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

Mikko Rapeli mikko.rapeli
Wed May 31 10:54:55 CEST 2006

On Tue, May 30, 2006 at 07:51:19PM -0700, Roman Shaposhnik wrote:
>   Ok, first of all -- what are you trying to accomplish here ? If you're
> trying to add native support for 32KHz sound then I'm not against it 
> in principle (and I will apply a clean patch) but I have no interest
> in working on it myself. Now here's why the current patch doesn't quite
> cut it:
>   1. I don't want 32kHZ sound to be at a target level. Simply accept
>      such streams when they are given. Better yet -- issue a warning.
>   2. 32kHZ should only be accepted for IEC 61834 profile. It is illegal
>      for SMPTE profiles.

True. Current patch is just for testing so I'll fix these after 32kHz
audio really works. My motivation is just to finish the video editing
projects on my 250 GB disk without having to buy more disk space :)

>   3. The hardest one: you have to figure out the correct sample
>      distribution policy akin to what's going on in 
>      dv_profiles[] .audio_samples_dist. So that there's no popping
>      sound. AFAIK, the only document that might specify it is a 
>      IEC DV spec.

So the popping comes when uninitialized memory is in the audio part of a
packet after the 32kHz samples. Without the spec I could try to figure
how many samples per frame are in the existing streams from the Sony
camera; dv_extract_audio function and smpls variable will propably help.
Thanks for the hint.

I don't quite understand the difference of audio_min_samples and
audio_samples_dist[]. I suppose samples_dist is used when samples don't
distribute evenly to every frame, and perhaps for some kind of padding,
which eases implementations. Is that it?


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