KR0179104B1 - Satellite channel hdtv incompatible with ground channel hdtv broadcasting - Google Patents

Abstract

The present invention relates to a satellite channel HDTV system that is compatible with a terrestrial channel HDTV broadcasting system in which a satellite channel HDTV broadcasting system is compatible with a terrestrial channel broadcasting system and obtains a desired picture quality. By subtracting the band where data can be sent and transmitting the data to improve the image quality only when the satellite channel is transmitted, the satellite and terrestrial HDTV systems are compatible with each other and do not cause waste of the frequency band of the satellite channel. At the same time, the desired image quality can be obtained. In addition, since encoding and decoding of transmission are configured differently because the channels are different, video / audio encoding and decoding can be used regardless of terrestrial broadcasting or satellite broadcasting, so that the compatibility between video encoding and decoding can reduce the time loss of encoding. This can reduce the cost of storing a large original image because only a bit stream can be stored or moved.

Description

Satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting

1 is a block diagram showing a general MPEG 2 encoding apparatus.

2 is a block diagram showing a general MPEG2 decoding device.

3 is a block diagram showing an embodiment of an encoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention.

4 is a block diagram showing an embodiment of a decoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention.

FIG. 5 is a detailed block diagram showing an embodiment of the second encoder of FIG. 3. FIG.

6 is a detailed block diagram showing an embodiment of the second decoder of FIG.

7 is a block diagram showing another embodiment of an encoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention.

8 is a block diagram showing another embodiment of a decoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention.

9 is a block diagram showing a transport layer of a satellite channel HDTV system according to the present invention.

10 is a block diagram showing a transport layer of a terrestrial channel HDTV system according to the present invention.

11 is a block diagram showing an embodiment of a receiver when receiving satellite broadcast according to the present invention.

12 is a block diagram showing an embodiment of a receiver at the time of terrestrial broadcast reception according to the present invention;

* Explanation of symbols for main parts of the drawings

10,31: first encoder 11,33,71: subtractor

12,51: DCT section 13,72: quantization section

14,73: VLC section 15,23,83: inverse quantization section

16,24: IDCT part 17,25,43,84: adder

18, 26: frame memory 19: motion estimation unit

19-5,27: motion compensation unit 20,41: first decoder

21,81: Channel buffer 22,82: VLD part

32: decoder 33: difference image generating unit

34,70: second decoder 42,80: second decoder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite channel HDTV system compatible with terrestrial channel high definition television (HDTV) broadcasting. In particular, the satellite channel HDTV broadcasting system is compatible with terrestrial channel broadcasting systems to achieve desired image quality. A satellite channel HDTV system compatible with channel HDTV broadcasting.

In other words, the US HDTV terrestrial broadcasting standard will be adopted by the GA (Grand Alliance) HDTV system. The GA HDTV terrestrial channel system uses the same 6MHz bandwidth as the current NTSC broadcasting bandwidth, and the transmission method uses a coded 8-side residual band (VSB).

At this time, the bit rate of pure data excluding roll-off-factor, signal for synchronization, and additional bit for error correction is about 20Mbps.

This pure data contains video, audio, and ancillary data, which are almost all of the video data. This bit rate is a very sensitive bit rate when transmitting a high-resolution screen with an effective pixel number of 1080 × 1920 or a screen with a highly moving object. When viewed in detail, a defect due to data compression / restore is quite visible.

However, since the terrestrial channel is allowed to broadcast simultaneously with NTSC broadcasting, more than 6MHz bandwidth is not allowed.

On the other hand, the satellite channel is irrelevant to the NTSC broadcast, it can use a frequency band within the range allowed by one repeater.

In general, a repeater of a satellite has a bandwidth of about 30 MHz and the transmission method used by the satellite mainly uses quadrature phase shift keying (QPSK).

At this time, about 30Mbps bits can be used to transmit pure video data except roll-off-factor, error correction bit, sync bit, audio bit, and various auxiliary data.

At this bit rate, no matter how high-definition or high-motion screens are, defects due to compression / restore of data are almost invisible. In other words, the HDTV system through the satellite channel can have a true high definition or high definition.

However, when transmitting over the terrestrial channel, the bit rate is not correct, and thus, transmission cannot be performed. In order to transmit the terrestrial channel, the original video data must be encoded again.

