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Audio clipping when downmixing - Printable Version

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+--- Thread: Audio clipping when downmixing (/showthread.php?tid=78546)



Audio clipping when downmixing - Wallinder - 10-16-2015

I'm running the latest stable version of OpenELEC on a Mac Mini (late 2009) which is connected to a stereo DAC via optical Toslink. I've remuxed all my Blu-ray movies with FLAC multichannel sound. Since I've 2.0 setup I'm letting Kodi/OpenELEC do the downmix for me.

Reading the documentation on: "Normalize levels on downmix"

Quote:Select how audio is downmixed, e.g. from 5.1 to 2.0. [Enabled] Maintains volume level of the original audio source however the dynamic range is compressed. [Disabled] Maintains the dynamic range of the original audio source when downmixed however volume will be lower. Note: Dynamic range is the difference between the quietest and loudest sounds in an audio source. Enable this setting if movie dialogues are barely audible.

I do not want to loose dynamic range, so I keep the option disabled. However, doing this introduces a lot of clipping in "loud" scenes. If I enable the option, I do not get any clipping. What could be causing this clipping?


Audio clipping when downmixing - Wallinder - 10-16-2015

I just did a test with eac3to using the parameters:

Code:
-downStereo -mixlfe

I remuxed the encoded two-channel audio into the movie and tested playback again. What a difference! :woohoo:
Audio is much lower (as it is described that it should be when maintaining the dynamic range) but the dynamic and bass is just amazing!
So this makes me wonder:
  • Does OpenELEC/Kodi keep the LFE when downmixing is performed?
  • Does OpenELEC/Kodi "forget" to lower the base-volume?



Audio clipping when downmixing - Wallinder - 11-02-2015

The problem still remains in OpenELEC 6.0. I think it has to do with multi-channel FLAC. I've tried downmixing a couple of videos with Dolby Digital and they do not introduce clipping.

Could it be something that only affects multi-channel FLAC?