GB2149608A - Digital picture signal transmission - Google Patents

Abstract

The invention relates to a method which assures compatibility between composite encoded and discrete coded colour television signals in the receiver unit. An accompanying identification signal is transmitted in a time multiplex frame of a broad band network, the frame structure of the time multiplexing system consisting of 32 horizontal lines and 68 vertical columns to provide 2176 time slots each time slot having 40 bits, and whereby the first time slot (column 0, line 0) is reserved for a synchronization. The identification signal ensuring automatic switch over of a coding-compatible receiver unit, comprising a synchro unit (3), a demultiplexer device (4), a buffer-store selector device (6), buffer stores (7, 8, 9) into which scanned values of the colour television signals are pushed with the aid of a selector signal generated by the buffer store selector device operated by the identification signal, and a decoder matrix (10) which in the case of component coding recovers the components by addition and in the case of composite coding feeds the stored scanned values into a multiplexer. The digital signals are then converted into analog signals by means of D/A converters and applied to the video unit of the TV receiver set. <IMAGE>

Description

SPECIFICATION Method and means for link-locked and discrete coded colour picture transmission This invention relates to a method and an apparatus for closed (complete) encoded and discrete coded transmission of colour pictures in a digital time multiplexing system having a bit clock frequency of 139,264 MHZ, the frame structure of which consists of 32 horizontal lines and 68 vertical columns to provide 2176 time slots each time slot having 40 bits, and whereby the first time slot (column 0, line 0) is reserved for a synchronization. This time multiplexing system is disclosed in the German Patent Application P32 13 534.

In the new digital cable transmission technology of colour television pictures the transmission of discrete red (R), green (G) and blue (B) colour signals is increasingly more widely adopted in order to avoid cross modulations and thereby to achieve improved picture quality.

It is the aim of the invention to provide a method within the time-frame referred to in the above mentioned German Patent Application which allows a hitherto conventional "closed encoded" FBAS colour picture signal or a "discrete coded" R.G.B.-colour signal to be detected in the receiver and to be processed, and also to create a coding-compatible receiver unit which is adapted without modification of its technical equipment at the user's place to be automatically switched over from the decoding of closed encoded picture information to the decoding of discrete coded picture information and vice versa.

In order to achieve the above stated aim the method according to this invention for closed encoded and discrete coded colour television transmission, in which closed encoded colour television pictures (FBAS signal, 4 x 10 bit) and discrete coded colour television pictures (R-,G-,B- signal, 5 x 8 bit) are transmitted in the constant length time slots reserved for picture transmission in a time multiplex system having a bit-timing frequency of 139m264 MHz for transmission and connection tasks in an integrated digital broad band network [see added wording in claim 1] is characterised by A) transmission of an accompanying identification signal within the above defined time multiplex frame beside the moving picture/sound channel;; B) automatic switch-over of a coding-compatible receiver unit in accordance with the received accompanying identification signal from closed encoded picture information to discrete coded picture information and vice versa.

The means or hardware for application of the method according to the invention is characterised in that the coding-compatible receiver unit comprises: a synchro-unit which seeks out the start of the 139,264 Mbit/s-data stream from the incoming dataflow at the input; a demultiplexer device arranged in succession with said synchro-unit and which splits out of the dataflow the picture data stream with 135 Mbit/s transmission rate and the code detection (closed or discrete coding) by virtue of a charge timing pulse which is recovered with the aid of a phase regulator circuit (not shown) at the input of the receiver unit (CE) from the untimed dataflow transmission, and which generates an accompanying timing pulse for the data stream at which the individual bits are charged in a succeeding 10 bit shift-register;; a buffer-store-selector device which, controlled by the code detection selects timing pulses generated by the demultiplexer device; buffer memories or stores into which are loaded the scanned data selected from the 1 Obit shift-register with the aid of a buffer-store selector signal generated by the buffer store selector device namely as follows for discrete coded transmission: 8bit for the R-Y-signal into the first buffer store, 8bit for the B-Y signal into the second buffer store, and 8bit for the Y-signal into the third buffer store; and for closed coding: 1 Obit-words from the 1 Obit shift-register into the third buffer store only; a decoder matrix which, for discrete coding compensates the time delays stemming from the transmission with stores, by addition in adding devices of the contents of the buffer stores recovers the components R = Y + R - Y; B = Y + B - Y; G = Y-(R+ B) and applies these to D/A converters arranged in succession with the stores which provide analog values for the RGB signals; for closed coding feeds the lObitwords which had been charged in the buffer store directly via a 2:1 multiplexer into a 1 Obit-D/A converter.

