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Old 2008-01-19, 04:05   Link #1
Senior Member
Join Date: Feb 2006
Screen capping h.264 in .mkv?

So how does one go about screen capping videos in h.264 in a .mkv container, frame by frame?

VirtualDub... doesn't work.

I tried using the ffdshow grab feature but the quality of the caps are much, much lower.

That and it sometimes screws up the image.


It seems that when I take a picture in Media Player Classic, it saves the pictures in 4:3 and then re-stretches the image to the original resolution. I want it to take the picture in the default ratio 16:9 in the original resolution.

Anyone know why it's doing that? Or is it cause I got a widescreen monitor and it's stretching it even more and the first screencap is actually correct? The second one still looks more "right" to me though.

Last edited by Myname; 2008-01-19 at 04:17.
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Old 2008-01-19, 04:28   Link #2
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Join Date: Feb 2006
I check the resolution of the top image and it is in 720x480, which is exactly the same resolution described in the video file's name. If anything, I think the MPC window was the stretched one.
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Old 2008-01-19, 10:08   Link #3
AS Oji-kun
Join Date: Nov 2006
Location: Hokkaido
Age: 69
Originally Posted by Myname View Post
So how does one go about screen capping videos in h.264 in a .mkv container, frame by frame?
I use mplayer for this task because you can designate a start and end time and have mplayer write out each frame as a JPEG, a PNG, or even an animated GIF. While I use mplayer on Linux, there are Windows ports available as well. You'll have to learn to use the command line, though, a skill I recommend to anyone with a computer.

There's also a lengthy thread on this issue already:
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Old 2008-01-19, 10:31   Link #4
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Join Date: Feb 2003
Location: Zürich, Switzerland
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This is probably a rip from an anamorphic DVD.
DVDs have a fixed resolution (for NTSC) of 720x480 which has a square-pixel aspect ratio of 4:3. So all 16:9 video on DVDs is encoded either stretched to fit or letterboxed with two black borders encoded on the video. The player then displays the video in it's correct 16:9 aspect ratio.

Important is: The pixel aspect ratio doesn't have to be the movie's actual aspect ratio. Many video formats can be encoded in various or even arbitrary pixel resolutions and then stretched to the correct one on playback.
That doesn't make much sense nowadays with digital video but helped to maximize the video information on film and later on analog television.

This means both screenshots are correct. The first one represents the actual pixels of video 1:1 while the second one is a stretched version to the video's aspect ratio of 16:9.
What you can is to simply open the screenshot in any image editing software and scale it to the correct aspect ratio. That's exactly what the player has done in the second screenshot.
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Old 2008-01-19, 23:23   Link #5
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Join Date: Dec 2005
Age: 35
FFDShow's Grab feature would technically be a higher quality screencap because it is taking the image directly from the decoder. Whereas using a screencap feature in MPC (or any other player) you are getting the output from the video renderer, which if you are using any of the VMR renderers you will likely get incorrect colors (see the joys of nVidia drivers).

Best to just take the ffdshow screencap and then resize it yourself (with as high quality/sharp a resizer as you want to use) to 16:9. So 720x480 to 16:9 would be 853x480. Done.

You can get an MKV into VirtualDub, you just have to feed it through AviSynth first. However you won't get the Display Resolution this way either (so it will be 720x480), but it does make it extremely simple to find the frame you want.
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