DE2348291A1 - Colour T.V. signals transmission system - transmits consecutively different colour signals in periodically recurring cycle - Google Patents

Abstract

The system can be used for recording or for a.t.v. telephone. The colour signals are consecutively transmitted in a compressed in time form during a line period. A wide band luminance signal and the above compressed colour signals are alternately transmitted from line to line or a luminance signal and two colour signals are so transmitted or luminance signal is so delayed, that it coincides during reproduction with the corresponding colour signals. Colour signals of an n-th line are compressed to a fraction of a line period and are transmitted after suitable delay in a following (n+1)th line.

Description

Licentia Patent-Verwaltungs-GmbH 6 Frankfurt / Main 70, Theodor-Stern-Kai 1

Hanover, September 13, 1973 PT-Wp / ds H 73/85

System for transmitting a color television signal, especially for a recording or for a

Television telephone

In color television broadcasting, it is well known that the two color signals which must be transmitted in addition to the luminance signal, transmitted with a color carrier, its frequency lies within the bandwidth of the luminance signal. In the PAL color television system, the color carrier is simultaneously with both Color signals quadrature modulated and has a frequency of about 4.43 MHz.

This type of transmission is possible because the frequency of the color carrier is outside the transmission bandwidth for narrow-band transmission lines, such as simple recording devices or television telephones, for example, which only have a bandwidth of 3 MlIz. The recording apparatus with a tin VBrnie d'i b ar en Ge s chwind igke itss cliwankuiig en b ewirksn Auss he de-n in a modulated with zvrei color signals color carrier Zeitfelilcr, -the lead to Farbtcmverfälschuiigen. Due to the non-linearity of such transmission, further errors arise, insl> o Condoro crosstalk. between the simultaneously transmitted pictures *

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It is also known (DT-AS 1 412 489), the luminance signal on the one hand and the two color signals on the other hand from line to line Record line alternately. There is crosstalk between the luminance signal and the color signals is not possible because these are no longer recorded at the same time. In this solution, however, the two color signals must be recorded simultaneously in a multiplex on the carrier, namely preferably in frequency division multiplex. Therefore, there is again the risk of cross-talk between the color signals due to non-linearities of the recording medium. In addition, means, e.g. switches, are required to separate the signals during playback.

It is also known for recording (DT-PS 1 261 876) to record the three color signals representing the primary colors alternately from line to line in tri-line sequential order. During the reproduction, line delay lines are provided which repeat each of the color signals in their dead times and thus make them available without any gaps. In this system, the sequential recording while in the upper frequency range of about 0.5 h s ± 3 »0 MHz constantly since luminance signal is recorded is carried out in a lower frequency range of 0 to 0.5 MHz etwa-. With this solution, the complete transmission of all three signals is completed after the expiry of three lines. In the case of dsr playback, three consecutive lines must therefore be evaluated in order to generate the luminance signal in the lower frequency range. That means an averaging over three lines. This tri-line sequential transmission therefore leads to errors in the reproduced image in the case of certain image contents, in particular in the case of information transitions in a vertical direction, that is to say, for example, in the case of horizontal edges.

The invention solves the problem of a sequential transmission: ~ syaton au create, with your at any time puiilct only one signal

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is transmitted, but for the transmission of all signals with a time shorter than three lines.

This object is achieved by the invention described in claim 1 solved. Advantageous embodiments and developments of the invention are specified in the subclaims.

The invention is based on the following knowledge: The available transmission bandwidth of a system is generally fully utilized by the luminance signal, which is decisive for the sharpness of the image. The color signals, on the other hand, which are only decisive for the coloration of the image, however, require a much smaller bandwidth of, for example, 25-30 % of the total bandwidth. If, according to the invention, the color signals are now compressed in time in order to transmit two or three color signals one after the other during a line, the bandwidth of these signals is increased. Since their bandwidth is actually less than that of the luminance signal, the color signals can be transmitted in a time-compressed manner instead of a luminance signal, that is to say over a significantly shorter period of time. In certain lines, for example, instead of a broadband luminance signal with a 3 MHz bandwidth, three inherently narrow-band color signals, each with a 1 MHz bandwidth, are transmitted time-compressed one after the other. Since two or three color signals are now transmitted one after the other during a line, the total time for the transmission of all signals is reduced. However, it is a pure sequential transmission of all signals, so that crosstalk between the signals is definitely avoided. The time compression necessary before the transmission and the time expansion necessary for the reproduction can be carried out economically with reasonable effort with neii-like components, such as electronic clocked memories, for example bucket chain connections.

