Development

This document describes how to develop and extend django-video-transcoding.

Developing

Running tests

$> src/manage.py test

Type checking

$> pip install mypy django-stubs
$> cd src && mypy \
    --config-file=../mypy.ini \
    -p video_transcoding \
    -p django_stubs_ext

Configuration

• All configuration is stored in video_transcoding.defaults module.
• Most important variables are configured from ENV
• settings.VIDEO_TRANSCODING_CONFIG may be used for overriding defaults.

Extending

Celery application

• if you are running transcoder in docker, make sure that celery master process has pid 1 (docker will send SIGTERM to it by default)
• when using separate celery app, send SIGUSR1 from master to workers to trigger soft shutdown handling (see video_transcoding.celery.send_term_to_children)
• celery master should set process group in order to send SIGUSR1 to workeres (see video_transcoding.celery.set_same_process_group)

Transcoding implementation

• extend video_transcoding.tasks.TranscodeVideo to change task behavior
• top-level transcoding strategy is selected in TranscodeVideo.init_strategy, see video_transcoding.strategy.ResumableStrategy as an example
• see video_transcoding.transcoding.transcoder module for low-level transcoding steps examples
• dealing with different intermediate files requires metadata extraction and specific logic for this process is implemented in video_transcoding.transcoding.extract.Extractor subclasses.
• missing metadata is restored by different analyzers in video_transcoding.transcoding.analysis module.

Model inheritance

• For preset-related models use <Model>Base abstract models defined in video_transcoding.models.
• For overriding Video model set VIDEO_TRANSCODING_CONFIG["VIDEO_MODEL"] key to app_label.ModelName in settings.
• Connect other django models to Video using video_transcoding.models.get_video_model().
• When Video is overridden, video model admin is not registered automatically. As with migrations, this should be done manually.