However, in this case, the encoding of video data is very complicated and time-consuming, which not only increases the cost but also increases the cost for the storage medium since the original video data is about 50 times more than the amount of data in the encoded bit stream. Will result.

For this reason, there are two satellite channel HDTV systems currently under discussion. First, the satellite channel video data bit rate should be the same as the terrestrial channel video data bit rate so as to be compatible with the terrestrial channel system, and the remaining bands are used to transmit data for other purposes. Is to transmit satellite channel HDTV data with a sufficiently large bit rate without any consideration.

Conventional HDTV video encoding and decoding uses the syntax of MPEG2, and one embodiment of video encoding and decoding for the above two cases is illustrated in FIGS. 1 and 2.

In this case, motion estimation and motion compensation in units of blocks are used to reduce temporal redundancy, and discrete cosine transform is used to reduce spatial redundancy. ; DCT) compression technique.

That is, when the subtractor 11 outputs a difference between the original image and the motion compensated image, the DCT unit 12 converts the image from the spatial domain to the frequency domain to remove data redundancy. do. At this time, since the image data has little change, the low frequency, especially the DC component, has a large value and the high frequency component has a relatively very small value.

On the other hand, the quantization unit 13 displays the data passed through the DCT unit 12 with a limited number of bits to reduce the data amount. That is, when the output of the DCT unit 12 is quantized, the horizontal, vertical, and low frequency components of the spatial frequency are large and the high frequency components are almost zero.

In the variable length coding (VLC) unit 14, a short code length is assigned to data with high frequency of appearance of data and a long code length is assigned to data with low frequency of appearance, thereby reducing the total number of bits to 20 or more. It transmits a bit stream at a bit rate of 30 Mbps.

On the other hand, for motion compensation and image storage, the output of the quantization unit 13 is restored to an image almost identical to the difference image output from the subtractor 11 via the inverse quantization unit 15 and the IDCT 16.

At this time, when the reconstructed picture and the motion compensated picture are added by the adder 17, an original picture is obtained.

On the other hand, since many changes do not occur unless the scene is changed between frames, only fewer bits will be required if only the difference between the frames is transmitted. For this purpose, the encoder and the decoder need a frame memory for storing a previous picture.

Accordingly, the original image output from the adder 17 becomes a previous image while being stored in the frame memory 18, and the motion estimation unit 19 compares the original image currently input with the previous image stored in the frame memory 18. Motion information, that is, the direction and magnitude (Motion Vector; MV) of the object is obtained.

In this case, the motion information (MV) is transmitted along with the transform coefficient information after the protection length is changed in accordance with the frequency of appearance of data in the VLC 14 to obtain the maximum coding efficiency.

Meanwhile, the motion compensator 20 predicts the original image by performing motion compensation on the previous image output from the frame memory 18 using the motion information output from the motion estimator 19.

At this time, if the compensation is correctly performed in the motion compensator 20, the output of the subtractor 11 is zero, but there is a slight difference between the original image and the motion compensated image due to noise.

On the other hand, the bit stream transmitted from the VLC 14 of the encoder of FIG. 1 is input to a variable length decoding (VLD) 22 through the channel buffer 21 to be variable length decoded, and then the inverse quantizer 23 and the IDCT. Through the process (24), a difference image between the original image and the motion compensated image is restored.

At this time, the motion compensator 27 predicts the original image by performing motion compensation on the previous image output from the frame memory 26 by using the motion information MV output from the VLD 22. The difference image output from the IDCT 24 and the prediction image output from the motion compensator 27 are added to restore the original image.

At the same time, the restored original image is output to the frame memory 26 to update the frame memory 26.

However, the encoder of FIG. 1 and the decoder of FIG. 2 described above cannot make the image quality as good as desired if the satellite channel video bit rate is equal to the ground channel video data bit rate so as to be compatible with the terrestrial channel system as described above. When the satellite channel HDTV data is transmitted large enough, the image quality can be as good as desired, but it is incompatible with the terrestrial channel system.

The present invention is to solve the above problems, an object of the present invention is to improve the image quality only when the satellite channel transmission by using the remaining band subtracting the band that can send the same data as the ground channel transmission of the satellite channel band The present invention provides a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting that transmits data so that the satellite channel and terrestrial channel HDTV systems are compatible with each other and at the same time obtain image quality without wasting satellite channel frequency bands. .

