Plot normalized waveform
The view of the waveform has proven to be very useful - in particular for onsets/offsets.
However, it doesn't appear to be normalized because in quiet tracks you don't see much.
#1 Updated by Matthias Mauch about 8 years ago
- Priority changed from Normal to High
This does not just apply to the waveform visualisation, but also to spectrogram visualisation and the actual PYIN processing, so I think normalisation is actually an important issue. Just discussing this with Simon: we would need that for our project.
So I set to high priority.
#2 Updated by Matthias Mauch about 8 years ago
So I've been looking around a little bit to get a feel how the normalisation should work.
Conceptually I think it's always going to look like this (sorry if this is obvious):
1. measure input gain
2. amplify so that new gain = x (where x is our chosen level)
Re 1: I think we should follow the Replay Gain guys, who calculate the gain of the original signal as the 95%ile of framewise (50ms) loudness measurements. This is apparently grounded in perception theory: http://wiki.hydrogenaudio.org/index.php?title=ReplayGain_specification
For simplicity we could just use the RMS on frames as our loudness measurement, so by taking the 95%ile of that we have our input gain.
Re 2: We need to decide how conservative we want to be on the output gain. If we do normalisation internally in Tony, then it's not a big issue, and we can adjust the floating point representation to look and sound right, e.g x = -10 dB, and abs values > 1 are fine. If we want to write a new file, which clips at abs values > 1, then we might need to be more conservative. x = -20dB seems to be what Brecht suggested, and in a few informal experiments on our singing data no clipping happened in that case.