Re: MPEG2 TS source filter

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From: Pascal Soveaux (PSoveaux_at_Reply.To.Group.Plz)
Date: 09/22/04 

Date: Wed, 22 Sep 2004 11:23:24 +0200

Hello Geraint,

> I think you're confusing a couple of clocks. The PCR tells you when this
> frame should be shown.
the Presentation Time Stamp indicates when a frame should be presented.

>The reference clock tells you what time it is now.
the Program Clock Reference is one of them.

>> The documentation states " With transport streams, the demux synchronizes
>> its clock to the PCR stream that corresponds to the audio or video stream
>> that was mapped last " does that mean that the demux wont use the PCRID
>> in PMT ?
I understand this sentence now. Imagine a simple MPTS containing 2 programs
each one having its own PCR.
In a graph built like this, mapped from top to bottom

                           --> PSI ...

                           --> Program 1 Video *PCR* --> Video
Decoder --> Video Renderer
                           --> Program 1 Audio --> Audio
Decoder --> Audio Renderer
TS --> DEMUX
                           --> Program 2 Video *PCR* -->
                           --> Program 2 Audio -->

the PCR from program 2 will be used because it was mapped last.

About my specific problem, it was a silly coding error (smart errors exist?)
I was doing Write(szBuffer,sizeof(szBuffer)) instead of Write(szBuffer,
dwBytesReceived).

Pascal

"Geraint Davies" <geraintd@_NO_THANK_YOU_REALLY_gdcl.co.uk> wrote in message
news:eahuJa9mEHA.3480@TK2MSFTNGP09.phx.gbl...
>
> "Pascal Soveaux" <PSoveaux@Reply.To.Group.Plz> wrote in message
> news:O5qTdPylEHA.2680@TK2MSFTNGP15.phx.gbl...
>> The documentation states " With transport streams, the demux synchronizes
>> its clock to the PCR stream that corresponds to the audio or video stream
>> that was mapped last " does that mean that the demux wont use the PCRID
>> in PMT ?
>
> I think you're confusing a couple of clocks. The PCR tells you when this
> frame should be shown. The reference clock tells you what time it is now.
> Most graphs measure time using the audio DAC clock; however, the demux
> measures time using the rate at which data is arriving -- this avoids
> overruns and underruns when the sender's clock runs at a different rate to
> your audio device. By buffering in a file, you deliver data to the demux
> at a different rate (presumably more bursty).
>
> You can force the graph to use the audio renderer's clock, but you would
> still be open to underrun problems if your system runs slightly faster
> than your source.
>
> G
>
>

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