A feature of the encoder of the satellite channel HDTV system compatible with the terrestrial channel HDTV broadcasting according to the present invention for achieving the above object is to encode the original image at 20Mbps bit rate using the MPEG2 encoding algorithm and transmit it as the main bit stream. A first encoder, a decoder for decoding the image encoded by the first encoder using an MPEG2 decoding algorithm, and difference image generating means for generating a difference image by extracting a difference between the original image and the image decoded by the decoder And a second encoder which encodes the difference image output from the difference image generating means at a 10 Mbps bit rate and transmits it as an additional bit stream.

Another feature of an encoder of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention is a first encoder for encoding an original image at a 20 Mbps bit rate using an MPEG2 encoding algorithm and transmitting it as a main bit stream. The second encoder extracts the difference between the DCT image and the IDCT image in the encoder and generates a difference image to compensate for the portion lost by quantization, encodes the generated difference image at a 10 Mbps bit rate, and transmits the additional bit stream as an additional bit stream. The point is composed of.

A decoder of the satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention is characterized by: a first decoder for decoding a main bit stream transmitted at a 20 Mbps bit rate using an MPEG2 decoding algorithm, and an additional transmitted at 10 Mbps bit rate. And a second decoder for specially decoding the bit stream, and an original image restoring means for adding the image decoded by the first decoder and the image decoded by the second decoder to restore the original image.

Another feature of a decoder of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention is a first decoder for recovering a main bit stream transmitted at 20 Mbps bit rate through VLD and dequantization, and a 10 Mbps bit rate. And a second decoder for restoring an additional bit stream to be processed through a VLD and inverse quantization process, and image restoring means for adding a dequantized picture in the first decoder and a dequantized picture in the second decoder. One decoder decodes an image output from the image restoring means, adds a motion compensated image, and restores the original original image.

Hereinafter, a preferred embodiment of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a block diagram showing an embodiment of an encoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention, wherein the original image is encoded at 20 Mbps, which is a terrestrial channel video data bit rate. A difference between the first encoder 31 which outputs stream 1), the decoder 33 which decodes the picture encoded by the first encoder 31, and the output of the decoder 33 from the original picture. A subtractor 34 for generating an image, and a second encoder 35 for specially encoding the difference image output from the subtractor 34 at a 10 Mbps bit rate to output an additional bit stream (bit stream 2). do.

In this case, the first encoder 31 may use the MPEG2 encoder as shown in FIG. 1, and the decoder 33 may use the MPEG2 decoder as shown in FIG.

In addition, the second encoder 34 for the additional bit stream encodes the difference picture, which is a picture in which motion compensation has already been performed in the first encoder 31 and the decoder 32. Therefore, in image coding and decoding, the hardware does not need the most complicated motion estimation or motion compensation process, and only needs to perform an intra picture encoding algorithm.

In this case, the intra coding method simply uses a differential pulse code modulation (DPCM) or a signal input from DPCM to quantize, modulate, and transmit a difference between a current input signal and a prediction signal by a previous signal. Adaptive DCCM (Adaptive DPCM), which adjusts the predictors according to the characteristics and quantizes the signal while minimizing the variance of the error signal, or the DCT 51, the quantizer 52, and the VLC 53 as shown in FIG. Use an encoder consisting of

Here, as shown in FIG. 5, a coding apparatus combining DCT and VLC is a part of an MPEG2 algorithm, and is generally more complicated but has very good efficiency.

FIG. 4 is a block diagram showing an embodiment of a decoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention. In FIG. 3, a main bitstream (bit stream 1) transmitted at a transmission rate of 20 Mbps is shown in FIG. First decoder 41 to decode the signal using the MPEG2 decoder as shown in FIG. 2, and a second decoder to specially decode and decode an additional bit stream (bit stream 2) transmitted at a transmission rate of 10 Mbps. (42), and an adder 43 that adds the outputs of the first decoder 41 and the second decoder 42 to restore the original original image.

At this time, the decoding apparatus for decoding the additional bit stream can be simply configured using a decoder suitable for the same as the encoding apparatus.

Accordingly, the second decoder may use a decoder composed of a VLD 61, an inverse quantizer 62, and an IDCT 63, which are generally more complicated but efficient, as shown in FIG.

The present invention configured as described above does not require a special theory at the time of broadcasting because it follows the syntax of MPEG2 as it is, and simply needs an additional part compared to conventional hardware, and the basic flow is the same as that of conventional video encoding and decoding. It transmits data for improving image quality only when satellite channel is transmitted by subtracting the band that can send the same data as terrestrial channel transmission among satellite channel bands.

