JPH06334978A - Decoder system - Google Patents

Abstract

PURPOSE:To operate decoders independently of one another to simultaneously decode and reproduce pictures of plural different channels by eliminating coupling between hierarchies by a changeover switch in a hierarchical decoder system. CONSTITUTION:External multiplexed picture data is inputted to a demultiplexer 10 and is separated into first and second encoded picture data. The first encoded picture data is decoded by a first decoder 5 to output a first reproduced picture. The output of the first decoder 5 is connected to an up sampling device 7 through a changeover switch 8, and its output is connected to the input of a second decoder 6. When the changeover switch 8 is closed, the first reproduced picture is converted to a second reproduced picture by the up sampling device 7. The second encoded picture data and the second reproduced picture are decoded by the second decoder 6 to restore and output a third reproduced picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decoding device for decoding a compression-encoded digital image.

[0002]

2. Description of the Related Art Recently, studies on the encoding of digital HDTV images have been advanced. Among them, as functional requirements, compatibility between current televisions and wide televisions and HDTV encoding systems, and scalability for changing image size are required. Hierarchical (pyramid) coding schemes are used to achieve compatibility and scalability.

The structure of the hierarchical coding system is shown in FIGS. 3 and 4. FIG. 3 shows an encoding device. The input image is an HDTV image and is input from the input terminal 46. The input HDTV image is subjected to format conversion by the down-sampling device 42 into a current television or an intermediate system according to the current television, and is input to the first encoder 43. In addition, in order to remove the redundant signal between frames, the signal of the previous frame decoded by the first local decoder 44 is motion-compensated and input to the first encoder 43 to be used as a prediction signal. To use. Hereinafter, such a prediction signal is referred to as an inter-frame prediction signal. The first encoder 43 takes the difference between the current television signal and the inter-frame prediction signal and encodes the residual. The encoded signal is output to the terminal 48 and, at the same time, is decoded by the first local decoder 44. The image thus decoded is fed back to the first encoder 43 for encoding the next frame.

The current television image decoded by the up-sampling device 45 is up-sampled and input to the second encoder 40. This up-sampled image is used as one of the prediction signals of the HDTV image, which will be referred to as a spatial prediction signal hereinafter.

On the other hand, the input HDTV image is input to the second encoder 40. Further, in order to reduce the redundancy of time and space, the inter-frame prediction signal from the second local decoder 41 and the spatial prediction signal from the upsampler 45 are input to the second encoder 40. . The second encoder 40 selects either the inter-frame prediction signal or the spatial prediction signal or the weighted average of the two under a predetermined evaluation function and takes the residual with the input HDTV image as the prediction signal. The data is encoded and output to the output terminal 47. At the same time, the second local decoder 41 performs decoding. The decoded image is fed back to the second encoder 40 for encoding the next frame. The output data of the output terminals 47 and 48 are multiplexed by the multiplexer 49 and transmitted or stored. When interframe predictive coding is not performed, that is, when only intraframe coding is performed, the first local decoder 44 and the second local decoder 4 are used.
1 is unnecessary.

Next, the hierarchical decoding device of FIG. 4 will be described. First, the hierarchically encoded and multiplexed data is separated by a demultiplexer 57 into HDTV component image data and current television component image data. The current television data is input from the output terminal 52 and decoded by the first decoder 54,
The current television image is restored and output, and the upsampling device 56 upsamples. This is the spatial prediction signal described above. The HDTV data and the spatial prediction signal are input to the second decoder 55 to be decoded and HD
Restore to TV image and output.

Although the HDTV and the current television have been described above as examples, hierarchical coding can be similarly performed between the HDTV and an image of an arbitrary lower resolution, or between the current television and an image of the lower resolution. In the following, HDTV and current television will be described as examples. Although the two-layer hierarchical encoding / decoding method has been described for simplification, the same applies to the case of M layers (M> 2) or more.

