[RESOLVED] Audio out of sync for iPhone 11 videos

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olex99
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[RESOLVED] Audio out of sync for iPhone 11 videos

Post by olex99 » Thu Nov 14, 2019 6:22 am

Trying to play around with a few videos of a concert that i recorded on my iPhone 11 however the audio in the output video is out of sync. Mediainfo is reporting the framerate as 29.706 fps, however it seems to be detected in DGIndexNV as 29.970fps. I think this might be why the audio is out.

Specs:
Windows 10 1903
DGIndexNV 2053.0.0.191
Geforce GTX 1050 Ti 388.71

I can cut the video and upload it somewhere if required but thought it might be a simple config option i've missed?

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Rocky
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Re: Audio out of sync for iPhone 11 videos

Post by Rocky » Thu Nov 14, 2019 8:50 am

Please upload a sample that I can use to duplicate the issue.

olex99
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Re: Audio out of sync for iPhone 11 videos

Post by olex99 » Sat Nov 16, 2019 7:42 pm

I couldn't cut the video as it wouldn't play once cut so here is the smallest video i could get to reproduce the issue. Its about 450mb.

https://1drv.ms/u/s!AlPNVpwJyv_fjeUp5UQ ... g?e=Xcz45c

The video when loading through DGIndexNV is about a second shorter as its playing at 29.970fps where i believe the framerate is around 29.7fps.

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Rocky
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Re: Audio out of sync for iPhone 11 videos

Post by Rocky » Sat Nov 16, 2019 8:31 pm

Thank you for your stream. First thing, you are lucky it actually works with DGDecNV as it does not formally claim to support MOV containers. But here the stream is close enough to an MP4, with supported audio, that things work.

The stream has a frame rate of 29.77 fps. DGDecNV normalizes all rates that are close to standard rates to those standard ones, so it gets "corrected" to 29.97. This normalization is something needed for compatibility with Vapoursynth. But do not despair. You can simply add AssumeFPS(29.77) after the DGSource() call in your script. You will end up with that weird rate of 29.77 but there will be AV sync. You'll have to use an encoder and container that can honor that rate. High priority is to first try to find out why the device is not using a standard rate. Perhaps it can't keep up and you need to sacrifice something. Or, worst case, consider an encoding process that converts the 29.77 stream to 29.97.

olex99
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Re: Audio out of sync for iPhone 11 videos

Post by olex99 » Sat Nov 16, 2019 9:28 pm

Thank you very much for your help. I didn't even think of using AssumeFPS to get it back to the original Frame Rate. I'm actually trying to convert it to 29.970 so it can work on the tv so i might try do AsumeFPS(29.77) and then ChangeFPS(29.970). Hopefully that will do the trick.

Yeah i've never had an issue with the iphone files before. This is the first night time recording though i've done on the iphone 11. I did notice there is a flag in the settings called "Auto Low Light FPS" which apparently reduces the frame rate to 24fps in low light for "improved low light video". I've turned this off so hopefully it will stick to 30fps from now on.

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admin
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Re: Audio out of sync for iPhone 11 videos

Post by admin » Sat Nov 16, 2019 10:03 pm

Cool, oleg99, sounds like you are rocking and rolling. Maybe it might help to reduce the bitrate (if possible), as you are capturing UHD. Bullwinkle would say: 29.77? Snort!

Best Thanksgiving wishes to you and all!

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Boris
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Re: Audio out of sync for iPhone 11 videos

Post by Boris » Sat Nov 16, 2019 10:14 pm

admin?!?!?! This forum's Mr Big? :P

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Bullwinkle
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Re: Audio out of sync for iPhone 11 videos

Post by Bullwinkle » Sat Nov 16, 2019 10:22 pm

Big is as big does. Give it serious thought.

Still waiting for my gold coins. Snort.

Sharc
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Re: Audio out of sync for iPhone 11 videos

Post by Sharc » Sun Nov 17, 2019 5:34 pm

Rocky wrote:
Sat Nov 16, 2019 8:31 pm
High priority is to first try to find out why the device is not using a standard rate. Perhaps it can't keep up and you need to sacrifice something. Or, worst case, consider an encoding process that converts the 29.77 stream to 29.97.
Is the video file reported as VFR rather than CFR? The .mp4 files of my mobile phone are always reported as VFR just because one or two frames are off the expected time stamp, resulting in an odd framerate which is slightly off the standard value and reported as VFR.

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