That is, the original image is encoded by the MPEG-2 encoding in the first encoder 31 at 20 Mbps, which is the terrestrial channel video data bit rate, and transmitted in the main bit stream (bit stream 1) having the same 20 Mbps transmission rate as the terrestrial channel transmission. The decoder 32 recovers by MPEG2 decoding.

At this time, the subtractor 33 subtracts the MPEG2 decoded picture from the original picture to generate a difference picture.

The generated difference image is encoded by the second encoder 34 at a bit rate of 10 Mbps using an encoding algorithm suitable for differential image encoding. Then, the encoded data is made into an additional bit stream (bit stream 2) at a 10 Mbps data rate to fit the MPEG2 transport layer, and then one program is added to the additional bit stream (bit stream 2) together with the main bit stream (bit stream 1). Give ID (Program Identifier; PID) to send additionally.

In the receiver, the main bit stream transmitted at 20 Mbps bit rate is decoded by MPEG2 decoding in the first decoder 41, and the additional bit stream transmitted at 10 Mbps bit rate is suitable for the additional bit stream in the second decoder 42. Is decrypted by

At this time, the adder 43 adds two pictures decoded by the first and second decoders 41 and 42 to obtain a final desired picture.

At this time, since the difference image is an image that has already been subjected to motion compensation, it can be encoded simply by performing only the intra coding algorithm. That is, the difference image is encoded by sequentially performing the processes of the DCT 51, the quantization unit 52, and the VLC 53 as in DPCM, ADPCM or FIG. 5, and the VLD 61 and inverse quantization unit as shown in FIG. 62), IDCT (63) process can be performed sequentially to decode.

FIG. 7 is a block diagram showing another embodiment of an encoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention, in which an original image is encoded by MPEG2 encoding at a terrestrial channel video data bit rate of 20 Mbps. The first encoder 10 outputting the bit stream (bit stream 1) and the difference image between the DCT image and the IDCT image in the first encoder 10 are generated and encoded at a 10 Mbps bit rate so that an additional bit stream ( And a second encoder 70 for outputting to the bit stream 2).

In this case, the first encoder 10 is the same MPEG2 encoding block as the first block, and the same block uses the same code and the description of the configuration is omitted.

The second encoder 70 detects a difference between an image DCT in the DCT unit 12 of the first encoder 10 and an image DCT reversed in the IDCT unit 16 to generate a difference image ( 71), a quantizer 72 for displaying the output of the subtractor 71 with a limited number of bits, and a VLC 73 for allocating code lengths according to the frequency of appearance of the output data of the quantizer 72. do.

8 is a block diagram showing another embodiment of a decoding apparatus of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting according to the present invention, and VLD and dequantization of a main bit stream (bit stream 1) transmitted at a transmission rate of 20 Mbps. A first decoder 20 for restoring through the process, a second decoder 80 for restoring the additional bit stream (bit stream 2) transmitted at a transmission rate of 10 Mbps through a VLD and inverse quantization process, and the first decoder And an adder 84 that adds the dequantized picture by the decoder 20 and the dequantized picture by the second decoder 80 and outputs them to the first decoder 20 IDCT 24.

Therefore, the first decoder 20 performs an inverse DCT on the original image output from the adder 84, and then adds the motion compensated image to restore the original original image.

In this case, the first decoder 20 has the same configuration as the MPEG2 decoding block of FIG. 2, and the same block uses the same code and the description of the configuration is omitted.

The second decoder 80 includes a channel buffer 81 for temporarily storing an additional bit stream, a VLD 82 for variable length decoding the additional bit stream output through the channel buffer 81, and the VLD. An inverse quantization unit 83 which inversely quantizes the data output from 82 and outputs the same to the adder 84.

7 and 8 have the same basic flow as the conventional video encoding and decoding, but only when the satellite channel is transmitted by using the remaining band after subtracting the band for transmitting the same data as the terrestrial channel transmission among the satellite channel bands. Send additional data to improve the image quality.

The difference between the original image and the encoded image in video compression is due to loss due to quantization. In other words, if there is no loss caused by quantization, the theoretically encoded picture is the same as the original picture. Therefore, the additional data to be transmitted should be properly compensated for the loss caused by quantization.

Therefore, the second encoder 70 of FIG. 7 encodes the loss part due to quantization at an appropriate bit rate. At this time, the coding method can be simply configured using quantization and VLC in the state of DCT, for two reasons.

