h265

README

h265

HEVC video and HEIC image codec in pure Go, decoding and encoding. No CGo, no dependencies.

The decoder is byte-exact on the JCT-VC HEVC v1 conformance suite. What the encoder writes is held to libde265, FFmpeg and libheif sample for sample.

SIMD support for amd64 (AVX2, AVX-512), arm64 (NEON) and riscv64 (RVV, with GORISCV64=rva23u64). Build with -tags noasm for pure Go everywhere.

Decoding

img, err := heic.Decode(r)

heic.Decode returns *image.NRGBA, or *image.NRGBA64 above 8 bits, and registers itself with image.RegisterFormat. The hevc package decodes the bitstream on its own, a NAL unit at a time:

d := hevc.Decoder{}

for _, nal := range nals {
    pics, err := d.DecodeNAL(nal)
    ...
}

Encoding

heic.Encode writes any image as a HEIC still, keeping alpha as the auxiliary item of ISO/IEC 23008-12 Annex F.

err := heic.Encode(w, img, heic.EncodeOptions{Quality: 60})

hevc.Encoder writes the bitstream on its own, as self-contained intra IDR access units:

enc, err := hevc.NewEncoder(hevc.EncoderOptions{Width: 1920, Height: 1080, QP: 26})
nals, err := enc.Encode(hevc.Frame{
    Y: y, Cb: cb, Cr: cr,
    StrideY: yStride, StrideC: cStride,
})
stream := hevc.MarshalAnnexB(nals)

Supported

Decoding: 8-16 bit, 4:2:0/4:2:2/4:4:4/monochrome, tiles, wavefronts, dependent slice segments, PCM, lossless, scaling lists, and the range extensions other than cross-component prediction, RDPCM and CABAC bypass alignment, which are refused rather than decoded wrongly. In the container alpha, grid, clap/irot/imir, colr, image sequences, Exif and XMP.

Encoding: 8-12 bit, 4:2:0/4:2:2/4:4:4/monochrome, intra only, deblocking, sample adaptive offset, wavefronts, PCM lossless, and alpha, grid, colr, Exif and XMP in the container. A picture too large for any HEVC level is written as a grid of tiles.

Decoding is threaded over grid tiles and wavefront rows; heic.Options.Threads and hevc.Decoder.Threads bound it.

License

MIT, in LICENSE. The decoder is a port of the pure-Rust rust_h265 and oxideav-h265 decoders and carries their notices.

This software implements a decoder and an encoder. It gives you no special rights on the HEVC patents. HEVC is covered by patents held by several pools and by unpooled holders; if you distribute or use this software you may need a licence from them.