture signal of an arbitrary channel is decoded and reproduced from a multiplexed moving picture coded signal, a correct decoded picture can be obtained at the time of channel switching. It is possible to effectively reduce the delay.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a moving picture decoding apparatus according to a first embodiment.

FIG. 2 is a block diagram showing a configuration of a moving picture decoding apparatus according to a second embodiment.

FIG. 3 is a block diagram showing a configuration of a moving picture decoding apparatus according to a third embodiment.

FIG. 4 is a diagram showing an example of a menu screen for channel selection created from a plurality of decoded images.

FIG. 5 is a block diagram showing an embodiment of a channel control circuit according to the present invention.

FIG. 6 is a diagram showing an example of contents of a data memory according to the present invention.

FIG. 7 is a flowchart showing a processing procedure of a channel control circuit according to the present invention.

[Explanation of symbols]

11 ... Multiplexing signal 12 ... Separation circuits 13-1 to 13-n ... Decoder 14 ... Selection circuit 15 ... Channel control circuit 16 ... Data memory 17 ... Channel changeover switch 18 ... Display device 21 ... Multiplexing signal 22 ... Separation circuit 23-1 to 23-2 ... Decoder 24 ... Frame memory 25 ... Channel control circuit 26 ... Data memory 27 ... Channel changeover switch 28 ... Display device 31 ... Multiplexing signal 32 ... Separation circuit 33 ... Decoder 34 ... Frame memory 35 Channel control circuit 36 Data memory 37 Channel switch 38 Display 40 Channel control circuit 41 Viewing time counting circuit 42 Selection frequency counting circuit 43 Priority calculation circuit 44 Control signal generation circuit 45 Channel switching Switch 46 ... Data memory 47 ... Decode channel control signal 48 ... Display channel control signal

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Claims (5)

(57) [Claims] 1. A separating means for selectively separating an n-channel (n ≦ m) moving image coded signal from a multiplexed signal obtained by multiplexing m-channel moving image coded signals, and the n-channel moving image. Specified 1 of encoded signals
For the channel , the video signal of the entire image is recovered with normal quality.
The first decoding means for encoding and the designated one of the n-channel moving image encoded signals.
A second decoding means for decoding a moving image signal of only a part of the image necessary as a reference image signal for the subsequent decoding of the image for the other n-1 channels other than the one channel ; and the first decoding means. A means for displaying the 1-channel moving image signal decoded by, and a storage means for storing the n-1 channel moving image signal decoded by the second decoding means as the reference image signal, said first decoding means, the channel switching signal for switching the channel of the moving image signal to be displayed on said display means when it is entered, stored in the storage means,該Chi
A moving image decoding apparatus, which uses a reference image signal before a channel switching signal is input to decode a moving image signal of all the images of one channel designated by the channel switching signal. 2. The second decoding means decodes a moving image signal by using only a component having a relatively low spatial frequency in the moving image encoded signal for the n-1 channel. 1. The video decoding device according to 1. 3. The moving picture coding apparatus according to claim 1, wherein said display means reduces and displays the moving picture signal of said n-1 channel. 4. The moving picture decoding apparatus according to claim 1, wherein said separating means updates the channel number of the moving picture coded signal of n channels to be selectively separated according to the past selection frequency. . 5. The separating means updates the channel numbers of n-channel moving image coded signals to be selectively separated in accordance with a predetermined priority order.
The moving picture decoding device described.