First, since the component to be sent is a component that has already been motion-compensated, it is not necessary to perform interframe encoding, which has good encoding performance but has a very complicated configuration. Secondly, the intraframe coding is a very good coding method in the DCT domain, and since the receiver can process the DCT coefficients in addition, the additional hardware becomes very simple.

Then, the second coder 70 creates an additional bitstream so that the encoded data is fit to the MPEG2 transport layer, and gives the bitstream together with the main bitstream to give one program identifier (PID). send.

Then, in the receiving unit as shown in FIG. 8, the main bit stream (bit stream 1) is decoded by the original MPEG2 decoder, that is, the first decoder 20, and the additionally transmitted bit stream (bit stream 2) is the second decoder. In operation 80, the VLD and the inverse quantization are decoded in order to decode and add the decoded image and IDCT before the first decoder 20. FIG. Signal processing after IDCT does not require any additional hardware, and signal processing can be performed in the same way as the existing one.

That is, when the subtractor 11 of the first encoder 10 outputs a difference between an original image and a moving-injured image, the DCT unit 12 displays an image from a spatial domain in order to remove redundancy of data. Convert to an area. At this time, since the image data has little change, the low frequency, especially the DC component, has a large value, and the high frequency component has a relatively small value.

On the other hand, the quantization unit 13 displays the data passed through the DCT unit 12 with a limited number of bits to reduce the data amount. That is, when the output of the DCT unit 12 is quantized, the horizontal, vertical, and low frequency components of the spatial frequency are large and the high frequency components are almost zero.

Then, the VLC unit 14 reduces the total number of bits by allocating a long code length to a data having a low frequency of appearance and a short code length to a data having a high frequency of data, and then a main bit stream (bit stream 1) at a bit rate of 20 Mbps. Send it.

On the other hand, for motion compensation and image storage, the output of the quantization unit 13 is restored to the difference image output from the subtractor 11 via the inverse quantization unit 15 and the IDCT 16.

At this time, the reconstructed difference image and the motion compensated image are added by the adder 17 to form an original image.

On the other hand, since many changes do not occur unless the scene is changed between frames, only fewer bits will be required if only the difference between the frames is transmitted. For this purpose, the encoder and the decoder need a frame memory for storing a previous picture.

Accordingly, the original image output from the adder 17 becomes a previous image while being stored in the frame memory 18, and the motion estimation unit 19 compares the original image currently input with the previous image stored in the frame memory 18. Motion information (MV) is obtained.

At this time, the motion information (MV) is transmitted along with the transform coefficient information after the code length is changed in accordance with the frequency of appearance of data in the VLC 14 to obtain the maximum coding efficiency.

Meanwhile, the motion compensator 20 predicts the original image by performing motion compensation on the previous image output from the frame memory 18 using the motion information output from the motion estimator 19.

At this time, if the compensation is correctly performed in the motion compensator 20, the output of the subtractor 11 is zero, but there is a slight difference between the original image and the motion compensated image due to noise.

On the other hand, the subtractor 71 of the second encoder 70 outputs the difference between the image DCT in the DCT unit 12 and the image IDCT in the IDCT unit 16 to the quantization unit 72, the quantization unit ( 72 displays the difference image data output from the adder 71 with a limited number of bits to reduce the data amount and output the data to the VLC 73.

The VLC unit 73 reduces the total number of bits by allocating a short code length to data having a high frequency of data and a long code length to data having a low frequency of appearance, and then an additional bit stream at a bit rate of 10 Mbps (bit stream 2). Send it.

Meanwhile, the main bit stream transmitted at 20 Mbps through the VLC 14 of the first encoder 10 of FIG. 7 is input to the VLD 22 through the channel buffer 21 of the first decoder 20 and is variable. The length is decoded and then dequantized by the dequantizer 23.

Further, the additional bit stream transmitted at 10 Mbps through the VLC 73 of the second encoder 70 of FIG. 7 is input to the VLD 82 through the channel buffer 81 of the second decoder 80 and is variable. The length is decoded and then dequantized by the dequantizer 83.

In this case, the adder 84 adds inverse quantized data by the inverse quantizer 23 of the first decoder 20 and inverse quantized data by the inverse quantizer 83 of the second decoder 80. The difference image between the original image and the motion-injured image is restored.

