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45cb15c6 by David LaPalomento
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Use more descriptive variables 

Replace more one-letter variables with more descriptive names.
1 parent 31680bd4
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Showing 2 changed files with 91 additions and 84 deletions
/*
* h264-stream
*
*
*
* Copyright (c) 2013 Brightcove
* All rights reserved.
......@@ -62,7 +62,7 @@
* NAL unit: Network abstraction layer unit. The combination of a NAL
* header and an RBSP.
* NAL header: the encapsulation unit for transport-specific metadata in
* an h264 stream.
* an h264 stream. Exactly one byte.
* RBSP: raw bit-stream payload. The actual encoded video data.
*
* SPS: sequence parameter set. Part of the RBSP. Metadata to be applied
......@@ -128,7 +128,7 @@
pic_width_in_mbs_minus1, // :int
pic_height_in_map_units_minus1, // :int
frame_mbs_only_flag, // :int
frame_cropping_flag, // :Boolean
......@@ -283,17 +283,17 @@
oldExtraData = new H264ExtraData(), // :H264ExtraData
newExtraData = new H264ExtraData(), // :H264ExtraData
nalUnitType = -1, // :int
state; // :uint;
this.tags = [];
//(pts:uint, dts:uint, dataAligned:Boolean):void
this.setNextTimeStamp = function(pts, dts, dataAligned) {
if (0>pts_delta) {
// We assume the very first pts is less than 0x8FFFFFFF (max signed
// We assume the very first pts is less than 0x8FFFFFFF (max signed
// int32)
pts_delta = pts;
}
......@@ -361,38 +361,40 @@
// A NAL unit may be split across two TS packets. Look back a bit to
// make sure the prefix of the start code wasn't already written out.
if (data[offset] <= 1) {
nalUnitSize = h264Frame ? h264Frame.nalUnitSize() : 0;
nalUnitSize = h264Frame ? h264Frame.nalUnitSize() : 0;
if (nalUnitSize >= 1 && h264Frame.negIndex(1) === 0) {
// ?? ?? 00 | O[01] ?? ??
if (1 === data[offset] && 2 <= nalUnitSize && 0 === h264Frame.negIndex(2)) {
if (data[offset] === 1 &&
nalUnitSize >= 2 &&
h264Frame.negIndex(2) === 0) {
// ?? 00 00 : 01
if (3 <= nalUnitSize && 0 === h264Frame.negIndex(3)) {
h264Frame.length -= 3; // 00 00 00 : 01
} else {
h264Frame.length -= 2; // 00 00 : 01
}
state = 3;
return this.writeBytes(data, offset + 1, length - 1);
}
if (1 < length && 0 === data[offset] && 1 === data[offset + 1]) {
if (length > 1 && data[offset] === 0 && data[offset + 1] === 1) {
// ?? 00 | 00 01
if (2 <= nalUnitSize && 0 === h264Frame.negIndex(2)) {
if (nalUnitSize >= 2 && h264Frame.negIndex(2) === 0) {
h264Frame.length -= 2; // 00 00 : 00 01
} else {
h264Frame.length -= 1; // 00 : 00 01
}
state = 3;
return this.writeBytes(data, offset + 2, length - 2);
}
if (2 < length &&
0 === data[offset] &&
0 === data[offset + 1] &&
1 === data[offset + 2]) {
// 00 | 00 00 01
if (length > 2 &&
data[offset] === 0 &&
data[offset + 1] === 0 &&
data[offset + 2] === 1) {
// 00 : 00 00 01
h264Frame.length -= 1;
state = 3;
return this.writeBytes(data, offset + 3, length - 3);
......@@ -403,19 +405,22 @@
// bytes a second time. But that case will be VERY rare
state = 2;
/* falls through */
case 2: // Look for start codes in data
case 2:
// Look for start codes in the data from the current offset forward
start = offset;
end = start + length;
for (t = end - 3 ; offset < t ;) {
if (1 < data[offset + 2]) {
offset += 3; // if data[offset + 2] is greater than 1, there is no way a start code can begin before offset+3
} else if (0 !== data[offset + 1]) {
for (t = end - 3; offset < t;) {
if (data[offset + 2] > 1) {
// if data[offset + 2] is greater than 1, there is no way a start
// code can begin before offset + 3
offset += 3;
} else if (data[offset + 1] !== 0) {
offset += 2;
} else if (0 !== data[offset]) {
} else if (data[offset] !== 0) {
offset += 1;
} else {
// If we get here we have 00 00 00 or 00 00 01
if (1 === data[offset + 2]) {
if (data[offset + 2] === 1) {
if (offset > start) {
h264Frame.writeBytes(data, start, offset - start);
}
......@@ -424,7 +429,9 @@
return this.writeBytes(data, offset, end - offset);
}
if (end - offset >= 4 && 0 === data[offset + 2] && 1 === data[offset + 3]) {
if (end - offset >= 4 &&
data[offset + 2] === 0 &&
data[offset + 3] === 1) {
if (offset > start) {
h264Frame.writeBytes(data, start, offset - start);
}
......@@ -482,9 +489,10 @@
}
h264Frame.startNalUnit();
state = 2; // We know there will not be an overlapping start code, so we can skip that test
// We know there will not be an overlapping start code, so we can skip
// that test
state = 2;
return this.writeBytes(data, offset, length);
/*--------------------------------------------------------------------------------------------------------------------*/
} // switch
};
};
......
