Speex dev - Nov 2005 - 8.4kbps data rate in 8kbps nb mode

I know that most of the narrow band submodes don't have an exact multiple of
eight bits in each frame

79 bits for 3.95kbps
119 bits for 5.95kbps ...etc

This means that you have a few unused bits when transporting Speex in the Ogg 
format (you can achieve a lower number of unused bits if you change the number 
of frames per Ogg packet to suit the mode).

However, in 8kbps mode, the number of bits per frame is 160. I would have 
expected this to fit into an Ogg segment 20 bytes long. However, when I use 
(speexenc -n --quality 3) to encode at 8kbps the Ogg segments are each 21 bytes 
long.

Is this an error, or is there extra information put in the 21st byte?

I'll have a hunt through the code, but thought someone might have come
across
this before.

Regards,

Andy

I'm not aware of this. How did you measure this value? Note that in
practice, there is a small overhead to Ogg packets.

	Jean-Marc

Le mercredi 16 novembre 2005 ? 12:18 +0000, Andy White a ?crit
:
> I know that most of the narrow band submodes don't have an exact
multiple of
> eight bits in each frame
> 
> 79 bits for 3.95kbps
> 119 bits for 5.95kbps ...etc
> 
> This means that you have a few unused bits when transporting Speex in the
Ogg
> format (you can achieve a lower number of unused bits if you change the
number
> of frames per Ogg packet to suit the mode).
> 
> However, in 8kbps mode, the number of bits per frame is 160. I would have 
> expected this to fit into an Ogg segment 20 bytes long. However, when I use
> (speexenc -n --quality 3) to encode at 8kbps the Ogg segments are each 21
bytes
> long.
> 
> Is this an error, or is there extra information put in the 21st byte?
> 
> I'll have a hunt through the code, but thought someone might have come
across
> this before.
> 
> Regards,
> 
> Andy
> 
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