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A particularly advantageous system is obtained when, according to a Embodiment of the invention alternating from line to line on the one hand a broadband luminance signal and on the other hand two time-compressed color signals transmitted one after the other will. Then only two lines are required for the sequential transmission of all three signals. aside from that the luminance signal, which is decisive for image sharpness, is present in every second line. That also enables a special one simple circuit for a black-and-white reproduction by simply evaluating the luminance signal and adding it to its Dead times is repeated with a delay line.

The invention is explained with reference to the drawing. 1 shows the principle of the transmission,

FIG. 2 shows a further development of the invention, FIG. 3 shows the principle of signal processing for transmission,

4 shows a block diagram for the preparation of the to be transmitted Signals,

Fig. 5 is a block diagram for reproduction and

Fig. 6 is a simplified block diagram for a pure Black and white rendering »

In FIG. 1, t denotes the line retrace time, t denotes the line trace time, Y a luminance signal of 3 MHz bandwidth and R, B two narrow-band color signals. The digits 1-5 indicate different times during the sequence of two lines. During the trace time of line 1 between times 2, 3, the broadband luminance signal Y is transmitted. According to the invention, the color signal R is transmitted in time-compressed form during the first half of the running time of line 2, that is to say in time 4-5. The signal R , which in itself takes up the duration of a line, is thus compressed with a time compressor atif half of the line duration, which doubles the bandwidth of the narrowband signals.

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■ will. During the second half of the trace time of line 2, that is to say during the time 5-1 », the color signal B is transmitted in the same way in time-compressed form according to the invention. During the trace time of line 3, the luminance signal Y is then transmitted again. It can be seen that it is a purely sequential transmission of the three necessary signals Y, R, B, and that nevertheless only two lines are required _{for the transmission of all three signals Y 5} R _{1 B.} It is particularly advantageous that the broadband luminance signal Y is fully available during every second line. This results in a good sharpness of the reproduced image.

In FIG. 2, according to a further development of the invention, the two color signals R ₁ B are compressed to less than half the line trace time. This creates a further free period during the forward time. According to the development, a further narrow-band signal T is transmitted in time-compressed form during this time. This signal can be, for example, a sound signal, a switching signal or the synchronization signal for the deflection.

Fig. 3 shows the principle of signal processing for transmission. During a period 1 the signals B, R, Y are available at the same time. During line 1, only the signal Y is transmitted. At the same time, the signal R is compressed to half the trace time and delayed so that it falls in the first half of the trace time of line 2. The signal B zeit3.ich is also compressed to half the trace time and delayed so that it falls in the second half of the entry time of line 2. This shift of the color signals to the next line is necessary because the zeitkompriniierten color signals can not be in the same line made available where they are per se.

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In Fig. 4 is from the constantly present color signals R, 6, B in an adder 6, a luminance signal Y is formed which leads to a switch 7 arrives. The signals R, B also reach the switch 7 via memory 8, 9, 10. The one in the direction of the arrow

rotating switch / is at the transitions between the contact tracks provided with numbers 1-5, which indicate the position of the switching arm in the times 1-5 according to FIG. the Contact tracks only symbolize the time range in which a certain line is switched through. In reality it happens the switching process via electronic switches, such as diodes or transistors, which are controlled accordingly.