The invention is hereinafter more particularly described with reference to examples of embodiments represented in the drawings in which: Figure 1 is a block circuit diagram of a coding-compatible receiver unit according to the invention; Figure 2 is a time diagram representing data direction at closed and discrete coding in the picture channel; Figure 3 is a block circuit diagram of the decoder matrix according to the embodiment of Figure 1; Figure 4 shows the time-multiplex frame used in the system, and Figure 5shows channel widths in the time multiplex frame according to Figure 4.

An input of the receiver unit CE (Figure 1) the start of the 139,264 Mbit/s datastream is picked out of the incoming dataflow at input terminal D with the aid of the synchro-unit (3) (TDM-Sync). Each data bit of the digital information flow D is associated with a charge timing pulse BT which, with the aid of a phase-regulating circuit at the input of the receiver (not here shown) is recovered from the untimed dataflow transmission.

In the following demultiplexer device 4 the picture data flow "D* with 1 35Mbit/s transmission rate and the code identification (closed or discrete) is split out of this dataflow D. Again an accompanying identification timing pulse BT* is generated for datastream D* so that the individual bits of D* can be charged in the following shift-register with 1 Obit length.

The serial data current D* has, depending on the picture coding, a structure as shown in Figure 2 at a constant transmission rate of 135 Mbitls. The 135 Mbit/s data current may be composed of scanned values up to 10bit (closed coding of an FBAS signal), at a scanning frequency of 13.5 MHz, or of a stream of 8bit words consisting of the luminance-components Y and the chrominance components B-Y, R-Y. In the last mentioned case the scanning frequency for luminance Y is 13.5 MHz and that for the chrominance components B-Y and R-Y in each case 6.75 MHz.

The further treatment of datastream D* will depend on the selected coding mode of the picture signal.

In the case of component coding (discrete coding) the datastream D* is first serially loaded into a 1 Obit shift register and from there, after inputting of 8bit with the aid of a selectively applied timing pulse BT*/8 (only with component coding), which is selected in a buffer store selector device 6, split up in three buffer stores: buffer store : 8bitforR-Y; buffer store : 8bit for B-Y; buffer store : 8bitforY.

In the case of closed coding only buffer store 9 is loaded with 1 Obit words from the 1 Obit shift register with the aid of timing pulse BT*/1 0. The switch-over of timing pulses BT*/8 and By*/10 is made in the buffer store selector device 6 controlled by the code detection.

The digitalised scanning words of the picture signal at the output of the buffer store are fed into a decoder matrix 10 (Figure 3) in which time delays caused by the transmission are initially compensated with stores 101,102 and 105 at the input. By means of the following adding devices 101, 102, 104 and 105 the components R=Y+R-Y B=Y+B-Y G = Y(R+B) are recovered by addition of the contents of buffer stores 7 to 9 (with discrete coding only). The following D/A converters 107,108 and 109 then convert the RGB signals into an analog form.

In order to produce the line-synchronism a synchronising start signal generated at source is split out of the dataflow D in DMX which is required to trigger the internal sawtooth generator of the TV (FS) appliance.

After the transmission of each synchronising start signal, or marker signal, one picture line can then be completed in CE for each line by subsequent counting of the scanned values.

In the case of closed encoding the buffer store 9 is charged only with 1 Obit words which are fed via a 2:1 multiplexer 106 direct into a DIA converter 109 (IObit width). Switchover is made by the code-related control signal which also changes the timing cycle from BT*/8 to By*/10. This switch-over control signal also serves to block the RGB signals in the direction of the picture tube when operating with closed encoding or the FBAS signal when applying the discrete coding mode.

