[Vorbis] Vorbis decoding/multi-channel mixing

[Ivo Emanuel Gonçalves]

Hello Joost,

I would like to say since you seem to understand what Vorbis is since
you are in the appropriate list that you should not refer to it as
"OGG".  First, because Ogg is not Vorbis --  it's a container.
Second, because Ogg is not an acronym.  Vorbis decoding help is what
you are looking for.

With that said, let's see if I can help you.

On 11/6/07, Joost Meijles <joostmeijles at hotmail.com> wrote:
> - Decoding on embedded hardware, ARM7 or ARM9.

There is an integer decoder specific for the ARM platform.

> - Mixing multiple audio streams/files on embedded hardware

I assume this is possible, because it is possible elsewhere.  You see,
Ogg can chain multiple Vorbis streams in one file.

> First of all how difficult is it to decode Vorbis on an ARM7/9 processor? I
> read that Vorbis decoding needs floating point support?

You read wrong.  Vorbis supports floating point decoding through the
standard library and fixed point decoding through Tremor.  I would
suggest you look into Tremor.

> Finally is it possible to mix Vorbis streams without first decoding them to
> PCM? I found a program that is mixing multiple Vorbis streams called
> "mixplayd", but I wasn't able to figure out if this program is first
> decoding and than mixing or if it is mixing native Vorbis and than decoding one
> mixed Vorbis stream.

I'm not sure about this, so I hope someone who knows more than me comes along.

-Ivo