Fast(er) transcoding from aac to mp3.

[Charles Johnson]

bat guano wrote:
> Hi
> I sometimes download BBC radio shows to listen on my mp3 player.
> It looks like I'm going to have to start transcoding them from aac to mp3.
>
> Using Ubuntu I did some tests to see just how long it takes to transcode these things.
>
> 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
>
> That's over 20 minutes!
> During the test I wasn't running any other heavy programs. I kept checking the System Monitor, it was
> always up there at 98%, 99%, 100%. There's nothing wrong with my ffmpeg, it's a new one from git.
> Doing the best it can on my Celeron D 2.26GHz computer.
>
> Then I repeated the test using GOGO-no-coda encoder, a turbocharged version of LAME.
> It needs wav as input so I piped it through ffmpeg.
>
> I converted the same show using this command:-
> time ffmpeg -i filename.aac -f wav - | gogo -b 128 -q 0 stdin test2.mp3
>
> The result:-
> real    10m30.195s
> user    8m12.411s
> sys    0m31.382s
>
> That's about half the time.
>
> If any of you feel like trying GOGO-no-coda it's available in Ubuntu's repo.
> Install it like this:- sudo apt-get install gogo
> Or download a deb from somewhere.
>
> For Windows users it's available from rarewares.org and other places.
>
> I suppose, if the programmes are talk-shows then it will be OK to reduce the q setting for gogo
> and also maybe reduce the bitrate to 96Kbps or 64Kbps. That would speed things up even more.
>
> If any of you have experience using different mp3 encoders it would be good to know how they compare with gogo.
>
> * I didn't listen to the show. For test purposes only. :-)
>  		 	   		  
>   
Phew that's a relief ;)

bg, this is all quite interesting for me:

It suggests (unless you've built it yourself) that your version of 
ffmpeg is built with libmp3lame support. This surprises me, as i thought 
that by default it hasn't that support?
Which git repo did you use? I gather there's been a bit of a catfight at 
chateau ffmpeg which has resulted in some sort of fork. Which version of 
Ubuntu.


I'm trying to build a static version of ffmpeg on Debian Lenny without 
much success. The closest i got is building one in Lucid (live) with 
libmp3lame-dev but it failed owing to its being tricky per se to build 
static with glibc (apparently) with some calls being troublesome, such 
as gethostbyname.

I'd be VERY interested in hearing from anyone who has, for some reason, 
a statically-linked ffmpeg with mp3 support.

CJ
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