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meccs
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2016-06-09, 15:31
(This post was last modified: 2016-06-09, 15:44 by meccs.)
That the "Sync Setting" doesn't do anything for 23.976 @ 24Hz was news to me. Every other discussion said you need to enable it if your TV only supports 24Hz.
24 returned: frequency(29)=74250000
23.976 returned: frequency(29)=74176000
Curious question though: if I don't need "sync playback" on a RPi why does it still adjust the PLL (according to CodecInfo) if I enable it? What is it correcting if there is nothing to correct?
Does it change the HDMI clock to the 24Hz equivalent if I enable "sync playback" and adjusts the PLL to correct it (acts basically if the RPi does only support 24Hz)? I have to test this, anything else wouldn't make sense.
Edit: Clock is the same with and without "Sync Playback". So the question is still: why does it still adjust the PLL if the HDMI clock is correct? (23.976 played at TV with 24Hz)
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"sync playback to display" enables resampling to keep audio/video in sync.
When display and video exactly match this doesn't do much, although there is a little adjustment done at start of playback to get audio/video offsets down to zero and presentation times at mid-point of vsyncs (may be heard as an audio warble).
This assumes a perfect file. Some files that have been through a few conversion steps or have had adverts cut out may have glitches in the timestamps which the resampling can correct for.
It also can handle the 24fps video on 50Hz display (by speeding audio up by 4%), and other minor speed adjustments to get video and display synced.
If "adjust display refresh rate" is enabled, then the correct 23.976Hz or 24Hz will be chosen regardless of other settings. It makes no sense to use 24Hz when the video is known to be 23.976Hz.
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2020-10-18, 21:06
(This post was last modified: 2022-01-16, 16:56 by Arkanon.)
I've just come across this problem with an old pi 2 I've set up as a media center with a 5.1 HT system. To get dolby 5.1 I need to enable transcoding, which can only be done using MMAL/Videoplayer and not OMXplayer. On the latest Libreelec MMAL still exhibits this frame skipping everyone's described. no longer an issue.