[vorbis] YA-2496

[gtgbr at gmx.net]

Michel Donais wrote:
> Here comes ogg format. Other than enabling a 24bit-integer format and
> adding 88.2/96KHz formats to the supported list, what is missing? If I

Internally, Vorbis uses floating point numbers only, i.e. you always
have 32bit float resolution - it's up to the player to reduce that to
24/16/8bit integer so the respective soundcard eats it. (Somebody please
correct me if I got that wrong.)

It depends on the encoding software that you choose to get your .ogg
files from ... and it's getting trickier here. AFAIK even oggenc
supports only 8 or 16bit integer or 32bit IEEE float input files. Mike
mentioned on IRC that he planned to add support for 24bit int input
files, but I don't know when this is going to happen. However, since
more-than-16bit support is natural for Vorbis by design, maybe there
already is an implementation that takes 24bit input without the
unnecessary step of converting to 16bit first. (You could also convert
to 32bit floats yourself and feed those to oggenc, but that'd mean quite
some time and diskspace effort.)

About the sample rate ... well, getting a tuned mode for >48kHz could
take really long, since that's way off normal use. You say that you
accept quality degration; why not "degrade" quality to 48kHz and
compress the whole thing with something lossless? If you want to make
another remix some day, a losslessly compressed source resampled back up
to 96kHz should give you better quality, especially since 96 = 2 * 48
... resampling would be pretty exact. E.g. if you play one of those
sources at a different pitch, previously inaudible differences made by
the psychoacoustic model might suddenly become audible, even at high
bitrates. A lossy Codec like Vorbis would discard/reduce most of the
information above 24kHz anyways, because inaudible audio information is
considered "not important".

A nice and free lossless Codec is FLAC (flac.sf.net).

<p>Moritz
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