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fix: handle av1 VideoDecoder errors #334

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Merged
siddharthvaddem merged 2 commits into from
Apr 7, 2026
Merged

fix: handle av1 VideoDecoder errors #334

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21361d9
fix: handle av1 VideoDecoder errors
matthew-hre Apr 5, 2026
2712d8a
fix: use view-aware byte extraction for BufferSource inputs
matthew-hre Apr 5, 2026
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58 changes: 57 additions & 1 deletion src/lib/exporter/streamingDecoder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,52 @@ import type { SpeedRegion, TrimRegion } from "@/components/video-editor/types";

const SOURCE_LOAD_TIMEOUT_MS = 60_000;

/**
* Build a full WebCodecs-compatible AV1 codec string from the AV1CodecConfigurationRecord.
* web-demuxer may return a bare "av01" when the WASM-side parser fails to read
* the extradata (e.g. raw OBU sequence header from WebM instead of ISOBMFF av1C box).
* This function parses the record if present, otherwise returns a safe default.
*
* @see https://aomediacodec.github.io/av1-isobmff/#av1codecconfigurationbox-section
*/
function buildAV1CodecString(description?: BufferSource): string {
const fallback = "av01.0.01M.08";

if (!description) return fallback;

const bytes =
description instanceof ArrayBuffer
? new Uint8Array(description)
: new Uint8Array(description.buffer, description.byteOffset, description.byteLength);

// AV1CodecConfigurationRecord layout (4+ bytes):
// Byte 0: marker (1) | version (7)
// Byte 1: seq_profile (3) | seq_level_idx_0 (5)
// Byte 2: seq_tier_0 (1) | high_bitdepth (1) | twelve_bit (1) | ...
// The spec says version should be 1, but Chrome/Electron's MediaRecorder
// may write version 127 (0xFF first byte). We accept any version as long
// as the marker bit is set and the record is long enough.
if (bytes.length < 4) return fallback;
if (!(bytes[0] & 0x80)) return fallback; // marker bit must be 1

// Byte 1: seq_profile (3) | seq_level_idx_0 (5)
const profile = (bytes[1] >> 5) & 0x07;
const level = bytes[1] & 0x1f;

// Byte 2: seq_tier_0 (1) | high_bitdepth (1) | twelve_bit (1) | monochrome (1) | ...
const tier = (bytes[2] >> 7) & 0x01;
const highBitdepth = (bytes[2] >> 6) & 0x01;
const twelveBit = (bytes[2] >> 5) & 0x01;
let bitdepth = 8;
if (highBitdepth) bitdepth = twelveBit ? 12 : 10;

const tierChar = tier ? "H" : "M";
const levelStr = level.toString().padStart(2, "0");
const bitdepthStr = bitdepth.toString().padStart(2, "0");

return `av01.${profile}.${levelStr}${tierChar}.${bitdepthStr}`;
}

export interface DecodedVideoInfo {
width: number;
height: number;
Expand Down Expand Up @@ -183,7 +229,17 @@ export class StreamingVideoDecoder {
}

const decoderConfig = await this.demuxer.getDecoderConfig("video");
const codec = this.metadata.codec.toLowerCase();

// web-demuxer may return a bare "av01" for AV1 in WebM containers when the
// extradata isn't in the expected ISOBMFF format. WebCodecs requires the
// full parametrized form (e.g. "av01.0.05M.08").
if (/^av01$/i.test(decoderConfig.codec)) {
decoderConfig.codec = buildAV1CodecString(
decoderConfig.description as BufferSource | undefined,
);
}

const codec = decoderConfig.codec.toLowerCase();
const shouldPreferSoftwareDecode = codec.includes("av01") || codec.includes("av1");
const segments = this.splitBySpeed(
this.computeSegments(this.metadata.duration, trimRegions),
Expand Down
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