Re: Recognizing iSight as audio input device?
Re: Recognizing iSight as audio input device?
- Subject: Re: Recognizing iSight as audio input device?
- From: Jeff Moore <email@hidden>
- Date: Fri, 24 Feb 2006 17:31:03 -0800
516 is a pretty weird buffer size. The default is 512, so to get 516,
somebody would have to be setting it on purpose. Given that you can't
change the buffer size of the iSight, why not just set the output to
800?
At any rate, I'm still a bit puzzled as to why I don't get the same
results that you do. My iSight seems to work just fine with the
ComplexPlayThru sample code on my G4 PowerBook running 10.4.5.
Whereas, you have seen this on two different machines. The only clear
difference I see is that the machines you are using have two CPUs and
my PowerBook has just the one. Do you get the same results if you
disable one of the processors?
On Feb 24, 2006, at 5:13 PM, Stephen Shaw wrote:
Looking at the # of frames on the inputProc it looks like using iSight
it is processing (and filling the ring buffer with) 800 frames instead
of the usual 512
Meanwhile the output proc is only processing (and pulling from the
ring
buffer) 516 frames per call, so it looks like it gets so far behind,
that the input proc just keeps overwriting it and resetting the read
start time.
Using HALLab, it looks like the firewire iSight is 48khz, and the IO
buffer size is 800, and the IO Buffer Size Range is 800 - 800.
In HALLab, the built-in audio has a rate of 48khz, and the IO buffer
size is 512, and the IO Buffer Size Range is 15-6144
I'm not certain how to prevent this overwrite from occurring, even
if I
increase the buffer, it will eventually happen.
Thanks!
-Stephen
According to the code for AudioRingBuffer::CheckTimeBounds, it
returns
kAudioRingBufferError_WayAhead when the requested range isn't
currently
in >the ring buffer.
I'd imagine that this implies that the input device isn't filling the
ring >buffer up for some reason.
--
Jeff Moore
Core Audio
Apple
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