Mode of action ; During the time 2-3, the switch 7 evaluates the luminance signal Y and feeds it to an adder stage. The luminance signal Y thus appears at the output 12 of the adder 11 during line 1. During line 1, the signals R, B are also stored in the memories 8, 9. For this purpose, the electronic, clocked memories are supplied via a line 13 from a switch 14 with a clock pulse sequence which is generated in a generator I5. The generator 15 is synchronized by the synchronizing signal S. The synchronizing signal S is also fed to the adder 11 via a line l6 and thus appears at the terminal 12. The generator I5 generates a pulse train with the frequency 2nf_ ,, where η is an integer of a few hundred and f _{T is} the line frequency. In a frequency divider 17, this becomes a clock pulse train with the frequency η. f "generated. This clock pulse sequence is fed to memories 8, 9 via line I3 during time 2, 3. The signals R, B are thus stored in the memories 8, 9 during the time 2, 3.

During the time 4-5, the switch 7 picks up the signal R from the memory 8. The memory 8 is now fed by the switch j 4 with a clock pulse sequence with twice the frequency 2nf ... This means that the signal R is now twice as high

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is read out from the memory 8 as fast as the input, i.e. during the time 4-5 zvaa switch 7 is reached. This forwards the signal to the adder 11 during the time 4-5. During the time 4-5, the signal B is also read out from the memory 9 during half the trace time. This signal is delayed by the memory 10 by the duration of half the linear delay time, so that it reaches the switch 7 during the time 5-1 according to FIG. During this time, the switch 7 now sends the time-compressed signal B to the adder 11. During the time 5-1, the memories 8, 9 are not controlled by the switch 14, since during the time 4-5 both signals R, B have already been read out and the next reading takes place in line *. It can be seen that in this way a signal according to FIG. 1 is produced at the terminal. The switches 7-14 are synchronized with one another and each make a full rotation for the duration of two lines.

In FIG. 5, the signal at terminal 12 in FIG. 4, which has the form according to FIG. The switches 22, 23 are operated as in FIG. During the time 2, 3j in which the luminance signal Y is present at the terminal 18, this signal is evaluated with the switch 22 and fed to a matrix 21. During the time 4-5, the switch 22 picks up the time-compressed signal R and sends it to the memory 24. This delays the signal R by half the trace time, so that the signal R reaches a memory 25 during the time 5-1. During this time the switch 23 supplies a clock pulse sequence with the frequency 2nf ", so that the signal R is quickly read into the memory 25 during half the trace time. At time 5-1, the switch 22 directly supplies the signal B and sends it to a memory 26. There, the signal B, like the signal R dm memory 25, is read in by the clock pulse sequence. During the next inch 3, the switch 23 supplies the memory 26, 2-5 with a clock pulse sequence with the frequency f ", which is generated by the frequency divider

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27 konunt. This clock pulse sequence now causes the signals R ₁ B to be read out slowly from the memories 25, 26, in each case during a trace time, so that the two signals R, B are now available at the outputs of the memories 25, 26 during line 3.

It can be seen that there is a time shift between Y on the one hand and R, B on the other, because the signals R ₁ B are delayed by one line duration both before transmission (FIG. 4) and during playback (FIG. 5). To compensate for this delay and to achieve the correct time correlation between Y and R, B, the delay line 28 is used, which delays Y by one line duration, or at least several lines.

The delay elements 29, 30 »31», each delaying by one line duration, and the adding stages 32-3k have the following purpose: It can be seen that both the signal Y and the signals R ₁ B are only available in every second line , i.e. missing in the lines in between. Therefore, each of the signals Y, R, B is repeated by one line with the delay elements 29, 30 »31, so that the stages 32, 3 ^ deliver the signals Y, B, R in each line. For example, the stage 32 receives the signal Y of the line 1 via the line 35 during a line in the period 2-3 and the same signal again via the delay element 29 in the next line. The matrix 21 thus constantly receives the signals Y, B, R at its three inputs in each row and uses them to form the complete composite signal at a terminal 36.

Fig. 6 shows a circuit for a pure black-and-white reproduction. From the signal according to FIG. 1, only the signal Y is evaluated with a line delay element 37 and a switch 39 actuated at a line frequency by a switching voltage 38 and is repeated during its dead times. The signals R, B are thus suppressed. The switching voltage 38 is in

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a generator 40 generated, which-by the synchronous signal S is synchronized. The synchronizing signal S is obtained from the BAS signal in a separation stage 4l. With the always available Made luminance signal Y, a black-and-white television receiver 42 is controlled. It is particularly advantageous that the luminance signal Y is transmitted in every second line and the transmission of the color signals is limited to one line is.

