DE2511682C2 - Device for processing PAL-coded color television signals or black-and-white television signals with integrated accompanying sound at the receiving end - Google Patents

Description

) The invention relates to a device for receiving processing of color television image signals, the the extended rear porch of the shoulder contain audio signals in digital form, their pulse train frequency equal to the color subcarrier frequency and whose phase is equal to the color subcarrier phai-c

Such a device is known from the journal EBU Review, Part A, Technical, No. 128, August 1971, pp. 145 to 148. It is used to convert the color image signals that the Fernschton on the extended rear black shoulder included in digital form to separate this again from the image signal and to bring the picture signal back into the standard form, as the conventional color television receivers cannot receive the transmitted "composite" video and audio signals.

In the case of the transfer method known from the above-mentioned literature point, blanking gaps in the horizontal of the Ferniehbildsignals during the duration of the back porch, sound signals from a or several channels as ternary coded PCM pulses tower over. This is the duration of the lower Demand a black shoulder by shortening the horizontal sync pulse. That with NTSC or PAL color broadcasts to synchronize the receiving side Farbträgergcneralors necessary color sync signal, also called burst, is used in this Procedure not separated from the audio signals, transmitted, as suggested in the earlier patent application DT-OS 23 50 477, but is included in these, in that the audio signals are transmitted with the standardized frequency and phase position of the F'irbsynchronsignals.

In the PAL application of the above known method, the PCM Tonsignalc are therefore according to FIG PAL standard from line to line by 90 'between 135 and 225 "switched.

Since the transmission of black and white television pictures should also be possible with PAL systems the audio signals of black and white broadcasts as in PAL color broadcasts as ternary coded PCM pulses transmitted during the duration of the back porch. The pulse repetition rate is expedient of these audio signals the PAL color subcarrier frequency, however, in contrast to PAL color broadcasts, the The phase position of the audio signals is constant, namely 180 °, since the audio signals in the case of black and white signals are not the Must contain information about the color sync signal required for color broadcasts.

The PCM audio signals are also in the black and white television pictures contain.

Standard-compliant black-and-white sniffer signals included but no color sync signal, so that when receiving the color channel in conventional receivers is switched off. If this were not done, the reproduced black-and-white image would be through a so-called "colored noise" disturbed.

Task:

It is therefore the object of the invention to provide a device that consists of the in the PAL application of the known transmission method composite picture-sound-television signal again separate standard-compliant Image and audio signals wins in such a way that conventional PAL receivers switch off their color channel, when black and white picture signals with built-in sound signals are transmitted.

This facility can either be at the end of a transmission link for which no HF Tonkanälc are provided at the television broadcaster that has the

standardized television channels that supply glue receivers, or directly at each home recipient. even if the television station does not have any HF 'Tonkanäic contains more.

The object is achieved with the means specified in the claims.

Embodiments:

The invention will now be explained in more detail with reference to the figures, for example. Ks shows

J shows the block diagram of the inventive Facility,

2 shows the block diagram of another embodiment the device according to F i g. I.

F i g. 3 signal forms for the F i g. 1 and 2.

The device according to FIG. 1 or 2 is an additional sound, without which a known PAL color television receiver cannot process the transmitted signals. As already mentioned, the direction of the signal produces standardized signal ratios. although it is not critical to the invention. at which point of the transfer path to the receiver this happens.

Should specifically / in order to combat signals that are transferred to the aforementioned process, a color television receiver is no longer built is bound to the previously valid standard. so this is to change towards known recipients / u. Included it is expedient to refrain from establishing signal ratios that are appropriate to the requirements. The receiving side Color carrier alarm is stalled by the color sync signal synchronized directly from the PCM audio signals, their phase and pulse repetition frequencies / equal to the of the burst signal. The reference oscillator 11 in FIGS. 1 and 2 can therefore be used. That which occurs anyway with PAL signals during the synchronization of the color carrier generator on the receiving end Signal of half the line frequency /. otherwise use it to control the PAL-Umschaltcr! will serve as a criterion for determining whether a color broadcast is present or not, and whether the color channel is on or is switched off.

The color carrier generator delivers the correct Taklimpulse for decoding at the output of the PAL switch dor sound signals.

