Excerpt creation from within mpv
The excerpt.lua script allows you to quickly create excerpts from media files, you just have to set begin and end markers.
(written by Lutz Vieweg)
Rationale / Use Case:
When you shoot video with your own camera, chances are you will want to retain only ~ 10% of your recordings for actual use in an edited, final cut.
Using video editors like kdenlive - see http://kdenlive.org/ - is great for assembling and post-processing your final cut, but it sucks when you try to use it with huge 3840 x 2160 x 24fps files that were recorded at 100 MBit/s - you'll want to reduce the amount of data you have to store and deal with to those parts of the raw video footage you really need.
Now mpv is a marvellous media player, and for me it is currently the only player that can replay 4k h.264 video files, as recorded by my Panasonic camera, with little CPU usage and no stuttering on my laptop.
Also, mpv is the only software that (by utilizing the h.264 decoder hardware well) can very quickly navigate through video files - the reaction to seek commands is almost instantaneous, much unlike with many pure software based editors.
For extracting the relevant excerpts from media files it seemed like an obvious idea to me to script mpv such that I can just set the "in" and "out" points for a file, then call "ffmpeg" as an external executable with the appropriate parameters to seek to the "in" position and copy the content to a new excerpt file until the "out" position. Without re-encoding, this process is very quick and does not loose any quality.
Prerequisites / Installation
In order to use excerpt.lua, you'll need to have the executables
- mpv
- ffmpeg
ready for execution in your $PATH.
(ffmpeg is probably already installed if you have mpv installed, as mpv makes use of the ffmpeg libraries.)
Copy the "excerpt_copy" shell script to some directory included in your $PATH. You might want to modify the excerpt_copy script if you want something else than simple, key-frame accurate extraction without re-encoding. If you want to change the names of the destination excerpt files, you have to chang the excerpt.lua script for now.
Usage:
First change your working directory to where you want your video excerpts to be written.
Then just start mpv like this:
mpv --lua /path/to/excerpt.lua -fs --script-opts=osc-layout=bottombar yourmediafile.mp4
Where "yourmediafile.mp4" is of course to be replaced by the file you actually want to extract from. You can also provide multiple file names, just press the "Return" key once you're done with a file.
The "-fs" and "--script-opts=osc-layout=bottombar" options are not strictly required, but IMHO the OSC interface is thus best suited for navigating through the files.
After start, the video replay will be paused at the begin.
Use the "left" or "right" cursor keys to seek to the previous/next frames, and "shift-left" or "shift-right" cursor key to seek to the previous/next keyframe. You can use the other usual mpv seek features, too, like the cursor up/down keys, the mouse wheel, the navigation bar for the mouse etc., and of course you can play/pause pressing the space bar - whatever you do, just seek to the position where you want your excerpt to begin.
You can use the "w" and "e" keys to zoom out and in, pressing Ctrl and left/right/up/down allows to pan around in the zoomed display.
Then press the "i" key to mark the begin (or "in"-position) of the excerpt.
Then seek to the position where you want your excerpt to end, and press the "o" key to mark the end (or "out"-position) of the excerpt.
You can also seek to the begin or end marks you already set by pressing shift-i and shift-o.
If you are not satisfied with your begin / end choice, you can press "i" and "o" again to move the marks to the current position.
Once To actually write the excerpt, press "x". The excerpt.lua script will create a filename that does not yet exist in your current working directory, files will be named "excerpt_000.mkv", "excerpt_001.mkv" etc. by default, and no existing files will be overwritten.
The actual extraction work is done by invoking the "extract_copy" shell script, which is given the source file name and the "in" and "out" position as parameters. The supplied extract_copy script will use ffmpeg to create the extract, by default without any re-encoding, and therefore only pricise to the keyframe. If you want frame-exact extraction, you will have to tell ffmpeg to re-encode your media file, which of course takes much longer, and might also lower the quality. So if you plan on post-processing the excerpts in another software (like kdenlive) anyway, don't bother with frame-exact extraction and fine tune the in/out positions using the post-processing software.
DISCLAIMER
This software is provided as-is, without any warranties.
Please notice that it is in an early stage at the moment, there is probably a lot that can be enhanced.