CN1052608C - Digital transmission method for high-definition television and transmitter-receiver - Google Patents

Abstract

The present invention discloses a digital high-definition television transmission method and an emitting and receiving device, which relates to a television system and a transceiver. The method of the present invention transmits line-by-line scanning image information less than 25Hz of frame frequency, the receiving end adopts an interpolation frame-doubling mode to restore image moving information, and a moving image recurrence effect with high quality is obtained. On the premise of not losing the image moving information, the present invention fully uses a transmission passband, avoids the inherent defects of the crawl of an interlacing system, interlines flicker, low vertical resolution, etc., and realizes the recurrence with high quality of an image.

Description

A kind of digital transmission method for high-definition television

The invention belongs to TV domain, particularly digital high sharpness colour TV standard.

Two big basic fundamental means of artificial reproduction activity scenery image are film and TV.Because the visual persistence of human eye, the fusion frequency that the motion scenery image sequence that presents by the width of cloth is obtained satisfied motion sense of continuity is about 24Hz.And on the other hand, the flicker of the just imperceptible scenery height of human eye the video repetition rate---critical flicker frequency is about 50Hz.Critical flicker frequency also increases and increases according to the high brightness of scenery, stands the upper limit when (being about 300abs) when the scenery image brightness reaches human eye, and critical flicker frequency increases to about 70Hz.Therefore, if the video repetition rate is higher than 70Hz, then human eye can be experienced the continuously active image of exempting flickering fully.

The artificial basic demand one that reappears active images is the motion sense of continuity, the 2nd, eliminate flicker.The simple recurrent frequency that improves certainly satisfies the requirement of this two aspect, but causes resource (film: film length always; TV: waste passband width).Thereby people have invented various methodologies, to save resource.

In film, adopted with the speed of 24 frame/seconds and taken, when projection then to the method for every frame image secondary light projector (repetition rate increases to 48Hz), concocted the gap of fusion frequency and critical flicker frequency, made the mankind watch graceful art of film, film length is saved half.

In television transmission standard development owing to there is not tangible recording medium in the transmission course, when invention, with regard to adopted another kind cleverly the method for " interlacing scan " make this gap up.One frame image is broken down into several rows, and wherein at first scanning transmission of odd-numbered line part is called strange.Scanning transmits the even number line part again, is called even.Thereby derived the basic conception of the interlaced scan tv standard of " two of frames, successively transmit ".For display screen, image is split into staggered two of parity rows, and the secondary that successively flashes is similar to the effect of secondary light projector.But total line number that per second transmits still remains unchanged, thereby has saved the frequency band of half.

In the three existing in the world big television systems, all adopted the interlacing scan standard.Wherein the TSC-system frame frequency is 30Hz, and field frequency is 60Hz, is used for the countries and regions of 60Hz power network; PAL, SEACAM system frame frequency is 25Hz, and field frequency is 50Hz, is used for the countries and regions of 50Hz power network.This is the formed 60Hz/50Hz of existing TV historical development process two big dividing lines.

Interleaved method saving under half the condition of transmission band, has guaranteed motion continuity effectively and has overcome flicker preferably.This method of interlacing scan has important contribution on TV history, and is in use among the high definition TV of new generation (HDTV) that is developing at present always.For example, the MUSE of digital processing---analogue transmission (day), HD-MAC (Europe) has also all adopted interleaved system.Rose in 90 years among the full digital HDTV that begins to develop, beautiful ADTV, Digicipher, Northern Europe Devine, standards such as moral HATV-T have also adopted this effective interlacing scan system scheme.

But, partiting row scanning system since with a frame image be divided into very, idol row is alternate two, only be similar to the full frame secondary light projector of mute, defective that this has just unavoidably brought some to have fundamental character is as creeping phenomenon (the vertical innervation of falseness); Interline flicker (flicker that horizontal sharp edge causes because of strange, even field brightness difference); Vertical definition reduces (Ke Er coefficient 0.7) or the like.The TV reproduction quality is required harsh day by day today, becoming the obstacle that continues to improve reproduction quality.

