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QuickTime and MP4 audio sync
I’m not sure if anyone’s noticed this, too, but lately audio sync is horrible with H.264 MP4 files playing in QuickTime player and VLC. The same files are fine in Switch. I can upload those files to Frame and the playback from Frame’s player is also fine. This is on Catalina Macs. I haven’t tested this too much with Big Sur, but it wouldn’t surprise me if it happens there, too. These are typically files created via Premiere Pro direct exports or through Adobe Media Encoder. Thoughts?
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8 Replies
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I’m not having any issues with those files from Resolve into VLC on Windows or Linux at 24 or 25fps. Pr can do weird things with variable frame rates? Maybe they have a metadata bug in Pr/ Media Encoder.
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Thanks. I’ll have to test a few different encoders.
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I’ve not tried it yet, but Adam Plouff’s Battle Axe has a new compression tool, Anubis.
https://www.battleaxe.co/anubis
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I also use Shutter Encoder for some background renders while I keep going in Resolve. They also have a Linux version which I run on my laptop.
https://www.shutterencoder.com/en/#downloads -
I can never figure out where sync problems like this originate. When I make stuff for youtube and facebook, I’m making mp4 files and they play with proper synch locally. Watching them stream on my facebook feed, they almost always look like the lip synch is off to me.
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I don’t see any sync problems on Catalina or Big Sur on my iMac Pro for Premiere-encoded H264 files viewed in Quicktime. I just tested a 4k/23.98 ProRes 422 file from a Sony A7RIII and Ninja V, imported to Premiere 15.1.0, exported as 4k/23.98 H264, and it played in sync on Quicktime and VLC.
If using an external monitor with audio separate from the monitor, there is a theoretical problem due to video processing delays in the monitor (esp. TV-type monitors). Sometimes this can vary randomly with scene type, as the monitor has fluctuating video processing latency. If the monitor is driven by external video hardware (Blackmagic, AJA, etc) that is another possible source. One way to test that is use local playback on an iMac or similar computer and no external or wireless audio.
If a file containing a slate clap (or hand clap) is imported to Premiere, FCP or any other NLE, the audio waveform should line up with the clap. If it lines up but there’s an audible sync problem when played back, that implies an A/V delay problem during playback. Usually that happens as video latency (IOW audio leads video). Observing whether video is late or audio is late can be a clue about possible causes. It can also be a clue to observe whether the mis-sync is constant or varies over the program.
If it appears mis-synced during local playback but in sync after upload and during streaming playback, maybe that’s because the streaming file has been re-encoded and is lower resolution? What if that re-encoded streaming file is downloaded and played back in Quicktime?
Are the problem files originally camera files with constant frame rate, or are they captured and encoded with variable frame rate?
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A follow-up. This is on Big Sur, too. Files are all edited and exported. These are H264 MP4 either directly exported from Premiere or encoded from ProRes masters via Media Encoder. They play fine in Switch. This happens on both local and network drives and machines with and without an audio interface for external audio. These iMacs do not have external video displays. MP4 files can be CBR or VBR encoding. 1080 or 720.
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Since Big Sur, playback on Quicktime goes out of sync while VLC player is fine. Anyone find a reason?
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