I recently bought season 1-9 of The Walking Dead on Blu-ray and muxed the episodes into a mkv file. However I noticed in some seasons the pitch for the German audio is way too low. I did a bit of research and this is a common problem with PAL Blu-rays which come with dubbed audio (for example Lost).
As far as I understand, the German audio was "recorded" in 25 fps (you get what I mean) for broadcasting purposes and then slowed down to 23,976fps to match the original video framerate. HOWEVER some studios seem to forget to correct the pitch so while the audio is slowed down, the pitch is also too low.
The audio track is encoded in DTS-HD MA 5.1 48.0 kHz @ 1 846 kbit/s (VBR).
My question is how can I (preferably batch) re-encode the audio with pitch correction but without the PAL speedup since the audio already matches the framerate of the video track?
I don't know what settings I should use, don't even know the unit for this (is it semitones?) and what software would be best to use for minimal quality loss.
If anyone can help me with this I'd be really grateful because there's no way I can make it through a whole season with this audio..
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Last edited by sebastiaaan; 17th Aug 2021 at 06:59.
Some background information; the pitch correction is actually not necessarily "forgotten", but it's quite plausible it was done without pitch correction on purpose. And the reason for that is, it is quite tricky to do a speed change (either direction) with pitch correction on anything other than plain stereo or mono audio without messing up the temporal placement of surround sounds. In other words without destroying the integrity of the surround sounds when listened to on a 5 speaker + LFE setup.
A pitch correction is always a trade-off. It can be done so that there is no temporal displacement between channels but this is quite prone to artifacts from the pitch correction itself and might sound obviously wrong occasionally.
I myself had the issue when converting 24p Blu-rays to 25p PAL DVDs with speedup. I actually decided to do a downmix to stereo first and then do a pitch corrected speedup, because I would be listening to it on a 2.1 setup only anyways. This results in a pretty much perfect audio for stereo playback.
Therefore, in case you are going to listen to this on a 2.0 or 2.1 setup or headphones, I would consider a downmix if I was you. It makes things a whole lot easier. If you need proper 5.1 that sounds great on a 5.1 setup then good luck with that.
Last edited by Skiller; 17th Aug 2021 at 09:19.
-speed up picture to 25fps (which is not visible to human eyes)
-speed up the sound easily by resampling with semitone up (back to where it came from)
This is clearly the cleanest solution. Dubs that had been recorded for 25fps (mostly tv-series) also sound too slow on 23.976fps, not only too low.