Lossless Cutting of Various Formats (GOP level)

[jmac698]

Hello,
I'm familiar most with mpeg, and I've used a program called mpg2cut2, which I know to be a lossless cutter for mpg files. Because mpg can only be cut at certain boundaries ,the program would only let you set start/end points within about half a second (known as a GOP level cutter).

I'm looking for a similar type of operation for other video formats; notably mov and avi, not sure which codecs yet but hopefully all. I'm currently evaluating one option called Free Video Dub. It's simple and I like it, but how can I know for sure it's doing lossless, GOP (or equivalent) cutting of my files?

The only test I can think of for now is decoding both files and doing a video image level comparison (for example subtract(original, cut) in Avisynth). Another indication would be to watch my CPU usage on a large file; re-encoding should be evident.

I'm just a little suspicious as this program let me set my in/out points with maximum precision; that shouldn't be possible. Is it in fact one of those nearly lossless cutters which re-encodes the half GOP on either side (like VideoRedo)? - That would be acceptable in fact, but I want to know that most of the video is untouched.

I'm hoping for an experts' opinion here, thanks.

[davexnet]

I think you can tell from the speed. Try it with a reasonable sized file. If it takes a few seconds,
it's surely doing a direct stream copy to 99% of the file.

I've seen it in Virtualdub with it's Smart Rendering. Works very well. I get 5000 - 6000 frames per second
in direct stream mode, and that's on my modest spec. box.
I thought only the first few frames were Smart Rendered not the last few?

[jmac698]

It seems that MPEGStreamClip advertises GOP level editing as well. It lets you set any in/out cut points, but silently deletes the half-GOPs when saving. There is also a preference to keep them, making the trim smaller (the saved part bigger) than expected.

I still don't know about other inter-frame codecs (intra-frame codecs can cut on frames).

Avidemux and virtualdub may also do this, but I'm not clear on how to tell the program is actually doing that.

[poisondeathray]

vdub and avidemux smart render for xvid/mpeg4-asp - and do it well, but not other compression schemes

vdub sort of works for h.264 but it's more miss than hit, there are way too many errors .

Not free, but solveigmm splitter and videoredo smart render for other formats and fewer problems, but even they have problems with certain h.264 files that have been encoded with some settings

Nothing works perfect for everything

[jmac698]

Awesome, thanks. I take it you have no opnion on streamclip. I will have to test it myself. I have a video where every frame is marked, so I can tell exactly what was cut. Then I will have to compare pixel-by-pixel to detect re-encodings.

[usually_quiet]

It seems that MPEGStreamClip advertises GOP level editing as well. It lets you set any in/out cut points, but silently deletes the half-GOPs when saving. There is also a preference to keep them, making the trim smaller (the saved part bigger) than expected..

MPEG StreamClip has a "Go to Keyframe" selection in the Edit menus, which is what I use to position cuts. I have only used MPEG StreamClip for editing MPEG-2 video, and s a GOP level MPEG-2 cutter it is OK. I have never tried to uaing it to edit other video formats, so I have no opinion on it except as an MPEG-2 editor.

[jmac698]

Thanks for the tip! And yes, that's my problem too, but I'll try to test it later today.

Update:
I've written a guide to lessless cutting with StreamClip
http://www.digitalfaq.com/forum/video-editing/4420-2997-frames-vs-2.html#post22190