Comment 43 for bug 602934

(In reply to comment #27)
> I think you will be able to repro it on Windows (and I assume on FFmpeg 0.6.1
> too, but I have not tried with 0.6.1 yet). What happens on Mac?
>
Same sort of thing. If I create a mono M4A file using 0.6.1 and then try to
import it using a v0.5 library, it will always import as stereo.

Maybe the the crux of the problem. Could be files structure is incompatible
between the releases.

>
> > One thing that I did discover is that on 2010-05-14, the native aac encoder
> > was updated and this caused a tremendous degradation in export quality. I do
> > not believe this to be an Audacity issue since the ffmpeg command produces
> > the same results.
>
> Agreed, but would still have to be release noted because we will be blamed
> otherwise.
>
> Or could/should we disable Audacity support for the native aac encoder via
> normal "M4A files" export? I think it would send an appropriate message.
>
I briefly looked into calling libfaac/libfaad dynamically, which could
certainly be done, but I think a release note or disablement would be the
better way to go. (Read that as "The easiest way." ;-))

>
> > Another thing is that exporting a 10 minute chirp on my system consistently
> > takes 22 seconds prior to the ffmpeg changes on 2010-04-02. After that date,
> > exporting the same chirp consistently takes 35 seconds. Again, I do not
> > believe this to be an Audacity problem since the ffmpeg command produces
> > nearly the same time difference as Audacity.
> That is a much less significant difference than that implied by the "3 - 4
> times slower" than Audacity export to other formats. Can you test on your
> system:
>
The only time I got the 3 - 4 times slower exports was after I'd imported an
OGG file. Can anyone else verify that the M4A exports (or any ffmpeg 0.6.1
file type) exports are WAY, WAY slower than with a previous version of
Audacity?

Leland