DE2615023A1 - METHOD OF DECODING COLOR TV SIGNALS - Google Patents

Description

The invention is based on a method for decoding of color television signals according to the PAL method which a channel filter decoder is used. There is already a method according to DBP 18 13 95 ^ "known, but how in other known methods - the following disorders appear:

1. Disturbances that start from the luninance signal in the chroninance signal occur, so-called Cr-oss-Color disorders, with diagonal line grids

2 .. Interferences from the (turoninance signal in luminance signal occur, so-called cross-luminans disorders, which can be eliminated by a bandstop filter (iTalle), but which inevitably reduce the luminance signal lowers in this area.

Naturally, these errors are particularly troublesome when transcoding one of the currently used Parbfernsehsystene in another or if in 'transmission system a! Color television signal encoded several times and is decoded, which may be the case with future digital transmission systems. These codings can take place on the analogue as well as on the digital level. Accordingly, the invention can be applied to either Layers are applied.

The arrangement according to the invention nit the characteristic In contrast, the feature of the main claim has the advantage that the disturbances mentioned have been greatly reduced.

709842/0218

Rl. -ITr. 1727/76 March 29th '! 976 PLI / Go / vL

Through the measures listed in the subclaims are advantageous developments and improvements of the The method specified in the main claim is possible.

An exemplary embodiment of the invention is shown in the drawing shown on the basis of the figure and in the following description explained in more detail.

The figure shows an exemplary embodiment in which the delay chain present in the comb filter decoder is also used for the another decoder is used. In addition, in the embodiment, the color difference signals become line sequential given as a sum or difference, which is advantageous in digital transmission, as in the patent application P 25 04-4-60 has been described.

In the framed part 16, the figure shows the well-known PAL filter decoder circuit according to DBP 18 13 95 *. ^{They can be implemented in} both analog and digital form with PCM-coded signals.

The circuit 16 is described in DBP 18 13 95 * and does not need to be explained here. The circuits added according to the invention have the task of to eliminate or significantly reduce the disadvantages mentioned. The principle of the circuit is based on the following two connections:

A. Cross-luminance interference only occurs if the ■

Chrominance information of consecutive lines: is not identical.

7098 * 2/0218

ROBERT BOSCH GMBH

Rl.-No. 1727/76

29.3.1976 PLI / Go / vL

2. Cross-color disorder of. I'AL decoders with delay lines and comb filter decoders differ in amplitude and location.

The color carrier trap is used to exploit the first relationship controlled in the luminance channel according to the occurrence of large luminance disturbances.

The direct F3A signal and the F3A signal delayed by two picture lines (128 / us) are each fed to a single PAL decoder 3.5 without a PAL delay line for demodulation. The color difference signals U and 7 obtained are checked for their correlation in 2 subtraction stages 6, 7. There is only one signal at output 6,7 if the Pa ^ 'bin information is consecutive :? Lines is different. The signals aac 6,7 are added to the J; ": carry in circuit, in the circuit; 9, which has a niclitliiienre U" transmission characteristic curve, in a suitable Uoise "way and then serve as a control voltage to control the color carrier trap 17 · If the controlled variable is ITuIl, the color carrier trap 17 remains switched off, the laminance frequency response is not reduced by the color carrier trap.

The second above-mentioned relationship is used to regulate the amplitude of the chrominance signal in the case of the exemplary embodiment, that is to say the signal IT + V, U-Y recognized gross oolor components exploited.

The U.-i -. 'V, U - -V Cliroma-Sigrial' obtained in the comb filter decoder becomes demodulated in a demodulation stage 12. It shows gross-color disturbances mainly at diagonal

7098? 2 ⁶ / Ö218

BATH ORIGINAL ROBERT BOSCH GMBH

2S15Q23

JH.-ITr. 1727/76

29.3.1976 PLI / Go / vL

Luminance bar structures. The input parb television signal becomes a normal PAL Uecoder without a PAL switch ('I, 2, 10) are supplied with a delay line, the delay line being used in the Eammfilterdecoder. Aa output of addition stage 11 is the same as at output 12 a TJ + V, U - IT chrominance signal on. These two chronic finance signals differ essentially only in their cross-color disturbances.

The signal from 10, 11 has cross-color disturbances on horizontal ones I / uminanasprängen (horizontal line grid) and in the case of diagonal luninance raster structures. the Interferences due to diagonal Luminans signal jumps however by approx. 3 d3 less than the corresponding cross-color disturbances at output 1.2. The subtraction circuit so always wins a signal when the gross color interference from 12 and from 10, 11 differ. An evaluated controlled variable is obtained from this information, the amplitude of the ghrominan signal from 12 (demodulated U + 7, U- Y signal of the usual Kamnifilterdecoder) or the amplitude of the Parb difference signals in known channel filter demodulators (18) controls, as indicated by dashed lines in the figure.

709842/0218

BATH ORIGINAL

Claims (2)

Patent claims My method for decoding color television signals according to the PAL method, in which a Eammfilterdecoder is used is characterized in that the color television signals also known devices for decoding without a comb filter are supplied and that the Output signals of this device with the output signals of the comb filter decoder. 2. The method according to claim 1 for reducing disturbances, which starting from the chrominance signal in the luninance signal occur, characterized in that the color television signal e ate each before and after the one-line delay in the comb filter via one Ho clip each one Bynchrondemodulatorpa ^ rCSinfach-rAIj-Denodulator) are fed, with between the output of the one-line delay and the one synchronous denodulator pair a further one-line delay is arranged that the pending at the outputs of a synchronous denodulator pair Color difference signals (U, V) subtracted from those of the other synchronous demodulator pair v / ground that the differences are added and that the amount of the sum to control the in the luminance channel of the comb filter decoder existing .band lock (color carrier trap) is used. Gene, which occur from the luminance signal based on the chrominance signal, characterized in that the color television signal e one hand unvei-delay, and secondly to a line duration minus a quarter Farbträger- - 3 · The method of claim 1 for the reduction of disturbances """ ROBERT BOSCH GMBH Rl.-Hr. 1727/7 6 29.3-1976 PLl / Go / vL period is delayed by a standard PAL decoder each a high-pass filter are supplied that the output signal ·? of the standard PAL decoder of which the chrominance relevant output signals of the comb filter decoder are subtracted and after an amount is calculated as a control variable, the amplitude of the output affects the chrominance related signals. 4-, method according to claim 3? characterized, that the chrominance signals alternate line by line as the sum and difference of the color difference signals occur that in 8tandard PAL Be coder Ice ine switchover the PAL-ochaltpaase is vorgonomen and that the color difference signals at the output of the Standard PAL decoder. 709842/0218