Cutting an AVI accurately?

[mojo2185]

I've tried cutting my AVI file accurately in Virtual Dub, but it seems this can only be done at a keyframe (i get a second or two of video that I don't want). Is there a different program I could use to cut my AVI file at the desired frame? Note that I'm cutting a 3 minute segment that starts near the end of the movie, and the last frame of my cut will be the end of the entire movie. I've heard AVISynth can do this, but I thought it was only a frameserver? Also, like virtual dub, this program shouldn't re-encode or change the video stream (should be a direct stream), I just want a cut in the place where I tell it.

Thanks

[Tommyknocker]

If you can run your AviSynth in Virtual Dub, use the Trim function for editing. Since AviSynth deeals in frames and not key frames, it does what I like to call "surgical editing". That is, right where you need it.

[mojo2185]

Great, sounds like what I need. Correct me if I'm wrong, but I should create a script file. Then I should load that script file as my movie, and save.
Where can I get a script for this operation (I'm new to the program).

WOW I tried my own script, and my 3 minute clip ballooned to 2 gigs! What the?! I made my avs file, then loaded it as the video in Virtual Dub, the preview played exactly what I wanted it to play. I changed the video to "direct stream copy", changed the framerate (yes in VDub because the rest of my clips were done in VDub, so I did this for compatibility). Then I saved it as a new file.
Here's what I put in my avs file:

AVISource("d:\AVP2\movie\clip1.avi")
Trim(79170,0)

Where did I go wrong?

Thanks

[Tommyknocker]

Whoi says you did something wrong? Remember we use codecs to compress our video, so when we save it, our three minute video does not ballon to two gigs.

Seriously, though, you only need to decide how you are going to compress your video now. DivX is good for AVI.

[mojo2185]

Whoi says you did something wrong? Remember we use codecs to compress our video, so when we save it, our three minute video does not ballon to two gigs.

Seriously, though, you only need to decide how you are going to compress your video now. DivX is good for AVI.

But if i did direct stream copy, shouldn't it be an exact copy of the file (except the part I cut out?). I've done direct stream copy for an entire movie and the filesize was less (because I didn't use the audio). In this case, I also discarded the audio. And the original source (which I'm cutting from, is 700ish mbs and is DivX)

Oh yeah, and I forgot to mention... there was no video when I tried playing it back too, just a black/grey screen...

[thor300]

If you dont want to re-encode you need to stick to keyframes in vdub. I asume this is what you want to do, use the direct stream copy for the video, right? You can only cut at keyframes when doing this, its logical if you consider it; you cannot start a video without a keyframe, and to make a non-keyframe into a keyframe you need to re-encode. If you want to use "surgical editing" then re-encoding is the only way. Re-encoding wil cause a small quality loss even at higher bitrates, so choose between quality loss or a few seconds of unwanted video in beginning and end of file.

[mojo2185]

Ok, that clears some things up. I was unaware that this process actually re-encodes. Now... how can I "re-encode" this, so I lose as little quality as possible. Also, I plan to merge this file with some other video streams that were edited in virtual dub (changed framerate, separated the audio). Will this end up causing any problems (the AVISynth process)?

Also... I still don't have picture in my video.?!?!

Thanks

[thor300]

Under Video - Compression in vdub you can choose a codec to re-encode, for example DivX5, then click on the Configure button to set desired quality.

[mojo2185]

Should the keyframe time ("Keyframe Every XX seconds") match my source movie (for compatibility for when I rejoin my AVI files)? If so, is there a place where I can find the keyframe rate of my source movie? I'm looking in Virtual Dub, but I can't seem to find it.

[thor300]

To check for keyframe rate in Virtualdub, click on the Key next button, the one with symbol of a key and a forward arrow. See how many frames it moves each time, and you have the rate. Im not sure if it need to match, its no disadvantage if it do. The framerate need to match for sure, and maybe also codec and so on, havent tried this so i cant say for sure. Hope someone else can tell you what parameters need to be the same for joining and still use "direct stream copy", and i like to know also without having to try it myself =). I hope you will post your experiences when you finished this project of yours.

[mojo2185]

Boy do I have a bunch of experiences with this, especially since I'm new to the
DivX->VCD thing.

Thor300, your tips about the re-encode really helped.
TommyKnocker, your tips about AVISynth made this easy for me.

It appears the keyframes made no difference, I've successfully joined all 3 AVI files. I used Gspot to check the codec, and used that codec to compress in Virtual Dub, I cranked up the bitrate, and adjusted some of the smoothness. I now have the file, perfectly cut where I want it. There is some quality loss, but it is only brief blockiness on a closeup shot, and its barely noticeable.

Thanks to all who have helped. Lookout for me in the audio section for posts... as I try to take my 3 AVI files, and merge it with 2 WAV audio tracks... in synch, lol!