[vorbis] Vorbis on Legacy hardware

[Kenneth C. Arnold]

Corey Miller wrote:

>> I seriously doubt you'd be able to play Vorbis files on a system
>> this slow.  All the developers have said that Vorbis takes roughly
>> the same about of CPU power to play that MP3 plays -- and I couldn't
>> play stereo 44 kHz MP3 files smoothly on my 486/66.  (I could just
>> *barely* play mono ones.)
>
>
>     The sound quality doesn't have to be terribly great, or good at 
> all.  The idea behind my distro is basically I know so many people in 
> their teens that live in my area that are given really old bad systems 
> that their parents used to use 10 years ago.  I just want them to be 
> able to quickly install something that gives them a computer that's 
> even remotely useful.  Music listening would be something highly 
> demanded by people of that age group, regardless of quality. 

<p>(note: nothing unobvious below:)

You may be able to get decent performance out of Tremor, especially with 
the low-accuracy modifications I've heard about. It may still be 
possible to squeeze the code tighter at the expense of accuracy, but not 
having tried it, I really don't know.

For Vorbis with channel coupling, decoding to mono is nearly as much 
effort as decoding to stereo. Perhaps some savings could be gained by 
just dropping off the second iMDCT for a stereo stream and treating the 
result as mono, though it would probably sound better to try to extract 
a "middle channel" earlier, in the decoupling code.

ogg123 can prebuffer its output buffer. Set it to a reasonably large 
size and 95% prebuffer. Even if the machine isn't able to decode in 
real-time, it should still be able to play a good portion of any song 
before becoming CPU-bound, at the expense of startup time.

I recently resurrected my old Media Vision Pro Audio Spectrum 16 card 
(wow, 16-bit!), which came with Trackblaster Pro, which played old .mod 
files (4 tracks, practically no effects, 8-bit samples). It took me a 
while to figure out that it was locking up because it couldn't mix at 
44.1k in real-time on the old 386SX, but once I dropped it down to 22k, 
I had a relatively stone-age computer playing half-decent music! The 
good old days...

IIRC, MP3 was the highest-complexity member of a family of 3 codecs -- 
layer 1, 2, and 3. It's been brought up before, but perhaps this is a 
reasonable opportunity to reconsider a "low-complexity" mini-Vorbis codec?

Ken

<p>--- >8 ----
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