Audio analysis: Move to loudness info

[wolfgangw]

As of now (v1.2014.11.21) dcp_inspect's audio analysis outputs RMS and peak values for any given reel. Which is useless in most cases.

Use loudness analysis and establish a link to B-chain:

• We want an error or a hint message saying that with the given audio levels/loudness we are too loud/too low in the cinema
• Calculate a correction value for both authoring (although we are already looking at the deliverable this will still be useful) as well as playback (CP650/750 Main Fader Knob correction)

This is in the works so expect something soon.

[matmat]

Oh, wow! This would be really nice feature. Right now I am doing this manually with ffmpegs ebur128 filter.

I have done some tests on quite a lot of commercially released DCP:s and the average "Integrated" Loudness (I) seems to be somewhere around -24.0 LUFS. Interesting to note is that for more professionally done content the Loudness Range (LRA) is much greater, i think this is probably because it correlates to the dynamic range of the sound track.

[overlookmotel]

@matmat I wonder if I could pick your brain a little?

It looks like dcp_inspect's development is halted, and I have a need for this functionality. I wondered if you could give any more info on the options you pass to ffmpeg's ebur128 filter to get a useful result?

My use case is normalizing programmes of short films so that all the films in a programme are at the same loudness.

In particular my issues are:

1. Matching loudness between stereo and 5.1 soundtracks so they play at equivalent perceived loudness in the theatre
2. Obtaining a figure in dB for how volume needs to be adjusted for each film
3. Scripting ffmpeg to adjust volume accordingly

Sorry to bother you so randomly. But I've had little success in finding solid info on this online, and it sounds like you're having success with this, so any pointers you can give would be much appreciated.