[speex-dev] ACM Format Tag for Speex Audio

Christian.Buchner
Fri, 06 Aug 2004 15:01:46 -0000

> Also, the WAVEFORMATEX structure must be planned so that it is extensible,
with
> backward-compatibility, without having to ring back Microsoft for further
> WAVE_FORMAT tags. For instance, it is a good idea to put a flexible
sub-format
> code in the structure that allows various layouts.

My WAVEFORMATEX contains a major and minor version in the first two bytes.
I also put the whole SPEEX header packet into that header, as well as a
short ASCII notice where to download the ACM codec.

Using this major and minor version my ACM codec can accomodate for different
payload versions. For example when I decide to implement a variable bitrate
mode, I will have to add synchronization markers into the bitstream. In that
case I would update the version requirement. The old ACM codec version will
then deny to decode any newer payload formats instead of just producing noise
or crash (worst case). ;)

Christian

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