Read from and seek into video files as if they were Python sequences of PIL.Image-s.
Project description
Quite often I find myself writing scripts which need to load a few frames from a video file, process them and save the result to disk. It’s a pain to implement video opening, seeking and decoding over and over again and complex Python bindings are a little overkill for my needs.:
from contextlib import closing from videosequence import VideoSequence with closing(VideoSequence("foo.mp4")) as frames: for idx, frame in enumerate(frames[100:]): frame.save("frame{:04d}.jpg".format(idx))
You can load a single frame from a sequence just as easily. Let’s dump the final frame to another JPEG:
from contextlib import closing from videosequence import VideoSequence with closing(VideoSequence("foo.mp4")) as frames: frames[-1].save("final-frame.jpg")
In general, the VideoSequence behaves as if it were a long list of each frame in the video.
What VideoSequence does
- Frame-accurate seeking
- Single frame indexing (vs[0], vs[-4], etc.)
- Querying the length of the video (len(vs))
- Slicing a sequence of frames (vs[100:], vs[-20:], vs[10:20], vs[::2], etc.)
- Frames are represented as RGB PIL Image objects.
- Can interoperate with numpy. E.g. np.asarray(vs[0]).
What VideoSequence does not
- Handle files without exactly one (and only one) video stream
- Audio
Caveats
- Iterating forward one frame at a time is fast. Tricks such as iterating backwards or skipping n frames at a time work but is likely to be slow.
- The implementation is based on GStreamer and so de facto only works on a modern Unix-alike such as Linux or FreeBSD.
- The PyGObject introspection libraries must be installed. (See below.)
Installing
See the sections below for any OS-specific instructions. VideoSequence can be installed from the PyPI:
$ pip install --user videosequence
It can also be installed directly from git:
$ pip install --user git+git://github.com/rjw57/videosequence
Ubuntu and Debian
To install the Python GObject bindings:
$ sudo apt install gir1.2-gstreamer-1.0 gir1.2-gst-plugins-base-1.0 \ python-gi python3-gi
GStreamer is almost certainly already installed if you’ve got some modern desktop environment. If not:
$ sudo apt install libgstreamer1.0-dev gstreamer1.0-plugins-good
Contributing
Bug fixes and ports to new backends welcome. Please make sure that the tests still pass via tox before opening a new pull request. New functionality should come with tests, please.
Videosequence is © 2016 Rich Wareham. Full licence details can be found in the LICENCE.txt file.
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