Changelog

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0.3.0 - 2026-05-20

Initial public release. Native Elixir bindings for FFmpeg 8 via the rsmpeg Rust crate, packaged as a Rustler NIF - in-process calls instead of shelling out to the ffmpeg / ffprobe CLIs.

Operations

  • Exmpeg.version/0 - linked FFmpeg sub-library versions and configure flags.
  • Exmpeg.probe/1 - container + per-stream metadata (ffprobe).
  • Exmpeg.remux/3 - stream copy between containers with optional start_s / duration_s window, :drop_audio / :drop_video / :drop_subtitles, and a :tags keyword/map for container metadata.
  • Exmpeg.extract_frame/3 - single-frame thumbnail at a timestamp, written as .jpg / .png / .bmp / .webp, with optional aspect-preserving resize.
  • Exmpeg.extract_audio/3 - decoded audio to .wav, .mp3, .m4a / .aac, .opus / .ogg, or .flac, with optional sample-rate / channel-count / bitrate selection. Sample rate snaps to the encoder's supported list when needed (e.g. libopus 8/12/16/24/48 kHz).
  • Exmpeg.concat/3 - join multiple inputs sharing the same stream layout into a single output without re-encoding.
  • Exmpeg.transcode/3 - per-stream re-encode with codec / bitrate / scale / fps / sample-rate selection driven by an AVFilterGraph, plus a raw :video_filter filter-graph spec. Streams marked "copy" are stream-copied.

Inputs and progress

  • Memory inputs - every read-side operation accepts {:memory, binary} in place of a filesystem path, backed by a custom AVIOContextCustom with read + seek callbacks so demuxers that seek (mp4 moov, matroska cues) work without a temp file.
  • Progress callbacks - remux/3, extract_audio/3, concat/3, and transcode/3 accept progress: pid() and send throttled {:exmpeg_progress, %{...}} messages plus a final tick after write_trailer.

Packaging

  • Precompiled NIFs for aarch64-apple-darwin, x86_64-unknown-linux-gnu, and aarch64-unknown-linux-gnu; other targets build from source with EXMPEG_BUILD=1.
  • The precompiled tarballs bundle an LGPL-only FFmpeg 8 (libmp3lame, libopus, libvpx; no --enable-gpl), so they redistribute cleanly under this package's MIT license. H.264 / H.265 software encoding (libx264 / libx265, GPL) is not in the precompiled binaries and returns :unsupported; build from source against a GPL-enabled FFmpeg 8 to use them. H.264/H.265 decoding is unaffected.

Safety

  • The Rust crate is built on rsmpeg's safe wrappers with #![deny(unsafe_code)] at the root. All unsafe is confined to ffi_helpers.rs, each block carrying a SAFETY: comment.
  • Every NIF entry point is wrapped in run_with_panic_protection, so a Rust panic surfaces as {:error, %{type: "nif_panic"}} instead of crashing the BEAM.
  • Size options (:width / :height / :sample_rate) are bounded at the API boundary so an absurd value cannot trigger an out-of-memory allocation inside the NIF.
  • Disk writes are atomic: operations write a <stem>.partial.<ext> sibling and rename onto the destination only after the muxer trailer is written; a mid-encode failure removes the partial.