Re: Difference in luma-chroma delay of C64/C128 compared to standard S-video

Date: Fri, 1 Sep 2017 11:45:35 +0200
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> On 2017-09-01, at 10:44, Pasi 'A1bert' Ojala <> wrote:
> On 01.09.2017 00:19, Mia Magnusson wrote:
>> For some reason the decoding process in a TV anyway needs a delay. It's
>> likely that the s-video standard were set to make a S-VHS player as
>> simple as possible, i.e. bypassing any delay that's needed for a VHS to
>> do composite -> separate chroma/luma -> FM modulate luma and frequency
>> shift chroma -> record to tape, playback from tape -> FM demodulate
>> luma and frequency shift chroma -> combine luma and chroma.
>> So therefore it makes sense that the signals could have different
>> timing specs for composite v.s. s-video in general.
> Hi Mia,
> The delay is only needed for PAL (Phase-Alternating Line), and some of the first PAL receivers didn't bother with having the delay.

Just for completeness - a delay line is not *only* for PAL, where it could theoretically be omitted, leading to Hannover bars effect ;-) it is also required for SECAM, where it acts as temporary storage between two consecutive lines. True there were no SECAM outputting CBM machines :-)

> In theory composite is produced by summing the Y and C of S-VIDEO. In practice you may get time shift whenever they are combined or separated.

Which is why studio equipment (TBCs and Co.) has adjustments for keeping them in sync.

SD! -

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Received on 2017-09-01 10:03:30

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