The display mode of lining by line scan then can exempt fully interleavedly creep, shortcoming such as interline flicker, under the line number of same every frame, its subjective vertical definition also rises to 1.3 times of partiting row scanning system.This method at first extensively adopts in Computer Graphic Demonstration, but does not relate to transmission.Also idol has employing in some special TV equipment, promptly sweep complete frame with row-by-row system, and frame frequency doubled (field frequency that equals interlacing system), the line number that per second transmits doubles, the interlacing system of taking twice transmission bandwidth, be called the NTSC television system NTSC of lining by line scan (work " digital televi-sion principles ", Science Press, 1987 such as seeing that Zhang Zhao raises).

The elementary object of a new generation's high definition TV provides the large screen television of 16: 9 the ratio of width to height, should obtain the Presence of viewing and admiring the 35mm wide-screen film when the screen Senior Three is doubly located to observe, and continues to leave interleaved defective therein and is difficult to tolerate.Therefore, the U.S. has two families (DSC CC-Digicipher) proposes to make line by line the HDTV scheme, and its principle is still the notion of using the above-mentioned system of lining by line scan.But because original bandwidth has increased by one times, harsher to the requirement that follow-up digital compression is handled, have no alternative but to cut down resolution (using inferior materials and turning out substandard goods to a certain degree), in the hope of reducing original bandwidth.According to reports, the television system of HDTV line by line of this form has been obtained than the interlacing drawing and has been resembled the higher whole structure of reproduction quality.

Task of the present invention is to form the unified optimization arrangement of science on (promptly transmitting standard) for TV of new generation provides from shooting, the system that is transferred to demonstration, creep to exempt in the existing interlacing system, interline flicker, inherent shortcomings such as vertical definition is low, the frequency band of also eliminating simultaneously the system line by line in the existing research takies the defective wide, that data volume is big, provides basic for the high quality image of high definition TV of new generation reappears.

The present invention makes full use of the digitized processing means of pictorial information, and to the processing mode of picture motion information processing employing different brackets, its middle-and-high-ranking processing mode has adopted the motion detection/compensation processor that is intended to realize real-time interpolation times frame.Motion detection/compensation processor is to design for information that frame image before the more accurate utilization has transmitted.At transmitting terminal, present frame is divided into the picture block of suitable size, each picture block is searched for coupling on every side in preceding frame corresponding position, promptly mobile picture block is also checked coincidence situation (with the quadratic sum or the absolute value of the difference of all pixels of picture block and all pixels of preceding frame image and be test stone), (Δ X, the Δ Y) that overlaps best-case is called the motion vector corresponding to this picture block.During actual transmissions, to the pixel difference of this picture block translatory movement vector and picture block.Thereby having significantly reduced redundant information, this is a motion detection.Motion compensation at receiving terminal then is opposite process.Motion vector according to biography is advanced takes out the pixel value of the decoded preceding motion-compensated correspondence position of frame image of receiving terminal, as the basic value of this picture block of this frame.Add the exact value that promptly obtains this frame image piece behind the picture block pixel difference.It is the most reliable at present to try to achieve motion vector with " exhaustive search algorithm " in the engineering practice, is finished by special chip.Motion vector is for whole pixel block, but also can be dispensed to each pixel according to adjacent each block motion vector variation tendency by certain interpolation method.

The objective of the invention is to realize by following method and apparatus:

(1) with progressive scan mode picked-up full frame, obtain the original picture sequence, the shooting frequency only needs near fusion frequency (about 24Hz) even be lower than fusion frequency, and frame number and the existing frame number of making line by line relatively are to delete one every one, save the redundant information that is helpless to show active images motion sense of continuity.Specific practice can be:

(a) to the countries and regions of present employing 50Hz field frequency, obtain the original picture sequence with lining by line scan for 25 frame/seconds;

(b) to the countries and regions of present employing 60Hz field frequency, obtain the original picture sequence with lining by line scan for 24 frame/seconds;

When (c) transferring TV signal to, change frame by frame by film, TV, obtain original picture with progressive scan mode by motion picture data;

(d) when being converted to film, change frame by frame by TV, film with viewdata.

(2) above-mentioned original picture sequence is carried out the A/D conversion and obtain the image sequence data, make motion detection then, obtain motion vector and motion compensation difference image.

(3) adopt information source band compression technique and channel error code control technology to encoding by the sequence data of (2) step gained and motion vector and motion compensation difference image.By international standard, wherein the backbone technology of source encoding has been the CCITT file defined H.261 of International Radio Consultative Committee (IRCC); Behind the channel error code control coding, Channel Modulation then adopts in the orthogonal frequency multiplex (MUX) mode, and each sub-band is that the mode of 16QAM modulation is carried out.

