| 摘要 |
The invention relates to a compatible transmission system for transmitting HDMAC signals through a channel of the MAC/Packet family either broad band (typically a satellite channel according to the CAMR 77 recommendation), or narrow band (typically a cable or radiowave terrestrial transmission channel). According to the invention, the said transmitted signal exhibits a digital component of sound and service data which is coded in duobinary of type D2 identical in broad band and in narrow band, an analog video component distinct in broad band and in narrow band, which, for narrow band transmission, is firstly sampled at a sampling frequency equalling x% of the sampling frequency of the video signal transmitted in broad band, and then undergoes a filtering processing in a Nyquist filter with cutoff frequency equal to x% of the cutoff frequency of the Nyquist filter used in broad band, before the filtered samples are finally re-read, for compression, at a frequency equalling x% of the frequency of reading of the samples in broad band.
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