In the decoder matrix (Figure 3) the two D/A converters 107 and 108 which are needed to produce the Rand B- signals may be replaced by a single D/A converter provided the latter is also operated in multiplex.

Figure 2 shows the data-progress in the case of discrete coding (Figure 2a) and in the case of locked coding (Figure 2b). Figures 4 and 5 show the arrangement of the channels in the timeslot matrix.

The coding-compatible receiver unit is presented via data input D with a dataflow at a total transmission rate of 139,264 Mbit/s. This information flow comprises 2176 timeslots each at 40bits, which may be arranged in a matrix system of 64 lines and 34 columns. Each of these time slots represents a 64 bitls channel and is compatible for the transmission of 4 x 1 Obit scannings of closed coded picture signals or of 5 x 8 bit scanned values of discrete coded picture signals.

This dataflow is reserved as follows: TDM-synchroword: 1 time slot picture channel: 2112 time slots = 135,168Mbit/s incl. stop marks=0.168 Mbit/s PCM 30-system: 32 time slots auxiliary channels sound: 16 time slots picture-Sync: 12 time slots + code detection test pattern: 4 time slots.

The above described coding-compatible receiver unit assures compatibility between discrete-and closed coded colour television pictures.

The described circuitry is simple and economically realised by integrated switching circuits.

Claims (4)

1. Method for a closed encoded and discrete coded colour picture transmission, in which closed encoded colour television pictures (FBAS-sig nal, 1 Obit resolution) and discrete coded colour television pictures (R-,G-, B-signal, 8bit resolution) are transmitted in a time multiplex system at a bit-timing frequency of 139,264 MHzfortransmission-and connecting tasks in an integrated digital broad band network, whereby a frame structure of the time multiplexing system consists of 32 horizontal lines and 68 vertical columns to provide 2176 time slots, each time slot having 40 bits, and whereby the first time slot (column 0, line 0) is reserved for synchronization characterised by:: A) transmission of an accompanying identification signal within the above timemultiplex frame beside the moving picture/sound channel; B) automatic switch-over of a coding compatible receiver unit in accordance with the received accompanying identification signal from closed encoded colour information to discrete coded colour information and vice versa.

2. Apparatus for the application of the method claimed in claim 1, characterised in that the coding-compatible receiver unit comprises: a lynch rio unit which picks out the start of the 139,264 Mbit/s datastream from the incoming dataflow at the input a demultiplexing device arranged in succession with the synchro-unit and which splits out of the dataflow the picture datastream with 135 Mbit/s transmission rate as well as the code identification (closed or discrete coding) by virtue of a charging time pulse which is recovered with the aid of a phase regulator circuit of known type at the input of the receiver unit from the untimed dataflow transmission, and which generates an accompanying timing pulse for said datastream at which the individual bit are fed into a subsequently arranged 1 Obit shift register;; a buffer store selector device which, controlled by the code identification, selects appropriate timing pulses generated by the demultiplexer device; buffer stores into which are loaded, with the aid of a buffer store selector signal generated by the buffer store selector device, scanned values retrieved from the 10bit shift register, namely; for discrete coded transmission: 8 bit for the R-Y-signal into a first buffer store, 8 bit for the B-Y-signal into a second buffer store and 8bitfortheY-signal into a third buffer store; and for closed coding: 10bit-wordsfrom the 1 Obit shift register into the third buffer store only; a decoder matrix which, in the case of discrete component coding: equalises time delays stemming from transmission with stores, by addition in adding devices of the contents of the first, second and third buffer stores recovers the components R=Y+R-Y; B = Y+ B-Y;G = Y-(R+B) and applies these to D/A converters which are arranged in succession with the stores and which generate the analog values or the RGB signals; in the case of closed coding, feeds the 1 Obit values which are fed into the third buffer store via a 2:1 multiplexer direct into a 1 Obit-D/A converter.

3. A method for a closed encoded and discrete coded colour picture transmission substantially as hereinbefore described with reference to the accompanying drawings.

4. Apparatus for application of the method claimed in claim 3, substantially as hereinbefore described with reference to the accompanying drawings.