Trying to cut a clip out of a video (AVC/x264) & can't figure it out; help?

[CuttingClips]

All I need to do is cut two clips from two video files and have the exported clips match the video/audio quality of the originals but as someone who doesn't know much about video editing outside of some basic VirtualDub experience, it's turning out to be quite a major hassle to figure out how to do this seemingly simple task.

Both video files that I need the clips from are MKV files and encoded with AVC/x264 - like I said, I don't know much about video editing and Virtualdub is the only program I'm even semi-familiar with so I downloaded the latest version and installed Virtualdub FFMpeg Input Plugin in order to get VirtualDub to open/edit MKV files. I can open them just fine and easily crop down to the necessary clip lengths I need but have no idea how to export that clip so that it's the same quality as the source using VirtualDub or any other software. I don't want to edit or convert anything, literally just crop and save two clips so that they have the same video/audio quality as the original, i.e. the same video/audio codecs etc.

Here are screenshots of the codec info from MediaInfo so you have an idea what I'm working with:
Video 1: https://forum.videohelp.com/images/imgfiles/wfzzZZB.png
Video 2: https://forum.videohelp.com/images/imgfiles/PosvgYS.png

Doing some research online it would seem that VirtualDub can encode to MKV using an external encoder but what I've seen regarding this seems over my head. It doesn't have to be VirtualDub; if there's another way I'd love to hear it; I just want to crop two clips from these two videos and have them be the same video/audio quality and codecs as the originals in a MKV container. Just a copy.

Apologies for how clueless I am for what I'd assume would be a pretty straightforward procedure, but if anyone could help me figure out what exactly I need to do to achieve this and how I'd greatly appreciate it.
Thanks in advance!

BTW: Operating system is Windows 7 64bit Professional and I'm using the 32 bit version of VirtualDub as per the site's recommendation.

[Kerry56]

I use tsMuxeR to cut out sections of H264 video, especially ones that use HD audio when I'm trying to keep the audio intact.

You'll find the cutting tools in the Split & Cut tab of tsMuxeR GUI, and you'll need to know the exact timing of the cuts. The tool can be adjusted for minutes, seconds or milliseconds. Just put a check mark in the box to enable cutting. You won't be able to output to an MKV file, but you can make .ts or .m2ts files and easily get them into an MKV using MKVToolnix.

[Baldrick]

You can also cut with mkvtoolnixgui under the output tab, splitting choose After specific time codes and specifiy them (see https://forum.videohelp.com/threads/359121-How-to-extract-parts-from-a-mkv-including-al...acks?p=2269899 ).

If you want an editor with a video preview then can you always try free avidemux(it often crashes though), xmedia recode or video to video converter.

[CuttingClips]

You can also cut with mkvtoolnixgui under the output tab, splitting choose After specific time codes and specifiy them (see https://forum.videohelp.com/threads/359121-How-to-extract-parts-from-a-mkv-including-al...acks?p=2269899 ).

If you want an editor with a video preview then can you always try free avidemux(it often crashes though), xmedia recode or video to video converter.

mkvtoolnixgui did the trick! Thank you!
However, it wasn't a perfect/exact result as there were some differences between the original and the clip so it's not a direct copy - the differences aren't THAT noticeable but I'm interested in knowing if there's a way of tweaking it for a "direct copy" result in the output clip, so I'll highlight the process I used and the differences between the original video and the clip.

Process: I opened the file in VirtualDub, used it to find and then copy the exact frame numbers for the start and end of the clip I wanted, installed mkvtoolnixgui, added the original video as the source file, went to Output, under "Splitting" changed it to "Split mode: by parts based on frame/field numbers" and then next to "Parts" entered the first and last frame numbers of the clip ("1324-9309" in this instance) and hit Start Muxing. 6 seconds later I had my clip. I didn't change any settings or do anything else.

To compare the original source video and the output clip video I used MPC-HC x64 to go to the exact same time in both the original and the clip and selected "File - Save Image" to capture a PNG screenshot from both files at that same time/frame, then used screenshotcomparison.com to compare them as well as loading both screenshots into Photoshop CS6, pasting one as a new layer over the other and clicking back and forth between the two for comparison and zooming in to see if there was any quality loss. I did this for two different frames. There is a significant change in the levels/brightness; the output clip is noticeably brighter than the original.

On the image quality front, no noticeable change in the first screenshot; no artifacts in the clip that weren't in the original, even after zooming in and checking all over. On the second screenshot, the image quality seemed poorer although it's hard for me to tell if it's just the levels/brightness accentuating/highlighting the artifacts so they're more visible yet no worse or if it in fact worsened the image quality any.
Here are the two screenshots for comparison - the first screenshot is from the original video and, when moused over, the same frame from the output clip is shown.

Comparison: Screenshot One
and
Comparison: Screenshot Two

Overlaying "Screenshot Two" in Photoshop and zooming in 300% showed some definite change in the image quality, although like I said, I'm not sure if that's the change in the levels/brightness accentuating artifacts more or if it's actually degraded. I cropped a section of the frame and enlarged it 3x to show what I mean (most noticeable on the wall beneath the scarf) -

http://screenshotcomparison.com/comparison/160201

I know I'm nitpicking, but just a bit curious as to what caused the change in levels/brightness and if the image quality is indeed degraded in the Clip version.

Also, here are side-by-side MediaInfo screenshots of the original MKV x264/AVC file (on left) and the resulting clip after using mkvtoolnixgui (on right) - https://forum.videohelp.com/images/imgfiles/3rDpe4n.png

The codec information is different in parts and, I'll admit, I don't know enough about this sort of thing to determine whether the changes in info between the two files is at all meaningful or changes (specifically, degrades) the audio/video quality of the resulting clip any but someone more knowledgeable than I may have some insight.

P.S.
Any idea what caused the change in levels/brightness in the output clip and how I could get a direct/exact copy instead?

P.P.S.
Unrelated (sorry!), but is there a good way to save a screenshot of the EXACT same time/frame in two different videos? My best idea was to use MPC-HC to open the Clip, use the "Go To" feature and paste in a frame number to jump to (let's say frame "7586"), then File-Save Image and then open the original video in MPC-HC and use the "Go To" feature again and I figured since I had cut off 1324 frames from the beginning of the video for the Clip, I'd add that number to the other frame number from the clip (7586 + 1324 = 8910) and go to frame "8910" to get the same still frame. However, this did not work as it was a different time in the video and not the same frame. After messing around with it I finally got the identical frame by trial and error/accident which ended up being frame number 8944 in this case. For the second screenshot I figured since the difference was 1358 frames according to MPC-HC, I'd add that number of frames to the frame number from the clip to get an identical screenshot, but this didn't work either. It was closer, but I still had to move forward a few frames in order to get the identical shot. Is there an easier, foolproof way of saving screenshots of identical frames from two different videos so they can be compared other than the guess and check method I used? Maybe using a different program or method? Sorry to go off-topic, but I didn't want to start a new thread and this would be very helpful to know for future use.

Thanks again!

[sneaker]

Mkvtoolnix does NOT cause any video quality degradation. The problem is in your player/the way you make screenshots. The YUV data has to be converted to RGB and there are different ways to do it.

[jagabo]

Yes, mkvtoolnix has no ability to reencode anything. Any differences you see have to do with how your player/editor handles different videos.

https://forum.videohelp.com/threads/329866-incorrect-collor-display-in-video-playback?p...=1#post2045481

The differences in levels is the difference between full range YUV (0-255) and limited range YUV (15-236).