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Output size is not same as clips

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Wed, 07/07/2010 - 20:43
#1
CharlemagneX
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Output size is not same as clips

Ok version 0.7.7.1 in Linux Mint 8 KDE

I've rendered files into AVI at 720x480

However, if I try to combine/mix these AVI files via another project and render them, the output is definitely smaller than the original clips. Yet original avi files and the new combined output files both say 720x480 in VLC Media Player. And Kdenlive is set that way.

Why is the output smaller... And is there any way to force the rendering to be exactly the same as the clips?
I've tried trial and error with different settings that don't make much sense to me.. to no avail.

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Thu, 07/08/2010 - 19:58
#2
Granjow
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Re: Output size is not same as clips

You mean the file size (10 MB eg)?

This is because most codecs (like XviD e.g.) are NOT lossless. It is like saving a JPG, opening it again, saving again several times, which results in loss of quality.

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Thu, 07/08/2010 - 21:58
#3
CharlemagneX
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Re: Output size is not same as clips

oh.. sorry. I meant the scale of the rendered video. I fixed the problem by trying Crop and just checking "Automatic center-crop" on each vid clip.

Basically learning the hard way here. Kdenlive seems pretty cool all in all. But the user manual appears not finished or not to address many things. Is there some good place or resources to learn about what are for me alien concepts like codec, lossless... NTSC or PAL, ..things like DV NTSC 4:3 to DVCPRO50 NTSC 16:9... relevant differences regarding Raw DV, AVI DV, MPEG-2, MPEG-4, XVid4, etc etc?

All of this stuff and more in the rendering options?
....even trying to read forum posts here seems Greek without some grasp of what everybody apparently is supposed to just know.

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Thu, 07/08/2010 - 23:50
#4
Pipoca
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Re: Output size is not same as clips

Try wikipedia. I'm a newbie too and have found excellent information there.

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Thu, 07/08/2010 - 23:55
#5
Weevil
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Re: Output size is not same as clips

Well for learning about videoformats you might like sites like Wikipedia for the general (or in-depth) knowledge. Maybe start at http://www.myformatfactory.com/Video

Videofiles of the same resolution but with different sizes are maybe caused by widescreen or anamorphic settings, where pixels are stretched? I'm no newbie at videostuff but I have to admit I'm usually experimenting some time before having a nice videoformat/conversion I'm happy with. If you're into learning it compare the file attributes with ffmpeg(, melt, Avidemux etc) otherwise maybe try exporting the original project to a somewhat 'safer' videoformat before using it in another project, like MPEG2 or DV.

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Fri, 07/09/2010 - 09:56
#6
Granjow
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Re: Output size is not same as clips

Please check your project settings then (Project > Project settings).
Make sure you are using a 720p profile.
To find out which one suits best (correct frame rate e.g.), you can display the clip properties in kdenlive (double-click or right-click > Clip Properties). Alternatively you can use
$ ffmpeg -i yourfile

Simon

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Fri, 07/09/2010 - 22:13
#7
Pipoca
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Re: Output size is not same as clips

Hello Simon,

Could you please explain the relationship - if any - between the video profiles at the project settings and the rendering profiles?

TIA,

Pipoca

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Sat, 07/10/2010 - 09:45
#8
Granjow
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Re: Output size is not same as clips

Hi Pipoca,

Sure.

It is quite similar to image editing tools like The GIMP. Your project (e.g. the photo you are working on) has a certain size (1280x720). This is the size of the original file. When you export it, you are free to scale it to any size first – with according loss in quality. So:

Video profile: Should match your input clips regarding resolution, frames per second, and aspect ratios. If you are not sure what to chose here, double-clicking on a clip in the Project Tree will show its properties. (See Wikipedia for DAR and PAR.) When working with input clips of different sizes I would probably chose the properties of the highest resolution video you have.

Render profile: Remember that this is just the «Save As» dialog. Scaling the video here does basically the same as when scaling an image before saving. Downscaling is okay, but if you enlarge it, you may see that the quality is not too good anymore.

You can easily test this. Here I've created two project profiles, one at a resolution of 200x150 and another one with 750x500. (They can be added/changed at Preferences > Manage Project Profiles.) Then I added a text clip and rendered both clips to 750x500; so the first one had to be scaled (not only the resolution differs, also the DAR is different: From 4:3 to 3:2) to 750x500 and the second one just remained as is.

Here the differences: The first one is the scaled one, the second one already was at 750x500. The unscaled (second) video maintains the display aspect ratio, whereas in the scaled one the rect becomes a square.

Scaled (click to enlarge)

Unscaled

Simon

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Sat, 07/10/2010 - 15:19
#9
Pipoca
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Re: Output size is not same as clips

Hi Simon,

Thank you very much for the detailed lesson.

Pipoca

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