RE: [Bluez-devel] sbc and fixed-point progress

Victor Shcherbatyuk
2005-08-24T12:18:30Z

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Brad,

I ran one more test and instead of -n flag for a2play I changed magic 87 to magic 50, CPU usage dropped >2 times to ~8% on ARM9@400Mhz and sound is still smooth. That's how it was tested in first place which is close to 30 MIPS I guess...

Regards,
Victor.

-----Original Message-----
From: bluez-devel-admin@lists.sourceforge.net on behalf of Victor Shcherbatyuk
Sent: Tue 8/23/2005 5:00 PM
To: bluez-devel@lists.sourceforge.net
Subject: RE: [Bluez-devel] sbc and fixed-point progress

Hello Brad,

I did some test runs on ARM9@400MHz, general fixed point encoder eats up ~40% of CPU time, while arm specific version - ~20%. And in both cases it runs quite smooth. So the drops you had should have been caused by something else (unless you run some othe applications cuncurently).

Victor.

-----Original Message-----
From: bluez-devel-admin@lists.sourceforge.net on behalf of Brad Midgley
Sent: Mon 8/22/2005 9:22 AM
To: bluez-devel@lists.sourceforge.net
Subject: Re: [Bluez-devel] sbc and fixed-point progress

Victor

>> I do not have HW to test arm specific version real time, hope no
>> suprises there, but I could have missed something when integrating it
>> into sbc code (it decodes well, but how fast, I will try only monday
>> evening).
>
>
> Ok, I'll load it on gumstix now and give it a try.

This is almost perfect. On a 400mhz gumstix (pxa255), I'm able to send a
5-minute audio stream with only about three breaks in the audio (about 5
seconds each).

I think it will work flawlessly in 4 subbands or if we can shorten a few
of the ops from 64 to 32 bit.

I committed what's there and used __arm__ for the conditional asm code.

>> Using a2play needs to tweak 87 magic number, otherwise it drops samples?
>
>
> yes, this is disappointing. We may need to find another way to get
> reliable timing than setitimer.
>
> I did change the first usleep(10) to usleep(1000) and that *may* help
> with this problem by ensuring that we always interrupt the usleep
> syscall consistently. I don't have my hp headphones (the set that's very
> sensitive to timing) handy to test.

fwiw, I had to use the -n flag to a2play so it wouldn't use itimer at
all. This flag tells a2play to just send the audio as fast as it can
encode it.

Brad

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