......@@ -39,7 +39,7 @@
duration = duration || 0;
audio = audio === undefined? true : audio;
video = video === undefined? true : video;
// signature
head.setUint8(0, 0x46); // 'F'
head.setUint8(1, 0x4c); // 'L'
......@@ -47,7 +47,7 @@
// version
head.setUint8(3, 0x01);
// flags
head.setUint8(4, (audio ? 0x04 : 0x00) | (video ? 0x01 : 0x00));
......@@ -74,7 +74,7 @@
return result;
};
self.flushTags = function() {
h264Stream.finishFrame();
};
......@@ -161,7 +161,7 @@
streamBuffer.set(dataSlice, streamBufferByteCount);
parseTSPacket(streamBuffer);
// reset the buffer
streamBuffer = new Uint8Array(m2tsPacketSize);
streamBufferByteCount = 0;
......@@ -174,7 +174,7 @@
// If there is no sync byte skip forward until we find one
// TODO if we find a sync byte, look 188 bytes in the future (if
// possible). If there is not a sync byte there, keep looking
dataPosition++;
dataPosition++;
}
// base case: not enough data to parse a m2ts packet
......@@ -205,19 +205,18 @@
// packet!
parseTSPacket = function(data) { // :ByteArray):Boolean {
var
s = 0, //:uint
o = s, // :uint
e = o + m2tsPacketSize, // :uint
offset = 0, // :uint
end = offset + m2tsPacketSize, // :uint
// Don't look for a sync byte. We handle that in
// parseSegmentBinaryData()
// Payload Unit Start Indicator
pusi = !!(data[o + 1] & 0x40), // mask: 0100 0000
pusi = !!(data[offset + 1] & 0x40), // mask: 0100 0000
// PacketId
pid = (data[o + 1] & 0x1F) << 8 | data[o + 2], // mask: 0001 1111
afflag = (data[o + 3] & 0x30 ) >>> 4,
pid = (data[offset + 1] & 0x1F) << 8 | data[offset + 2], // mask: 0001 1111
afflag = (data[offset + 3] & 0x30 ) >>> 4,
aflen, // :uint
patTableId, // :int
......@@ -242,29 +241,29 @@
// Continuity Counter we could use this for sanity check, and
// corrupt stream detection
// cc = (data[o + 3] & 0x0F);
// cc = (data[offset + 3] & 0x0F);
// Done with TS header
offset += 4;
// Done with TS header
o += 4;
if (afflag > 0x01) { // skip most of the adaption field
aflen = data[o];
o += aflen + 1;
aflen = data[offset];
offset += aflen + 1;
}
if (0x0000 === pid) {
// always test for PMT first! (becuse other variables default to 0)
// if pusi is set we must skip X bytes (PSI pointer field)
o += pusi ? 1 + data[o] : 0;
patTableId = data[o];
offset += pusi ? 1 + data[offset] : 0;
patTableId = data[offset];
console.assert(0x00 === patTableId, 'patTableId should be 0x00');
patCurrentNextIndicator = !!(data[o + 5] & 0x01);
patCurrentNextIndicator = !!(data[offset + 5] & 0x01);
if (patCurrentNextIndicator) {
patSectionLength = (data[o + 1] & 0x0F) << 8 | data[o + 2];
o += 8; // skip past PSI header
patSectionLength = (data[offset + 1] & 0x0F) << 8 | data[offset + 2];
offset += 8; // skip past PSI header
// We currently only support streams with 1 program
patSectionLength = (patSectionLength - 9) / 4;
......@@ -273,26 +272,26 @@
}
// if we ever support more that 1 program (unlikely) loop over them here
// var programNumber = data[o + 0] << 8 | data[o + 1];
// var programId = (data[o+2] & 0x1F) << 8 | data[o + 3];
pmtPid = (data[o + 2] & 0x1F) << 8 | data[o + 3];
// var programNumber = data[offset + 0] << 8 | data[offset + 1];
// var programId = (data[offset+2] & 0x1F) << 8 | data[offset + 3];
pmtPid = (data[offset + 2] & 0x1F) << 8 | data[offset + 3];
}
// We could test the CRC here to detect corruption with extra CPU cost
} else if (videoPid === pid || audioPid === pid) {
if (pusi) {
// comment out for speed
if (0x00 !== data[o + 0] || 0x00 !== data[o + 1] || 0x01 !== data[o + 2]) {
if (0x00 !== data[offset + 0] || 0x00 !== data[offset + 1] || 0x01 !== data[offset + 2]) {
// look for PES start code
throw new Error("PES did not begin with start code");
}
// var sid:int = data[o+3]; // StreamID
pesPacketSize = (data[o + 4] << 8) | data[o + 5];
dataAlignmentIndicator = !!((data[o + 6] & 0x04) >>> 2);
ptsDtsIndicator = (data[o + 7] & 0xC0) >>> 6;
pesHeaderLength = data[o + 8]; // TODO sanity check header length
o += 9; // Skip past PES header
// var sid:int = data[offset+3]; // StreamID
pesPacketSize = (data[offset + 4] << 8) | data[offset + 5];
dataAlignmentIndicator = (data[offset + 6] & 0x04) !== 0;
ptsDtsIndicator = (data[offset + 7] & 0xC0) >>> 6;
pesHeaderLength = data[offset + 8]; // TODO sanity check header length
offset += 9; // Skip past PES header
// PTS and DTS are normially stored as a 33 bit number.