At this time, the motion compensator 27 of the first decoder 20 performs motion compensation on the previous image output from the frame memory 26 by using the motion information MV output from the VLD 22 to perform the original image. The predictor 25 adds the difference image output from the IDCT 24 and the predictive image output from the motion compensator 27 to restore the original image.

At the same time, the restored original image is output to the frame memory 26 to update the frame memory 26.

In addition, the present invention is different for satellite and terrestrial channels when mixing the basic bitstream in the transport layer. In other words, the satellite channel HDTV broadcast signal has four basic bitstreams, which include a main picture coded bitstream (bit stream 1), an additional coded bit stream (bit stream 2), an audio bit stream, and broadcast signal control. Data bit stream.

They have their respective PIDs and the receiver can decode each bit stream separately or in association.

In this case, as shown in FIG. 9, when the four basic bitstreams are combined in the multiplexer 101 and the bit rate is 30 Mbps, and this is transmitted through the 30 MHz satellite transmission channel 102, the demultiplexer 103 is transmitted. Restores the original data into the main bitstream, the additional bitstream, the audio bitstream, and the data bitstream.

Meanwhile, in terrestrial channel transmission, three of the four bit streams are transmitted in the same manner, and no additionally encoded bit stream (bit stream 2) is transmitted.

Thus, in terrestrial channel transmission, as shown in FIG. 10, when the three basic bitstreams are summed together in the multiplexer 104 and the bit rate is about 20 Mbps, and the transmission rate is transmitted through the 6 MHz terrestrial transmission channel 105, the original demultiplexer 106 performs the original operation. Restore the main bitstream, the audio bitstream, and the data bitstream as data.

11 is a block diagram illustrating an embodiment of a receiver at the time of receiving a satellite broadcast according to the present invention, in which a satellite broadcast is performed at a bit rate of 30 Mbps by mixing a main bitstream, an additional bitstream, an audio bitstream, and a data bitstream. A transport demodulator 112 that demodulates into a primary bitstream, an additional bitstream, an audio bitstream, and a data bitstream when transmitted over a MHz transmission channel 111; and a primary bitstream demodulated by the transport demodulator 112. Or a high quality decoder 113 for decoding an additional bitstream, an audio bitstream, and a data bitstream at high quality, or demodulating the transport demodulator 112 and the transport demodulator 112. And a general quality decoder 113 that decodes the stream, the audio bitstream, and the data bitstream and reproduces them in general quality.

Here, since the high quality decoder 113 further includes a circuit capable of decoding the coded bit stream, the high quality decoder 113 can decode both the main bit stream and the additional bit stream so that the picture becomes clearer and the original picture before the code is encoded. You can play with almost the same high quality. However, the general picture decoder 114 is reproduced with the same general picture quality as the terrestrial channel decoder because there is no circuit for decoding the additionally coded bit stream.

12 is a block diagram showing an embodiment of a receiver at the time of terrestrial broadcast reception according to the present invention, wherein a 6 MHz satellite transmission channel 121 has a bit rate of 20 Mbps which is a terrestrial broadcast by mixing a main bitstream, an audio bitstream, and a data bitstream. The transport demodulator 122 recovers the main bitstream, the audio bitstream, and the data bitstream when the data is transmitted through the decoder, and decodes the main bitstream, the audio bitstream, and the data bitstream demodulated by the transport demodulator 112. A high quality decoder 113 or a general definition decoder 114 for reproduction.

That is, since there is no additionally encoded bit stream in terrestrial broadcasting, the picture reproduced by the high quality decoder 113 or the general picture decoder 114 is the same.

At this time, the transport demodulator 112 of the satellite broadcast receiver and the transport demodulator 122 of the terrestrial broadcast receiver may have the same function but only different speeds.

Here, the higher speed may include the functions of the lower speed. In general, a 30Mbps bitstream is designed to be sufficiently included.

Therefore, a receiver including a transport demodulator with a speed of 30 Mbps or more can receive terrestrial broadcasts or satellite broadcasts, and the received picture quality of satellite broadcasts differs according to the cost of the receiver.

However, transmission must be different from satellite and terrestrial channels, so different hardware must be used.

That is, the same video / audio code can be coded and decoded using and decoders regardless of terrestrial or satellite broadcasting.

As such, the phase channel HDTV system is configured to be compatible with the ground channel HDTV system so that the bitstream generated through one encoding can be transmitted through the satellite and the ground channel.

