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pyvo
talk_video_maker
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README.rst
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setup.py

README.rst

Takes a video recording of a presentation, and video grabbed from the screen (for example via recordmydesktop), does serious time-warping magic to sync them up, composes them with captions and titles and such, and throws the video to Youtube for all to see.

Or, it will do that. Someday. So far it just creates the resulting video.

Installation

You need Python 3, ffmpeg, and Inkscape. Inside a virtualenv, install with:

(venv)$ pip install Cython numpy
(venv)$ pip install -e.

Most talk-video-maker dependencies provide pre-compiled wheels for common platforms and Python versions. But if these aren't available for your system, you'll need to install their build-time requiremens. Some of those are:

  • for Numpy: BLAS and a C compiler
  • for PyYAML: libyaml-devel
  • for Scipy: a Fortran compiler

Usage

Make a template SVG file with rectangles where the videos should be, and assign nice IDs to those rectangles (Inkscape: right-click, Object Properties). An example is at pyvo/pyvo-640x480.svg

Then you have to write a little script that puts the videos together. An example is at pyvo/make_vid_simple.py. (There's also make_vid.py which is pretty complex, handling most cases needed for videos from our meetups. If you need something that's not in that example, then it's probably not implemented yet; sorry.)

After that, just run the script, and it'll do the magic!

To return the result (or to quickly check some intermediate output -- video, image, etc.), do:

return result_object

and then run the script. It'll generate the file, and give you the filename.

All generated files are stored in a __filecache__ directory under a hash, so that they are not built again if needed in a subsequent run. If you change the talk_video_maker internals, or if you start running out of space, you might need to delete the cache directory.

Pyvec-videomaker

If you need a simpler script, try Martin Bílek's pyvec-videomaker, the inspiration for this monstrosity: https://bitbucket.org/fragariacz/pyvec-videomaker

Architecture and Ideas

This project is an experiment. I didn't know much about video processing when I started, and it shows. Things are held together with digital duct tape.

When I rewrite this one day, these pieces will remain:

  • Intermediate files are saved under a hash of their inputs, so when they need to be recomputed, they can justr be read off disk. Each result that could be somehow saved to a file has a hash; but not everything that could be saved is -- intermediate video files are a great way to lose quality. But, you can save things manually when debugging/playing with the pipeline.
  • Multimedia is composed of multiple streams, and each streams has several channels. An audio stream can have one (mono), two (stereo), or more channels. Video streams theoretically have a channel per color, but that's not too useful to know.
  • There are filters that work on streams, for example "overlay" merges two video streams, and "amix" mixes some audio streams together. A filter can have zero or more inputs, zero or more outputs, and some configuration.
  • Streams, filters, multimedia objects, templates (SVGs) -- all are immutable. Changes result in new objects (with new hashes) being created.
  • The multimedia objects are little more than a collections of streams, with convenience operations defined. Filters work on individual streams; a simple collection of streams can be encoded into a file. It's all streams underneath; what usually happens that the audio and corresponding video have quite disjoint sets of filters applied to them: "resize" only applies to video, and "mute" to audio. But, the multimedia objects are easier to think about when writing the processing algorithm.
  • In ffmpeg, a stream connects exactly two filters (except input & output streams); there are "split" filters to clone streams ans "nullsink" filters to not use a stream. In talk-video-maker, each stream has one source, but can be an input to 0 or more filters. The splits and nullsinks are inserted automatically.
  • There is a routine to output the filtergraph, as a graph, on the terminal. Extremely useful when debugging (until the graph is 4 pages long).

Some of the worst parts of the code are opts.py (coded offline; I'm pretty sure it reinvents some wheel) and hashing in __init__ (too WET). Also, streams store much too little information about themselves; they should keep everything ffprobe tells us, and filters should update the info accordingly. SVG operations should probably rely on a different attribute than ID, so that sets of objects can be targeted for removal/replacement. If I had the time, you could do "vid[5:10]" to trim videos, "vid[:5]+vid[10:]" to cut a piece out, "vid[:, 30:50, 30:50]" to crop. Defaulting to seconds for time, but making frame-/sample-based indexing possible (video/audio, resp.). And positioning overlays by padding is probably wasteful; it should be possible to do "vid1 | vid2.at(30, 50)".