Virtualdub changing video on direct stream copy

[LSchafroth]

I have a video in MPG42 format from a screen capture I did of a siminar.

All I wanted to do was to place it in VirtualdubMPG2 and crop a portion and cut out parts. I set compression to NONE, and the resulting output is blurry. It is screen captures so there is a lot of text and it comes out blurry and blotchy.

I removed the cropping and just cut out portions then did a direct stream copy and the resulting output is the same. No matter what i do the fonts are messed up and unreadable.

Is there a way to retain the resolution of the footage?

LS

[Baldrick]

Video->Direct stream copy does not change the video at all. Must be something else, corrupt header, video decoder problem. Try play with vlc and see if you get same problem.

[TBoneit]

Or since it is MPG format edit it with somethin like VideoReDo. I've never had the kinds of problems you are having.

VRD will not encode at all if you cut on GOPs if you cut between it win only re-encode the parts that were between GOPS to maintain integrity of the video

[Baldrick]

I think it is some kind of mpeg4....not mpeg2 or mpeg1.

[Cornucopia]

I think the OP used MS MPEG4v2 (precursor to v3 and later WMV), which IIRC is a VFW codec usable in AVI, so Vdub should be able to use it.

My guess is that the [Compression:None] setting is screwing it up--making it NOT DirectStream copyable. If it's compressed MPEG42, that's what the setting should be, right?

Or,
Being MPEG4, it uses GOPs, and the editing isn't being done on GOP I-frame boundaries, forcing it to recompress (certainly at least those sections).

Scott

[jagabo]

If you are in Direct Stream Copy mode VirtualDub won't let you select a compression codec. The menu item is greyed out.

[LSchafroth]

Or since it is MPG format edit it with somethin like VideoReDo. I've never had the kinds of problems you are having.

VRD will not encode at all if you cut on GOPs if you cut between it win only re-encode the parts that were between GOPS to maintain integrity of the video

I'll try the VRD and see what happens. I think is definetly something to do with the MPEG4 v2 format.

LS

[jagabo]

Divx was originally based on Microsoft's MPEG4 V2 codec. MPEG4 V2 is simply an early implementation of MPEG4. Microsoft abandoned it because it wanted a proprietary codec and container (WMV) in it's quest to lock people into Windows.

[LSchafroth]

I'll try the VRD and see what happens. I think is definetly something to do with the MPEG4 v2 format.

LS

It will not load AVI files so I was not able to try it.

LS

[jagabo]

VirtualDubMPEG2:

1) File -> Open Video File
2) Video -> Direct Stream Copy
3) Audio -> Direct Stream Copy (the default, but just in case)
4) [Mark-in, Mark-out, Del] each part you want to remove. Note any part you retain must start with a key frame.
5) File -> Save as AVI

[LSchafroth]

VirtualDubMPEG2:

1) File -> Open Video File
2) Video -> Direct Stream Copy
3) Audio -> Direct Stream Copy (the default, but just in case)
4) [Mark-in, Mark-out, Del] each part you want to remove. Note any part you retain must start with a key frame.
5) File -> Save as AVI

Yes, that i what I am doing. The resulting file is fuzzy and blotchy when viewing the areas with text. That was the reason for my post.

LS

[jagabo]

I take it the text is clear in your source? Always works for me.

[LSchafroth]

I take it the text is clear in your source? Always works for me.

Yes, perfectly clear. This is the first I've ever seen VirtualDub mess something up.

LS

[jagabo]

I found an old video with the fourcc M4S2 and used VirtualDub to trim in direct stream copy mode. It didn't have any text but the trimmed file turned out fine. I don't have the old MS codec installed, I used ffdshow as the decoder.

[LSchafroth]

I found an old video with the fourcc M4S2 and used VirtualDub to trim in direct stream copy mode. It didn't have any text but the trimmed file turned out fine. I don't have the old MS codec installed, I used ffdshow as the decoder.

The screen capture is an odd size, not divisible by 8. Would this be the problem?

Should I pad to make it divisible by 8?

LS

[jagabo]

The screen capture is an odd size, not divisible by 8. Would this be the problem?

I don't know what the M4S2's frame size requirements were. Most codecs require multiples of 2 or 4. Multiples of 16 are usually the most efficient -- all MPEG codecs use 16x16 blocks of pixles internally.

To pad the frame size you'll have to reencode. That means decompressing, adjusting the frame, and reencoding. Decompressing for display and decomrpessing for editing are likely to have the same problems.

I'd try using a different decoder. ffdshow has two choices for M4S2 video. You often find the same kind of issues with Divx and Xvid. Sometimes a particular video will play properly with one but not the other.