[packman] AC3 encoder broken - simply noise

Carl Eugen Hoyos cehoyos at ag.or.at
Wed Apr 13 09:15:41 CEST 2011

Carl Eugen Hoyos <cehoyos at ...> writes:

> Linuxoid Oz <linuxoidoz at ...> writes:
> > I spent 2 weeks trying to burn a DVD with K3B, DeVeDe, ManDVD, Kdenllive and
> > don't remember what else in openSUSE-11.4 and KDE-4.6 (default install).
> > 
> > If I re-encode audio (AC3) then the sound is just cracking noise on both a
> > DVD player and computer.
> Disclaimer:
> I don't know anything about how "K3B, DeVeDe, ManDVD, Kdenllive" encode audio.
> FFmpeg's AC3 encoder was changed to expect float (instead of int16). The new
> encoder is faster on typical hardware (and at least not worse in quality). To
> get the original behaviour, the programs have to open "ac3_fixed" instead of
> "ac3". (And yes, I know I've claimed in the past we do not break ABI,)

In case this is unclear:
In the past, there was one AC3 encoder in FFmpeg. It expected int16, and had the
name "ac3". Now there are two encoders: One with the name "ac3" expecting
floats, and one that's called "ac3_fixed" (the same one as the older one, just
with another name) that expects int16. If the (new) "ac3" encoder is fed with
ints, it will produce noise.

There might be a bug in FFmpeg that it does not refuse to encode if the
application did not explicitly announce to provide float data, but I can't
confirm this since I don't know much about the encoding interface.

Carl Eugen

More information about the Packman mailing list