Becky Weiss [MS]
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 Posted:
Sat Sep 25, 2004 2:27 am Post subject:
RE: A/V Sync in IWMWriter::WriteSample issue |
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If I understand correctly, although you have no guarantees about how you're
receiving audio and video relative to each other, you're just timestamping
video according to the amount of audio you've received.
While the WMFSDK writer won't have a problem with video frames being
timestamped erratically, it might be that when you're trying to convert it
into some other format, that code is getting flummoxed by the fact that your
samples' timestamps aren't following a nice frame rate. That's my guess as to
why that "regulate timecode" business is helping.
If you did know the frame rate of your incoming video, you could possibly
use that to assign more regular timestamps: just a thought.
One other thing it's worth mentioning is that you should pass samples into
IWMWriter::WriteSample as in-sync as you can. This helps make sure nothing
gets dropped and that memory usage isn't unnecessarily high.
Becky
This posting is provided AS IS with no warranties and confers no rights.
"hcurreem" wrote:
| Quote: | I created an application that can mix audio sample and video frames into an
wmv file. However I found that there might be something wrong when I
calcuate the sampletime when I call the WriteSample method. My application
provides an API for another application to insert audio or video buffer.
Therefore audio and video samples comes randomly. I keep a global variable
that keep track of the current movie time. Whenever there is an audio
sample (8k Sampling rate), I increase this global variable. As for video
samples, I didn't modify this global variable. Is there anything wrong
with my calcuation? The problem is that when I play the movie in Media
Player, it runs smoothly. But when I try to convert it to 3gpp format
(Using the nokia converter). Only part of the video can be coverted. If I
run RiverPast's VideoCleanup application with "regulate timecode" option
on. The output file can be converted correctly. So I suspect my sample
time calculation might be incorrect. Does anyone know what's the common
equation to calcuate the movie sample time? note that the video sample
comes randomly. Therefore I cannot assume any constant framerate.
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