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I have a video (720p) that is 37 minutes long, with a bitrate of ~3000kb/s.

This video is a game recording, so 37 minutes worth of this footage was written in 37 minutes, while other extremely CPU, GPU and hard-drive intensive operations were occurring.

If the recording program can record and output at the same rate as is being played, I don't understand why rendering with blender at the same exact settings, same codec, same container type, same bitrate and size, the only difference being that I removed about 4 seconds from the beginning, is going to take 5.3 hours to render.

I've disabled every feature under user preferences that are said to increase performance, I disabled rendering of the 3D scene (which is empty anyways). I set the sequencer memory cashe limit higher, I've increased the number of prefetch frame which is supposed to help with multicore rendering.

What else can I do to make the rendering faster? I've used blender for years for 3D, and I'm getting into recording videos for YouTube, all the good programs for video editing are very expensive. But those programs can render 37 minute videos in 10-20 minutes, not 5.3 hours. I don't understand why it's so slow, it's so slow to the point it's unusable.

Replies to Comments

@user277143: My guess: try increasing the cache of blender itself too (alongside the Sequencer's cache). Also, having meshes in the scene will cause them to be reloaded for every frame. That can cause problems. So, go to the 3D-view and delete everything. Also, off topic, check the resolution multiplier in the render settings. I have screwed up many sequence renders by having it at 50%.

I have already done the cache of Blender as well. I already have nothing in the 3D scene, and I even have that entire render layer disabled in the outliner.

@gandalf3: Related:

I've seen all of those, none of them provide any help that has altered the result. Those issues were due to bugs, or a settings issue. In the past I've been able to render at around 50-60 outputted frames per second, so rendering a 30 minute video in 15-18 minutes. Only in the last 3 weeks has this started to take this long, so there is a way somehow to speed it up, and I haven't touched any settings on the program.

