It takes a lot of time to render to webm and eventually crashes, even if the projects has no effects just some clips to put together. I have a core i7 4.5ghz 8cpus, 8gb ddr3, ATI 1gb.

My cpu gets overheated and the pc freeze. I suspect the video-card is as well since the monitor shuts down lie losing signal many times.

It only happens when it takes a lot of time to render a file (20-30 min and over).

Thing is I need webm since has the best quality at a very low file size.

I changed the threads from 1 to 8 and still the same problem.

What version of kdenlive and MLT? Distro version or mac?

So this sounds like a hardware issue !!! Is your fan working properly?

Version 0.9.6
Ubuntu 12.04

MLT ? Am sorry do not know where to look for that (new to linux).

The fan is working properly. Perhaps this happened since the last kdenlive update because I rendered many clips before. It is taking way to long to render now : a 40 min video takes about 3-4 hours, considering that the video has no effects applied. And it seems to make no difference if I use 2 threads or 8. Same speed, only difference is more likely to crash when I use all 8 cores since the cpu temperature raises a lot.

in a terminal

melt -version

I just rendered a 49sec mp4 clip to webm and it took 1min 11secs. Which is a pretty normal render time for my machine.
So I cant reproduce your issue.

kdenlive 0.9.6-0ubuntu0~sunab~precise1
frei0r 1.4.0+git20130403.245bb387-0ubuntu0~sunab~precise1
melt 0.8.9+git20130413.3d1f9695-0ubuntu0~sunab~precise1

It might be a change in ffmpeg - because I think that is what is used to do the rendering.

you can find the version with ffmpeg -v in a terminal
Mine is 0.8.6-4:0.8.6-0ubuntu0.12.04.1,

3-4hrs for 40mins of video does seem a long time. What format is the source material in?

melt 0.8.8

The clip I want to render is WEBM, I need to cut some parts of it, and render it again in WEBM.

You say it only happens on big render jobs and you say the cpu overheats. These two things suggest that it is a hardware problem - the job is using lots of CPU (as video renders always do) and over a long period this causes the heat to build up in the CPU and then the the PC shuts itself down to prevent over heating.

Have you tried rendering the same 40min video to other formats?

Have you tried rendering different source video format?

ie is it only WEBM?

You are ruling out hardware issues because you have successfully rendered before. But it could just as easily be a new hardware issue as it could be a new software update issue.

Rendered webm to webm 34secs of footage in 41sec render time. So webm as a source works for me.

Try running system tests. Ubuntu has "System Testing" that can run tests on bits of hardware.

Am trying to render again that webm and is doing this for about 2 hours now and it says there are 3 more hours to render. My cpu is starting to overheat and I use only 1 threads now. I tried other formats, seems the same, the render is very very slow. If it was a hardware problem at least the render should not last so long. Few weeks ago it seems to render much faster.

I noticed that it takes 2 minutes or so to even start the render for any video I tried or format.

Will try to run a system test tomorrow though am not sure how to, but will search the web for that.

". If it was a hardware problem at least the render should not last so long."
Unless when CPU gets hot it slows it self down to prevent it killing itself?
Not sure if CPUs do this but they do keep track of how hot they are

webM encoding via libvpx is painfully slow and inefficient. h264 is a far better option unless there's some really really important reason to use webM.

But would suggest encoding to a high quality dnxhd, x264 intermediate, lossless x264 even, from kdenlive to bake all the effects and transitions etc in once. Then reencode using the HQ intermediate to required output formats using ffmpeg, x264, handbrake etc because a good portion of the encoding time is also taken up with working through the processing effects and transitions, color space conversions etc, personally I really only want to do that once.

I know you say this is a quick edit, cutting webM, no effects but the principle remains.

I left that clip to render overnight and I see it rendered it in 4 hours total. The clip was 40 min long.

I need to use webm since has the bets quality for the lowest file size, and I need the lowest filesize for a great quality....x264 always is much worst quality and bigger filesize.

I will render the same clip sing x264 to see the result but I tried before and teh quality was worst and filesize bigger.

I rendered many videos in different formats, seems to be slow for all formats. Am not sure why is 4 times slower than a month ago.