Re: [Bluez-devel] headset audio playback real slooowwww

[Ken Koster <ken.koster@elektrobit.com>]

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On Saturday 10 November 2007, Jim Carter wrote:
> On Fri, 9 Nov 2007, Koster Ken wrote:
> 
> > bluez-lib and bluez-util to 3.19 and I'm attempting to make use of the 
> > audio service to send audio to a bluetooth headset.
> > 
> > Everything is working with the exception that the playback is at half the
> > normal speed, so everything recorded is lower in pitch and takes twice
> > as long.  (a seven second sound sample takes fourteen to play back)
> 
> You mentioned SCO later in the message; this protocol is monophonic.  If 
> the sound clip were recorded in stereo (I'm assuming 44100 Hz), with 
> independent channels (not joint stereo), then there would be two 
> nearly-identical copies of each sound sample, and if you forced it to go 
> out as mono, it would play at half speed.  There would be a 22 KHz whistle 
> as you alternated between possibly unequal stereo tracks, but since SCO is 
> at 8000 Hz, this would be inaudible after the sound stream was resampled 
> (or maybe being imaged down to 2 KHz but very quiet due to averaging).  
> Maybe that's what happened.

Unfortunately the clip is mono, recorded at an 8k rate.

I'm rapidly learning far more about SCO than I ever planned :-)

-- 
Ken Koster
Senior Software Engineer

EB - Discover the Experience 
22745 29th Dr. SE, Suite 200
Bothell, WA 98021, USA 
Tel: +1 425-444-2691 
Fax: +1 425-686-3102 
ken.koster@elektrobit.com 
www.elektrobit.com


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