RU2153236C2 - Method, encoder and decoder for processing of supplementary signals in tv signals - Google Patents

Abstract

FIELD: TV equipment. SUBSTANCE: method for transmission of supplementary signals in SECAM standard uses post box format in order to ensure backward compatibility with existing 4:3 format receivers in PAL+ standard. This is combined with transmission of supplementary HS signal in black frequency band. Same PAL+ procedure for supplementary signal processing in SECAM causes noise in black frequency band in 4:3 receivers because of absence of frequency-modulated carrier. Goal of invention is achieved by parallel generation of balanced artificial carriers with quadrature phase shift with respect to phase of carrier, which is modulated by supplementary signal, in order to ensure compatibility with SECAM. This results in possibility have compatible playback by existing 4:3 receivers, while in receivers with enlarged frame format, supplementary signal is separated from artificial carriers by means of production demodulator and is used for recovery of source image signal with enlarged frame format. This ensures possibility of 16:9 compatible transmission through existing TV channels. EFFECT: increased functional capabilities. 9 cl, 4 dwg

Description

 The invention relates to a method, encoder and decoder for processing auxiliary signals in accordance with SECAM standards, which allows compatible 16: 9 transmission over existing television channels.

State of the art
An aspect ratio of 16: 9 can be found in any new television broadcast standard. Regarding PALplus, an extension of the existing PAL standard, problems associated with processing widescreen images while maintaining backward compatibility with existing receivers have been reached, and the first PALplus receivers are already on the market.

 An object of the present invention is to provide a method for transmitting television signals having a 16: 9 format compatible with the SECAM standard. This objective is achieved by the inventive method described in paragraph 1 of the claims, and the encoder and decoder that use the inventive method. This goal is achieved by the encoder described in paragraph 5 of the claims, and by the decoder described in paragraph 9 of the claims, respectively.

 In the extension of the existing SECAM standard - in the SECAMplus mentioned below, the most significant change is to change the 4: 3 frame format to 16: 9. In order for the SECAMplus decoder to have a low added value, SECAMplus should satisfy the PALplus standard as much as possible.

 In PALplus, the mailbox format was selected at the same time as the auxiliary signal was selected in the areas of the black frequency range, as described in EP-A-0445177 and EP-A-0451205. Since there is no need to transmit information about a color image in the frequency range of black, the auxiliary signal is modulated in amplitude as a color subcarrier. The same format conversion technique can be used for SECAMplus, however, if the modulation of the auxiliary signal is directly borrowed from PALplus, then strong interference will occur in the areas of the black frequency range from bursts of large color areas. This flicker occurs due to the loss of a frequency-modulated subcarrier in a compatible SECAM receiver for small amplitudes of auxiliary signals.

 In accordance with the present invention, artificial, coherently weighted quadrature phase shift subcarriers are created with respect to a subcarrier modulated by an auxiliary signal to ensure compatibility with SECAM. This allows compatible reproduction by known receivers with 4: 3 formats, while for receivers with a larger frame format, the auxiliary signal is separated from the artificial subcarriers by the product demodulator and is used to reconstruct the signal of the original image with a larger frame format.

 In fact, the invented method processes auxiliary signals in enlarged aspect ratio television signals that are compatible with known television standards, the video signals being decomposed into auxiliary signals and mailbox signals, to which a coherently weighted subcarrier with a quadrature phase shift with respect to the subcarrier is added modulated by an auxiliary signal, and the composite signal is included in the region of the frequency range of black, the image signal, consisting of and the signal of the mailbox and the signal of the frequency range of black is transmitted and can be decoded at the receiving end by both well-known 4: 3 receivers and receivers with an increased frame format, in which auxiliary signals are separated from the artificial subcarrier and used to reproduce the original image signal with an enlarged format frame.

 Useful additional embodiments of the invented method are obtained from the corresponding dependent claims.

