[FFmpeg-soc] ALAC Benchmarks

[Jai Menon]

Hi,

On Thursday 21 Aug 2008 9:06:59 pm Guillaume POIRIER wrote:
> Hello,
>
> On Wed, Aug 20, 2008 at 6:52 PM, Jai Menon <realityman at gmx.net> wrote:
> > On Wednesday 20 Aug 2008 9:33:25 pm Guillaume POIRIER wrote:
> >> I have a question about your ALAC encoder: since this is a lossless
> >> compression, is it safe to assume that no listening test is needed to
> >> compare your encoder to other encoders?
> >>
> >> Guillaume
> >
> > Yes. The decoded output is bitexact to the original source. You could do
> > ABX tests to convince yourself though :-)
>
> Ok. Would your mind giving me a sample commandline to compress a WAV
> to ALAC? I imagine that there are several options that control your
> ALAC encoder that need to be tried out?

There are options to select min and max prediction orders but till I finish 
tuning the encoder completely, you could try something like :

./ffmpeg -i <file.wav> -acodec alac <output.m4a>

That should give you pretty decent compression.

> Is it necessary to use MP4 container to store ALAC audio?
>

If you want the encoded alac stream to playback on an ipod, then you should 
mux into mp4(m4a). The alac stream in a mov container is iirc not acceptable 
to the ipod. Both work on itunes though.

> > And please do not pay heed to the doubting hordes at Hydrogenaudio who
> > say that the encoded audio "lacks bass" and assorted nonsense :-) [1].
> >
> > I'm no expert but I think you don't need any listening tests to confirm
> > if its lossless.
>
> That's what I thought too.
>
> Guillaume

Well if you try it out, tell me how it goes!

Regards,

Jai Menon