The transition between the color signals in the course of a line, that is, at the time 5 in Fig. 1 may additionally be marked by an identification pulse to ensure a handoff of the switch 7 ₅ l4, 22.23 i ^m at the right time. The clock pulse sequences controlling the memory in FIG. 4, 5 are derived from the signal selbsi, for example by multiplying the line frequency. This has the advantage that even with a fluctuating line duration, such as, for example, a signal in front of a recording device, the control of the memory is always in the correct ratio to the line duration.

The invention was made for the transmission of two color sigrials R, B described. It is also possible to have several color signals, e.g. R, G, 3 time compressed during a line trace time to be transmitted one after the other.

When recording the signal processed according to the invention on a recording medium along a track with side by side lying track sections, the spatially identical places consecutive images are assigned, the recording takes place advantageous so that on η adjacent track sections signals of the same type are recorded, e.g. on adjacent track sections "always Y or R or B. Such a type of recording is described in DT-PS 2 042 434.

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Claims (12)

- 10 - H 73/85 Claims / ι) System for the transmission of a color television signal, in which several different color signals are transmitted one after the other in a periodically recurring cycle, in particular for a recording or for a television telephone, characterized in that the color signals (R ₁ B) each during a line duration in time-compressed form are transmitted one after the other. 2. System according to claim 1, characterized in that a broadband luminance signal (Y) and the time-compressed color signals (R, B) are transmitted alternately from line to line. 3. System according to Claim 2, characterized in that a luminance signal (Y) and two color signals (R, B) are transmitted alternately from line to line. 4. System according to claim 2, characterized in that the luminance signal (Y) is delayed (stage 28 in Fig. 5) that it inimt in time with the associated color signals (R, B) over it e in st during playback. 5. System according to claim 1, characterized in that the color signals (R ₁ B) of a line numbered in time sequence with η are time-compressed to a fraction of the line duration and after a corresponding delay (steps 8,9,10) during a temporally following line ( n -f- l) are transmitted. 6 * System according to claim 1, dad urch g6ke nnzeich.net that in the line _s in which the color signals (R, D) to be transmitted, by a greater time compression of the color signal © another Vic.iteros signal (T) as a sound signal , Control signal or synchronous signal offset in time; ίίΐ color signals transmitted v. ^r ird. 509816/0435 BATH ORIGINAL - 11 - H 73/85 7. System according to claim. I ₁ characterized in that the transition from one color signal to another color signal in the course of a line is marked by an identification signal. 8. System according to claim 1, characterized in that during reproduction the color signals (R ₁ B) are time-expanded again to their original duration (steps 25, 26 in Fig. 5) and are brought into a time position required for color image reproduction. 9. System according to claim 1, characterized in that when playing back a signal (Y, B, R) in the lines in which it is not transmitted, is repeated by a memory (29 -31) for line duration (Fig. 5) · 10. System according to claim 2, characterized in that for a black-and-white reproduction only the luminance signal (Y) is evaluated and repeated with a cell delay element (37) in its dead times (Fig. 6). 11. System according to claim 1 or 8, characterized in that the time compression and / or the time expansion is carried out with an electronic, clocked memory (8,9; 25,26) controlled by a clock pulse train (Fig..4,5). 12. System according to claim 11, characterized in that the clock pulse sequence is derived from the signal that compression and expansion are in the correct ratio to the line duration even with fluctuating line duration. 13 * System according to claim 12, characterized in that the frequency of the respective clock pulse sequence is a multiple of the line frequency. - 12 - 509816/0435 BATH ORIGINAL - 12 - H 73/85 lA. System according to Claim 1, characterized in that when the signal is recorded along a track with track sections lying next to one another to which spatially identical locations of successive images are assigned, the recording is carried out in such a way that signals of the same type (Y ₁ Y or R ₁ R or B, B) are recorded. · 509 8 16/0435 Blank page