[Libav-user] Re : ALAC codec I am not sure it's really lossless

kurdy_ch-forum at yahoo.fr kurdy_ch-forum at yahoo.fr
Sat Jun 2 10:34:55 CEST 2012


As flac is lossless the number of frame and md5 code of the track 
should be the same. 

But I did the test you propose, I extract from the 
flac the wav and I launch: 

avconv -i file.wav -acodec alac file.m4a 

and surprise ! I got an Apple lossless audio 

What I was suspecting is true  the conversion from flac to m4a using alac codec create an acc 128 !!!

Conclusion the command below create an acc even using codec alac I think this a bug.    

avconv -i file.flac -acodec alac file.m4a  

Many people using avconv or ffmpeg to create Apple lossless from flac got acc 128 

My version is avconv 

version 0.8.1-4:0.8.1-0ubuntu1, Copyright (c) 2000-2011 the Libav developers


 De : Claudio Freire <klaussfreire at gmail.com>
À : "This list is about using libavcodec, libavformat, libavutil, libavdevice and libavfilter." <libav-user at ffmpeg.org> 
Envoyé le : Samedi 2 juin 2012 6h05
Objet : Re: [Libav-user] ALAC codec I am not sure it's really lossless
On Fri, Jun 1, 2012 at 3:58 PM, kurdy <kurdy_ch-forum at yahoo.fr> wrote:
> From a flac file I did avconv -i f.flac -acodec alac f.m4a
> then back to flac  avconv -i f.m4a -acodec flac f.flac

Better try some other reference format (pcm ideally), as flac may have
multiple representations of the same waveforms.
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