[Bluez-devel] Question about cvsd input and output

[Bluez-devel] Question about cvsd input and output

[Jui-Hao Chiang]

Hi, all

I have looked all the old articles, but still have a question.
In the Bluetooth spec, it said the CVSD input shall be 64ksample/s and 16-bit
linear PCM.
It also says the output of the CVSD decoder are 16-bit linear PCM
digital samples, at a sampling frequency of 8 ksample/sec.

I am a little confused about the data rate of the input side (64k*16bit =
1024kbps), which seems 8 times faster than the output of decoder.

Besides, I tried to open a SCO socket between two adapters (scotest), and the
maximum data rate in one direction is 128kbps.
Thus, I don't think we can actually feed 64ksamples/sec, 16-bit voice data into
the CVSD codec of the adapter. 

Am I right? or it's just the limitation of my adapter
(Cyber Blue, Bluetooth EDR USB dongles,class II,V2.0)?

Bests


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Re: [Bluez-devel] Question about cvsd input and output

[Marcel Holtmann]

Hi,

> I have looked all the old articles, but still have a question.
> In the Bluetooth spec, it said the CVSD input shall be 64ksample/s and 16-bit
> linear PCM.
> It also says the output of the CVSD decoder are 16-bit linear PCM
> digital samples, at a sampling frequency of 8 ksample/sec.
> 
> I am a little confused about the data rate of the input side (64k*16bit =
> 1024kbps), which seems 8 times faster than the output of decoder.
> 
> Besides, I tried to open a SCO socket between two adapters (scotest), and the
> maximum data rate in one direction is 128kbps.
> Thus, I don't think we can actually feed 64ksamples/sec, 16-bit voice data into
> the CVSD codec of the adapter. 

the CVSD is only used over-the-air. The input for the host adapter is
based on the voice setting which defaults to 16-bit linear PCM.

Regards

Marcel



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