Fast(er) transcoding from aac to mp3.

[bat guano]

----------------------------------------
> Subject: Re: Fast(er) transcoding from aac to mp3.
> From: dinkypumpkin at gmail.com
> Date: Fri, 18 Mar 2011 15:02:16 +0000
> To: get_iplayer at lists.infradead.org
>
> Not really comparing like-for-like, but with 2010 Macbook Pro (2.66 Ghz Core i7, 8Gb) and ffmpeg HEAD, transcoding a 3-hour program gives these numbers:
>
> real 5m7.197s
> user 4m56.078s
> sys 0m6.127s
>
> Just for kicks, in a 32-bit 1-CPU Ubuntu 10.10 VM (via VMWare Fusion) on the same machine I get this for the same file:
>
> real 5m48.907s
> user 5m30.741s
> sys 0m11.337s
>
> ffmpeg saturated one of the CPU cores in both cases, so the difference is more-or-less from the VM overhead. That's OK for my purposes, but it's not hard to see how it could be pokey on older hardware.
>
> On 18 Mar 2011, at 12:52, bat guano wrote:
>
> > I downloaded a 3-hour show (Steve Wright in the Afternoon*) and calculated the time taken
> > to convert it using ffmpeg.
> > This is the command:-
> > time ffmpeg -i filename.aac -acodec libmp3lame -ab 128k test1.mp3
> >
> > The result:-
> > real 20m42.369s
> > user 17m40.318s
> > sys 0m56.812s
>
>
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Hi
I followed on with this. (From here:- http://lists.infradead.org/pipermail/get_iplayer/2011-March/001035.html)
Using gogo 128Kbps and q7.

For the 3-hour program using a command like this:-
time ffmpeg -i filename.aac -f wav - | gogo -b 128 -q 7 stdin output.mp3

Result:-
real    4m55.204s
user    3m48.478s
sys    0m27.574s

I also tested Helix v5.1 mp3 encoder using a command like this:-
time ffmpeg -i filename.aac -f wav - | ./hmp3 - output.mp3 -X2 -D -M1 -U2 -B64

Result:-
real    5m38.097s
user    3m42.894s
sys    0m26.682s


Helix is definitely a fast encoder, but on my system it didn't perform better than gogo q7.

I'm going to use the gogo q7 method.
The convert time is quite respectable.
The quality is OK - certainly good enough for earbuds.

So I've made a script called 'fastmp3' and put it in my /usr/local/bin folder.
I can convert a file now by entering a command like this:- fastmp3 filename.aac
:-)

@ dinkypumpkin
If you were to install gogo into your Ubuntu vm it would probably convert the file before
you could step back from the keyboard!
;-)