Re: Stereo Mixer Static...sometimes.
Re: Stereo Mixer Static...sometimes.
- Subject: Re: Stereo Mixer Static...sometimes.
- From: William Stewart <email@hidden>
- Date: Mon, 15 Nov 2004 12:27:04 -0800
Hmmm... With the two inputs - if you have no input data are you memsetting
the buffers to zero (and ideally also in this case, setting the isSilence
flag/bit to true)...
You mention how you are scaling LAME's output... The question is the same
for the QT output - where are you getting this from? How are you adding this
into the mix (AU's nominally expect a range of -1 to 1, and the SoundMgr/QT
will give you back shorts in a -32768 to 32767 range)
It sounds to me like there's some garbage or out of range values in the
mixers inputs:
LAME active (QT inactive) - no noise
LAME inactive (QT active) - noise (are the LAME input buffers being set to
zero/silence)
Both inactive ?
Both active ?
Bill
On 15/11/04 12:12 PM, "Dominic Feira" <email@hidden> wrote:
> 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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