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remove annex b #3

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merged 1 commit into from
Dec 29, 2022
Merged

remove annex b #3

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78 changes: 2 additions & 76 deletions mp4box.html
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Original file line number Diff line number Diff line change
Expand Up @@ -79,50 +79,10 @@
});

encoder = new VideoEncoder({
output(chunk) {
output(chunk, metadata) {
let uint8 = new Uint8Array(chunk.byteLength);
chunk.copyTo(uint8);

// https://stackoverflow.com/questions/53992918/about-fmp4-encoding-how-to-fill-the-mdat-box-wit-h264-frame

// Find the offset of the first NAL that contains picture data (of type 5 or 1).
// Note that it is not safe if the initial NAL contains escaped 00 00 00 01 sequences
let startOfPictureNAL = null;
let pps_start = null;
let pps_end = null;
let sps_start = null;
let sps_end = null;
for (let i = 0; i < chunk.byteLength; ++i) {
if (
uint8[i] === 0 &&
uint8[i + 1] === 0 &&
uint8[i + 2] === 0 &&
uint8[i + 3] === 1
) {
const type = uint8[i + 4] & 31;

if (pps_start !== null && pps_end === null) {
pps_end = i;
}
if (sps_start !== null && sps_end === null) {
sps_end = i;
}

if (type === 5 || type === 1) {
startOfPictureNAL = i;
break;
} else if (type === 7) {
pps_start = i + 4;
} else if (type === 8) {
sps_start = i + 4;
}
}
}

if (startOfPictureNAL === null) {
throw "Couldn't find Picture NAL";
}

if (trackID === null) {
trackID = mp4boxOutputFile.addTrack({
width,
Expand All @@ -131,41 +91,10 @@
timescale: 90000,
language: 21956,
name: 'VideoHandler',

// https://gist.github.com/uupaa/8493378ec15f644a3d2b
avcDecoderConfigRecord: (new Uint8Array([
1, // configurationVersion
77, // AVCProfileIndication
0, // profile_compatibility
40, // AVCLevelIndication
0b111111 << 2 ^ // reserved
3, // lengthSizeMinusOne
0b111 << 5 ^ // reserved

1, // numOfSequenceParameterSets
(pps_end - pps_start) >> 8, (pps_end - pps_start) >> 0, // sequenceParameterSetLength
...uint8.slice(pps_start, pps_end), // sequenceParameterSetNALUnit

1, // numOfPictureParameterSets
(sps_end - sps_start) >> 8, (sps_end - sps_start) >> 0, // pictureParameterSetLength
...uint8.slice(sps_start, sps_end), // pictureParameterSetNALUnit
])).buffer,
avcDecoderConfigRecord: metadata.decoderConfig.description
});
}

const size = chunk.byteLength - startOfPictureNAL - 4;

// Remove all the NALs before the ones containing the picture.
// Note that this is not safe in the general case, this assume that
// the NAL with the picture is the last one.
uint8 = uint8.slice(startOfPictureNAL);

// Replace "00 00 00 01" sequence by the size encoded in a 32 bits number
uint8[0] = size >> 24;
uint8[1] = size >> 16;
uint8[2] = size >> 8;
uint8[3] = size >> 0;

mp4boxOutputFile.addSample(trackID, uint8, {
duration: 1491,
is_sync: chunk.type === 'key',
Expand All @@ -180,9 +109,6 @@
codec: 'avc1.4d0034',
width,
height,
avc: {
format: 'annexb',
},
hardwareAcceleration: 'prefer-hardware',
bitrate: 9_000_000,
});
Expand Down