VirtualDub questions & answers

[gadgeteer]

Use Avidemux instead - it has a Smart Copy feature that re-encodes just the frames between the desired inpoint and the source's first keyframe, and then losslessly copies the rest of the clip. It's much more accurate and the small number of re-encoded frames aren't usually very noticeable.

[prof_derzshowitz]

Originally Posted by 2Bizzy

Hey ya, im trying to cut a scene using Virtualdub, but when i save and play it, it starts like 3 seconds back from where i set the video to start at, does anyone know how to make it so it doesnt do that??

I too have had this same type of problem. It seems to be almost unavoidable in Virtual Dub. I basically had to keep on pushing my "start" marker a little bit further along the timeline (to the point that what "appeared" to be my starting frame on the V-Dub preview screen was a number of seconds past my intended position), until I ended up with a video that began close enough to where I wanted. It was pretty painstaking, and a bit frustrating.

There is a some mention of Virtual Dub editing in this thread here (http://vintage-erotica-forum.com/t71...avi-files.html), and on the second page the user razor_king mentioned his preference for a variation of Virtual Dub called Virtual Dub Mod (http://vintage-erotica-forum.com/sho...5&postcount=15).

I haven't tried it out yet, but I wonder if it might do a more accurate job of frame cutting than the original software, since it appears to be a more complex and upgraded version. The link to the download site for the software is included in that same thread, inside my response to his post.

[prof_derzshowitz]

Originally Posted by gadgeteer

Use Avidemux instead - it has a Smart Copy feature that re-encodes just the frames between the desired inpoint and the source's first keyframe, and then losslessly copies the rest of the clip. It's much more accurate and the small number of re-encoded frames aren't usually very noticeable.

Though I really like Virtual Dub, this software does sound interesting as well. However, I have to ask two very important questions before seeking it out:

1) Is it freeware?

and

2) Does it only support .avi's, (as is the case for the standard Virtual Dub program), or can it handle a wider number of video formats?

Thanks,

P.D.

[Shirtfull]

Try smart rendering in virtualdub

[prof_derzshowitz]

Originally Posted by Shirtfull

Try smart rendering in virtualdub

Thanks for the suggestion. I presume this option would allow for greater accuracy in frame marking, so that the timeline location you selected as the starting point of the movie in Virtual Dub will be the same after exporting is complete?

I did notice, however, that on the "Video" drop-down menu, "Smart Rendering" only appears to be available with Full-Processing Mode. When Direct Stream Copy is chosen, the "Smart Rendering" option is then greyed out, and un-selectable.

I am concerned that although "SR" might make the editing process more accurate, if it can only be enabled in FPM it might defeat part of the purpose of editing/extracting a scene.

For example, if your intention is to cut out a section from a longer, larger video file, and create a shorter clip with a smaller video size, Direct Stream Copy would be your mode of choice, as FPM tends to create significantly larger files. Yet it appears that DSC is not available when editing with "Smart Rendering."

[Shirtfull]

It reencodes up to the next keyframe and then DSCs the rest.

[Shirtfull]

Here is a little practical demonstration of smart rendering in Virtualdub.
Using one of the two vids I've uploaded, try and cut the vid in direct stream mode at frames 150 to 350 with no audio. You will find that the produced video will start at frame numbered 100 because this is the preceding keyframe needed.
Now select full processing mode and then smart rendering and also the codec of the vid you're using, configure the codec to one pass mode for a bit rate of 1000kbps, and repeat the cut. This time the produced vid will start at frame numbered 150 with the numbered frames 150 to 199 recoded and the rest are directly copied. The produced vid should have keyframes at frame 0,50,150.
Test vids 640x480 40Secs 1000 numbered frames at 25fps and keyframes at every 100 frames. No audio.
Divx version 4Mb
http://rapidshare.com/files/253040256/Test_Divx_25.avi
Xvid version 4Mb
http://rapidshare.com/files/253040010/Test_Xvid_25.avi
I hope this makes it clear that to cut an avi accurately you need to reencode upto the next keyframe. To make the recoding as best as possible, force the codec to produce keyframes for every frame.

[prof_derzshowitz]

Originally Posted by Shirtfull

Here is a little practical demonstration of smart rendering in Virtualdub...

Thank you very much, Shirtfull, for taking the time to explain, in detail, the necessary steps for the use of "Smart Rendering" in Virtual Dub, in order to accurately designate the Start and Finish points for exported vidoes. I have not yet had the chance to test the process myself, but I am confident that I will be able to implement it succesfully, thanks to your directions.

I must admit, however, that I am still a somewhat confused regarding the ways in which the use of Direct Stream Copy vs. Full Processing Mode (With Smart Rendering) can, respectively, have significantly different effects on the temporal placement of Key-Frames within the Virtual Dub timeline.

(The differing results/effects from the use of DSC vs. FPC/SR are described below, as mentioned in your last post

Originally Posted by Shirtfull

Using one of the two vids I've uploaded, try and cut the vid in direct stream mode at frames 150 to 350 with no audio. You will find that the produced video will start at frame numbered 100 because this is the preceding keyframe needed.

Now select full processing mode and then smart rendering and also the codec of the vid you're using, configure the codec to one pass mode for a bit rate of 1000kbps, and repeat the cut. This time the produced vid will start at frame numbered 150 with the numbered frames 150 to 199 recoded and the rest are directly copied. The produced vid should have keyframes at frame 0,50,150.

Given the information describe in the above quote, could you possibly explain why:

a "Cut Selection at Frames 150 to 350...[processed] in direct stream mode will start at frame... 100,"

BUT:

if you "select full processing mode and then smart rendering... and repeat the cut... [this] will produce the vid at frame numbered 150 with the numbered frames 150 to 199 recoded..." ?

---

I apologize for asking such a specific question, but I am quite puzzled as to why a DSM cut marked at Frames 150-350 would bump the opening marker back 50 Frames, while a FPM Smart cut marked at the same locations (Fr. 150-350) would retain the proper start location (i.e. Frame 150), but would only re-encode up to the Frame 199 mark.

Thank you for your earlier help regarding this matter, and I hope my additional questions are not too much of a bother.

P.D.

[Shirtfull]

@ prof dershowitz

Quick reply
Have a look at virtualdub help, search for smart

[prof_derzshowitz]

Originally Posted by Shirtfull

@ prof dershowitz

Quick reply
Have a look at virtualdub help, search for smart

Thank you once again, Shirtfull, for your additional suggestion. Although I put in a considerable amount of time attempting to phrase my question(s) as clearly as possible, I seemed to have forgotten to follow the unofficial 1st and 2nd rules of Computer Software Troubleshooting,
(intended to allow oneself to personally solve a particular technological problem), which are described below:

The Rules


#1 - RTFM: (Read The F**king Manual).

... and if that does not provide the answer to the problem, then...

#2 - FGI: (F**king Google It).

---

From here on out, I'll be sure to conduct my own examination of the "Help" contents of V-Dub (as you suggested), and will seek out further answers through Google, before posting further questions.