QUOTE(de Mon @ Sep 26 2003, 12:58 PM)
iRiver's buffer works also on Audio CD tracks (more than 1100 kbs). So I don't think the problem lays in bitrate and size.
Actually Vorbis seems to use a very different buffering approach during decoding than CDA or other audio formats. My experience is not as a developer, but I did do pretty extensive tests on the Tremor decoder for the PhatNoise (/Kenwood) Music Keg for Vorbis-encoded files, and I found that (in it's current incarnation) the maximum nominal bitrate it can do consistently is 136kbps (-q 4.25, Post 1.0 CVS). However, it decodes 1411kbps PCM WAVs just fine and ~750-850kbps FLACs fine as well.
But give it, say, a -q 5.00 Vorbis file, and it'll balk
if the actual bitrate spikes too far over ~210kbps. I have some Kraftwerk and Fatboy Slim tracks that spike
up to ~210kbps even at -q 4.25, and it still doesn't fail, but the decoder is close to it's limit. I measured that anything much over that bitrate would cause playback to skip and distort in pitch. The guy who modded the Tremor code for this platform said it seemed the buffering wasn't keeping up with real-time playback, and the buffer would run out periodically, causing these problems (if I'm remembering his description correctly).
A specific example, Fatboy Slim's
Kalifornia would skip and distort severely in the opening 14 seconds if encoded with anything over -q 4.25. You should hear -q 10...~499kbps nominal. Playback sounded like a guitar phrasing pedal was being used to drop the pitch dramatically, and there was also bad distortion and skipping (playback stopping entirely for fraction of a second as the buffer "refilled") every couple of seconds.
So playing back CDA at 1411kbps seems to require much lower memory and/or buffering overhead than decoding Vorbis at considerably lower bitrates (even using the integer-based Tremor libs).
Also, for reference, I used FLAC exclusively on the same device for a month or so with no audible playback errors. My FLACs average between 750-850kbps or so.
Edit: Note that my experience is with a different piece of hardware, but I think the same buffering problems with Vorbis playback may exist between the iRiver device and the PhatBox/Music Keg. Didn't want to mislead anyone.