In the following, the oiler 2 shown in FIGS Addition / circuit according to the invention for known PAI color television receivers explained.

The black-and-white image signal IiAST or the PAL-coded color image signal FBAST, which contains the sound on the elongated rear porch (F-'ig. 3a). reaches in the low frequency range from the demodulator to a gate circuit I. / u a synchronous signal regenerator 2 and to a Tondckoder 8. The synchronous signal generator 2 extracts the start pulses for time signals 19, 20 and 21, which generate the gate pulses necessary for signal processing, from the horizontal synchronizing pulse. In addition, it generates standard-compliant sync signals (A. S). Controlled by the timing circuit 19, the gate circuit 1 separates the video signal from the PCM audio signal. The image signal arrives via a line 5 to a separator 3, which separates it from the synchronous pulses that have changed compared to the standard and adds standard-compliant synchronizing pulses (A. S) generated in the Sy η-6s chronsignal regenerator 2. In the case of color transmissions, the image signal leaving the separator 3 is only missing the color sync signal.

^{The F 5} CM audio signals separated from the image signal reach a bandpass filter 7 via a line 4. The output signals of the bandpass filter 7 are converted in an amplifier-limiter 9 into a symmetrical oscillation train that determines the frequency and phase of the color sync signal * FSS (Fig. 3c ) but still has the length of the transmitted audio signal and not the standardized burst length. F i g. 3b shows this signal together with the associated phase positions.

Since this color sync signal has slight phase fluctuations, it will be used in the following described embodiment (Fig. I) not added directly to the image signal, but for synchronization of a reference oscillator 11 whose output oscillation is then added to the image signal as a burst signal. A phase comparator is used for this 10, the output oscillations arriving via lines 22 and 23 (Fig. 3b) of the amplifier-limiter 9 and the reference / oscillator Π compares and so via a line 12 the referring oscillator II synchronized in terms of frequency and phase.

If the received signal is a PAL-coded color television signal, they are also PCM pulses of the sound information and consequently also clic output oscillations of the amplifier limiter 9 in their phase position from line to line by 90 between 135 and 225 '. With black and white image transmission the phase is a constant 180. In any case, the reference oscillator U is set to the mean Phase position of 180 synchronized.

A phase splitter, not shown, provides oscillations of the phases at the output of the Rcfccnzoszillators II 135, 180 and 225 ready.

In the case of PAL-coded color transmissions, an oscillation of half occurs in the phase comparator 10 Line frequency //// 2.

In the invention it forms the criterion as to whether a PAL color television signal or a black and white signal is present.

Controlled by this oscillation, a phase switch supplies 14 oscillations of the larbtra'gci frequency, the phase of which is line to line between 135 and 225
alternating rope.

In the case of black-and-white broadcasts, there is no oscillation of half the lines in the phase comparator 10. because the phase position of the PCM tone impulses is a constant 180. Therefore the phase switch remains 14 in its middle position and oscillations ran with the color carrier frequency and the constant phase position from 180. This arrangement means that the same signals are available at the output of the phase switch 14 as at the Output of the amplifier limiter 9, but with less phase fluctuation

Since the color sync signal ISS only has to be added to color broadcasts. A Gleicnriehtcr 15 generates a control voltage from the oscillation of half the line frequency resulting from color transmissions at the output of the phase comparator 10, which closes a sounder lh, so that it fades out 8-10 oscillations via a gate circuit 17, which from the output signal of the phase switch 14 conforms to the standard 8-10 oscillations Switch 16 arriving color sync signal FSS is added to the image signal in the adder 6. The gate circuit 17 is controlled by the timing circuit 21 from the horizontal sync pulse of the synchronsignalregcneralors. The position and length T of the gate pulse is shown in FIG. Jc shown. The length 7 "is (8-12) times the

Color vehicle period Tu-. With .Schwarz-Weil.t broadcasts, the switch 16 remains open, since the oscillation of half the Zcilenfreqiienz Ι'μ / 2 in the phase comparator 10 does not occur.

Since no color sync signal is transmitted for the duration of the vertical blanking, a /.eil a switch 18 is opened by the vertical synchronization pulse appearing at an output of the synchronizing signal regenerator 2 is controlled. By this circuit arrangement is achieved that according to the Found the regenerated standard-compliant color sync signal FSS only for color transmissions in one Addicrslufe 6 to the image signal on the back porch is added, so that the conventional color television receiver for Sch was / -Weiß broadcasts, So if there is no color sync signal, switch off your color channel.

