mob_video

On-device video processing for Mob apps, backed entirely by the platform video toolkits — no ffmpeg.

Android uses MediaExtractor / MediaMuxer / MediaMetadataRetriever; iOS uses AVFoundation (AVAssetExportSession passthrough, AVAssetImageGenerator). The operations here are the ones the OS does natively, losslessly, and hardware-accelerated.

Operations

# All async — results arrive in handle_info/2. dst paths go under app storage
# (e.g. Mob.Storage.dir(:cache)); src is a local file path.

MobVideo.probe(socket, src)
#=> {:video, :info, %{duration_ms:, width:, height:, rotation:,
#                     has_audio:, bitrate:, frame_rate:}}

MobVideo.clip(socket, src, dst, start_ms: 1_000, end_ms: 5_000)
#=> {:video, :clipped, %{path:, duration_ms:}}      # stream copy, no re-encode

MobVideo.thumbnail(socket, src, dst, at_ms: 2_000, max_width: 480)
#=> {:video, :thumbnail, %{path:, width:, height:}}

MobVideo.extract_audio(socket, src, dst)
#=> {:video, :audio_extracted, %{path:}}

Errors come back as {:video, :error, reason} where reason is :not_found, :unsupported, :io_error, or :bad_range.

Install

# mix.exs
{:mob_video, "~> 0.1"}

# mob.exs
config :mob, :plugins, [:mob_video]
config :mob, :trusted_plugins, %{mob_video: "ed25519:<fingerprint>"}

Run mix mob.plugin.trust mob_video to record the fingerprint, then mix mob.deploy --native.

Why no ffmpeg

A clipper, a thumbnailer, an audio-extractor and a prober are all stream-copy or single-frame-decode operations — the platform does them for free, losslessly, and with the hardware codecs. ffmpeg would add tens of MB to the app, drag in the GPL/App-Store licensing problem (its useful encoders are GPL), need a hand-rolled cross-compile now that ffmpeg-kit is archived, and run video encode in slow software. None of that buys anything for the operations above.

ffmpeg only earns its weight for re-encoding, filters, overlays, and concat-across-codecs — deliberately out of scope here. If you need those later, they slot in behind this same plugin's API; the cheap, common 80% should not pay ffmpeg's cost.

Permissions

Processing a file the app can already read needs no runtime permission. Reading from the shared media store needs READ_MEDIA_VIDEO (Android 13+) / Photos access (iOS) — pick through mob_photos first and hand the resulting local path here.

License

MIT.