Community
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D3_JMultiply
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  • My guess: try increasing the cache of blender itself too (alongside the Sequencer's cache). Also, having meshes in the scene will cause them to be reloaded for every frame. That can cause problems. So, go to the 3D-view and delete everything. Also, off topic, check the ressolution multiplier in the render settings. I have screwed up many secuence renders by having it at 50%. – Mörkö Sep 16 '15 at 05:58
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    Related: http://blender.stackexchange.com/q/7738/599, http://blender.stackexchange.com/q/15835/599, http://blender.stackexchange.com/q/27855/599, http://blender.stackexchange.com/q/27007/599, and http://blender.stackexchange.com/q/19627/599 – gandalf3 Sep 16 '15 at 07:31
  • Just get Fusion, it's free. It's like Nuke or AfterFX. Don't use Blender sequencer, as you said it's useless when Fusion is free. – Jaroslav Jerryno Novotny Sep 16 '15 at 19:15
  • Addressed the comments at bottom of question. – D3_JMultiply Sep 18 '15 at 02:18
  • @D3_JMultiply If it's slowing down for no reason (identical setup performs significantly faster in old version than latest version), then that sounds like a regression which should be reported. – gandalf3 Sep 18 '15 at 18:18
  • That's the thing, it's also the same version. Been using 2.74 since it came out, I know 2.76 is out, just never upgraded, maybe upgrading will have performance increases. For now I don't really struggle too much with the render time, I just render overnight. – D3_JMultiply Sep 18 '15 at 18:33
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    Have you recently checked Antialiasing? It needs quite some performance. Is your input and output resolution the exact same? Scaling every frame takes time as well. When you Crop/Offset your footage, will it move our stay at its place? Does this help? Is your footage on a fragmented hard drive? Can you unchecked Compositing in your Render Settings? Have you tried a test render in a fresh factory reset startup file? Try upgrading to a recent build as there have been some VSE performance improvements lately. – Samoth Jan 22 '16 at 23:59
  • Any updates to this question? It'd be nice to get it off the "unanswered" list. – Matt May 19 '16 at 21:35
  • If you are editing video I suggest you use a dedicated video editing app. If you are using Windows or Mac, the free version of Resolve would make your life easier... –  May 20 '16 at 00:05
  • @Matt No, feel free to close this if you wish. I was mostly trying to figure out why it's so slow. i mean the Blender Foundation uses the sequencer with their own open movie projects, so i don't understand why it would be so under-optimized. It's not that hard to process frames, so I simply don't get what the sequencer is doing that makes it so slow. – D3_JMultiply May 27 '16 at 22:28
  • @cegaton I've tried a lot of software, and all free ones I can find always seem to have issues. That's why i tried Blender, because it's a software I've used for over 12 years. I'll check out Resolve though, thanks. – D3_JMultiply May 27 '16 at 22:28
  • @D3_JMultiply I use blender constantly too, but It's important to be aware of its shortcomings. It's an amazing 3D creation suite, but not a full fledged, optimized and responsive video editing app. –  May 27 '16 at 22:38
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    @cegaton yeah, I'm aware, I don't use it anymore really for videos. However my confusion still exists. The Blender Foundation Open-Movie projects have all been 100% Blender except the audio design. Modeling, Animation, Rendering, Compositing, Sequencing, etc, all done in Blender. If the Blender Foundation themselves is using the sequencer for such, why would they not spend time optimizing it. they stated in the past that the Open-Projects are to use Blender for a real-world project, specifically to see what parts of it need to be further developed or added to. So why is is still so slow, idk. – D3_JMultiply May 27 '16 at 23:10
  • @cegaton um, the page for the free version of Resolve says 1 TB disk spare required, 16 GB memory recommended 8 GB minimum, i7 recommended. Looks like a good program, but that's even pushing higher-end computers. – D3_JMultiply May 27 '16 at 23:58
  • @D3_JMultiply I'm not interested in it being closed... I'm interested in it being answered ;-) I've used the VSE a lot, too. And especially because the Blender movies have used it, I suspect that there's a setting or something that needs to be changed. If it WERE this slow simply because of a bug, they WOULD have fixed it. Since they HAVEN'T I think it's reasonable to conclude that it's a UI/User issue, rather than a software issue. – Matt May 31 '16 at 13:25
  • @Matt Then I'm unsure, I have literally turned off and on essentially every single option in blender, including ones you can only change through the console or python, and it still has issues. Although, what I will say is that there's a chance that it may be related to file formats. Using Intermediate formats or distribution formats. In Intermediate formats (which are designed for editing) it uses intra-frame compression instead of inter-frame compression, allowing each frame to be obtained selectively from the file, instead of being calculated based on other frames, which speeds up gathering. – D3_JMultiply Jun 01 '16 at 00:59
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    Although at the same time, the issue with distribution formats occurs mainly when dealing with changing position randomly, and less when exporting. Distribution formats are made to be compressed, but fast to read when frames are being read in sequence, being played back. And in rendering, it should be able to work the same, only instead of playing the frame back, exporting it to a file. But if Blender was designed to work with Intermediate file formats, then depending on implementation, delivery formats (like MPEG-4 formats) may suffer in performance. I'll check into this theory. – D3_JMultiply Jun 01 '16 at 01:04
  • I've not had any performance trouble with intermediate formats, so I doubt that's the cause of your trouble :-/ But it's worth looking into. Any chance you could share your blender file and source video? Or a representative sample of your source video? – Matt Jun 01 '16 at 13:11
  • No, I mean performance issues from NOT using intermediate formats. for example I'm using a .ts file (Transport Stream) which is an H.264 container and thus uses inter-frame compression, and is not optimized to be able to pick a frame out from anywhere in the file. Intermediate formats on the other hand only use intra-frame compression and you can lookup a specific frame without needing to calculate other frames first. – D3_JMultiply Jun 03 '16 at 21:27
  • I had a lot of trouble converting a game recorded movie in the VSE and ended up texturing a plane with the movie and using the camera view to "film" it again at my preferred 25 fps, BUT - rendering it with the OpenGL render. It worked and played through whilst rewriting at pretty much normal speed. The output was AVI as I recall and was converted to mp4 externally for a superior result. – Edgel3D Mar 19 '17 at 23:33
  • Interesting Edgel3D, may have to check that out, if that's the case, then they're doing something strange with the VSE, if the 3D render can go faster than just a flat image rendering. Either way, this is a bit old, but thanks for the info. – D3_JMultiply Mar 22 '17 at 05:05
  • have you tried to create proxy files for the videos that you're editing. I found that helps tremendously. The playback is at the correct frame rate. https://blender.stackexchange.com/questions/32203/how-do-i-use-proxies-in-the-vse-correctly – Eternity Tomorrow May 17 '17 at 01:02
  • This has been answered many times and covers a vast number of details. Codec, nature of frame layout, scaling, etc. all contribute to the decoding speed. It isn't as simple as suggesting that all I framed encodes would be fine. – troy_s Sep 08 '17 at 20:40
  • @troy_s this question was posted over 2 years ago, before having posted this I searched and at that time there were not other questions on this topic that had been asked. If you re-read my replies to comments someone suggested a few related questions, none of which actually were experiencing the same issue I was. – D3_JMultiply Sep 16 '17 at 20:15
  • Gotcha. I should date check on the necromancers. My bad. Apologies. Hopefully at some point the VSE can be made fully offline and will dump all but two or three codecs to support. – troy_s Sep 16 '17 at 21:52

