Hey hey,
I have digitised a few last tapes. The sound isn't too bad, but all tapes
appear to be a little too bass heavy. Since I only work in the terminal I
approach the issue with Csound that provides a lot of tools. All kinds of
filters, rms/peak metres, an lufs metre and more.
First: did I miss an obvious commandline tool that would produce a
reasonable solution for that?
There are two main issues that I try to improve halfway automatically. 1.
Sometimes the stereo balance is a little wrong with one channel being slightly
louder than the other. 2. Imrpoving the frequency spectrum, flattening it a
little bit.
For 1. I have started by taking the file's peak of both channels seperately
and simply multiplying them so the peaks match. Over a whole tape side this
should be approximately the same. Or should I go with a different measurement?
lufs integrated loudness, momentary or short term maximums?
For the second issue, I am unsure. I have split the audio into frequency bands
using octaves, more or less. So the first band goes up to 100Hz, the next to
200, then 400, 800 and so on. I have used Csound's tone and atone filters:
atone highpass filter:
https://csound.com/manual/atone.html
and the matching tone lowpass filter:
https://csound.com/manual/tone.html
Then on each band for each channel I run the lufs metre, storing the maximum
momentary and short term values and the integrated loudness.
Though I wonder: are the frequency ranges and type of filter reasonable? If so
how would I approximate a reasonably flat spectrum? Which values to
compare to what? I mean: what kind of measurement to use and should I
compare adjecent bands and extrapolate fitting values from that or
compare one frequency band's measurement to the same measurement on the
unprocessed full-band audio?
Any hints and practical suggestions are very welcome.
Thank you and best wishes,
jeanette
--
* Website: http://juliencoder.de - for summer is a state of sound
* Youtube: https://www.youtube.com/channel/UCMS4rfGrTwz8W7jhC1Jnv7g
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* GitHub: https://github.com/jeanette-c
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