Re: Stereo Mixer Static...sometimes.
Re: Stereo Mixer Static...sometimes.
- Subject: Re: Stereo Mixer Static...sometimes.
- From: Dominic Feira <email@hidden>
- Date: Mon, 15 Nov 2004 15:12:43 -0500
The data is being read in from a file and buffered. This is all done
with Core Audio AudioFile routines. The input data is the same
regardless of wether or not the data is being written with Quitcktime
or LAME.
It doesn't matter which of the 2 inputs on the mixer I set to zero. If
either one of them is set to zero, then there is no crackling.
Dominic Feira / Code Monkey / Ambrosia Software, Inc.
P.S. I didn't mean to take this off of the list...this message is back
on it.
On Nov 15, 2004, at 2:35 PM, William Stewart wrote:
On 15/11/04 11:11 AM, "Dominic Feira" <email@hidden> wrote:
I will get together a smaller example that demonstrates the problem.
I
do have one questions first before I go through the trouble. Prior to
writing the audio data to an mp3 with LAME, I scale all of the data by
32768.0, because LAME's floating point format requires this. Could
this somehow be preventing the pops and crackling?
I don't think so - but in the QT case where are you getting the data
from -
is that being scaled correctly?
I doubt that it is the mixer... If you set the volume of a mixer input
to
zero then it doesn't mix that input... All that this is telling you is
that
the static has something to do with that input - I suspect that you
haven't
scaled the input you are getting from QT correctly...
Bill
Dominic Feira / Code Monkey / Ambrosia Software, Inc.
On Nov 15, 2004, at 1:52 PM, William Stewart wrote:
If you could file a bug report with code to reproduce it at
http://bugreporter.apple.com we'd be happy to look at this
Bill
On 13/11/04 9:54 PM, "Dominic Feira" <email@hidden> wrote:
Hello.
I have an AUGraph set up that looks like this:
This graph is not run in real-time, I am using AudioUnitRender to
pump
it manually.
[AUConverter] -----
[Stereo Mixer] ------
[Converter]
--------- [Quicktime or LAME] ------- [ File ]
[AUConverter] -----
Quicktime or LAME and File obviously aren't part of the graph.
Here's the part that is boggling my mind:
If I use LAME to encode everything works perfectly, I end up with a
perfectly mixed mp3, it sounds great!
If I use Quicktime, I end up with static in my audio. I have
determined that the fault lies with the mixer. If I set one of the
input levels on the mixer to 0.0 then there aren't any pops or
crackles
in the audio. This leads me to conclude that the mixer is
introducing
the static.
The only difference that I can find that could possibly introduce
the
static is that using Quicktime for encoding is more CPU intensive
that
LAME. This doesn't seem like it should matter though, because I am
pumping the graph manually. Does anybody have any ideas? I wish I
had
a more specific question, but I am stumped.
Dominic Feira / Code Monkey / Ambrosia Software, Inc.
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