Re: DES - DV to Mpeg1 compression

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On 23 Nov 2006 13:40:23 -0800, Jean-Marc wrote:

Iain wrote:
Have you tried setting the SyncSource to NULL? this turns of the clock
which lets the graph run as fast as it can / needs. So if the CPU is too
low, the process will take > real time, but with no drop outs.

Hi lain,

Thank you for replying.

I did not try because I thought it would loose synchronization between
sound and video. Is it right?
There should be no loss of synchronisation. The graph remains internally
consistent, but ceases to care about the 'real' world.

By the time, I downloaded a toolkit that does convertion over DShow and
made some testing with it. I used GraphEdit for monitoring the graph
they build for conversion and I saw a filter chain like:

audio source ... -> synchronization -> compressor -> Gate -> Sample
Corrector -> Mux ...
video source ... -> synchronization -> compressor -> Gate -> Sample
Corrector -> Mux ...

The names are suggesting that Dataflow is controlled from within those
filters sharing/exchanging timing info. Could that be the way to do it
(with a null sync source) because at the time of writing this message,
it might as well be that a toolkit is about to be sold.
This should be unnecessary. It sounds that the graph you present is doing
much more than transcoding. If you have live sources, then you can get
sync problems over time due to drift between the camera clock and hte audio
clock. These problems are difficult to solve, but don't apply to
(correctly recorded!) stored data.

Iain
--
Iain Downs (DirectShow MVP)
Commercial Software Therapist
www.idcl.co.uk
.

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