[vorbis-dev] Just to dispel any hopes -- RC3 really low bitrate

[oddsock]

in case your curious as to what low bitrates sound *with* resampling, check 
out http://www.oddsock.org/vorbis_streams

there are 2 streams there, one with RC3 32/22/Mono, and one with LAME 
32/22/Mono....the source is the same for both streams...I personally think 
that the 32/22/Mono of RC3 is quite spectacular...

oddsock
At 10:25 PM 1/1/2002 -0500, you wrote:
>I've just done some rudimentary testing to see how Vorbis degrades at
>absurdly low bitrates without downsampling. In summary, don't hope for
>anything decent below -q 0 for now. I tried oggenc -b <bitrate> -M
><bitrate> for the below and a few in between:
>
>24k - spectral energy "floor" captured decently, but many pure-tone
>blips (think old computer movie sound effects) in mid to high
>range. Totally untolerable.
>
>...
>
>35k - blips mostly gone, audio present but very muffled (high
>frequency basically gone). Occasionally it will "open up" a little and
>get some high-end, and stay like that for maybe a second (definately
>more than one block), then close up again. I might be able to live
>with this, it sort of sounds like Real at 16k or so.
>
>...
>
>45k - now most of the time it sounds like 35k when it opened up, and
>like 35k there are times when it'll pull in another block of
>higher frequencies. The average quality level seems about consistant
>with what I'd expect a stream coming down from my 28.8 modem (~24k) to
>sound like, if the rough edges were smoothed over a little.
>
>...
>
>64k - just to try what (ideal) single-channel ISDN would sound like;
>generally quite tolerable. Still munges high frequency, but nearly an
>order of magnitude less perceptably than lower bitrates. Note that
>this is not the VBR 64k mode; I've essentially locked the codec at 64k
>and below. It still should sound roughly like 64k normally (which I
>can live with for e.g. background music), but it has more obviously
>bad spots.
>
>Definately some improvement in tuning elsewhere too. Quality around 2
>gets me roughly the same result I've come to expect from 128k --
>pretty much transparent unles listening very closely -- but at around
>30kb/s less than RC2. Those with more "golden ears" than I may contest
>that as a general statement, but I think I'll encode at around 2.5 for
>most things.
>
>For future Vorbis development, I think the quality scale should be
>shifted lower, or perhaps made logrithmic -- the marginal benefit per
>unit bitrate is much more at lower quality settings than higher (I
>doubt I would be able to hear any difference at all for 5 and above,
>while 0 through 3 were obvious step-ups). Also, if possible lower
>bitrates should degrade more gracefully. Gradually add
>high-frequencies, not in chunks. Does the bitrate limiting engine have
>any linkup with psycoacoustics? -- it doesn't sound like it, at least
>not for lower bitrates. I'd experiment with adding in harmonics of the
>highest frequency coded to fill in the high end; it may be better to
>have a wrong high-end than no high-end, psycoacoustically speaking.
>
>Note that the Vorbis internals have changed significantly since I
>last really tried to study them, so pretend that I don't know what I'm
>talking about and you'll probably be right.
>
>--
>Kenneth Arnold <ken at arnoldnet.net>
>- "Know thyself."

<p><p>--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.