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I got some footage from a band who played playback on a stage for a music video. Now I am putting it all together in VSE with the audiofile (studio recording) they used for playback.

My machine is usually quite capable of handling FullHD video (GTX 970, 32 GB Ram, i7 4790K), but this time the video playback during editing starts to lag as hell when the current frame enters a new strip. That's quite annoying, since these transitions are the parts I am most interested in.

Here an example - to the left of the green marker: smooth 25 FPS playback. Once entering the second stip - image stops for more than 1 second and continues stuttering (not very helpful) playback afterwards. It basically skips the middle strip completely during playback.

enter image description here

Some notes, which may help encircle the problem:

  1. I remember a "Prefetch Frames" setting, which should preload a certain number of frames into memory. For some reason, this has vanished in 2.79.
  2. The Memory Cache Limit in User Preferences -> System is set to 16000, so I don't expect this to be a problem.
  3. I guessed that blender is trying to load something from harddisk - but when I look at the Windows Resource Monitor and filter for "blender.exe", it shows no hard disk activities.
  4. The files I am working with are quite long (4-5 Min), and I only am interested in sub-sequences in the second half. Maybe this is some codec-video seeking issue!?
  5. Speaking of codecs: I have files with .mov and .mp4 endings. According to the tool MediaInfo, the .mov is a MPEG-4 (Quicktime) Container with an AVC ([email protected])(CABAC/2 Ref Frames) video stream and the .mp4 files are MPEG-4 (Base Media) containers with AVC ([email protected])(CABAC/16 Ref Frames) video streams.
  6. I am using soft cuts (K and not shift-K).
  7. In the movie clip editor, there is a purple stipe at the bottom of the screen, which shows how much frames are loaded already. At least I understood it like that. Example below. Probably this is what's happening in the VSE in my case - not loaded frames. But there is no similar visual feedback for the user in the VSE. Right?! enter image description here

Any suggestions to ensure smooth playback WITHOUT using proxies are highly appreciated. I would like to avoid the overhead of generating temporary files or re-converting the footage to other codecs.

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1 Answer 1

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Encode your video files with post-production codec.

First thing you should look at is what a video codec you use. Every codec has a different use. In fact, most codecs that compress the video stream are only for linear playback.

So when you try to use codec what designed just for playing in videoplayer, it can be slow in non-linear playback. If you need fast workflow, use a special post-production codec. In blender good variant is a Avid DNxHD codec. Also you can try Apple ProRes

Unlike other programs, in the blender you must process the source material manually (if necessary). If you use another application, you will see, that most other programs will re-encode the video before adding it to the editing line. In this there are pluses and minuses, but this is so.

Therefore, you still need to transcode the video, but next time you will encode into the right format. If you use files, that are not optimized to work in the video editor, there are no ways to make the workflow fast.

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  • $\begingroup$ Thanks for your feedback. But well, I had like 30 GB of footage and no choice of the codec. I had to scale down some 4K footage to FullHD before starting to edit, this took 5 to 6 hours. Passing the whole thing through whatever converter is no option for me, this would take a whole day I guess. $\endgroup$
    – AeroLynx
    Oct 21, 2017 at 22:22
  • $\begingroup$ Blender is light years behind other video editing apps when it comes to versatility, compatibility and real time performance orplayback. Editing events with different codecs, different frame rates, or mismatched dimensions will slow things down. You could increase the memory cache limit and enable "Frame Dropping" to get a bit a bit smoother playback (at the cost of accuracy)... but in my opininon using a dedicated video editing app (resolve free, premiere, etc) will be a much more rewarding experience. In resolve you should be able to work in 4k wtih no proxies or transcoding... $\endgroup$
    – user1853
    Oct 21, 2017 at 22:54
  • $\begingroup$ Thanks for the hint. Frame dropping is no option, I want to see every single frame in sync with the audio - that's crucial. I always enjoyed the lightweight style of the VSE. Most of the time I just do simple cuts, transitions and some audio synching with the drawform visualisation. As a hobbyist, that has been totally fine so far. However, I will certainly take a look at Resolve! Looks top-notch. $\endgroup$
    – AeroLynx
    Oct 22, 2017 at 9:28
  • $\begingroup$ If you use another application, you will see, that most other programs will re-encode the video before adding it to the editing line. Therefore, you still need to transcode the video, but next time you will encode into the right format $\endgroup$
    – Crantisz
    Oct 22, 2017 at 10:27
  • $\begingroup$ @Crantisz not all editing app need to re-encode. Resolve and Premiere can do realtime playback of different codecs, framerates or frame format on the fly out of the original files... Only on heavy processing sections (some effects or multiple layers) do they need to create files optimized for playback. $\endgroup$
    – user1853
    Oct 22, 2017 at 15:44

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