DE3831103A1 - Transmission system - Google Patents

Abstract

Because of the transmission channels adjoining the band, such a signal is divided into two signal components, the first signal component representing a standard TV signal and the second component representing the high-frequency excess. A signal having the same spatial resolution of the output signal is transmitted as second signal component. The temporal resolution is reduced. Compatible television transmission system for an HDTV signal. <IMAGE>

Description

The invention relates to a transmission and reception system for an image signal.

In the conference proceedings of the HDTV Colloquium 1987, Ottawa, dated 04.-08. 10. 1987 is by William E. Glenn and Karen G. Glenn from the New York Institute of Technology under "Improved HDTV with Compatible Transmission "on pages 4.5.1-4.5.12 a transmission system has been proposed which covers both the Reception of a high-definition television signal, hereinafter Called HDTV signal, as well as one Standard television signal, in the following standard TV signal called, enables. This is done by a source supplied HDTV signal using a digital Signal processor and a two-dimensional local Filtering split up as a result Standard TV signal and a signal representing the high supplies local frequency components of the HDTV signal, arises.

These two signals are separated via two separate ones transmit band-limited channels, one channel being the Standard TV signal transmits and that as an additional channel acting second channel the high local frequency components of the HDTV signal.

On the recipient side is then by means of a Standard TV receiver to receive the standard TV signal.

A suitable HDTV receiver is by evaluating the Signals from both channels are capable of being from the source to reconstruct and reproduce the delivered image.  

The information of the additional channel is not reproduced possible, since there is no locally high resolution from this alone Image can be reconstructed.

The invention is based on the object Transmission system as well as a receiver for a to specify high-resolution television signal, which at existing band-limited transmission channels on the Reconstruction of image information on the receiver side too enabled when only one channel is received.

This object is achieved by the in claim 1 and Claim 13 specified features solved. Beneficial Further developments of the invention are in the subclaims reproduced.

On the transmitter side, an HDTV signal with high local and temporal resolution split into two signals. The first signal has a low local but high temporal resolution and can by appropriate Coding into a standard TV signal, e.g. PAL, Secam, NTSC or D2-MAC or digital with or without data reduction, implemented and over a first band-limited channel be transmitted.

The second signal has a high local but low temporal resolution. This can e.g. by omitting Images, preferably every other image, can be achieved. With an appropriate coder it can e.g. in a HD-MAC signal implemented or directly digital with or without data reduction over a second band-limited channel be transmitted.  

With the help of the first channel is on the receiving end complete locally low and temporally high-resolution Image signal can be received.

Via the second channel is compared to the prior art a complete temporally and locally high-resolution image signal can be received, from which by appropriate decoding and measures for image regeneration adequate locally high-resolution image signal, hereinafter Called HD signal, can be reconstructed.

The regeneration measures are used by the on the receiver side by omitting pictures, especially at moving sequences, lost information largely reconstructed.

In order to regenerate a complete HDTV signal, emp evaluate both channels on the catcher side. To do this, especially with movement defects, during reconstruction of the HD image, the temporally high-resolution image information of the first channel.

This advantageously results in the over according to the invention support system the introduction of a conventional Transmission systems compatible HDTV transmission system, where the first channel is an image signal with today's Provides resolution corresponding to television standard and the second channel a full picture signal high provides local resolution.

An embodiment is shown below with reference to Drawing explained in detail.

Show it  

Fig. 1 2-channel HDTV transmission system

Fig. 2 shows a transcoder in the transmitter (encoder)

Fig. 3 shows a transcoder in the receiver (decoder)

Fig. 4 is an HD encoder (in the transmitter)

Fig. 5 shows a HD decoder (in the receiver)

Figure 6 is a Bildregenerator.

Fig. 7 shows an example of the operation of an image regenerator

Fig. 8 is a local-time filter.

Fig. 1 shows a 2-channel HDTV transmission system. An HDTV signal generated by a source becomes a first transmission path, consisting of a transcoder 1 , a TV encoder 2 , a TV decoder 3 and a transcoder 4 , and a second transmission path, consisting of an image suppression circuit 5 , an HD encoder 6 , an HD decoder 7 and an image regeneration circuit 8 .

The transcoder 1 of the first transmission path reduces the horizontal resolution of the image by 2: 1 and the vertical resolution by 3: 2 by appropriate filtering. In addition, the HDTV signal without interlacing is converted into a signal with interlacing, whereby the temporal resolution is maintained remains. The output signal of the transcoder 1 is fed to the TV encoder 2 , which generates a standard TV signal, for example in PAL, Secam, NTSC or D2-MAC, and whose output is connected to a first transmission channel. However, if the output signal of the transcoder is to be stored, for example, on a digital recorder, it is either given directly or via a data reduction device to the first transmission channel, ie the recording channel.

