Re: 192000 Hz won't render
Re: 192000 Hz won't render
- Subject: Re: 192000 Hz won't render
- From: Jeff Moore <email@hidden>
- Date: Fri, 30 Mar 2007 11:36:12 -0700
On Mar 29, 2007, at 6:39 PM, Christopher Ashworth wrote:
On Mar 29, 2007, at 3:41 PM, Jeff Moore wrote:
One thing you might run into though is that to maintain an ~11.5ms
IO cycle, the buffer size would increase from the default of 512
frames to 2048 frames.
Dumb question just to make sure I'm following you: Which buffer are
you referring to here?
That would be the IO buffer size in the HAL for this device. AUHAL
inherits this buffer size as part of doing it's job, but other AU's
use a default size that is usually smaller in these situations, which
is why you need to tell them what to do.
If this is the case, you probably need to update each AU's
kAudioUnitProperty_MaximumFramesPerSlice property to be large enough.
Are there guidelines for how to make sure we're setting the
kAudioUnitProperty_MaximumFramesPerSlice to ensure that it is the
right size for a particular I/O cycle of a particular device? The
way you phrase it above makes me think there is a straightforward
calculation that will give the right answer, but if so I'm ignorant
of it. (This is probably related to my ignorance of where you got
the 11.5ms number for the I/O cycle.)
Generally speaking, kAudioUnitProperty_MaximumFramesPerSlice
represents the largest number of frames you are going to call an AU to
render. This allows the AU to know how big to allocate its internal
buffers and what not. If this is too small, an AU might refuse to
honor a Render call that asks for more.
--
Jeff Moore
Core Audio
Apple
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