Speex dev - May 2007 - Regarding mismatch in data rates of speex codec

Hi all,

Accoring to the Table.8.1 and Table.8.2 of  speex manual (Version 1.2 Beta 2),
the
data rates supported by speex codec for narrowband are 3.95, 5,95 ,8 ,11 ,15
,18.2 and 24.6kbps.

But when I run the code(downloaded from www.speex.org), I am getting data rates
of
4,6,8,11.2,15,2,18.4 and 24.8 kbps.

That is, for an input of 20ms frame  the number of output bits I am getting are
80,120,160,224,304,368 and 496 whereas
the number of bits given in the Table.8.1 are   79, 119, 160, 220, 300, 364 and 
492 .

Can anybody help me in finding out the reason behind this mismatch.

Thank you
Murali

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T Murali Mohan wrote:
> Accoring to the Table.8.1 and Table.8.2 of  speex manual (Version 1.2
> Beta 2), the
> data rates supported by speex codec for narrowband are *3.95, 5,95 ,8
> ,11 ,15 ,18.2 and 24.6kbps*.
>  
> But when I run the code(downloaded from www.speex.org
> <http://www.speex.org>), I am getting data rates of
> *4,6,8,11.2,15,2,18.4 and 24.8 kbps.*
> ** 
> That is, for an input of 20ms frame  the number of output bits I am
> getting are *80,120,160,224,304,368 and 496* whereas
> the number of bits given in the Table.8.1 are   *79, 119, 160, 220, 300,
> 364 and  492 .*
> ** 
> Can anybody help me in finding out the reason behind this mismatch.
Easy. Most of the time when you're encoding, the number of bits gets
rounded up to the next full byte. However, if you were to pack 8 frames
in a packet, you'd see the same values as the manual has.

	Jean-Marc

Hello,

On 5/31/07, Jean-Marc Valin <jean-marc.valin@usherbrooke.ca>
wrote:
> T Murali Mohan wrote:
> > Accoring to the Table.8.1 and Table.8.2 of  speex manual (Version 1.2
> > Beta 2), the
> > data rates supported by speex codec for narrowband are *3.95, 5,95 ,8
> > ,11 ,15 ,18.2 and 24.6kbps*.
> >
> > But when I run the code(downloaded from www.speex.org
> > <http://www.speex.org>), I am getting data rates of
> > *4,6,8,11.2,15,2,18.4 and 24.8 kbps.*
> > **
> > That is, for an input of 20ms frame  the number of output bits I am
> > getting are *80,120,160,224,304,368 and 496* whereas
> > the number of bits given in the Table.8.1 are   *79, 119, 160, 220,
300,
> > 364 and  492 .*
> > **
> > Can anybody help me in finding out the reason behind this mismatch.
>
> Easy. Most of the time when you're encoding, the number of bits gets
> rounded up to the next full byte. However, if you were to pack 8 frames
> in a packet, you'd see the same values as the manual has.
I think it's a common misunderstanding, so wouldn't it be nice to have
a "Note: " with warning about rounding to 8 bits and/or table or
column in
existing table with values for 20ms frames. It may be helpful for people
who just want use Speex.

-- 
Regards,
Alexander Chemeris.

SIPez LLC.
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