Hi,
After a whole lot of testing and listening it came to me: "-mj nor
-ms" are optimal quality-wise.
* -ms unnecesarely wastes bits most of the time
* -mj has M/S making too much unnecesary mistakes:
If I understand correctly, the "-mj" is evaluating if a frame
qualifies for M/S coding beforehand, and if so, it will then be coded
in M/S, independent of the outcome.
I've heard my fair share of examples where lame opts for M/S, but
afterwards this is a bad choice, giving a M/S frame sounding much worse
than S would have, or in vbr, more bytes are used on the M/S frame
compared to the S frame.
problem: once the criterium is met, and a frame tagged as
"M/S"-material, it will always be a M/S, even if S would have been
better.
Big advantage of this prediction method is the speed.
Since you never have 100% accurate prediction this is one of the most
prominent causes of poor quality in -mj mode. (read that post
of me referring to 192JS of the Velvet track)
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What I'm suggesting: a "-mx" mode (or whatever letter)
it would be a JS mode, but unlike the "-mj" mode it would not try to predict
anything, but just achieve optimal quality in an empirical way.
-----------
for cbr: encode each set of samples to both a M/S and a S frame and
take the one with least amount of introduced distortion.
(can you use the calculation that now is used in vbr?)
for vbr: see how low you can go in M/S, and then check if at this
bitrate if S gives equal or better results.
If so see how low you can go in S...
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I'd be slow, but it'd be the best possible quality for cbr and best quality/size
for vbr. (as far as I can see)
The advantages would be noticable:
- low bitrate cbr mp3's (128kb/s,...) could harvest the full M/S potential and
get extra bits where possible and would (theorethically) never sound worse (in
distortion) than their S peer. If a M/S frame comes out sounding
worse than S, the latter would be chosen.
- vbr files would become smaller for the same quality as they are
today, and I think that for higher -V* the quality effects would
also be very noticable.
I realise there will probably be complications if it's
practically realised, but I think the idea behind it is ok.
Any comments or action welcome :))
thanks
--
Best regards,
Roel/r3mix.net mailto:[EMAIL PROTECTED]
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