(4) will be by the transfer of data behind (3) step coding to acceptance point, transmission means can be wireless and wired.Wherein:

(a) to the countries and regions of present employing 50Hz field frequency, transmission rate was 25 frame/seconds;

(b) to the countries and regions of present employing 60Hz field frequency, transmission rate was 24 frame/seconds;

(c) viewdata of 50Hz, the exchange of 60Hz field frequency countries and regions, same mode with every frame correspondence is accelerated or the transmission rate that slows down by the transmission frame number of this area in the transmission.Its rate variation only is ± 4%, does not influence viewing effect.

(5) at receiving terminal, earlier the digital signal that receives is decoded, recover coding preceding sequence data and motion vector and motion compensation difference image, carry out times frame with interpolation method then and handle.The zero level interpolation repeats N-1 time with simple every frame and finishes; The one-level interpolation is finished in corresponding points linear interpolation mode between two frame image sequences; The secondary interpolation is then made motion compensated interpolation with the motion compensated interpolation value of calculating two frame image sequence corresponding points.The multiplying power of times frame then can be two times of frames, three times of frames, four times of frames etc.Its compound mode can be down table pack:

The area interpolation method	The 50Hz country		The 60Hz country
					Times frame number of times	Display frequency (Hz)	Times frame number of times	Display frequency (Hz)
	Zero level interpolation (the simple repetition)	2	50	Weigh 2 heavy by 1 (1/2 * 3+ 1/2 * 2)					60
3					75	3	72
		4	100	4				96
One-level interpolation (linear interpolation)					2	50
	3	75	3	72
					4	100	4	96
	Secondary interpolation (motion compensated interpolation)	2	50
3					75	3	72
		4	100	4				96

Table 1: the various combination of interpolation method and times frame number of times

(6) the sequence image data after the interpolation times frame processing being done the D/A conversion send display unit to show.

Realize the dispensing device of said method, its input signal is the frame signal that subtracts of lining by line scan, comprise around this characteristics dispensing device: the interface circuit that carries out the A/D conversion at the image sequence (promptly subtracting the frame information source) that subtracts behind the frame, motion detector, source encoding circuit, chnnel coding circuit, digital carrier modulation and power amplification parts, sending signal section at last and be antenna when wireless, is output interface when wired.

The receiving system of realizing said method comprises selective frequency amplifier circuit, digital carrier demodulator, channel decoder and source decoder, times Frame Handler and can send interface circuit and the display unit that meets display requirement that its core is a times Frame Handler.

For ease of the description to times Frame Handler, image is done following sign convention: the pixel value of (X, Y) coordinate points of establishing the k frame image that subtracts the frame image sequence of transmitting terminal is S _{(k, 0)}(X, Y), it is f that the corresponding points of this frame image that receiver recovers after decoding are rung plain value _{(k, 0)}(X, Y), m interpolation frame corresponding points pixel value after N time times of frame handled is f _{(k, m)}(X, Y), wherein m=1,2 ..., N-1 N is a times frame number of times.Times frame device utilizes the computer digit image processing technique to carry out the motion compensation interframe interpolation, will finish following function:

(1) zero level interpolation method (the simple repetition)

f _(k，m)(x，y)＝f _(k，0)(x，y)

m＝1，2，…，N-1，

(2) one-level interpolation method (linear interpolation) $f_{(k,m)}(x,y)=\frac{N-m}{N}\·f_{(k,0)}(x,y)+\frac{m}{N}\·f_{(k+1.0)}(x,y)$

m＝1，2，…，N-1

(3) secondary interpolation method (motion compensated interpolation)

By f _{(k, 0)}(X, Y) and f _(k+1.0)(X Y), utilizes motion detection technique such as piece coupling or pixel recurrence to obtain the motion vector in pixel source; If (X, Y) some the motion vector to (k+1) frame is by the k frame

