Friday, February 04, 2011

Rise times in HD TriSyncs

To my shame I haven't blogged for a month! We are starting to pick up at work with projects on the go and the BVE trade show at Earls Court in just over a week (I'm presenting each day - will post my slides next week).

These are two traces from two separate TriSync generators - The blue trace represents a correct waveform and as every superhero will realise you're looking at the line timing pulse. Here is the diagram from rec-709 (the spec for HD video);

It clearly shows that rise time is to be equal between the start, middle and end of the line-sync pulse. The rep from the manufacturer of the green pulse insisted that his waveform was a lot sharper - but given the ringing on it I think they just aren't filtering it properly to comply with the rise time spec - seen here (again from rec-709) as being 4 clock cycles +/- 1.5

Thanks to an unnamed ex-colleague(!) for engaging me in this conversation! The link in the title is to the summary document PDF of rec-709.

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