In other words, the encoding and decoding of the transmission can not be different anyway as long as the channel is different, but the video / audio encoding and decoding can be used regardless of terrestrial broadcasting or satellite broadcasting.

At this time, HDTV can modularize each part, so it is not entirely compatible, but if there are many parts, different parts can be designed to be interchangeable.

Compatible with video encoding and decoding can reduce the time loss of encoding and can save the cost of storing a large original image because only a bit stream can be stored or moved.

As described above, according to the satellite channel HDTV system compatible with the terrestrial channel HDTV broadcasting according to the present invention, only the satellite channel transmission is performed using the remaining band after subtracting a band capable of transmitting the same data as the terrestrial channel transmission. By transmitting data for improving image quality, the satellite TV and terrestrial channel HDTV systems are compatible with each other, and at the same time, it is possible to obtain desired image quality without causing waste of the satellite channel frequency band. Also, since the encoding and decoding channels are different, the video / audio encoding and decoding can be used regardless of terrestrial broadcasting or satellite broadcasting. This can reduce the cost of storing a large original image because only a bit stream can be stored or moved.

Claims (9)

A first encoder which encodes the original image using the MPEG2 encoding algorithm at the terrestrial channel video data bit rate and transmits it to the main bit stream, and decodes the image encoded by the first encoder using the MPEG2 decoding algorithm. A difference image generating means for generating a difference image by extracting a difference between the original image and the image decoded by the decoder, and a difference image output from the difference image generating means at a satellite channel video data bit rate. Encoder of a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting comprising a second encoder that encodes at a bit rate minus a video data bit rate and transmits the additional bit stream. The method of claim 1, wherein the first encoder encodes the difference picture by a differential pulse code modulation (DPCM) method in which the difference between the current input signal and the prediction signal by the previous signal is quantized, modulated, and transmitted. Encoder for satellite channel HDTV systems compatible with terrestrial channel HDTV broadcasting. The method of claim 1, wherein the second encoder is an adaptive differential pulse code modulation (ADPCM) method of quantizing while minimizing dispersion of error signals by adjusting predictive variables according to characteristics of a signal input from differential pulse code modulation (DPCM). An encoder in a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting, characterized by encoding a difference picture. The satellite of claim 1, wherein the second encoder encodes a difference image by sequentially performing a discrete cosine transform (DCT), quantization, and variable length coding (VLC) process. Encoder for channel HDTV systems. A first decoder which decodes the main bit stream transmitted at the satellite channel video data rate using the MPEG 2 decoding algorithm, and specially decodes an additional bit stream transmitted at the bit rate obtained by subtracting the terrestrial video data bit rate from the satellite channel video data bit rate. Decoding of a satellite HDTV system compatible with terrestrial channel HDTV broadcasting comprising a second decoder and an original image restoration means for adding an image decoded by the first decoder and an image decoded by the second decoder to restore an original image. group. 6. The terrestrial channel HDTV broadcasting according to claim 5, wherein the second decoder decodes an additional bit stream transmitted by sequentially performing variable length decoding (VLD), inverse quantization, and inverse discrete cosine transform (IDCT). Decoder of satellite channel HDTV system compatible with. Difference between a first coder that encodes an original picture at a terrestrial channel video data bit rate using an MPEG 2 encoding algorithm and transmits it to a main bit stream, and a difference between a discrete cosine transformed image and an inverse discrete cosine transformed image in the first encoder To generate a difference image to compensate for the part lost by quantization, and encode the generated difference image at a bit rate obtained by subtracting the ground channel video data bit rate from the satellite channel video data rate and transmitting the resultant image as an additional bit stream. Encoder of terrestrial channel HDTV system composed. 8. The encoder of claim 7, wherein the second encoder encodes a difference image through a quantum and variable length coding (VLC) process. A first decoder for restoring the main bit stream transmitted at the satellite channel video data rate through variable length decoding (VLD) and dequantization, and an additional bit transmitted at the bit rate obtained by subtracting the terrestrial video data rate from the satellite channel video data rate. A second decoder for restoring the stream through a variable length decoding (VLD) and inverse quantization process, and image restoring means for adding a dequantized picture in the first decoder and a dequantized picture in the second decoder, The first decoder is a satellite channel HDTV system compatible with terrestrial channel HDTV broadcasting, characterized in that to perform an inverse discrete cosine transform to the image output from the image restoring means and to add a motion compensated image to restore the original original image. Decoder.