So I completed a workflow that enables FFmpeg batch smart-rendering of a custom list of files and edit-point generated in Sony Vegas Pro. It's possible that the workflow could be adapted to work with a standard EDL exported by other NLEs too. See http://www.sonycreativesoftware.com/forums/showmessage.asp?messageid=932826
A couple of updates on this....
I have worked with the author of Vegasaur to improve its Smart Trim functionality, which uses FFmpeg under the hood. If you use Sony Vegas Pro then Vegasaur 2.4 now provides an effective solution to smart rendering GH4 footage, but note that there are still issues with the ends of the files that need to be dealt with. See my latest posts on http://www.sonycreativesoftware.com/forums/showmessage.asp?messageid=932826 for full details.
Vegasaur: http://vegasaur.com/Vegasaur
Also, I tested the current trial version of VideoReDo with some GH4 MP4 UHD 30p footage. In my first test, it crashed during the render. I did then manage to trim and render 2 files, but they do not decode properly in Vegas Pro 13. Much of them appear as green thumbnails on the timeline, they don't play back properly, and the end is not quantized. So I really don't have much faith in VideoReDo for doing this. I'm also doubtful that there any way to get an edit list into it from an NLE.
TMPGEnc MPEG Smart Renderer 5 preview trial version is out. http://tmpgenc.pegasys-inc.com/en/product/tmsr5.html Worth a try. Would be disappointing if it still doesn't work with GH4 UHD/4K footage.
I have no technical knowledge on these matters but I have noticed that that the version of PHOTOfunSTUDIO that comes with the G7 (Version 9.7PE) is far quicker at trimming clips than previous versions I have used. Does that suggest it is smart-rendering the clips?
Have a look at Slicer - http://hdcinematics.com/Slicer-UserGuide.html
I just tested TMPGEnc Smart Render 5.0.7.9, the latest version. Unlike my previous test, it does now "mostly" smart render GH4 footage. However with my UHD 30p MP4 clips it re-renders the first 64 to 74 frames (more than 2 seconds) and the final 2 to 12 frames. It does make a good job of the re-render though, and the quality of the re-rendered part can be set. The main body of the clips is identical to the original, as is the audio. And when the rendered clips are decoded in Vegas Pro there are no repeat or glitched frames that need trimming, as happens with FFmpeg.
However the bigger problem for me is that the batch list format (*.tmsr5b) is a closed/compiled/encrypted format so it's impossible to get a batch list into it in text format from another NLE. This makes it useless for my purposes.
My solution using FFmpeg from Vegas Pro has been moved to https://www.vegascreativesoftware.info/us/forum/smart-rendering-in-a-batch-with-ffmpeg-gh4-etc--101381/ since Magix bought the Vegas.
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