F i g. 3d shows for two consecutive rushes the for PAI-coded color broadcasts in the Addicrstiife 6 to be added color sync signal FSS with the associated phase positions 135 "and 225".

The color signal thus formed by the adder 6 1 "BAS shows the F" i g. 3c.

So that in the Tondekoder6 the PCM Tonsignalc in correct clock are queried, the tone decoder 8 receives its Takiimpulsc from the output of the phase switch 14 via a line 24. It also receives it from the synchronizing signal generator 2 via a timing circuit 20 Synchronization pulses of the line frequency / '//. The Taklimpulse, the tone decoder 8 receives, so have the frequency and phase of the PCM Tonsignalc. the is either a constant 180 '' (black-and-white image) or from line to line between 135 'and 225 (PAI.-color image) changes.

Fine compared to the circuit arrangement according to Fig. I shows a slightly modified circuit I i g. 2. As already mentioned, the color sync signal can already after amplification and limitation to the image signal can be added if one makes less stringent demands on its phase stability. To do this, the Output signalc of the amplifier-limiter 9. those in 3b, via a further bandpass filter 25 and the switches 18 already described. 16 and the gate circuit 17 of the Addicrsiufc 6 supplied, instead of being taken from the output of the phase switch 14, as in FIG. The control this switch, like the function of the other modules, does not differ from the Circuit according to Fig. I. F. Corresponding assemblies have the same reference symbols and throughout therefore do not require an explanation of their own.

The output signals of the additional circuit according to FIG. I. or 2 can be sent to the recipient in various ways. For example, the known Receiver with a video input for the composite signal and an LF input for the tone signals supplied by the tone decoder 8. Another It is possible to use the additional sound system according to FIG. To accommodate 1 or 2 in a F.nipfangszentrale, which are the separated audio signals and image signals again via standardized television channels to the home receivers which even then does not send out any

20th

Need 30 additional devices.

For this purpose 3 sheets of drawings

Claims (5)

Palent claims: 1. Device that separates color televisor signals and audio signals transmitted over the same RF channel are transmitted, the color television signals the audio signals on the extended rear Black shoulder included in digital form and the pulse repetition frequency of the audio signals equal to that Color subcarrier frequency and its phase is equal to the color subcarrier phase, and that of the digital audio signals decoded and from the color television image signals that have been changed compared to the standard again conforming to the standard Signals wins, with a regenerated from the audio signals color sync signal added to the color image signal in accordance with the standard, d a characterized in that it is used for processing both from PAL encoded color television signals as well as black and white television signals, which each contain audio signals, the phase of these audio signals that are used in PAL color broadcasts from Line to line changes by 90 "and for black and white broadcasts remains constant (180), evaluated and only when receiving PAL color television signals the color sync signal (FSS) regenerated from the audio signals in accordance with the standard / around image signal added up. 2 Device according to claim 1, characterized in that in order to obtain the color synchronous signal (FSS) to be added to the television signal in PAL color television pictures, the audio signals are fed to a phase comparator (10) via a bandpass filter (7) and an amplifier limiter (9) , which synchronizes a reference oscillator (11) with respect to frequency and phase and when receiving color television signals from the line-frequency changing phase position of the audio signals an oscillation of half the line frequency (fn) , which on the one hand controls the PAL standard-compliant switching of the phase of the output signals of the reference oscillator ( U) is used in a phase changeover switch (14) and on the other hand to close a switch (16) when receiving color images, via which the regenerated color sync signal arrives at an adder (6) which adds it to the television signal. 3. Device according to claim 2, characterized in that the output signals of the phase switch (14) a sound decoder (8) as clock signals for decoding the digital sound information are fed. 4. Device according to claim 3, characterized in that the regenerated color sync signal (FSS) the output signal of the phase switch (14) used and in a gate circuit (17) to the standard length is brought (Fig. 1). 5. Device according to claim 4, characterized in that that the output signal of the amplifier limiter (9) as a regenerated color sync signal is used and brought to the standard length in a gate circuit (17) (FIG. 2).