// JavaScript does not have a integer type larger than 32 bit
......@@ -301,25 +300,25 @@
// significant bit (the same as dividing by two) then we can
// divide by 45 (45 * 2 = 90) to get ms.
if (ptsDtsIndicator & 0x03) {
pts = (data[o + 0] & 0x0E) << 28
| (data[o + 1] & 0xFF) << 21
| (data[o + 2] & 0xFE) << 13
| (data[o + 3] & 0xFF) << 6
| (data[o + 4] & 0xFE) >>> 2;
pts = (data[offset + 0] & 0x0E) << 28
| (data[offset + 1] & 0xFF) << 21
| (data[offset + 2] & 0xFE) << 13
| (data[offset + 3] & 0xFF) << 6
| (data[offset + 4] & 0xFE) >>> 2;
pts /= 45;
if (ptsDtsIndicator & 0x01) {// DTS
dts = (data[o + 5] & 0x0E ) << 28
| (data[o + 6] & 0xFF ) << 21
| (data[o + 7] & 0xFE ) << 13
| (data[o + 8] & 0xFF ) << 6
| (data[o + 9] & 0xFE ) >>> 2;
dts = (data[offset + 5] & 0x0E ) << 28
| (data[offset + 6] & 0xFF ) << 21
| (data[offset + 7] & 0xFE ) << 13
| (data[offset + 8] & 0xFF ) << 6
| (data[offset + 9] & 0xFE ) >>> 2;
dts /= 45;
} else {
dts = pts;
}
}
// Skip past "optional" portion of PTS header
o += pesHeaderLength;
offset += pesHeaderLength;
if (videoPid === pid) {
// Stash this frame for future use.
......@@ -336,31 +335,31 @@
}
if (audioPid === pid) {
aacStream.writeBytes(data, o, e - o);
aacStream.writeBytes(data, offset, end - offset);
} else if (videoPid === pid) {
h264Stream.writeBytes(data, o, e - o);
h264Stream.writeBytes(data, offset, end - offset);
}
} else if (pmtPid === pid) {
// TODO sanity check data[o]
// TODO sanity check data[offset]
// if pusi is set we must skip X bytes (PSI pointer field)
o += (pusi ? 1 + data[o] : 0);
pmtTableId = data[o];
offset += (pusi ? 1 + data[offset] : 0);
pmtTableId = data[offset];
console.assert(0x02 === pmtTableId);
pmtCurrentNextIndicator = !!(data[o + 5] & 0x01);
pmtCurrentNextIndicator = !!(data[offset + 5] & 0x01);
if (pmtCurrentNextIndicator) {
audioPid = videoPid = 0;
pmtSectionLength = (data[o + 1] & 0x0F) << 8 | data[o + 2];
pmtSectionLength = (data[offset + 1] & 0x0F) << 8 | data[offset + 2];
// skip CRC and PSI data we dont care about
pmtSectionLength -= 13;
pmtSectionLength -= 13;
o += 12; // skip past PSI header and some PMT data
offset += 12; // skip past PSI header and some PMT data
while (0 < pmtSectionLength) {
streamType = data[o + 0];
elementaryPID = (data[o + 1] & 0x1F) << 8 | data[o + 2];
ESInfolength = (data[o + 3] & 0x0F) << 8 | data[o + 4];
o += 5 + ESInfolength;
streamType = data[offset + 0];
elementaryPID = (data[offset + 1] & 0x1F) << 8 | data[offset + 2];
ESInfolength = (data[offset + 3] & 0x0F) << 8 | data[offset + 4];
offset += 5 + ESInfolength;
pmtSectionLength -= 5 + ESInfolength;
if (0x1B === streamType) {
......