The incoming standard TV signal is decoded in the TV decoder 3 in the receiver of the first transmission channel. The standard TV signal can then be reproduced at the output of the TV decoder 3 .

The HDTV signal which is fed to the second transmission link is subjected to an omission of images in order to adapt to a band-limited second transmission channel. With the help of the image suppression circuit 5 , for example, only every second image is transmitted. For signals with static picture content, it is conceivable to suppress more than just every second picture, so that the channel capacity that is then freed is available for coding and transmission of the other pictures. The output signal of the image suppression circuit 5 reaches a second transmission channel via the HD encoder 6 . The HD encoder generates either an analog signal, e.g. HD-MAC, or a digital signal that is transmitted over the channel directly or after data reduction.

The incoming signal is fed to the HD decoder 7 in the receiver of the second transmission channel. The output of the HD decoder 7 is connected to the image regeneration circuit 8 , which uses a motion estimation to perform a reconstruction of the images omitted on the receiver side by means of block comparison. At the output of the image regeneration circuit 8 , an HD signal with high local resolution and an image repetition rate of, for example, 50 Hz can then be reproduced, but with possible errors in the area of moving image content.

In order to minimize these errors in the area of moving picture parts and thus to achieve the high temporal resolution of the input HDTV signal, the transcoder 4 converts the sampling rate conversion of the transcoder 1 from the standard TV signal. Both signals, that of the transcoder 4 and that of the image regeneration circuit 8 , are fed to a combination filter 9 which, by suitable weighting, delivers an HDTV output signal of high temporal and local resolution.

Fig. 2 describes the transcoder 1 in the transmitter. The incoming HDTV signal is fed to a horizontal transcoder filter 9 , which lowers the horizontal sampling rate by 2: 1 by suitable filtering. A basic process for this is described in Pirsch, P .; Bierling, M .: "Changing the Sampling Rate of Video Signals by Rational Factors", Proc. EUSIPCO '83, Signal Processing II: Theories and Applications, EURASIP 1983, pp. 171-174. The signal then passes through a vertical transcoder filter 10 , which lowers the vertical sampling rate by 3: 2. The output signal then goes through a vertical low-pass filter, followed by an interlacer 11 , which performs a field-dependent vertical subsampling of 2: 1 to generate an interlaced image signal.

If the HDTV signal at the input of transcoder 1 has 1440 864 active pixels per picture with a refresh rate of 50 Hz and progressive scanning of 1: 1, the picture format is reduced in the following steps:

1. 720 _* 864, 50 Hz, 1: 1
2. 720 _* 576, 50 Hz, 1: 1
3. 720 _* 576, 50 Hz, 2: 1

Fig. 3 shows the transcoder 4 in the receiver. The incoming standard TV signal, in the form of digital samples, is fed to a deinterlacer 12 which, by field-dependent line transfer and interpolation of the intermediate lines, converts an image signal in the format 720 _* 576, 50 Hz, 2: 1 to an image signal in the format 720 _* 576 , 50 Hz, 1: 1 generated. This signal is fed to a vertical transcoder filter 13 , which regenerates a signal in the format 720 _* 864, 50 Hz, 1: 1 by vertical sampling rate conversion by 2: 3. A subsequent horizontal transcoder filter 14 with a horizontal sampling rate conversion of 1: 2 produces a signal comparable to the HDTV input signal in its format with 1440 _* 864, 50 Hz, 1: 1.

Fig. 4 shows the HD encoder. 6 The HDTV input signal passing through the image suppression circuit 5 is supplied to both a mode selection circuit 23 and a block search circuit 31 .

In the mode selection circuit 23 , either an interframe or an intra-frame mode is selected by comparing the input signal with the output signal of the block search circuit 31 for coding the input signal. The coding is done, for example, uniformly for a block containing 8 _* 8 pixels. If, for example, the deviations of the current picture from the previous picture are large, intra-frame coding is carried out. In the other case, interframe coding is used for data reduction. In the interframe mode, the image signal is predicted along determined motion vectors and the difference signal between the original and prediction signal is forwarded. In intraframe mode, the input signal itself is forwarded. The block search circuit 31 determines a motion vector for each current block. The motion vector can e.g. B. from the minimum sum of the absolute values of the differences, the minimum sum of the alternating energy or minimal variance.

Following the mode selection circuit 23 , the signal is fed to a discrete cosine transformer 24 . Its output signal is sorted in a sorter (scanner) 25 and then fed to a weighting circuit 26 and a quantizer 27 . The output signal of the quantizer 27 is fed both to a coder 28 and for the reconstruction of the image signal via a circuit for inverse weighting 36 , an inverse sampler 35 and an inverse discrete cosine transformer 34 to a block reconstruction circuit 33 , the output of which is connected to an image memory 32 .

