difference between project profiles and render profiles

It has never been clear to me what the difference between project profiles and render profiles is.

There is a page in the manual http://userbase.kde.org/Kdenlive/Manual/Projects_and_Files/Project_Settings that says

" You should carefully choose your project format and select the one that fits better with what you want to output. All video operations on the project (like compositing, scaling, etc) will then use this profile.

For example, if your goal is to create a DVD, you should use a DVD profile with the correct frame rate (PAL / NTSC) and display ratio (widescreen or not). "

But why should we do this? Surely it is the rendering that defines what sort of video we get.

I guess the manual page goes some way to explain what the project profile provides. Is it saying that if you don't match the project profile to the profile you render with at the end then the video operations that Kdenlive does will not be accurate because the frames per second or line count will not be correct ?

Can we be more explicit about what the project profile does?

Forums:

Can anyone explain this things? because I have the same problem.
In my project profile I have HD 720p 50frames/second and when I have to render the movie I cant find this profile format (HD 720p 50frames/second) in the render profile list!

Please help!

The project profile defines how kdenlive handles the imported files in your project.
The render profile defines the output format of your project.

While you will have only one project profile setting, you may render your project to several different output formats (each defined by one render profile).

The handling of your input files may vary depending on the project profile. So, if you choose DVD/Pal-wide and import 4:3 material it will be stretched to fit the screen, while importing the same 4:3 file into a 1024x576 pixel (size is equal to Pal-wide) project profile, kdenlive will center the clip without stretching and leave black bars left and right. Both project profiles will render properly to DVD format, mpeg4 or so. (Note: Maybe the profiles are named differently, writing without having kdenlive open).

If you are satisfied with a HD 720p 50fps project profile, you may render your project to any output format. If you want to keep the input format, you may want to create a custom render profile, that matches your needs.

But this is my (user) interpretation, maybe the developers and other users have a different view on this... :)

Cheers, Achim

+1 to what al25fps said, I was just writing something similar!

For example, I messed up the other day, as a previously used project profile was being used, 720p@30FPS. But my source video was 1080i@25FPS.

So when cutting video etc, Kdenlive was seeing my video as 30FPS, which messed things up, it also messed up title clips, as they were created at a lower resolution.

I found in rendering profiles an option to create custom profiles as you sayd al25fps, but i don`t understad the PARAMETERS. I want to keep my input files properties, because if i change these parameters affects my video quality.So.. where can i find a guide how to create custom rendering profile?

My video properties are :

Video
Dimensions: 1280 x 720
Codec: H.264/ AVC/ MPEG-4 AVC/ MPEG-4 part 10
Scanning: Progresive
Framerate: 50fps
Pixel aspect ratio: 1
Pixel format: yuv420p
Bitrate 12012 kb/s
Colorspace: ITU-R 709
File Type: MP4

AUDIO:
codec: MPEG-4AAC
channels: Stereo
Sample rate: 48000 Hz
Bitrate: 128 Kbps

Can anyone tell me how to create a custom profile?

Thank you

Thanks al25fps and moorsey. My take home from what you are saying is that the manual I referred to is wrong when it says make the project profile match what you want to "output". It should in fact match the format of the files you are going to input.

I guess this means we have a problem if we are combining sources from disparate formats. Would it be recommended to convert disparate  formats into a common format before doing serious editing on them?

@ttguy
I've just read that section of the Manual, talk about confusing!!

Mixing formats:-
I set up a Project with 1080 50i (25 fps) which is the same as my camera, then load one of it's .MTS clips, all is fine. There is nothing stopping me from adding a clip from my old camera (4.3 pal) , they both play fine. One shows in HD and the other in SD . Matching framerates is what seems to be more important.