From: Andrew Hart <ahart_at_dim.uchile.cl>
Date: Fri, 01 Jun 2007 15:44:33 -0400

Magnus Holmgren wrote:
> Binder, David wrote:
>
>> I just tried playing an M4A file that was created using FAAC encoder on
>> the latest version of Rockbox but it failed (no error message, no
>> sound). Is this supported?
>
> It could be that it isn't "streamable". The function "Optimize MP4
> Layout" in Foobar2000 (among others) can fix that.

It sounds like the playing of aac/m4a in Rockbox isn't fully supported
if only certain kinds of aac can be played or if they need to be
optimised for streaming. Is this the fault of the aac codec Rockbox
uses, a problem in certain aac encoders or is there something else going
on I'm missing here? I don't use aac myself, but it's a popular format
for MAC/Ipod/Itunes users. I'd be pleased if someone could educate me.

I borrowed a couple of aac files from my brother last year when I first
started using aac. At that time, the aac codec was in its infancy. It
had no problem reading and playing the file, except that it would stop
every 2-4 seconds for a moment. Since then, from what I've read, the
Rockbox crew have optimised the AAC codec and so aac files are supposed
to play without any stuttering nowadays. I haven't gone back to look at
aac again as yet, but am curious. I've read material that seems to
suggest higher bit rate aac is generally comparable to mp3 at a rate
approx. 64kbit higher, e.g., 192Kbit aac is roughly equivalent to 256
Kbit mp3 and 256 Kbit aac is equivalent to 320 Kbit mp3, etc. Of
course, I use "roughly equivalent" in a very general sense here;
everyone's ears are different. I don't know about lower bit rates, but
if what I've read is true, then aac could have the potential to reduce
space while maintaining quality or delivering better quality for the
same space. However, if there aren't any decent encoders around (apart
from Itunes), I won't waste my time looking into it again until a
worthwhile command-line encoder is available. In the mean time, I'll
stick with ogg, mp3 and flac.

Cherio and thanks for any advice,
Andrew.
Received on 2007-06-01