The encoder 28 receives weighted transformation coefficients quantized as an input signal in a sequence determined by the sampling. For data reduction, it carries out coding with variable word lengths and provides coded coefficients and addresses as an output signal. This is fed to a video multiplexer and buffer memory 29 .

The data stored in the image memory 32 is data from the previous image. They are required to determine movement information for a current block. For this purpose, a block of the current picture, for example 8 _* 8 pixels, in a search area of the previous picture, for example 16 _* 16 pixels, is varied in its position within the 16 _* 16 block with the help of so-called block matching, until a position of the current block in the previous one Block is found, in which the smallest deviations are found. A vector is determined from this resulting position and is supplied to the mode selection circuit 23 and a coder 30 . This coder 30 also carries out coding with variable word length and forwards the coded motion vector for temporary storage in addition to the corresponding signal data to the video multiplexer and buffer memory 29 . To control the quantization, the buffer memory 29 is connected to the quantizer 27 .

The result of the mode selection is fed to the video multiplexer and buffer memory 29 and to the block reconstruction circuit 33 for correct block reconstruction.

The output signal of the buffer memory 29 is fed to the second transmission channel at a constant data rate.

Fig. 5 shows the HD decoder 7 to a buffer memory and video demultiplexer 15 °. One output each of the buffer memory 15 leads to a decoder 16 or 21 . An output of the decoder 16 leads to a block reconstruction circuit 20 via an inverse weighting 17 , an inverse sampler 18 and an inverse discrete cosine transformer 19 . The output of the block reconstruction circuit 20 leads to the image regeneration circuit 8 and to an image or block memory 22 . The output of the decoder 21 with the decoded motion vectors also leads to a further input of the image or block memory 22 .

In the decoder 16 , the addresses and coefficients are decoded back into their original form. The decoder 21 does the same for the motion vectors.

An information line 54 leads from the buffer memory 15 to the block reconstruction circuit 20 with the information as to whether the block was encoded in the interframe or in the intraframe mode. Another line 56 leads from the buffer memory 15 to the decoder 16 , which transmit buffer status and information about the quantizer status.

Fig. 6 shows the Bildregenerator 8 again. The output signal of the HD decoder 7 is fed to an image memory 38 . An output of the image memory 38 leads to an image interpolation circuit 37 , a further output to an image memory 39 and a multiplexer 40 .

Further inputs of the image interpolation circuit 37 carry further data from the HD decoder 7 , for example the motion vectors 53 and the encoder mode information 54 , that is to say information about interframe or intraframe coding. An output of the image interpolation circuit 37 leads to the multiplexer 40 . An HD signal with 1440 _* 864 pixels, 50 Hz, 1: 1 can be tapped at the output of the multiplexer 40 .

The mode of operation of the image regenerator 8 , FIG. 6 is illustrated in FIG. 7 using a one-dimensional example.

Each image m output by the HD decoder is stored in the image memory 38 of the image regenerator, and the previously transmitted image m -2 is held in the image memory 39 . The intermediate image m -1 was omitted on the transmission side by the image suppression circuit 5 .

Figure 7 shows the signals on the image interpolation circuit 37 . An input carries the output signal 46 of the image memory 39 with the image information 49 and 50 . The second input carries the output signal 48 of the image memory 38 . The output signal 47 with the image information 51 is fed to the multiplexer 40 .

Was transferred block 52 of the currently processed image in the intra-frame mode via the channel, block 51 is the intermediate image from the image m -1 m -2 m and the image directly on a block basis by point-wise averaging of the image contents determined. This is not shown in Fig. 7.

However, if there is an interframe coding, the motion vector 53 of block 52 is known from the HD decoder. For block 51 of the image to be interpolated, block 50 of image m -2 ( 46 ), offset by half the motion vector 54 , is adopted.

Fig. 8 shows the spatial and temporal filter 9. The temporally high-resolution, locally interpolated and thus the format corresponding to the HDTV picture generated by the transcoder 4 is fed to a summer 41 . The output signal of the image regeneration circuit 8 is also supplied to the summer 41 . The summer 41 determines the sum of the absolute gray value differences of the two differently regenerated image signals via a point by point over an n _* n window. The sum forms a value Z per window size n _* n .

From the value Z , 43 factors for weighting the TV and HD image signals are determined in the circuit. Thus, the TV signal is multiplied by a in a multiplier 42 , and the HD signal is multiplied by 1- a in a multiplier 44 . Depending on the value Z , the weighting factor a can assume a value between 0 and 1.

If the value Z is large, that is to say that incorrect movements in interpolation results in the image regenerator 8 , FIG. 6, the factor a = 1 and thus the image information of the TV signal is adopted. If, on the other hand, the value Z is very small, ie if there is static image content, for example, the data is taken from the HD signal, since this represents the original high resolution from the source to the sink.