3 Answers3

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Keep UI

  • render with "Keep UI" option in the Render properties panel under Display (Just don't let blender display the rendering process in any window.) That was a noticeable speed up for me.

Multicore rendering

  • use one of the available scripts for multi-core rendering. Basically a script that opens as many instances of Blender as you have cpu cores or as many as you specify. (Blender use for VSE render only one core of CPU by default. So even with a two core processor you get only half the render time. If you have an 8core CPU it would be great speed boost for you.)

Parallel Render - Addon, simple to use, but it generates separate movie files - one for each blender instance (that runs on each core separately). After download, installation, enable ... you run this script with SPACEBAR search, type "parallel ..."

enter image description here

video_editor_render_script - A python script whit it you need to arrange a few things first, but then it's a ONE-CLICK option with one animation file. (Namely -download also ffmpeg and specify paths to blender and to ffmpeg in the script. Just follow instructions. In general it also generates separate files for each core first, but than use ffmpeg to merge them in one file.)

vklidu
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Try creating a proxy to reduce the load on your system.

If that doesn't work, there isn't much more you can do. Blender was not designed for video editing, it was an afterthought. Therefore it lacks certain things (like fast scrubbing through clips) that other software packages have (Vegas, Premiere, FCPX, etc).

I'm probably not explaining this very well, but what I'm trying to say is that Blender was designed as a 3D modelling and animation application, not a video NLE. Therefore it's performance in that department is severely lacking. I tried editing gaming footage in Blender and the VSE was just so painfully slow even on a high end system. It was a real shame.

Pyroglyph
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You can't do a straight comparison of a game to a Blender render,
because a lot of the procedures that Blender does,
have already been done before you get your game.

Essentially the game has had textures pre-baked with bump-mapping,
normals, levels-of-detail to reduce polygon count in the distance...

The game has optimized framerate by doing all those steps beforehand.

Doyousketch2
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  • This is an older question and you misunderstood. I know games do lots of stuff beforehand, but what I'm stating is that A game has to load more textures into memory, has to physically render 3D geometry, perform shading, handle inputs, etc. All the blender sequencer is doing during editing a video vile is reading in an array of bytes as pixels and outputting an array of pixels, and in my case wasn't even performing any operation on them other than discarding the frames I cut out. The point is that what a game does is many times more intensive, and yet it still outputs more. – D3_JMultiply Mar 22 '17 at 04:59
  • I would understand Blender being slow is I was adding effects or rendering 3D geometry onto the sequencer, but I'm not, Blender is simply not optimized, considering pretty much any video editor can output frames literally tens of times faster, Blender is running some routine that it doesn't need to for what I've given it to process, that's an inefficiency. Last of all, I was never comparing the game output to the video editing output, I'm saying the recording software I use can read the screen and output at 30 fps, but Blender, doing less work, can't even get 10 frames outputted per second. – D3_JMultiply Mar 22 '17 at 05:03