[Ffmpeg-devel] Re: dv video format with 32 kHz audio?

Mikko Rapeli mikko.rapeli
Fri Apr 21 23:39:41 CEST 2006

(wasn't subscribed to the list so copy-pasting a bit)

Roman Shaposhnick rvs at sun.com wrote
> 32 kHz in DV is quite evil. Stay away from it. Really, why do
> you have to use it, anyway ?

I was a succer and bought a Sony DCR-PC106E, which only does 12 bit
samples at 32 kHz in stereo mode, and now my disk is full of raw videos
from the camera. If I had the disk space with current projects I'd convert
these videos with ffmpeg to 48kHz, but I don't. Yet. I'm almost ready to
throw money on this issue, but a software solution would be nice. 

I'm editing things in Kino which does not handle different sampling
rates at all and the end result is crackling on the speakers. I 
want to convert some videos from other digital and cell phone cameras to
a format where I can combine all of these in Kino. Disk limitations take
me to the 32 kHz point.

dvgrab gives this format from the camera (ffmpeg -i):
  Stream #0.0: Video: dvvideo, yuv420p, 720x576, 25.00 fps
  Stream #0.1: Audio: pcm_s16le, 32000 Hz, stereo, 1024 kb/s

(I don't know where the 12 bits were transformed to 16 - camera manual
says 12 bits with stereo)

This format I'd like to create with ffmpeg from various AVI and other
sources. Is it possible by combining current code in some way like I
naively tried?

> Yeap. Supporting 32kHz requires a different encoding of audio
> samples.

I don't know much about the dv format, but I suppose the audio codec 
CODEC_ID_PCM_S16LE would stay the same and only the number of audio samples
per video frame would be smaller, plus the header changes to indicate a
32kHz sample rate. Does this translate to changes in libavformat/dv.c?

Is there a better dv format description than
http://en.wikipedia.org/wiki/DV on the net?


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