, wherein the component of directions X and Y direction is respectively MVX _{(k, k+1)}(X, Y) and MVY _{(k, k+1)}(X, Y), then: $f_{(k,m)}(x,y)=\frac{N-m}{N}\·f_{(k,0)}(x+\frac{m}{N}\mathrm{MV}{X}_{(k,k+1)}(x,y),y+\frac{m}{N}\mathrm{MV}{Y}_{(k,k+1)}(x,y))$ $+\frac{m}{N}{f}_{(k+\mathrm{1,0})}(x+\frac{N-m}{N}\mathrm{MV}{X}_{(k+1,k)}(x,y),y+\frac{N-m}{N}\mathrm{MV}{Y}_{(k+1,k)}(x,y))$

m＝1，2，…，N-1

For finishing above-mentioned three rank interpolation functions, times Frame Handler by motion compensation processor, high speed high-order digit signal processor (DSP), subtract frame image Frame memory, program storage, interpolation frame data storage, the work RAM of real-time address converter, video transformation and output circuit, D/A translation circuit and DSP forms.They link mutually by system bus and address control line, under DSP control, at different interpolation level requirements, carry out interpolation frame between consecutive frame and handle in subtracting the frame image data storage.The program diagram of processing procedure such as Fig. 5, T is the frame transmission cycle among the figure, is (1/25) second at 50Hz field frequency area T, is (1/24) second at 60Hz field frequency area T:

Actual receiver can possess three kinds of interpolation level functions simultaneously, " inserts rank, also can only possess a kind of interpolation level by every machine, produce different class receivers thus in being selected voluntarily by the user.

The present invention proposes the new method that is different from existing various television systems (comprising in the research).Technical solution of the present invention is not transmitted the redundant information that is helpless to show active images motion sense of continuity, makes frame number line by line and reduces by half than existing, saves the transmission passband of half, inherent shortcoming such as avoided the creeping of interlacing system fully, the interline flicker vertical resolution is low.Its interpolation times frame display mode surmounts the film reproduction quality for the TV reproduction quality, for multiple display mode and deposit competition development receiver kind, 50Hz/60Hz two big TV dividing lines promote the formation of unification standards to create condition in order to be in harmonious proportion in the world.

Fig. 1 subtracts frame to transmit 3 times of frame interpolation schematic diagrames

Fig. 2 is a television transmitter signal processing schematic diagram

Fig. 3 is a television receiver signal processing schematic diagram

Fig. 4 is a kind of structure principle chart of times Frame Handler

Fig. 5 is times flow chart of Frame Handler processing procedure

The invention will be further described below with reference to embodiment, Fig. 1, shown in be that the image that will obtain with progressive scan mode transmits after a frame is deleted a frame, wherein the dotted line frame is deleted frame.After arriving receiving terminal, show in 3 times of frame modes, the picture frame that the thick line frame recovers for decoding, the fine rule frame then is an interpolation frame.This moment, the actual displayed frame number was 1.5 times that make the production frame number line by line by existing, and the interpolation level of interpolation frame can be 0～2 selection, so the reproduction quality of motion video will improve greatly.

Use when of the present invention with the radio transmission mode, relate to television transmitter and television receiver.Television transmitter has and the corresponding input interface circuit of existing television transmitter, source encoding, volume chnnel coding, digital carrier modulation, power amplification and transmitting antenna, what difference came from television transmitter acceptance used in the present invention is to subtract the frame information source line by line, the information source frame frequency is not more than 25Hz, consider the demand of secondary interpolation when receiving simultaneously, after the A/D conversion, need carry out motion detection before the coding, obtain the motion vector of image.

The TV signal frequency-selecting that television receiver will receive from antenna is earlier amplified, and sends into digital carrier decoder, channel decoder, source decoder and decodes, and recovers the image sequence data before the transmitter coding, sends into then to carry out times frame in times Frame Handler and handle.Times frame number of times and interpolation rank are inserted with giving the mode of putting, and are required to handle according to giving putting by DSP control in times Frame Handler.Dispose and the gained data are carried out the D/A conversion obtain vision signal and advance display unit and show.

Transmitting terminal to the standard of having given line by line image sequence (50 frame/second) delete one every one, what obtained for 25 frame/seconds subtracts the frame image sequence.After H.261 standard information source compression method carries out encoding compression and chnnel coding, reach the recipient through class, carry out corresponding channel-decoding and source coding and recover, obtain the recovery image sequence of 25 frame/seconds.Adopting the method for every frame reproduction secondary then (is the zero level interpolation, two times of frame frequencies) carried out moving image sequence and dynamically reappeared, and shown side by side simultaneously, observed through many-sided expert and general spectators with the original picture sequence, all be unaware of appreciable difference, subjective effect is good.

