Preserve original quality as much as possible

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Wed, 11/19/2008 - 12:29

Dave M G

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Preserve original quality as much as possible

Kdenlive Users,

I realize that when one takes a compressed video format, like AVI, and re-renders it as another AVI, there will undoubtedly be some quality loss.

However, I'm wondering what settings might be ideal for preserving as much as possible a level of compression and quality that is equal to the original.

To be more specific, I have some AVI files from a digital video camera of some live performances. All I intend to do is combine them into one video, maybe with a fade in and out of black between them. The goal is just to archive the performances into one video clip.

The videos are 640x480, NTSC format.

In my initial experiments, the output video is noticeably more compressed than the original. Lots of JPEG-like artifacts and blocks.

Is there a way to get the output to closely approximate the input?

Thanks for any advice.

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Wed, 11/19/2008 - 15:39

Weevil

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Re: Preserve original quality as much as possible

Well if you just want to join them without any fade you might just wanna use ffmpeg join command from the terminal. It has the option -sameq to keep, you guessed it, the same quality for output. For other conversions you can also use -vcodec copy and -acodec copy to keep codecs the same.
Check here >

http://ffmpeg.mplayerhq.hu/faq.html#SEC31

In using KDEnlive or any other program my guess would be to stick as close as possible to the original codecs and scaling as possible to avoid as much conversion as possible... but if there is a better way I'm very curious too!

*edit
The ffmpeg might be a little confusing, an easier method is explained here:

http://www.arsgeek.com/2006/08/07/how-t ... mpg-files/

Thu, 11/20/2008 - 03:26

cinephiliac

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Re: Preserve original quality as much as possible

If you're using the current version (0.7 - the KDE 4 one) there are options for outputting lossless which shouldn't lose any quality at all. It will be larger file sizes (possibly much larger) but the quality should be identical. To do this just lick on render, choose "Lossless" from the bottom of the left column and choose one of the profiles on the right. Click "Start rendering" and you're good to go. :)

Thu, 11/20/2008 - 03:49

Dave M G

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Re: Preserve original quality as much as possible

Cinephiliac,

Thank you for responding.

Quote:

there are options for outputting lossless which shouldn't lose any quality at all

That option does preserve the original quality, but it increases the file size considerably, as you say.

I guess what I'm looking for is a way to make the output file the same compression, codec, and everything as the input file.

Is there a way I can probe the input file to find out it's parameters, and then input that into Kdenlive?

Weevil,

Quote:

you might just wanna use ffmpeg join command from the terminal

Thanks for the suggestion, but for too many reasons to go into, I don't want to use the command line.

Dave M G

Thu, 11/20/2008 - 04:08

cinephiliac

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Re: Preserve original quality as much as possible

Well, I'd say without using lossless or the command line, that your best bet is to match both the project settings (Project -> Project Settings) and the Render settings (Render -> Pick your settings) to be as similar to your original project as possible*. OK, with the exception of compression, where less will obviously always be better. You are still going to get loss from recompression, but that's just a fact of video editing life. More generations of copying = more loss of quality.

The only other option I can think of is to see if any specialty program has a specific GUI option to use ffmpeg's join option. I don't like your chances, but if I was to guess, I'd guess at AVIdemux.

Best of luck!

Thu, 11/20/2008 - 12:30

madsdyd

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Re: Preserve original quality as much as possible

Dave M G wrote:

Cinephiliac,
Is there a way I can probe the input file to find out it's parameters, and then input that into Kdenlive?

After adding a clip to kdenlive, you can right click it to get some information. Other than that, running

ffmpeg -i youfile.something

is the best bet (thats command line, I know :-( )

Fri, 11/21/2008 - 03:59

cinephiliac

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Re: Preserve original quality as much as possible

Heh,

I've been meaning to file a wishlist item to have the clip bin show more info on clips (eg framerate, resolution, audio and video codecs and bitrate).

Maybe tomorrow, unless some kind person beats me to it ;-). (I'm just re-arranging my entire office atm :))