The multiplication results of the multipliers are fed to a summer 45 , the output signal of which corresponds to the original HDTV signal.

The HD images transmitted in the second transmission channel are sent directly to the output of the combination filter 9 , corresponding to a = 0 for the entire image.

Claims (29)

1. Transmission system for a temporally and locally high-resolution image signal of high bandwidth for transmission over two transmission channels of lower bandwidth, a first transmission channel transmitting image signals of a first standard of low local resolution, characterized in that a second transmission channel transmits a locally high-resolution, temporally low-resolution image signal. 2. Transmission system according to claim 1, characterized characterized in that the second transmission channel at most every second picture of the temporally and locally transfers high-resolution image signal. 3. Transmission system according to claim 2, characterized characterized in that the image signal of the second Transmission channel is encoded for data reduction. 4. Transmission system according to claim 3, characterized characterized in that depending on the Interframe coding or an image information Intra-frame coding is performed.   5. Transmission system according to claim 4, characterized characterized that the coding in blocks is carried out. 6. Transmission system according to claim 4, characterized characterized in that to decide on the Coding type a block shift of the current one coding block in a window of the previous one Image with more samples than the current block is carried out. 7. Transmission system according to claim 6, characterized characterized that according to a decision after the minimum sum of the absolute values of the differences or sum of alternating energy or minimal variance a motion vector is determined. 8. Transmission system according to claim 7, characterized characterized in that a coding of the Motion vectors with variable word length performed becomes. 9. Transmission system according to claim 5, characterized characterized that a transformation is performed becomes. 10. Transmission system according to claim 9, characterized characterized in that a weighting is carried out. 11. Transmission system according to claim 9, or claim 10, characterized in that a quantization is carried out. 12. Transmission system according to claim 11, characterized characterized in that a coding of the values and  Address information of the coefficients with variable Word length is performed. 13. Receiver for a transmission system according to claim 1, characterized in that the receiver contains a transcoder ( 4 ) with a deinterlacer ( 12 ) which generates an image without interlacing by field-dependent line transfer and interpolation. 14. Receiver according to claim 13, characterized in that the transcoder ( 4 ) contains a vertical transcoder filter ( 13 ) and / or a horizontal transcoder filter ( 14 ) for sampling rate conversion. 15. Receiver according to claim 13 and / or claim 14, characterized in that the receiver contains an HD decoder ( 7 ). 16. Receiver according to claim 15, characterized in that a buffer memory and video multiplexer ( 15 ) is provided for decoding the received signal. 17. Receiver according to claim 16, characterized in that the output signal of the buffer memory ( 15 ) a decoder ( 16 ), with subsequent inverse weighting ( 17 ), and / or inverse scanner ( 18 ) and / or inverse dicrete cosine transformer ( 19 ) and / or block reconstruction circuit ( 20 ) is supplied. 18. Receiver according to claim 17, characterized in that the output signal of the buffer memory ( 15 ) is fed to a decoder ( 21 ) for decoding coded motion vectors. 19. Receiver according to claim 17 and / or claim 18, characterized in that the decoded signals are stored in a memory ( 27 ). 20. Receiver according to claim 19, characterized in that an image memory ( 38 ) is present which stores the last decoded image. 21. Receiver according to claim 20, characterized in that an image memory ( 39 ) is present which stores the preceding decoded image. 22. Receiver according to claim 21, characterized in that an image interpolation circuit ( 37 ) is connected to the image memories ( 38 , 39 ). 23. Receiver according to claim 22, characterized in that the image interpolation circuit ( 37 ) receives information about encoder mode information ( 54 ) and / or data from motion vectors ( 53 ). 24. Receiver according to claim 20, 22 and / or 23, characterized in that a multiplexer ( 40 ) is present which supplies an HD signal for image reproduction. 25. Receiver according to one and / or more of the preceding claims 13-24, characterized in that the local-time filter ( 9 ) contains a summer ( 40 ) whose inputs with the outputs of the block regeneration circuit ( 8 ) and the transcoder ( 4th ) are connected. 26. Receiver according to claim 25, characterized in that the output signal ( 2 ) of the summing ( 41 ) is fed to a weighting circuit ( 43 ). 27. Receiver according to claim 26, characterized in that a multiplier ( 42 ) is connected to the output signals of the transcoder ( 4 ) and the weighting circuit ( 43 ). 28. Receiver according to claim 26, characterized in that a multiplier ( 44 ) is connected to the output signals of the transcoder ( 4 ) and the HD decoder ( 7 ). 29. Receiver according to claim 27 and claim 28, characterized in that the multipliers ( 42 , 44 ) are connected to an adder ( 25 ).