Package limn.video.ffmpeg

package limn.video.ffmpeg

H.264 and AAC out of MP4, through a trimmed FFmpeg behind a hand-written JNI shim.

This is the only package in Limn with a native payload, and it is a module of its own so that it stays the only one. limn-toolkit depends on nothing and carries no native, so its pure-Java decoders cost an application that never plays an MP4 no codec on its classpath, and no FFmpeg at all.

The library is not in this repository and Gradle does not build it. It is the limn-ffmpeg-natives artifact, versioned with FFmpeg (ADR 037): this module brings its JNI shim along, and an application adds the natives-<os>-<arch> classifier for its platform. A build that added none has no library, which is an ordinary case rather than a broken one. Everything here is written so that absence is ordinary: FfmpegVideoDecoder.supports(java.nio.file.Path) answers false, FfmpegLibrary.isAvailable() answers false and never throws, and any decoder installed behind this one is reached exactly as if this one were not there.

Two entry points, for the two shapes a caller wants:

• FfmpegVideoDecoder is the SPI implementation: install it and Videos.open returns pictures. Video only, because that is what the facade's signature carries.
• FfmpegMedia is the container; it opens a file once and hands out both tracks, as the two types the toolkit already publishes, for an application that wants the soundtrack as well.

The licence is LGPL-2.1-or-later and the FFmpeg libraries are linked dynamically, which is what keeps it so. Nothing here may be built with --enable-gpl, and a test reads the linked library's own configure line to make sure nothing has been.

Related Packages

Package	Description
limn.video	Backend-neutral video: a pooled VideoFrame of planar YCbCr samples described by a PixelFormat layout and a VideoColor interpretation, produced by a VideoStreamSource that a VideoDecoder opened through the Videos facade, timed by VideoClock and shown by uploading it to a VideoSurface that the VideoSurfaces facade created, or, where no device conversion exists, turned into RGBA by YuvConverter.
limn.video.decode	Decoders, and the pooling every decoder needs.

Class	Description
FfmpegException	What every failure inside the FFmpeg decoder arrives as, including every failure that started in C.
FfmpegLibrary	Finds and loads the native library the FFmpeg decoder needs, and answers whether it is there.
FfmpegMedia	An open container, and the tracks inside it: one picture stream, and whichever of its soundtracks is playing.
FfmpegMedia.AudioTrack	One of a container's audio tracks, as the container describes it: read once at open, from the file's own stream headers, without opening a decoder for it.
FfmpegMedia.ClipAudioTrack	One audio track of a written clip.
FfmpegMedia.ClipCodec	How a written clip's pictures are coded.
FfmpegMedia.Hardware	Whether to decode on a platform accelerator, and therefore what shape this container's pictures have.
FfmpegMedia.SubtitleTrack	One of a container's subtitle tracks, as the container describes it: read once at open, from the file's own stream headers, without opening a decoder for it.
FfmpegVideoDecoder	Decodes H.264, HEVC, VP9 and VP8 video and AAC, Opus and Vorbis audio out of MP4 and Matroska/WebM, through a trimmed FFmpeg behind a hand-written native shim.
SubtitleCues	The cues of a container's selected subtitle track, asked for by position: what is on screen at this moment.
SubtitleCues.Cue	One subtitle cue: its text, and the interval it is on screen for.