An encoder for processing auxiliary signals in television signals with an enlarged aspect ratio in accordance with the present invention comprises a format conversion unit in which the video signal is decomposed into a mailbox signal and an auxiliary signal, an encoder for processing mailbox signals, a modulation unit for an auxiliary signal, which comprises:
- pre-processing unit,
- the first modulation block, where the pre-processed auxiliary signal is modulated into one or more corresponding subcarriers,
- an amplitude detector circuit to which a subcarrier is transmitted, modulated by a specific auxiliary signal, and which transmits a normalized detection signal,
- an adder in which the control signal is estimated by subtracting the normalized detection signal from 1,
- a second modulation block in which one or more artificial subcarriers is multiplied by a control signal to control their amplitudes,
- an addition unit in which one or more artificial subcarriers are added to the corresponding subcarriers of the auxiliary signal with a quadrature phase shift,
- a post-processing unit for half filtering by Nyquist one or more composite signals and for selecting one filtered signal in the case of more than one composite signal, as well as a selection device by which the processed auxiliary signals and mailbox signals are combined.

 Useful additional embodiments of the inventive encoder are obtained based on the respective dependent claims.

The decoder for processing auxiliary signals in television signals with an enlarged aspect ratio in accordance with the present invention contains:
- a filter unit in which the signals of the black frequency range are filtered according to Nyquist,
- a unit that transmits a composite video signal to subsequent devices upon receipt of the blanking pulse pad,
- a PLL circuit for recovering frequency modulated carriers in a video signal,
- phase shift device 90 degrees,
- a selection device that selects filtered according to the Nyquist corresponding signals of the black frequency range and phase-shifted frequency-modulated carriers,
- demodulator of the product, where the signal of the black frequency range is filtered, filtered according to Nyquist, and the phase shifted frequency modulated carrier,
a low-pass filter for extracting a carrier component from a plurality of carrier frequencies,
- as well as a post-processing unit to increase the amplitude of the auxiliary signal.

In FIG. 1 shows a flowchart of processing on the transmitting side,
FIG. 2 is a block diagram of an auxiliary signal modulation,
FIG. 3 is a more detailed block diagram of an auxiliary signal modulation,
FIG. 4 is a block diagram of a demodulation of an auxiliary signal at a receiving side.

Preferred Executions
In FIG. 1 shows the operation of the encoder on the transmitting side in the case of television signals with an enlarged frame format, which is compatible with well-known television standards. After converting the format, in particular, from 16: 9 to 4: 3 in the FC block, the video signal is decomposed in the case of a television signal with 576 active lines into an LS signal of a mailbox with 432 active lines in a frame and an auxiliary signal HS with paired 72 active lines in frame. The mailbox signal is transmitted through the standard ENC encoder, which outputs a composite signal, while the auxiliary signal is processed in the MOD block. The processed auxiliary signals as well as the mailbox signals are then combined by the SELE1 selection device.

 The invented method for incorporating a coherently weighted artificial subcarrier into the black frequency range region is shown in FIG. 2. First, preprocessing of the auxiliary signal HS in the PREE unit is performed. After passing through the low-pass filter LPE1, the horizontal spectrum is compressed, the look-up table LUT compands, and the next low-pass filter LPE2 is used to suppress harmonics caused by non-linearity. After that, the pre-processed auxiliary signal is modulated in the MODH modulator into a subcarrier having a frequency that is one fourth of the used sampling frequency. Then the amplitude of the total signal is set by the amplitude detector circuit AD, which contains in series: a band-pass filter BP, an amplitude measurement circuit AM and a non-linear element NL. The amplitude detector circuit ensures that, in the absence of a powerful auxiliary signal, an artificial subcarrier with a quadrature phase shift is added in the QP block, thereby keeping the total amplitude within the necessary limits. For this purpose, the amplitude control of the artificial subcarrier in the MODA block is controlled by the CS control signal, which is determined by subtracting the normalized detection signal NS from 1 in the ADD block. The subsequent Nyquist half-filter NF implements the Nyquist half-steepness at the subcarrier frequency, which should be used in the case of selecting a partially suppressed sideband transmission. The inclusion of an artificial subcarrier with a quadrature phase shift allows, after transmission at the receiving side, a simpler separation of the auxiliary signal and the artificial subcarrier by means of a product demodulator.

