[Ffmpeg-devel] Newbie question about pcm_s16le

[michele tavella]

On Fri, 04 Aug 2006 11:11:29 +0200
Benjamin Larsson <banan at student.ltu.se> wrote:

| > michele tavella wrote:
| > > Dear all, 
| > > I subscribed to ffmpeg-devel two days ago. I'm working on my
| > > master thesis and (as the first task) I have to synchronize two
| > > streams:
| > > - a standard DV stream
| > > - a PCM audio stream
| > >
| > > I understand that my question could be off-topic, so I'm sorry if
| > > I bother you, but it is the first time I approach the audio/video
| > > field.
| > >
| > >   
| > Yes it's off-topic.
Thanks a lot for you answer.

| > > I'm currently using the FFMPEG API to handle decoding of a DV Raw
| > > stream acquired via "dvgrab" (dvvideo + stereo pcm_s16le).
| > >
| > > Following the examples I did find googling around, I have
| > > successfully decoded the video frames.
| > >
| > > I've also decoded the PCM stream and I can handle the stream as a
| > > vector of shorts.
| > >
| > > On a couple of guides said that the PCM stream should alternate
| > > Left channel samples with right channel samples, something like
| > > this: Channel	L R L R L R ...
| > > Index	0 1 2 3 4 5 ...
| > >   
| > This seems to be correct.
| > > In image_001.png you can find a plot of the even and the odd
| > > samples of an audio frame.
| > >
| > > The Odd Samples signal looks to me like a synchronization signal! 
| > > I'm now wondering how the stream is organized.
| > >
| > >   
| > You plot the values in an unsigned way when they actually are
| > signed. (Unsigned range 0->2^16, signed -2^15->2^15-1).
Thanks a lot... Now I realize how dumb was the question.

| > > Any help would be great, also in terms of documentation/books.
| > >
| > > Thank you for your time, 
| > > mt
| > >
| > > --
| > >
| > >
| > >      home  tavella.michele at gmail.com	
| > >  LIRA-Lab  michele at liralab.it 
| > >   OpenPGP  98E66CEC
| > >       web  http://mt.homelinux.org 
| > >   
| > 
| > MvH
| > Benjamin Larsson
Take care, mt

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| > ffmpeg-devel at mplayerhq.hu
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--


     home  tavella.michele at gmail.com	
 LIRA-Lab  michele at liralab.it 
  OpenPGP  98E66CEC
      web  http://mt.homelinux.org 

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