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.
Videosequence is a library which hides the complexity of simply opening a video file in Python as a sequence of images. It exposes a video file as just that: a Python sequence type containing PIL Image-s.
For example, suppose you want to dump every frame from a video stored in foo.mp4 starting from frame 100:
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 videosequenceIt can also be installed directly from git:
$ pip install --user git+git://github.com/rjw57/videosequenceUbuntu 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-giGStreamer is almost certainly already installed if you’ve got some modern desktop environment. If not:
$ sudo apt install libgstreamer1.0-dev gstreamer1.0-plugins-goodContributing
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.
Copyright and licensing
Videosequence is © 2016 Rich Wareham. Full licence details can be found in the LICENCE.txt file.
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