Re: Bug? Clicks while recording audio (In) from MIDI (out)
Re: Bug? Clicks while recording audio (In) from MIDI (out)
- Subject: Re: Bug? Clicks while recording audio (In) from MIDI (out)
- From: Kurt Bigler <email@hidden>
- Date: Sat, 22 Feb 2003 15:36:32 -0800
on 2/22/03 1:47 PM, Josh Whitver <email@hidden> wrote:
>
My theory is that it's purely a software issue, ie, there's something in the
>
audio-in code of CoreAudio that winces whenever the CoreMIDI aspect of
>
CoreAudio is busy. So, whenever there's a MIDI event, CoreAudio's Audio In
>
just hiccups.
If CoreAudio hiccups, changing the input buffer size would probably affect
the resulting sound. I lost the beginning of this thread so don't remember
what your application is - whether you have control over the audio buffer
size. If you change the buffer size and the hiccup changes, then that will
also make a case for a software issue. (But if the hiccup doesn't change
this doesn't much prove anything.)
>
>
The only reason the interference is so regular is that there's a steady
>
stream of eighth-note triplets in the string section, and the piece is at a
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quarter note=130, which is really close to 2 beats/sec, which is a tempo
>
that tends to resonate strongly with people's minds.
>
>
> It sure *sounds* a lot like what I hear when I connect a MIDI Out to an
>
> Audio In ... +5V at 31250 bps.
>
>
>
> It's very hard to imagine how MIDI bits could find their way into a
>
> digital audio stream. I assume you're recording with built-in audio?
>
>
Yes, but it's the last model that had analog audio-in. Also, like I
>
mentioned above, I'm operating under the assumption that it's a purely
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software-related issue (the audio is actually coming in crystal-clear, but
>
CoreAudio just can't handle listening to the audio-input port while it's
>
busy sending MIDI data out).
>
>
>
> It's not hard to imagine there being an electrical issue (grounding? I
>
> dunno, I do software) ...
>
>
>
> You're right that it gets harder to imagine why, if it were hardware,
>
> it's not happening on 9. But the drivers on the two platforms are very
>
> different, and therefore it is possible that the hardware is being
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> configured differently.
>
>
>
> An interesting avenue of investigation would be to see if the noise,
>
> when analyzed in a sample editor, has a regular mathematical pattern.
>
> If so, then the interference is happening in the digital (i.e.
>
> software) domain. If the noise is jagged and irregular, then it's
>
> definitely coming from the analog (i.e. hardware) domain.
>
>
>
> Doug
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