dart_vp8

Pure-Dart VP8 video decoder (RFC 6386). Correctness-focused reference port of the upstream libvpx decoder; no SIMD, no platform plugins, no dart:io dependency in the library.

Status

Functionally complete. All 62 official VP8 conformance vectors from libvpx's kVP8TestVectors list decode byte-exact against the upstream reference (MD5 of the raw I420 output, every frame, every vector):

Suite	Vectors	Status
vp80-00-comprehensive	18	✔ pass
vp80-01-intra	4	✔ pass
vp80-02-inter	4	✔ pass
vp80-03-segmentation	22	✔ pass
vp80-04-partitions	3	✔ pass
vp80-05-sharpness	10	✔ pass
vp80-06-smallsize	1	✔ pass
Total	62	✔ pass

Plus 14 robustness tests covering malformed / truncated / corrupt input.

Features

• Pure Dart, zero runtime dependencies.
• Decodes any conforming VP8 stream: key + inter frames, all four MV partitionings (16x16, 16x8, 8x16, 4x4 SPLITMV), B_PRED intra, multi- token-partition (1 / 2 / 4 / 8), full segmentation with per-segment Q / LF deltas, normal + simple loop filter at all sharpness levels, hidden reference frames (show_frame=0).
• Includes a minimal IVF demuxer, a WebM/Matroska demuxer (V_VP8 video tracks) with Cues-based seeking, a streaming WebM reader for chunked input, and a WebmWriter for muxing raw VP8 frames into .webm files. Use Vp8Reader to auto-detect IVF or WebM.
• Library imports only dart:typed_data — runs on the VM, AOT, and Flutter Web.

Performance

Indicative AOT throughput on a single core (dart compile exe):

Vector	Resolution	FPS
vp80-00-comprehensive-013 (small)	176x144	~1500
vp80-01-intra-1411 (intra-only)	320x240	~600
vp80-00-comprehensive-014 (SPLITMV-rich)	176x144	~575

This is a correctness reference, not a production codec — expect a hardware decoder or libvpx itself to be roughly an order of magnitude faster.

Usage

dependencies:
  dart_vp8: ^0.1.0

import 'dart:io';
import 'dart:typed_data';

import 'package:dart_vp8/dart_vp8.dart';

void main(List<String> args) {
  final bytes = Uint8List.fromList(File(args.single).readAsBytesSync());
  // Auto-detects IVF (.ivf) or WebM (.webm) from the magic bytes.
  final reader = Vp8Reader(bytes);
  final decoder = Vp8Decoder();

  while (true) {
    final pkt = reader.nextPacket();
    if (pkt == null) break;
    final out = decoder.decodeBytes(pkt.data);
    if (!out.isShown) continue; // hidden / alt-ref reference

    // out.y, out.u, out.v are Uint8List planes at strides
    // out.yStride and out.uvStride. Crop to out.width x out.height.
    print('${out.width}x${out.height} '
        '(${out.isKeyFrame ? "kf" : "inter"})');
  }
}

The returned Uint8List planes alias the decoder's internal buffers and are overwritten on the next decode() call; copy them out if you need to keep them around.

API surface

The high-level entry points live at the top of the library:

• Vp8Reader / Vp8Packet — container-agnostic demuxer (IVF or WebM).
• IvfReader / IvfFrame — IVF-only demuxer.
• WebmReader / WebmFrame / WebmTrack — WebM/Matroska V_VP8 demuxer with seekToTime.
• WebmStreamReader — incremental WebM reader for chunked input.
• WebmWriter — mux a sequence of VP8 frames into a .webm file.
• Vp8Decoder — stateful decoder; one instance per stream.
• DecodedFrame — decoded I420 output (Y, U, V planes + metadata).

Lower-level primitives (boolean decoder, frame header parser, IDCT, intra / inter predictors, loop filter, etc.) are also exported so they can be exercised in isolation by tests; most callers do not need them.

Testing

dart test                                  # full suite (~6 s)
dart test test/conformance_suite_test.dart # 62 conformance vectors
dart test test/robustness_test.dart        # malformed-input fuzz

The 62 conformance .ivf / .ivf.md5 fixtures live under test/fixtures/. Fetch them with:

bash tool/fetch_vectors.sh

(downloads ~3 MB from storage.googleapis.com/downloads.webmproject.org/test_data/libvpx).

Benchmarking

dart compile exe bin/bench.dart -o bin/bench.exe
./bin/bench.exe test/fixtures/vp80-00-comprehensive-014.ivf 20

Non-goals

• VP8 encoder.
• VP9 / AV1 decoders.
• MP4 demuxer (use a separate package — WebM is supported in-tree).
• Audio decoding (Vorbis / Opus). The WebM demuxer ignores audio tracks.
• Hardware acceleration / SIMD.
• Real-time playback guarantees.

License

BSD-3-Clause, matching upstream libvpx. The reference C source this project ports from is libvpx (chromium.googlesource.com/webm/libvpx), copyright the WebM project authors.