[Bluez-devel] Re: btsco occasional loud bursts of static

[Bluez-devel] Re: btsco occasional loud bursts of static

[Chase Douglas]

> Chase
> 
> One thing to check is the code we have to accommodate a byte getting
> lost. If we don't watch for this, subsequent samples have what should be
> a high byte in the low position and vice-versa, so the result is loud
> noise for the remainder of the connection.
> 
> I haven't looked closely at this, but it's really baffling to think a
> single byte could be lost from a stream of 16-bit samples like that. The
> protocol should drop entire samples when the signal is bad--losing
*> *half** a sample is a worst-case scenario.
> 
> Brad
> 
> > I have a dlink dbt-120 rev. b4 bluetooth adapter with a motorola hs850
> > and I use btsco to talk with people online. When I have my laptop
> > sitting on my lap, everything works fine. However, when I start to walk
> > around, the sound transmitted to the other person from my headset will
> > have bursts of loud static. I am guessing that this is a problem with
> > the connection being worse. I would like to get this resolved, and I can
> > do some coding as well. I have a 2 MB hcidump which somewhere near the
> > end has the offending sound packets. I can't find any documentation on
> > the SCO protocol, so I can't find where the static was. Can anyone point
> > me in the right direction?
> > 
> > Thank you,
> > Chase Douglas
> > 
> > 
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I'd love to hlp in any way I can. I'm not sure where this code is that you
wrote of. Could you point me in the right direction? Also, I am going to need
some kind of documentation on the sco protocol. Do you know where I could find
these?

Thanks



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Re: [Bluez-devel] Re: btsco occasional loud bursts of static

[Brad Midgley]

Chase

> I'd love to hlp in any way I can. I'm not sure where this code is that you
> wrote of. Could you point me in the right direction? Also, I am going to
> need
> some kind of documentation on the sco protocol. Do you know where I
> could find
> these?

This is currently all in the kernel.

In the btsco project, you'll see in kernel/btsco.c where sock_recvmsg()
gets data from the set and is followed immediately by some
AUTO_FIXUP_BYTESHIFT code. This is the workaround for the problem.

The sco generic transport is implemented in the kernel source in
drivers/net/bluetooth/sco.c.

The hardware interaction is in net/bluetooth/hci_{conn,core,event}.c and
I suspect this is where things may need work. This is also where hacks
for broadcom sco would probably end up.

Brad


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Re: [Bluez-devel] Re: btsco occasional loud bursts of static

[Brad Midgley]

Chase,

>>I'd love to hlp in any way I can. I'm not sure where this code is that you
>>wrote of. Could you point me in the right direction? Also, I am going to
>>need
>>some kind of documentation on the sco protocol. Do you know where I
>>could find
>>these?

Go sign up for a free account at bluetooth.org and download
documentation there.

Do not use the search page to find documents. After several frustrating
attempts, I found out the search returns urls that you're not allowed to
open using the free account.

Brad


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