libvpx

libvpx, the VP9 video codec, and libwebm, the WebM container, through C++23 modules.

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mcpplibs.mwrap.libvpx 1.17.0 encodes and decodes VP9, the royalty-free video of the Web, and writes and reads WebM, the container every browser plays. The upstream APIs are unchanged: vpx_codec_enc_config_default, vpx_codec_encode, vpx_codec_get_cx_data, vpx_codec_decode, vpx_codec_get_frame, vpx_img_alloc … are libvpx's globals, and mkvmuxer::Segment, mkvparser::Segment, mkvmuxer::IMkvWriter, mkvparser::IMkvReader … are libwebm's classes in their own namespaces. The libraries are compat.libvpx 1.17.0 and compat.libwebm 1.0.0.32. The headers' typed controls (vpx_codec_control_VP8E_SET_CPUUSED …) are adapted under the same names, and the macros are constants and functions. On every CI run the files written are byte-identical to upstream's own vpxenc, and vpxdec reads them to the same frames.

Modules

• import mcpplibs.mwrap.libvpx;: the encoder and decoder (vpx/vpx_encoder.h, vpx/vpx_decoder.h, vpx/vp8cx.h, vpx/vp8dx.h …), re-exporting the two below
• import mcpplibs.mwrap.libvpx.webm;: libwebm's mkvmuxer, mkvparser and libwebm namespaces
• import mcpplibs.mwrap.libvpx.macros;: VPX_DL_REALTIME, VPX_FRAME_IS_KEY, VPX_CODEC_CAP_ENCODER, vpx_codec_enc_init … in mcpplibs::mwrap::libvpx::macros

More Modules API -> Usage and API

Getting started

mcpp new clip --template mcpplibs.mwrap.libvpx@1.17.0
cd clip
mcpp run -- clip.webm

The default template encodes two seconds of moving pictures, muxes them into a WebM in memory, parses it back, decodes every frame and prints the file's size and the worst PSNR; given a file name it also writes the WebM.

[dependencies]
"mcpplibs.mwrap.libvpx" = "1.17.0"

import std;
import mcpplibs.mwrap.libvpx;

namespace m = mcpplibs::mwrap::libvpx::macros;

int main() {
    vpx_codec_enc_cfg_t cfg;
    vpx_codec_enc_config_default(vpx_codec_vp9_cx(), &cfg, 0);
    cfg.g_w = 320;
    cfg.g_h = 180;
    cfg.g_timebase = {1, 30};
    vpx_codec_ctx_t encoder;
    m::vpx_codec_enc_init(&encoder, vpx_codec_vp9_cx(), &cfg, 0);
    mcpplibs::mwrap::libvpx::vpx_codec_control_VP8E_SET_CPUUSED(&encoder, VP8E_SET_CPUUSED, 6);
    vpx_image_t img;
    vpx_img_alloc(&img, VPX_IMG_FMT_I420, 320, 180, 16);
    // … fill img.planes, then vpx_codec_encode(&encoder, &img, pts, 1, 0, m::VPX_DL_GOOD_QUALITY)
    vpx_img_free(&img);
    vpx_codec_destroy(&encoder);
    std::println("{}", vpx_codec_version_str());
}

The libraries

compat.libvpx builds the 101 C files upstream's own configure --target=generic-gnu --disable-vp8 --enable-vp9 compiles: libvpx's portable C, without SIMD, assembler or run-time CPU detection, so one configuration builds on x86-64 and aarch64, Linux, macOS, Windows and wasm32-emscripten. One thread (the default) gives the same bytes on every target; more threads tile the work (on Emscripten without pthreads, in turn on one). VP8 is not built. compat.libwebm builds upstream's webm library (mkvmuxer, mkvparser and the common helpers). mkvmuxer gives a track a random UID unless one is set (Track::set_uid): set it for reproducible files. Details and limits: docs/usage.md.

Examples

• examples/vpxwebm: encodes Y4M to VP9 in WebM or IVF, decodes WebM or IVF to raw I420 and describes a WebM, written against the module; tools/run_conformance.py compares it with upstream's vpxenc and vpxdec.

Build and testing

Linux (x86_64 GCC and LLVM, arm64 GCC), macOS, Windows and wasm32-emscripten (under node) CI build the modules and run the tests in the dev and release profiles: VP9 at good quality, real time, four threads and lossless, muxed into WebM, parsed and decoded back, each file's bytes pinned; every macro mapping against the raw headers; every exported function linked. The native rows also run the export audit (tools/check_exports.py: the generated modules are fresh, every declaration exported, every macro mapped or accounted for) and, but on Windows, the conformance run against upstream's tools. A separate job scaffolds the template as an installed package and runs it.

License

Apache-2.0 for the wrapper, by mcpp-community; libvpx and libwebm remain BSD-3-Clause with the WebM project's patent grant (upstream/libvpx/LICENSE, upstream/libvpx/PATENTS, upstream/libwebm/LICENSE.TXT, upstream/libwebm/PATENTS.TXT).