[0008]

As described above, the hierarchical decoder has a plurality of decoders (M decoders for the M-layer hierarchical encoder, and M> = 2). However, only one image can be played. This is because all the decoders are combined and operate synchronously. Therefore, for example, when two signals of the current television are received and decoded by the first decoder 54 and the second decoder 55, respectively, like the two-layer hierarchical decoding device shown in FIG. 4, The signal of the first decoder 54 passes through the up-sampler 56, interferes with the operation of the second decoder 55, and cannot be decoded normally.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above problems, and in order to make full use of the existing plurality of decoders of a hierarchical decoder, a changeover switch is provided between the decoders, Connect or disconnect the connections between the decoders. By opening the change-over switch and separating the coupling, the decoder can operate independently and it is possible to decode and reproduce a plurality of different images. That is, for example, in the case of a two-layer hierarchical decoding device, hierarchically encoded HDT
It is preferable to close the changeover switch when decoding and reproducing the V image and to open the changeover switch when decoding and reproducing the image that is not hierarchically encoded.

[0010]

By providing a selector switch between a plurality of decoders in the hierarchical decoding device and opening the switch, the decoders can operate independently, and a plurality of images of different channels can be received and decoded. It will be possible. For example, a two-layer hierarchical decoding device can simultaneously reproduce two-channel images. It is possible to display a plurality of images on one display terminal and output them to different display terminals.

[0011]

EXAMPLE A first example will be described with reference to FIG. This is a two-layer hierarchical decoding device. In the figure, 1 and 2
Is an output terminal, 3 and 4 are output terminals, 5 is a first decoder,
6 is a second decoder, 7 is an upsampler, 8 is a changeover switch, 9 is a control circuit, and 10 is a demultiplexer. The first decoder 5 has the ability to decode and play current television pictures, and the second decoder 6 has the ability to decode and play HDTV pictures.

First, the decoding of a hierarchically encoded HDTV image will be considered. In this case, the control circuit 9 closes the changeover switch to display the image data of the current TV component and the HDTV.
The demultiplexer is controlled so that the image data of the component is separated and supplied to the first decoder 5 and the second decoder 6, respectively. When the changeover switch 8 is closed and operated, it becomes the same as the conventional hierarchical decoder shown in FIG. In this case, from the output terminal 3, an image with the resolution of the current TV,
Then, an image having the resolution of HDTV is obtained from the output terminal 4. However, the two images have the same content (that is, the same program) and only have different resolutions.

Next, the decoding of images of different channels will be considered. In this case, the control circuit 9 uses the changeover switch 8
Then, the demultiplexer is controlled so that the coded image data of the current television of channel A is input to the output terminal 1 and the coded image data of the current television of channel B is input to the output terminal 2. The two coded images are not hierarchically coded. When the changeover switch 8 is opened, the first and second decoders 5 and 6 operate independently and the first decoder 5
Decodes and reproduces the program of channel A, and the second decoder 6 decodes and reproduces the program of channel B. Since the second decoder 6 has the ability to decode and reproduce HDTV images,
Can decode and play images on current television. The two different programs played can be displayed on the same screen or monitor, or can be displayed on two different screens or monitors.

Further, the encoded image data of the current television is output to the output terminal 1 and the HD not hierarchically encoded to the output terminal 2.
If you input TV image data and open the changeover switch 8,
The first and second decoders 5 and 6 operate independently, the first decoder 5 decodes and reproduces the current television image, and the second decoder 6 decodes and reproduces the HDTV image. The reproduced current TV and HDTV images can be superimposed and displayed on the same screen or monitor, or can be displayed on two different screens or monitors (current TV and HDTV).

Since the decoder for HDTV has more than double the processing capacity of the decoder for current television, the second decoder 6 in FIG. Can be decoded and reproduced. In this case, the hierarchical decoder as shown in FIG. 1 can decode and reproduce a plurality of (three or more) current television images. A plurality of reproduced different images can be displayed on the same screen, or a plurality of different screens can be displayed. Moreover, there are terrestrial broadcasting, satellite broadcasting, cable TV, videophone, etc. as sources of a plurality of images, and it becomes possible to simultaneously decode and reproduce programs of different sources with the same decoder.
The HDTV and the current television have been described above as examples, but the present invention is not limited to this. The same applies to the current television and the hierarchical decoding device that decodes the lower resolution image.

