Hi I have been using Kdenlive for a few weeks now, I am very impressed with what you have done here. I work with video professionally and this is on par with most professional packages.

But there is one issue that I have and that is rendering, I have recently produced three ten minute files where the quality is not important so have rendered at a relatively low quality, I am changing the format afterwards so they can play on a Windows machine. The problem I have is that a ten minute video could take well over an hour to render, during the rendering process I can't do anything else with the computer as it takes up all the resources. My computer is pretty high spec and when I used windows and Adobe Premier to render a 10 minute video it could take a fraction of the time of what it does with Kdenlive. On average with Adobe Premier to render a ten minute video it would take a couple of minutes.

Does anyone know how this can be rectified?

Give more information on the source files format and at least if you are using a dual core or quad core computer and with which profile you are rendering (Linux and Windows)...

What OS, system specifics? Is it a real-time kernel?

I am using Ubuntu 9.04

CPU is Intel(R) Celeron(R) M CPU
RAM 2GB

The initial project settings I have been using is 384x288 4:3 PAL
Frame Rate, 25/1
Pixel aspect ratio 1:1
Display aspect ratio 4:3

No matter which format I try and render to it always takes in excess of an hour, more or less the same time whether it is as an AVI or MPEG4.

Did you build FFmpeg yourself? If so, you probably want to install yasm and then rebuild. As for the process consuming your system, basically making useless, somewhere in the bug tracker I have suggested the option to launch the render process with 'nice' to lower its priority, but that is not available yet.