Audio Filter Overrides - Feature Requests - CHDK Forum

Audio Filter Overrides

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Audio Filter Overrides
« on: 09 / April / 2010, 21:23:05 »
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On my particular Canon (SD780IS), and likely others, the audio recorded along with the video is aggressively compressed (as in dynamic range) and and highpassed. I find this rather sad, as it's recorded in 44.1khz-16bit PCM. This should be high quality (CD, in fact, minus stereo) but instead sounds rather painful whenever there's music or percussive sounds anywhere in the movie. It would be excellent if either of these filters could be turned off, and in the case of the Dynamic Range Compression, a volume/sensitivity/trim setting implemented. (This is necessary, because without the compression, it'd clip like mad if you weren't careful.) I'm not yet experienced enough at hardware hacking to try it myself, but I'm getting there (that's what college is for, supposedly)

If this would be better moved to another topic, I apologize. A quick search for "Dynamic Range Compression" and "Highpass" yielded nothing related, but wasn't super thorough.

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Offline fudgey

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Re: Audio Filter Overrides
« Reply #1 on: 10 / April / 2010, 05:59:32 »
Older thread about this (there may be others, this was the first match I found):
http://chdk.setepontos.com/index.php/topic,2433.msg22519.html#msg22519

In short: currently we can't do this and there's probably nobody working on it either.

It may be physically possible to control the audio chip (or the DSP section of the Digic if some of it is not done in the external audio chip) but we don't know how. Canon uses and has used a rather wide variety of chips for audio input, meaning it will likely only help a small portion of users if we learn to control one chip.

 

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