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Voice setting for U-law and A-law.

Bluez-devel Ivy 1 participant 1 message Sep 25, 2005 Bluetooth drivers

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Hi Marcel , Andy ..

Thanks for bare with me so far ...

Based on your input and Mailing list info, I have choosen alternate setting 1 in interface 1. I am using CSR chipset Bluetooth Dongle. My voice setting value is 0x140. (mu-law). If i am submitting URBS to read, my system is hanging.. I am using 2.6.12 kernel. if i am setting default voice setting value 0x60... It is not hanging ... I dont know what would be the probelm... Any one tips to track down this problem ...

Thanks
-Ivy

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Quoted 16 lines · --- Andreas Beck
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xxxxxxxxxx1xxxxx Input Sample Size: 16 bit (Can i use 8 bit ?)

IMHO you should, if you want alaw/ulaw.

You meant to use 16 Bit or 8 bit ?..

8 bit.

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xxxxxxxxxxx010xx # of bits padding at MSB: 2 (if i use 16 Bit, 2bit's of MSB is needed for padding, coz only 14bits are enough for u-law)

AFAIK 8 bits are enough - could you explain?

U-LAW takes 14bits of linear PCM data as input and generates 8 bit compressed data. Am i correct ?

Yes. That is correct.

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Thatswhy i assume that it needs 16 bits for INPUT Sample size and 2 bit offset in MSB position.

No - I suppose this is a misunderstanding about "input".

The SCM link via bluetooth uses its own encoding anyway (see the comment about on air coding at the end of the list).

SCO LInk via bluetooh uses CVSD encoding...

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INPUT means what you feed in/get out at the driver side.

That is, if you choose alaw, you already feed alaw data.

Otherwise you could just use linear anyway. There would be no use in converting to alaw first and then again to the air coding format.

Basically you will want to use alaw/ulaw, if you want to feed the received data directly into a device that wants this data format anyway, saving unnecessary conversions.

xxxxxx01xxxxxxxx Input Coding: u-law xxxxxxxx01xxxxxx Input Data Format: 2"s complement xxxxxxxxxx0xxxxx Input Sample Size: 8 bit xxxxxxxxxxx000xx # of bits padding at MSB: 0 xxxxxxxxxxxxxx00 Air Coding Format: CVSD

               0101000000 = 0x140 is the correct value ?. isnt it ?

hciconfig hci0 voice 0x140. Is it necessary to change my USB alternate setting for the above changes ?. Right now it is placed in alternate setting 2. (Endpoint value 17). Thanks for bare with me

Thanks
-IVY

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CU, ANdy

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