Just wanting to get some feedback on this.

With a quad-core Intel Core i7-6600U running at 2.6 GHz it takes me about an hour to an hour and a half to render a less-than-7 minute video. Nothing terribly fancy. Just a few cuts on a 1920x1080 50Hz video. Running Kdenlive 20.4.3 on a Linux 5.4.48 kernel. Performance governor and all four cores at 2.6 GHz.

Any thoughts as to what on earth is going on, or avenues to pursue?

can you give us some more infos about project? resolution? output codec/format?

bartoloni wrote:can you give us some more infos about project? resolution? output codec/format?

Sure: Resolution is 1920x1080 @50 fps (as noted), have tried WebM, MP4, MPEG-2, and lossless H.264 (libx264+aac). MP4 fares the best, but is still attrocious.

Thanks for taking a look at this!

zmjbs wrote:

bartoloni wrote:can you give us some more infos about project? resolution? output codec/format?

Sure: Resolution is 1920x1080 @50 fps (as noted), have tried WebM, MP4, MPEG-2, and lossless H.264 (libx264+aac). MP4 fares the best, but is still attrocious.

What is the source format? MP4? What effects, compositions etc. are in the project? Any transformations? Keyframes?
Video editing is a very computational intensive undertaking. Your CPU has 2 cores with multi-threading making it look like there are 4 cores. How much RAM do you have? And what is the make and model of your HDD/SSD?

berndmj wrote:What is the source format? MP4? What effects, compositions etc. are in the project? Any transformations? Keyframes?
Video editing is a very computational intensive undertaking. Your CPU has 2 cores with multi-threading making it look like there are 4 cores. How much RAM do you have? And what is the make and model of your HDD/SSD?

Source: An MP4 (audio removed for rendering) and an MP3 audio track.

No effects, transformations or anything of the sort. Just a video track and an audio track rendered as the same resolution and framerate as the original.

16 GB of RAM for which ramspeed gives me:
INTEGER & WRITING 4096 Kb block: 14052.13 MB/s
INTEGER & READING 4096 Kb block: 17501.14 MB/s

The hard drive is a 512 GB Toshiba XG4 (THNSF5512GPUK) solid state disk. The hdparm utility gives me:
Timing cached reads: 14586 MB in 1.99 seconds = 7311.82 MB/sec
Timing buffered disk reads: 3146 MB in 3.00 seconds = 1048.06 MB/sec
which seems decent from what I've seen from elsewhere.

I've rendered the same two clips on an inferior machine (slower CPU, less memory) running Kdenlive under Windows and it completes the task in under 10 minutes...

Link to another topic with similar issues: viewtopic.php?f=272&t=168327&p=440117#p440117

bartoloni wrote:Link to another topic with similar issues: viewtopic.php?f=272&t=168327&p=440117#p440117

Thanks! Disabling parallel processing (checkbox at the bottom of the dialog that pops up when pressing the render button) cut the render time down to around 15 minutes!

Don't know how the Windows machine would fare with this exact project, but I think it (despite much lower specs) would still quite easily beat this. Perhaps that's just the difference between a working and broken parallel processing?

If it's this buggy, it should possibly be off by default on Linux or come with a warning of some sort, or is it just on rare systems that the problem arises? Then perhaps put together a blacklist?

Also, is there a standard project that one can use to benchmark one's system? Would be nice to see if this is a decent performance for a fairly recent i7 with 16 GB of RAM to help track down the issue.