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Design notes

← Documentation ・ ← SmartCut ・ 日本語

Decision: a Rust core with a Tauri GUI.

  • Core: demux, packet selection and mux are all driven directly through ffmpeg-next (the libavformat / libavcodec bindings).
    • Timestamps are assigned by us, so the seam problem disappears by construction
    • nal_ref_idc can be read straight off the packet, so the sampling of #3 is not needed
    • No intermediate files, and no multiple ffprobe passes
  • GUI: Tauri (Windows / macOS / Linux, small distribution size). The timeline UI can be built with web technology.

The Python prototype is kept as a reference implementation and test oracle. tests/run_tests.sh (Python) and tests/run_rust_tests.sh (Rust) share the same frame-hash comparison.

Licence and patents

It ships under GPL-3.0: of the two ways out below, the software encoders are the side that was taken.

  • x264 / x265 are GPL. Linking them makes the whole application GPL.
  • The way around that is a hardware encoder (NVENC / QSV / VideoToolbox / AMF). Only partial GOPs get re-encoded, so the quality compromise is small and the licence situation is clean. The prototype can switch between them with --video-encoder.
  • The patent licences for H.264 / HEVC (MPEG LA / Access Advance) need separate consideration for commercial distribution.