[FFmpeg-user] How to convert 48000/2/FLOATLE AC3 to 48000/2/S16LE MP3

[Carl Eugen Hoyos]

Rene Herman <rene.herman <at> gmail.com> writes:

> $ ffmpeg -i "$SRC" -c:v mpeg4 -vtag xvid -vf 
> crop=1280:550:0:$(((720-550)/2+2)),scale=640:-1 
> -b:v 900k -c:a libmp3lame -af aformat=s16 -b:a 128k 
> -map_metadata -1 "$DST"

lame accepts s32, s16 and float as input.
I suspect that for speed and quality reasons, it 
is best not to force a conversion.
(This may be wrong, it assumes that lame internally 
does no slow conversion.)

Concerning the decoding:
There are two mp3 decoders in FFmpeg (and both can 
be used from MPlayer), one outputs floats and is 
faster on typical hardware (modern x86 and ppc), 
one is faster on some embedded hardware.
Except for the speed, there should be no measurable 
difference between the two, if there is, it may be 
a bug.

Generally, if you want help on this mailing list, 
please post your command line together with the 
complete, uncut console output.

Carl Eugen