31.8.0

Features

• New burn action/generator: draws a subtitle file (.srt, .ass, or a file's text stream) over a section or on its own layer, e.g. add:burn:talk.srt, with overrides for font, size, colors, and alignment.
• New text action/generator: writes text over a section or on its own layer, e.g. add:text:Chapter 1, with the same overrides and an optional vertical layout.
• burn without a file draws the subtitles of the media under it: its first text subtitle stream, else a .srt or .ass with the same name. They stay on their words through cuts and speed changes.
• New --font option, the default font for burn and text.
• New scale action: scales the picture about its center without growing the frame, e.g. scale:0.8 or scale:0.4:1.
• New turn action: turns the picture clockwise about its center without growing the frame, e.g. turn:15.
• New convolve action: runs audio through an impulse response file, or a folder of H_LL/H_LR/H_RL/H_RR.wav files for true stereo.
• mask and confine take poly=x1/y1/x2/y2/... for any closed polygon.
• Keyframes can say when they are with value@time, in frames, sec, or % of the section, e.g. zoom:1@0..2@1.5sec..1@100%.
• FCP7 XML import reads transitions as dissolves.
• Exporting to an editor warns about the actions and tracks its format can't hold.
• Enable the MJPEG encoder.

Performance

• x265 uses its assembly on arm64 for 10-bit encoding.
• zoom scales only the part of the frame that stays visible and reuses its scaler, making 4K renders with zoom 1.4–1.9× faster.
• Exporting to Premiere, Resolve, Final Cut Pro, Shotcut, and Kdenlive uses far less memory and is up to 1.6× faster. A 50,000-clip timeline peaks at 0.6 GiB instead of 2.1 GiB for Premiere, and 0.2 GiB instead of 1.6 GiB for Shotcut.
• Importing FCP7 XML streams the file and uses about a third of the memory: a 50,000-clip Premiere XML peaks at 0.7 GiB instead of 1.8 GiB.
• Loading a timeline where many clips have different actions no longer slows down quadratically: 50,000 clips, each with its own volume, load in 0.5 seconds instead of 12.

Fixes

• WebP images, still and animated, can again be used as inputs. Required enabling FFmpeg's vp8 decoder.
• RGB sources keep their colors when encoded to YUV, instead of a strong green/purple shift (#1289).
• Runs on older x86_64 CPUs. Checks for SSE4.2 when it runs, rather than requiring it, which crashed CPUs without them.
• A sample aspect ratio set by the container (an MP4 pasp box, Matroska) is kept, in info and in renders. Before, only the one in the video bitstream was used.
• A video-only file whose stream has no duration of its own, like Matroska, no longer gives an empty timeline.
• Copying H.264 from Matroska with B-frames no longer fails with "Could not write packet: Invalid argument".
• MJPEG video in avi/mov no longer freezes on its first frame.
• Cover art is skipped for output formats that can't hold it.
• Motion analysis no longer writes out of bounds when a stream changes resolution.
• An unknown audio codec reports an error instead of crashing.
• Subtitle cues starting before 0 no longer crash subtitle analysis.
• Deeply nested --edit expressions report an error instead of overflowing the stack, and an invalid regex pattern reports an error instead of crashing.
• Actions reject nan and inf values.
• A speed too small to store in v1 timelines or FCP7 XML time remaps reports an error instead of hanging.
• FCP7 XML import rejects bad integer fields, a timebase of 0, and clips that end before they start.
• Exporting to Premiere, Resolve (FCP7 XML), Shotcut, or Kdenlive with an output path that can't be written reports an error instead of crashing.
• FCP7 XML import reads text in CDATA sections, such as a <pathurl>, instead of dropping it.
• Importing an FCP7 XML file that doesn't exist reports an error instead of crashing.

Misc.

• Can be now be used as a Nim library, without going through command-line strings.
• Use whisper.cpp 1.9.5.

Full Changelog: 31.7.2...31.8.0