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Loading and Showing Videos

The MgVideo class is the main entry point for working with video files. It holds a reference to the file, applies preprocessing, and exposes all analysis methods.

Loading

Pass the path to your video file to create an MgVideo:

import musicalgestures as mg

mv = mg.MgVideo('/path/to/video.mp4')

MgVideo accepts most common video formats (MP4, AVI, MOV, MKV, etc.). See Preprocessing for options you can apply at load time.

Showing

Call show() on any MgVideo to display it:

mv = mg.MgVideo('/path/to/video.mp4')
mv.show()                   # opens in a separate window (default)
mv.show(mode='notebook')    # embeds inline in a Jupyter notebook

In notebook mode, show() converts the video to MP4 automatically if the format is not browser-compatible. In Google Colab, notebook mode is always used regardless of the mode argument.

Referencing results by key

After running a process on a video, the result is attached to the source MgVideo. The key parameter on show() lets you display a previously computed result without keeping a reference to the return value:

mv = mg.MgVideo('/path/to/video.mp4')
mv.motionvideo()
mv.flow.dense()

mv.show(key='motion')   # shows the motion video
mv.show(key='dense')    # shows the dense optical flow video

mv.motionvideo(threshold=0.15)
mv.show(key='motion')   # shows the newly rendered motion video

Supported key values:

Key Result shown
'motion' Motion video
'history' History video
'motionhistory' Motion history video (chained)
'mgx' Horizontal motiongram
'mgy' Vertical motiongram
'vgx' Horizontal videogram
'vgy' Vertical videogram
'ssm' Self-similarity matrix
'blend' Blended image
'plot' Motion plot image
'sparse' Sparse optical flow video
'dense' Dense optical flow video
'pose' Pose estimation video
'warp' Warped audiovisual beats video
'blur' Face-anonymized video
'subtract' Background-subtracted video

Getting video metadata

info() returns technical metadata about the file:

mv = mg.MgVideo('/path/to/video.avi')
mv.info()           # prints all metadata (video + audio + format)
mv.info('video')    # video stream metadata only
mv.info('audio')    # audio stream metadata only
mv.info('format')   # container/format metadata only

For a quick human-readable overview, use info('summary') — it prints resolution, frame count, fps, duration, colour mode, video codec/profile, colour profile, and audio codec/sample-rate/bit-rate, and returns the values as a dict:

summary = mv.info('summary')
# File:         video.avi
# Resolution:   1920 × 1080 px
# Frames:       750  @  25 fps
# Duration:     0:30.00  (30.000 s)
# Color:        color
# Video codec:  h264 (High)
# Audio:        aac (48,000 Hz, 192 kbps)
# File size:    42.3 MB
print(summary['fps'], summary['video_codec'])

I/P/B frame types

To inspect the compression frame types in the video:

mv.info('frame')                    # renders a plot of I/P/B frame distribution
mv.info('frame', autoshow=False)    # returns the dataframe without plotting

Key properties

mv = mg.MgVideo('/path/to/video.mp4')

mv.filename     # full file path
mv.width        # frame width in pixels
mv.height       # frame height in pixels
mv.length       # duration in seconds
mv.fps          # frame rate
mv.framecount   # total number of frames
mv.color        # True for colour, False for grayscale

Next steps