[Vorbis] OGG decoding/multi-channel mixing

[xiphmont at xiph.org]

On 11/6/07, Joost Meijles <joostmeijles at hotmail.com> wrote:

> - Decoding on embedded hardware, ARM7 or ARM9.

Tremor is well suited to ARM and even includes some of the most basic
ARM asm needed to take better advantage of the hardware.

> - Mixing multiple audio streams/files on embedded hardware

You mean multiple concurrent streams?  There's no accelerated software
for that (just multiple stream decode and post-mix), not sure it would
be worth it.  You'd get to save at most the iMDCT....

> First of all how difficult is it to decode OGG on an ARM7/9 processor?

At last check on an ARM7TDMI, Tremor mainline required about 40-45MHz
for stereo decode of one stream, assuming a setup using slow offboard
DRAM at 7-14 wait states and using on-board fast SRAM as a random
replacement cache.

> Finally is it possible to mix OGG streams without first decoding them to PCM?

I am unawareof any software that does it.  Only about half the process
(the final iMDCT) would be sharable, but that's in theory.  I'm
unaware of it having been done.

Monty