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Add codec string parsing for h264, h265, and mp4a #4996

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merged 3 commits into from
May 30, 2023
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Add codec string parsing for h264, h265, and mp4a #4996

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0be885e
Add codec string parsing for h264, h265, and mp4a
uvjustin Oct 28, 2022
76b297a
Update default HEVC codec string
uvjustin Oct 29, 2022
e99a16c
Update comments
uvjustin Oct 29, 2022
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3 changes: 1 addition & 2 deletions src/remux/passthrough-remuxer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -234,11 +234,10 @@ function getParsedTrackCodec(
if (parsedCodec && parsedCodec.length > 4) {
return parsedCodec;
}
// Since mp4-tools cannot parse full codec string (see 'TODO: Parse codec details'... in mp4-tools)
// Provide defaults based on codec type
// This allows for some playback of some fmp4 playlists without CODECS defined in manifest
if (parsedCodec === 'hvc1' || parsedCodec === 'hev1') {
return 'hvc1.1.c.L120.90';
return 'hvc1.1.6.L120.90';
}
if (parsedCodec === 'av01') {
return 'av01.0.04M.08';
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103 changes: 97 additions & 6 deletions src/utils/mp4-tools.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -242,12 +242,103 @@ export function parseInitSegment(initSegment: Uint8Array): InitData {
let codec;
if (stsd) {
codec = bin2str(stsd.subarray(12, 16));
// TODO: Parse codec details to be able to build MIME type.
// stsd.start += 8;
// const codecBox = findBox(stsd, [codec])[0];
// if (codecBox) {
// TODO: Codec parsing support for avc1, mp4a, hevc, av01...
// }
// Parse codec details to be able to build MIME type
// TODO: Codec parsing support for AV1
const toHex = (x: number): string => {
return ('0' + x.toString(16).toUpperCase()).slice(-2);
};

// Handle H264
if (
codec.slice(0, 3) === 'avc' &&
codec[3] >= '1' &&
codec[3] <= '4' &&
stsd.length > 102 &&
bin2str(stsd.subarray(98, 102)) === 'avcC'
) {
// profile + compatibility + level
codec +=
'.' + toHex(stsd[111]) + toHex(stsd[112]) + toHex(stsd[113]);
}

// Handle H265
else if (
(codec === 'hev1' || codec === 'hvc1') &&
stsd.length > 102 &&
bin2str(stsd.subarray(98, 102)) === 'hvcC'
) {
// Profile Space
const profileByte = stsd[103];
const profileSpace = { 0: '', 1: 'A', 2: 'B', 3: 'C' }[
profileByte >> 6
];
const generalProfileIdc = profileByte & 31;
codec += '.' + profileSpace + generalProfileIdc;

// Compatibility
let reversed = 0;
for (let i = 0; i < 4; ++i) {
// byte number
for (let j = 0; j < 8; ++j) {
// bit number
reversed |=
((stsd[i + 104] >> (7 - j)) & 1) << (31 - 8 * i - j);
}
}
codec += '.' + toHex(reversed >>> 0);

// Tier Flag
codec += (profileByte & 32 ? '.H' : '.L') + stsd[114];

// Constraint String
let hasByte = false;
let constraintString = '';
for (let i = 113; i > 107; --i) {
if (stsd[i] || hasByte) {
constraintString = '.' + toHex(stsd[i]) + constraintString;
hasByte = true;
}
}
codec += constraintString;
}

// Handle Audio
else if (codec === 'mp4a') {
// Parse ES Descriptors
let i: number;
// oti
for (i = 0; i < stsd.length - 5; ++i) {
if (
stsd[i] == 4 &&
stsd[i + 1] == 128 &&
stsd[i + 2] == 128 &&
stsd[i + 3] == 128
) {
codec += '.' + toHex(stsd[i + 5]);
break;
}
}

// dsi
for (i = 0; i < stsd.length - 6; ++i) {
if (
stsd[i] == 5 &&
stsd[i + 1] == 128 &&
stsd[i + 2] == 128 &&
stsd[i + 3] == 128
) {
let dsi = (stsd[i + 5] & 248) >> 3;
if (dsi == 31 && stsd[i + 4] >= 2) {
dsi =
32 +
((stsd[i + 5] & 7) << 3) +
((stsd[i + 6] & 224) >> 5);
}
codec += '.' + dsi;
break;
}
}
}
}
result[trackId] = { timescale, type };
result[type] = { timescale, id: trackId, codec };
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