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Declipping audio with Postfish

I was recently asked to do a basic master of a live recording. It was captured on a Zoom portable microphone and the audio clipped quite a bit at various times during the performance. Usually the solution is simply to rerecord but in this instance that was not really an option.

I searched the internet a while back for a FOSS declipping tool and stumbled upon Postfish.

First I lowered the gain of the audio I got sent by 10dB and then ran the Postfish declipper over it. Here is a visual comparison of the before and after:

I wasn't expecting any sort of magic from the tool as the audio simply wasn't captured completely in the first place. That said, I'm pretty happy with the result. The audio opened up a fair amount and didn't sound as harshly limited at it did before. Anything closer to a more listenable sound is good in my books.

First you will need to grab the code from the repository and compile it:
svn checkout https://svn.xiph.org/trunk/postfish/
cd postfish
make

You need to specify the input and output file locations from the command line. For example:
./postfish in.wav > out.wav
Once you have adjusted all the effects to your liking, you will need to click the play button to stream the audio to disk.

Here are the settings I used on the declipper:

One final thing to take note of is that you need to acivate the "Atten/Mix" effect for all the channels you need otherwise the output will be muted.

Here is the result. Thank you Postfish.

Published: Aug. 6, 2016

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