[FFmpeg-devel] MPEG Audio encoding

[Gabriel Bouvigne]

John Sigler a ?crit :
> AFAIU, Layer I is "worse" than Layers II and III in every metric?
> (Except perhaps algorithmic complexity?)
Yes
> LAME seems (??) to have removed MP1 support some time ago.
LAME never had encoding support for MP1

> If I understand the code correctly, when I pick a sampling frequency
> from the set { 44100, 48000, 32000 } then lsf = 0 which means the set of
> available bitrates is { 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192,
> 224, 256, 320, 384 }
> 
> When I pick a sampling frequency from the set { 22050, 24000, 16000 }
> then lsf = 1 which means the set of available bitrates is { 0, 8, 16,
> 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160 }

The first set is the MPEG1 sampling freqs, the second set is the MPEG2 
sampling freqs.

> And mpegaudio.h defines
> 
> #define MPA_STEREO  0
> #define MPA_JSTEREO 1
> #define MPA_DUAL    2
> #define MPA_MONO    3
> 
> But joint stereo and dual mono do not seem (??) to be supported by
> the encoder. Is that correct?

Last time I checked, only regular stereo was supported.

> Were joint stereo and dual mono actually defined for Layer II,
> or did they only show up later in Layer III?
 From memory, I'd say that dual channels is also supported by Layer II 
(anyway, dual channels mode is mainly a matter of semantics).
Joint stereo is also supported by Layer II, but only in the intensity 
stereo mode (ie no mid/side stereo).


-- 
Gabriel Bouvigne
www.mp3-tech.org
personal page: http://gabriel.mp3-tech.org