Re: Setting a graph's sample rate
Re: Setting a graph's sample rate
- Subject: Re: Setting a graph's sample rate
- From: William Stewart <email@hidden>
- Date: Thu, 2 Mar 2006 15:48:46 -0800
On 02/03/2006, at 3:16 PM, Geoff Hufford wrote:
On 3/2/06 1:04 PM, "William Stewart" <email@hidden> wrote:
Before you call AUGraphInitialize, go
through all of the nodes in the graph and set all of their outputs to
48000 (except of course the output unit, where you can't set the
hardware side's format).
So, then when you connect the graph up (this is one of the things
AUGraphInitialise will do for you), the source of a connection is
used to define the format of the connection. So, the formats you have
established at the output stages (48000) will then propogate through
to the input side of each connection.
Thanks Bill. That fixed it with the addition of also needing to set
the
Input of the Output unit.
I am curious if there is a way to gauge if it makes a difference
with the
performance. Using 7 48k stereo sound files playing simultaneously,
activity
monitor didn’t show a noticeable difference whether my graph was at
44k or
48k. I believe that having the graph at 48k means that the 7
sources are
mixed together and then a single SR Convert to change it to 44k for
the
output. Whereas if the graph is at 44k then all 7 sources get
converted to
44k prior to mixing.
prior to output - the conversion is done between the input and output
of the AUHAL (the output unit)
You are unlikely to see top reflect this - have a look at the AUGraph
api for CPU Load, they should give you a more accurate representation
of the load of the graph at least (which would include the rate
conversion in the output unit)
Bill
Is the built in sound output on a PB G4 limited to 44100? Do other
machines
support different rates with the built in hardware? I assume there
is a way
to inquire what rates the sound hardware supports, but I will
tackle that
later on.
Geoff
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