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I'm editing an HDR project in Adobe Premiere Pro 2020 and I'm having issues with preserving the HDR data while transcoding, but that's an issue for another post. The thing is that I edit with proxies, and I usually get sync issues between the source file (H.264, CBR, high 10, level 5, UHD, 4:2:0) and the proxies (for example, sometimes the proxy has a several seconds delay from the source file, which defeats all purposes for editing).

It appears to have something to do with the codec used or a setting while transcoding the proxies (or source file), because those delays differ depending on those things. For example, Prores gets sync issues of several seconds (useless for editing in this case), DNxHR is better but also has sync issues. I've tried every codec possible and tweak almost every setting I've come across, and the one thing I noticed is that, when using DNxHR for both the source file and proxy, I get no sync issues. The same happens if I use AVI uncompressed for the proxies and DNxHR for the source file, no sync issues. That lead me to believe that it may be related to VBR (source file is CBR, and the problem seem to get worse with VBR codecs for proxies) vs CBR, or something else that I'm not aware of.

Because of the color problem it's not an option to transcode the source file to a high quality DNxHR 444 or HQX file and use DNxHR LB as proxies (that combination doesn't produce sync issues), and working with an UHD HDR H.264 file as source file without proxies is obviously painfully slow to edit.

Any ideas of what could be causing the sync issues? Anyone with the same problem? For the record, the same happens when using Adobe Premiere Pro 2019.

Thanks in advance.

PS: Is intra-frame H.264 a good option for using it as source file? I could work with that without proxies if it's fast for editing, but I don't know if it has any downside compared to DNxHR or Prores as an "intermediate" codec (nobody seem to use it for editing, and I don't know why). I don't seem to find useful info on this regard.

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