Howto cut avi specific to the frame?

[Danuvius]

Is there any way (non-gui, ideally) to cut avi files with accuracy down to the frame?

i.e.: I want to create movie_cut.avi from content somewhere right in the middle of movie.avi

[lonex]

No, cutting most avi files precisely to the frame most likely won't be possible. Most avi files nowadays are encoded using some sort of mpeg4 video codec, like divx or xvid, and those only have a full frame every few seconds or so, and all other frames in between are derived from that single full frame. So you can only make a cut on each of those full frames, unless you re-encode the part you want to cut out, but that means losing quality.

[Danuvius]

No, cutting most avi files precisely to the frame most likely won't be possible. Most avi files nowadays are encoded using some sort of mpeg4 video codec, like divx or xvid, and those only have a full frame every few seconds or so, and all other frames in between are derived from that single full frame. So you can only make a cut on each of those full frames, unless you re-encode the part you want to cut out, but that means losing quality.

Errr... pretty sure avidemux does it. And re-encoding at a high enough quality will produce no visible quality loss.

So my question was "how", not "is it possible". It is, albeit like with the caveats you mention.

[moob7]

Errr... pretty sure avidemux does it. And re-encoding at a high enough quality will produce no visible quality loss.

According to the docs avidemux will break on a non i-frame boundary. It is supposed to re-encode the frames from that point up to the next i-frame and then the frames after that are passed though in copy mode. In theory. I have had problems with it for this particualr task but it may work fine for you. The probelm I tend to have with clips cut out with avidemux is what I call "jerking". The video seems to jerk (play faster/slower) for the first second or so until it catches up to (syncs with?) the audio.

So my question was "how", not "is it possible". It is, albeit like with the caveats you mention.

Don't you hate when you phrase a question simply and directly yet someone still mis-reads it and answers it as a different question? The other day I posted a question and clearly phrased it so that the answer could only be "yes" or "no". I even put "(y/n)" as part of the topic/title. Still someone posted an irrelevent answer.

That said, let me give you an answer to your original question.

I use transcode to cut on precise boundaries. As already stated, it has to re-encode the video but with the right settings (bit rate high enough, essentially) it works fine. It also cuts the audio correctly along with the video which is nice. I use avidemux to ascertain the frame numbers. Then I writ ethem down. Then I exit avidemux and then call transcode (command line only, yay!!) to chop that bad boy out.

Extra tip: depending on what are going to use extracted clip for, you may want to have transcode re-encode to a lossless format such as yuv or dv (or even a directory full of tga or png files) with a separate wav file containing the audio part.

[argasek]

Is there any way (non-gui, ideally) to cut avi files with accuracy down to the frame?

i.e.: I want to create movie_cut.avi from content somewhere right in the middle of movie.avi

I think with mencoder from MPlayer you can do this (without re-encoding).

[Danuvius]

Errr... pretty sure avidemux does it. And re-encoding at a high enough quality will produce no visible quality loss.

According to the docs avidemux will break on a non i-frame boundary. It is supposed to re-encode the frames from that point up to the next i-frame and then the frames after that are passed though in copy mode. In theory. I have had problems with it for this particualr task but it may work fine for you. The probelm I tend to have with clips cut out with avidemux is what I call "jerking". The video seems to jerk (play faster/slower) for the first second or so until it catches up to (syncs with?) the audio.

I went with the avidemux way... despite my original wish for a non-gui solution, I think it may have saved me some time that I could use the gui to specify thinks. The splicing ended up being far more complicated than I originally suspected.

The jerking prospect does frighten me though... I guess I shall have to wait and see.

So my question was "how", not "is it possible". It is, albeit like with the caveats you mention.

Don't you hate when you phrase a question simply and directly yet someone still mis-reads it and answers it as a different question? The other day I posted a question and clearly phrased it so that the answer could only be "yes" or "no". I even put "(y/n)" as part of the topic/title. Still someone posted an irrelevent answer.

That said, let me give you an answer to your original question.

Kindred souls are we! Thanks.

I use transcode to cut on precise boundaries. As already stated, it has to re-encode the video but with the right settings (bit rate high enough, essentially) it works fine. It also cuts the audio correctly along with the video which is nice. I use avidemux to ascertain the frame numbers. Then I writ ethem down. Then I exit avidemux and then call transcode (command line only, yay!!) to chop that bad boy out.

Unfortunately due to the specifics of what I am doing, the audio cannot be cut correctly... it has to be further manipulated, separately of the video, to achieve something proper. I am sure I am going to suffer like hell with audacity... urgh. ;-(

Extra tip: depending on what are going to use extracted clip for, you may want to have transcode re-encode to a lossless format such as yuv or dv (or even a directory full of tga or png files) with a separate wav file containing the audio part.

Not an option... the original (which is encoded as DVD video) is 25 GB (just the video--no audio). I suspect any lossless format may ultimately find the 600+ GB hard drive space I have insufficient.

Thanks for the tips though... for now I am managing ok with avidemux.

If you have any suggestions for how I could go about cutting/fitting/cross-fading multiple 6 channel and 2+ GB .wav files... I would be most grateful. audacity, alas, only supports 2 channel audio .wav files *for exporting/saving*.

[Danuvius]

Is there any way (non-gui, ideally) to cut avi files with accuracy down to the frame?

i.e.: I want to create movie_cut.avi from content somewhere right in the middle of movie.avi

I think with mencoder from MPlayer you can do this (without re-encoding).

I think mencoder would force the cuts to happen at keyframes... which may be the only possibility without reencoding, but are nonetheless unsatisfactory.

[richardash1981]

Support for exporting to multichannel wav files is in current audacity CVS (so will be in 1.3.1).

[Danuvius]

Support for exporting to multichannel wav files is in current audacity CVS (so will be in 1.3.1).

Do you know when 1.3.1 is due out?

[richardash1981]

Depends on developer time to get remaining bugs removed. Probably in the next month or so unless people are very busy. May well be preceded by 1.2.5 (which doesn't change much except some obscure bugs in 1.2.4).