The mode of motion compensation secondary interpolation.Under the situation of having considered each picture element movement vector field of image, interpolation gained interpolation frame image meets the rule of each relative motion of object, and subjective quality is very good.

Claims (4)

1. digital transmission method for high-definition television, it comprises the following steps:

(1) with progressive scan mode picked-up full frame, obtained the original picture sequence, the frame rate of image sequence was not more than for 25 frame/seconds, and the image that obtains in the mode of lining by line scan transmits after a frame is deleted a frame;

(2) the image sequence signal with (1) gained carries out the A/D conversion, obtains the image sequence data, and obtains motion vector and motion compensation difference image as motion detection;

(3) the image sequence data of (2) gained and motion vector and motion compensation difference are encoded with information source band compression technique and channel error code control technology, wherein the backbone technology of source encoding is by the CCITT of International Radio Consultative Committee (IRCC) file defined H.261, and it is that the mode of 16QAM modulation is carried out that channel error code control coding back Channel Modulation then adopts each sub-channel in the orthogonal frequency multiplex (MUX) mode;

(4) data after will encoding reach acceptance point, and transmission means can wherein be respectively 25 frame/seconds and 24 frame/seconds in 50Hz field frequency area and the regional transmission frequency of 60Hz field frequency for wireless or wired;

(5) receiving terminal is decoded the digital signal that receives earlier, recovers coding preceding image sequence data and motion vector and difference, carries out interpolation times frame with interpolation method then and handles;

(6) the image sequence data after the interpolation times frame processing are sent with a times vertical sweep frequency, and done the D/A conversion, send display unit to show.

2. transmission method according to claim 1, it is characterized in that the interpolation method that interpolation times frame is handled is divided into three grades: repeat N-1 time and finish, N is a constant for a times frame times N, and N is a times frame number of times, and the pixel value of (X, Y) coordinate points of promptly establishing the K frame image that subtracts the frame image sequence of transmitting terminal is S _{(k, 0)}(X, Y), the corresponding points of this frame image that receiver recovers after decoding are rung plain value f _{(k, 0)}(X, Y), m interpolation frame corresponding points pixel value after N time times of frame handled is f _{(k, 0)}(X, Y), m=1 wherein, 2 ..., N-1, the one-level interpolation is finished do linear interpolation with the pixel value of corresponding points between two frame images, and the secondary interpolation is finished as motion compensated interpolation with the motion compensated interpolation value of the pixel value of calculating two frame image corresponding points.

3. transmission method according to claim 1 and 2 is characterized in that the frame doubling frequency that interpolation times frame is handled is two times of frames or three times of frames or four times of frames.

4. transmission method according to claim 1 and 2 is characterized in that interpolation times frame is handled to adopt a following step to finish:

(1) interpolation times frame working procedure and computing formula are deposited in the memory under program;

(2) start-up system, high speed high-order digit signal processor (DSP) follow procedure counter content get finger, executable operations and according to the content update program counter of performed instruction, the follow procedure flow process is carried out computing;

(3) program is carried out interpolative operation according to giving an interpolation rank and a times frame times N of putting;

(4) under zero level interpolation situation, the data so that times frame rate is read each pixel by the pictorial data frame memory are sent to output register, carry out the D/A conversion and obtain vision signal;

(5) under the situation of one-level interpolation, read the data of the corresponding pixel of two frames by front and back two frame image Frame memories with times frame rate, when m=0, frame before read-only, multiply by (N-m)/N and m/N respectively and make weighted sum, N is a constant, m by 0 to N-1 by program control, be sent to output register, carry out the D/A conversion and obtain vision signal;

(6) under the situation of secondary interpolation, with the appropriate address (this position by motion vector by specification described formula calculating got) of times frame rate by the different position of front and back two frame image data, read the pixel value of two frame images, read-only preceding frame when m=0, make weighted sum with (N-m)/N and m/N respectively, N is a constant, and m=0 to N-1 is by program control, be sent to output register, carry out the D/A conversion and obtain vision signal;

(7) program is the basic cycle to carry out circular treatment to be not more than 1/25 second, is circulated by external control (as changing platform or shutdown) signal ended.

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