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Trimming Matroska Files Not Working Properly

TaaDow

New member
#1
Hello, everyone.

When I use the trim function to simply trim a matroska video without re-encoding anything, I get proper sized files but there are no video or audio streams in the files. Anyone else have this issue with this container or any others when trimming? If so, do any of you know what could be done to correct this issue?

Thank You
 

jmc

Active member
#2
I'm using VRD Pro but yes, there is a problem.

When trim&copy on a MKV file...

H.264.mkv
mpg.mkv

The file output, when placed back into VRD pops up a message about elementary streams and do I want to
open it in the Elementary Stream muxer. When I say yes and then save the file again
I get a functional good video file with NO audio...of course, as the Muxer shows no audio when muxing.

----------------
VLC won't play the "Original" trim&copy bit.(NOT MUXED)
MPClassic plays very broken video with no audio.
 
Last edited:

jmc

Active member
#4
Grab the latest build from here and see if that resolves the problem:

http://www.videoredo.com/Installs/VRDPro/VRDPro-5-90-90-770a.exe

Ok, redid the Trim&Copy MPG.MKV test.
I had Trim&Copy trim using the "section markers" setting.

VRD says elementary stream with the (unplayable) Trim&Copy segment and MUXING makes it a playable file with no audio.

MUXing mpg.mkv to mpg.mkv... now plays but bad quality video. (video jumpy,blocky,jerky,green flashes)

MUXing mpg.mkv to H264.mkv... Quality MUCH MUCH better...smooth, not perfect tho, a "block" here,there.

Forgot to mention, the MUX always crashes but leaves behind the "now playable" video file with no audio.


VRDPro-5-90-90-770a,
W7/64, Intel 6core 3930

Thanks,
jmc
 
Last edited:

Danr

Administrator
Staff member
#5
Sorry, misread your original message. You shouldn't use trim and copy on MKV files, or MP4/MOV files either. Trim and copy really primarily useful for program stream and transport stream files.
 

jmc

Active member
#6
Sorry, misread your original message. You shouldn't use trim and copy on MKV files, or MP4/MOV files either. Trim and copy really primarily useful for program stream and transport stream files.
Ok, good to know.

Trim&Copy does give a warning for .MP4 files but nothing for MKV files.

Thanks,
jmc
 

Dan203

Senior Developer
Staff member
#7
Yeah most files have a header so if you trim them they are no longer valid. TS and PS have a repeating header in the stream, so they can be trimmed like this without issue. TiVo files only work because after the header they're just standard PS or TS so we copy the header first, then trim the remaining part of the file. That doesn't work with other files as the headers contain byte offsets to frames, streams, etc...
 
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