[FFmpeg-devel] [PATCH] Add libavsequencer.

Sebastian Vater cdgs.basty
Wed Aug 18 23:52:39 CEST 2010

Ronald S. Bultje a ?crit :
> Hi,
> On Wed, Aug 18, 2010 at 4:48 PM, Sebastian Vater
> <cdgs.basty at googlemail.com> wrote:
>> So I think, the best way to continue this discussion is to decide to
>> keep mixers in avseq or to move somewhere else, if the latter one then
>> where it should finally go? avfilter?
> I think I'm confused, but what is lavseq if it's not the mixer? It
> can't be BSS, because BSS will be in libavcodec/, since the decoders
> out there will depend on it for parsing mod files.

Just another point I might should mention...

A mixer can also be used perfectly to convert a simple WAV file input
sampling rate to a different sampling rate.

To accomplish that, you would (for a mono WAV) simply allocate one
channel in the mixer, set it's to input sample frequency, bit depth, set
volume to full (0xFF), panning to left and set the mixer output
frequency to target sampling rate desired.

You'll get a (32-PCM version) though of the input WAV file at the target
sampling rate. Just dither that to the WAV file input sampling rate, and
you have simple resampling.

Another example would be stereo to mono conversion of a WAV file:
In that case allocate 2 channels in the mixer, set output mixing rate ==
input sample rate of WAV. Assign full volume (0xFF) to both channels,
set pan to 0 of first channel and 0xFF of second channel.

Set the mixer to output mono only: Result will be that the WAV file
which is an exact stereo => mono conversation of it.

Another way would be to accomplish the same task:
Allocate 2 channels as above, out mix rate == in sample rate of WAV.
Full volume to both channels again, set pan to 0x80 in both channels and
mixer output to stereo.

Again you have a mono WAV file but encoded as stereo, i.e.
non-interleaved stereo output of mixer is left channel == right channel.

Maybe this clarifies how the mixer is useful for non-MOD files?


Best regards,
                   :-) Basty/CDGS (-:

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