In accordance with a pair of different frequencies for the color-difference signal components in the SECAM standard, for the well-known SECAM 4: 3 receiver, it is possible to suppress too noticeable flicker by including only one artificial subcarrier, but the regions of the black frequency range remain somewhat colored. This coloration can be suppressed by using two subcarrier frequencies for the two color difference signal components, as shown in more detail in FIG. 3. After preprocessing, the auxiliary signal HS is modulated by modulators MODH1 and MODH2 into two different subcarriers with frequencies fs / 4 and fs / 4 - Δf, respectively, where for the digital SECAM decoding, the used sampling frequency is fs = 17.54 MHz. The SELE2 selection device selects the high-frequency subcarrier for component D _R , and the low-frequency subcarrier for component D _B , and they are transmitted to the amplitude detector AD, which generates a normalized detection signal NS. After subtracting it from 1, the control signal CS is obtained, which controls the amplitude of the pair of artificial subcarriers, also having frequencies fs / 4 and fs / 4 - Δ f, by means of modulators MODA1 and MODA2. The respective subcarriers and artificial subcarriers are summed with a quadrature phase shift in blocks QP1 and QP2, and the summed signals are each transmitted to the Nyquist half filter filters NYQE1 and NYQE2, respectively. The filtered signals are switched by the SELE3 selection device.

On the receiving side, auxiliary signals can be demodulated in a manner similar to that shown in FIG. 4. The signal of the black frequency range first goes through Nyquist half-filtering in the NYQD1 or NYQD2 filter blocks, which are identical to the NYQE1 and NYQE2 filter blocks used on the transmitting side, respectively. The first SELD1 selection device switches this pair of Nyquist filtered black frequency range signals from line to line. In parallel with the processing of the black frequency range, the necessary auxiliary signal carriers should be reproduced. For this purpose, the GAT block transmits the composite video signal VS to the second selection device SELD2, if at the beginning of the frame line in the region of the back pad of the BP quenching pulse a frequency modulated packet is transmitted that corresponds to the quadrature phase of the carrier used in the encoder. The SELD2 selection device switches from line to line of two separate PLL circuits PLL1 and PLL2, in which two different frequency-modulated carriers are reproduced. After the third selection SELD3 device for switching the pair of rows frequency modulated carrier requires the use of PS phase shift device 90 ^o for synchronous demodulation of amplitude of the auxiliary signal. The demodulator of the DEM product, where the Nyquist-filtered black frequency range signal and the phase-shifted frequency-modulated carrier are multiplied, produces a demodulated auxiliary signal, which must be filtered by the lower frequency in order to get rid of the carrier components at the doubled frequency of the carrier. After filtering in the LPD block, the auxiliary signal is subsequently processed in the POSTD block, where the increase in the amplitude of the auxiliary signal is taken into account. There is no need to limit the spectrum of the output signal, just as it does in the encoder.

 The use of two artificial subcarriers causes a decrease in color in the region of the frequency range of black in known SECAM 4: 3 receivers to insignificant levels.

 Another useful improvement of the inventive method is the inclusion of a subcarrier with a constant or even consistently increased amplitude to where the auxiliary signal is significantly different from zero if the blanking level or black level in the auxiliary signal is slightly increased to ensure the minimum difference between the synchronization pulse and the largest negative value of the range signal black frequencies. The artificial background corresponding to this shift can be eliminated by a smoothing circuit in a compatible receiver.

 The present invention can be used, for example, in television receivers SECAMplus and VCP.

Claims (9)

