Re: Decoding AAC/Apple Lossless mono to lpcm stereo
Re: Decoding AAC/Apple Lossless mono to lpcm stereo
- Subject: Re: Decoding AAC/Apple Lossless mono to lpcm stereo
- From: Dominic Feira <email@hidden>
- Date: Mon, 27 Nov 2006 20:37:36 -0500
Thanks Bill. You are correct, the problem was from setting the
cookie and not the reset. I'm also glad to hear that I don't
necessarily have to scale the volume on the mono-stereo audio. I'm a
lazy programmer, so I'm taking the easy way out on that issue.
I'll let you and Brad fight out what is technically correct. It
would be great if that discussion takes place that it were on the
list. I'm sure a lot of us on the list aren't very familiar with
audio theory.
The only issue I see with this discrepancy is inconsistent results
from various playback applications.
Dominic Feira / Code Monkey / Ambrosia Software, Inc.
On Nov 27, 2006, at 8:19 PM, William Stewart wrote:
Ahm, I would not be so sure about this mono-stereo thing. The
common practise is to duplicate the mono channel as is to the two
stereo channels - otherwise you end up with an attenuated signal
and this is as undesirable affect as any increase in the volume.
We did uncover a problem where the channel map was lost when the
cookie was set on the converter. So, to avoid this (we don't think
we'll change this at this point) is:
- new audio converter
- set cookie on converter
In other words, treat the cookie as a part of the general process
of constructing a converter. I don't think the problem is Reset
(but if it is can you please file a bug).
Thanks
Bill
On 27/11/2006, at 4:25 PM, Dominic Feira wrote:
Brad,
Thanks for the fast response.
This isn't mixing. As you say, this just replicating the audio
data to multiple channels. This is what the channel map property
is for AFAIK.
Also, I seem to have just figured out the problem. I always
figure things out right after I hit send. Apparently
AudioConverterReset() throws out the channel map for some
converters and not others. I'm not sure what the defined behavior
is supposed to be.
Thanks for the additional info though. I didn't realize that by
replicating the mono audio to both stereo channels that this was
considered too loud.
Dominic Feira / Code Monkey / Ambrosia Software, Inc.
On Nov 27, 2006, at 7:20 PM, Brad Ford wrote:
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