parse-trun.js
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var parseSampleFlags = require('./parse-sample-flags.js');
var trun = function(data) {
var
result = {
version: data[0],
flags: new Uint8Array(data.subarray(1, 4)),
samples: []
},
view = new DataView(data.buffer, data.byteOffset, data.byteLength),
// Flag interpretation
dataOffsetPresent = result.flags[2] & 0x01, // compare with 2nd byte of 0x1
firstSampleFlagsPresent = result.flags[2] & 0x04, // compare with 2nd byte of 0x4
sampleDurationPresent = result.flags[1] & 0x01, // compare with 2nd byte of 0x100
sampleSizePresent = result.flags[1] & 0x02, // compare with 2nd byte of 0x200
sampleFlagsPresent = result.flags[1] & 0x04, // compare with 2nd byte of 0x400
sampleCompositionTimeOffsetPresent = result.flags[1] & 0x08, // compare with 2nd byte of 0x800
sampleCount = view.getUint32(4),
offset = 8,
sample;
if (dataOffsetPresent) {
// 32 bit signed integer
result.dataOffset = view.getInt32(offset);
offset += 4;
}
// Overrides the flags for the first sample only. The order of
// optional values will be: duration, size, compositionTimeOffset
if (firstSampleFlagsPresent && sampleCount) {
sample = {
flags: parseSampleFlags(data.subarray(offset, offset + 4))
};
offset += 4;
if (sampleDurationPresent) {
sample.duration = view.getUint32(offset);
offset += 4;
}
if (sampleSizePresent) {
sample.size = view.getUint32(offset);
offset += 4;
}
if (sampleCompositionTimeOffsetPresent) {
if (result.version === 1) {
sample.compositionTimeOffset = view.getInt32(offset);
} else {
sample.compositionTimeOffset = view.getUint32(offset);
}
offset += 4;
}
result.samples.push(sample);
sampleCount--;
}
while (sampleCount--) {
sample = {};
if (sampleDurationPresent) {
sample.duration = view.getUint32(offset);
offset += 4;
}
if (sampleSizePresent) {
sample.size = view.getUint32(offset);
offset += 4;
}
if (sampleFlagsPresent) {
sample.flags = parseSampleFlags(data.subarray(offset, offset + 4));
offset += 4;
}
if (sampleCompositionTimeOffsetPresent) {
if (result.version === 1) {
sample.compositionTimeOffset = view.getInt32(offset);
} else {
sample.compositionTimeOffset = view.getUint32(offset);
}
offset += 4;
}
result.samples.push(sample);
}
return result;
};
module.exports = trun;