 1. A method of processing auxiliary signals in television signals with a larger frame format, which are compatible with known television standards, where the video signals are decomposed into auxiliary signals (HS) and mailbox signals (LS), characterized in that the coordinated weighted artificial subcarrier (ASUB) is added with quadrature phase shift to the sub-carrier modulated auxiliary signal (HSUB), the composite signal (BS) is included in the black region, an image signal consisting of the mail signal is transmitted the second box and the signal of the frequency range of black, and this signal at the receiving end can be decoded by both well-known 4: 3 receivers and receivers for a larger format frame, in which auxiliary signals (HS) are separated from the artificial subcarrier and used to reproduce the original signal images with a larger aspect ratio.  2. The method according to p. 1, characterized in that the auxiliary signals (HS) are modulated into two subcarriers (SUB11, SUB12) with different frequencies, where the first frequency is approximately equal to or identical to the frequency of the subcarrier of one of the components of the color difference signal, and the second frequency is approximately equal or is identical to the subcarrier frequency of the other color-difference component, as well as the fact that a coherently weighted artificial subcarrier (ASUB1 or ASUB2) is added to each quadrature-shifted subcarrier modulated auxiliary signal (HSUB1 or HSUB2) gom phase, in which the image signal is performed to switch the pair of composite signals from line to line.  3. The method according to claim 2, characterized in that a constant or even consistently amplified subcarrier (ASUB1 or ASUB2) with a significant amplitude is used if the amplitude of the auxiliary signal is significantly different from zero and the black level in the auxiliary signal increases.  4. The method according to any one of claims 1 to 3, characterized in that the transmitted television signals with an enlarged aspect ratio are compatible with the SECAM television standard and the enlarged aspect ratio is 16: 9.  5. An encoder for processing auxiliary signals in television signals with a larger frame format, which are compatible with well-known television standards, where the video signals are decomposed into auxiliary signals and mailbox signals, in accordance with the method according to any one of claims 1 to 4, comprising a format conversion unit (FC), in which the video signal is decomposed into a mailbox signal (LS) and an auxiliary signal (HS), an encoder (ENC) for processing the mailbox signal, a modulation unit (MOD) for the auxiliary signal, characterized in which contains a pre-processing unit (PREE), a first modulation unit (MODH), where the pre-processed auxiliary signal is modulated into one or more suitable subcarriers, an amplitude detector (AD) circuit to which the output signal of the first modulation unit is transmitted and which generates a normalized detection signal ( NS), a first combining device (ADD) in which a control signal (CS) is generated by subtracting said normalized detection signal (NS) from 1, a second modulation unit (MODA), in which the bottom or more of the artificial subcarriers are multiplied by a control signal (CS) to control their amplitudes, a second combining device (QP), where the output signals of the second modulation block are combined with the corresponding subcarriers of the auxiliary signal with a quadrature phase shift, the post-processing block (POSTE) for half filtering by Nyquist the output signal of the second combining device and for selecting one of the filtered signals in the case of more than one composite signal, as well as a selection device (SELE1), by By which the processed auxiliary mailbox signals are combined to form said compatible television signals.  6. The encoder according to claim 5, characterized in that the first modulation block (MODH) contains two modulation blocks (MODH1, MODH2) for modulating the pre-processed auxiliary signal into two subcarriers in accordance with the two color difference components in SECAM and the first selection device (SELE2 ) to perform line switching of a pair of modulated subcarriers, the second modulation block (MODA) contains two modulation blocks (MODA1, MODA2), in which two artificial subcarriers corresponding to two subcarriers of the auxiliary signal are multiplied by the signal Board (CS), a second combining device (QP), consisting of two additional blocks (QP1, QP2), in which the corresponding sub-carriers of the auxiliary signal and the artificial sub-carriers with a quadrature phase shift are summed, while the post-processing unit (POSTE) contains the output signal of said additional blocks is a filter block (NYQE1, NYQE2) for Nyquist filtering and a second selection device (SELE3) configured to select the output signals of said filters in accordance with the lines for I handled properly and the modulated signal in the black range of frequencies.  7. The encoder according to claim 5 or 6, characterized in that the pre-processing unit (PREE) for the auxiliary signal comprises a low-pass filter (LEP1), a look-up table (LUT) and a low-pass filter (LEP2) in series.  8. The encoder according to any one of claims 5 to 7, characterized in that the amplitude detector (AD) comprises a bandpass filter (BP), an amplitude measurement circuit (AM), and a nonlinear element (NL). 9. A decoder for processing auxiliary signals in television signals with an increased aspect ratio, which are compatible with well-known television standards, where the video signals are decomposed into auxiliary signals (HS) and mailbox signals (LS) in accordance with the method according to any one of claims 1 to 4 characterized in that it contains filter blocks (NYQD1, NYQD2) in which the Nyquist-filtered black frequency range signal (BS), a first selection device (SELD1) for performing line switching of two black frequency range signals, from filtered by Nyquist unit (GAT), configured to transmit a composite video signal (VS) to a second selection device (SELD2) upon reaching the blanking pulse area (BP), the PLL scheme (PLL1, PLL2) for reconstructing frequency-modulated carriers from the video signal , a second selection device (SELD2), linking the unit (GAT) to one of the circuits (PLL1, PLL2) between which line switching is performed, a third selection device (SELD3) for performing line switching of two frequency-modulated carriers, a shift device ha phase by 90 ^o (PS) signals from (SELD3), product demodulator (DEM), for multiplying the Nyquist filtered frequency range signal of the black and phase-shifted frequency-modulated carrier, low-pass filter (LPD) associated with the demodulator products for extracting carrier components from a plurality of carrier frequencies, as well as a subsequent post-processing unit (POSTD) to increase the amplitude of the auxiliary signal.

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