The second embodiment will be described below with reference to FIG. FIG. 2 shows an M-layer hierarchical decoding device which is a generalization of FIG. 20, 21, 22, 23 are decoders, 24, 2
5 and 26 are upsampling devices, and 27, 28 and 29 are changeover switches. That is, the M-layer hierarchical decoding apparatus has M decoders, (M-1) upsampers, and (M-1) changeover switches. M
The decoder has at least the capability of decoding and reproducing the picture of the current television.

Consider decoding of an image coded and multiplexed in M layers. In this case, the control circuit 30 closes all the changeover switches and controls the demultiplexer so as to separate and output the image coded and multiplexed in the M layer. Each layer image data is decoded and reproduced by a corresponding decoder, but M images having the same content (program) but different resolutions can be obtained. This is a conventional M-layer hierarchical decoding device.

Next, consider the decoding of images of different channels (programs) that are encoded not hierarchically but independently. In this case, the control circuit 30 opens all the changeover switches,
The demultiplexer is controlled to supply images of different channels (programs) to the decoding device. Since the M decoders operate independently, one decoder can decode and reproduce one program. The M layer hierarchical decoding apparatus will decode and reproduce images of M different channels (programs). The same applies when the M input image data includes an image encoded hierarchically and an image encoded independently.

[0019]

As is apparent from the above description, according to the present invention, in the M-layer hierarchical decoding apparatus, each decoder is provided by providing the changeover switch for disconnecting the coupling between the respective decoders. Can operate independently, allowing multiple images on different channels to be received and decoded.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a two-layer hierarchical encoding device.

FIG. 4 is a block diagram of a conventional two-layer hierarchical decoding device.

[Explanation of symbols]

 5 1st decoder 6 2nd decoder 7 Upsampling device 8 Changeover switch 9 Control circuit 10 Demultiplexer

Claims (4)

[Claims] 1. A demultiplexer, a first decoder, a second decoder, a changeover switch, an upsampling device, and a control circuit are provided, and image data from the outside is demultiplexed. Input to a multiplexer, the demultiplexer separates the multiplexed image data into a first encoded image data and a second encoded image data, the first encoded image data Input to the first decoder to be decoded and restored to the first reproduced image and output, and the output of the first decoder is connected to the up-sampling device via the changeover switch, The output of the upsampling device is connected to the input of the second decoding device, and when the changeover switch is closed, the first reproduction image is converted into a second reproduction image by the upsampling device. Second The encoded image data and the second reproduced image are input to the second decoder, decoded, restored to a third reproduced image and output, and the control circuit includes the changeover switch and the demultiplexer. And a decoding device characterized by controlling and. 2. When the first reproduced image and the third reproduced image have the same contents and different resolutions, the control circuit closes the changeover switch, and the first code having the same contents and different resolutions. Decoding according to claim 1, characterized in that the demultiplexer is controlled so as to supply the encoded image data and the second encoded image data to the first decoder and the second decoder, respectively. apparatus. 3. When the first reproduced image and the third reproduced image have different contents, the control circuit opens the changeover switch, and the first coded image data and the second encoded image data having different contents are displayed. 2. The decoding device according to claim 1, wherein the demultiplexer is controlled so as to supply the encoded image data of 1) to the first decoder and the second decoder, respectively. 4. A demultiplexer, M (M> = 2) decoding devices, (M-1) upsamplers, (M-1) changeover switches, and a control circuit. The demultiplexer separates the multiplexed external image data, supplies M encoded image data to the M decoders, and the m-th (m = 1, 2, ..., the output of the M-1) decoder is connected to one changeover switch, and the changeover switch is connected to one upsampling device, and the output of the upsampling device is the (m + 1) th decoding device. A decoding device for controlling the (M-1) changeover switches and the demultiplexer, the decoding device being connected to an input of a demultiplexer and decoding M images having the same content but different resolutions. When reproducing, the control circuit When the switch is closed and the demultiplexer is controlled so as to supply the coded image data having the same content at different resolutions to the decoder to reproduce M images having different content. The decoding device is characterized in that the control circuit opens the changeover switch and controls the demultiplexer to supply the encoded image data having images of different contents to the decoder.