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/**********
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)
This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
more details.
You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
**********/
// "liveMedia"
// Copyright (c) 1996-2005 Live Networks, Inc. All rights reserved.
// RTP sink for MPEG video (RFC 2250)
// Implementation
#include "MPEG1or2VideoRTPSink.hh"
#include "MPEG1or2VideoStreamFramer.hh"
MPEG1or2VideoRTPSink::MPEG1or2VideoRTPSink(UsageEnvironment& env, Groupsock* RTPgs)
: VideoRTPSink(env, RTPgs, 32, 90000, "MPV") {
fPictureState.temporal_reference = 0;
fPictureState.picture_coding_type = fPictureState.vector_code_bits = 0;
}
MPEG1or2VideoRTPSink::~MPEG1or2VideoRTPSink() {
}
MPEG1or2VideoRTPSink*
MPEG1or2VideoRTPSink::createNew(UsageEnvironment& env, Groupsock* RTPgs) {
return new MPEG1or2VideoRTPSink(env, RTPgs);
}
Boolean MPEG1or2VideoRTPSink::sourceIsCompatibleWithUs(MediaSource& source) {
// Our source must be an appropriate framer:
return source.isMPEG1or2VideoStreamFramer();
}
Boolean MPEG1or2VideoRTPSink::allowFragmentationAfterStart() const {
return True;
}
Boolean MPEG1or2VideoRTPSink
::frameCanAppearAfterPacketStart(unsigned char const* frameStart,
unsigned numBytesInFrame) const {
// A 'frame' (which in this context can mean a header or a slice as well as a
// complete picture) can appear at other than the first position in a packet
// in all situations, EXCEPT when it follows the end of (i.e., the last slice
// of) a picture. I.e., the headers at the beginning of a picture must
// appear at the start of a RTP packet.
if (!fPreviousFrameWasSlice) return True;
// A slice is already packed into this packet. We allow this new 'frame'
// to be packed after it, provided that it is also a slice:
return numBytesInFrame >= 4
&& frameStart[0] == 0 && frameStart[1] == 0 && frameStart[2] == 1
&& frameStart[3] >= 1 && frameStart[3] <= 0xAF;
}
#define VIDEO_SEQUENCE_HEADER_START_CODE 0x000001B3
#define PICTURE_START_CODE 0x00000100
void MPEG1or2VideoRTPSink
::doSpecialFrameHandling(unsigned fragmentationOffset,
unsigned char* frameStart,
unsigned numBytesInFrame,
struct timeval frameTimestamp,
unsigned numRemainingBytes) {
Boolean thisFrameIsASlice = False; // until we learn otherwise
if (isFirstFrameInPacket()) {
fSequenceHeaderPresent = fPacketBeginsSlice = fPacketEndsSlice = False;
}
if (fragmentationOffset == 0) {
// Begin by inspecting the 4-byte code at the start of the frame:
if (numBytesInFrame < 4) return; // shouldn't happen
unsigned startCode = (frameStart[0]<<24) | (frameStart[1]<<16)
| (frameStart[2]<<8) | frameStart[3];
if (startCode == VIDEO_SEQUENCE_HEADER_START_CODE) {
// This is a video sequence header
fSequenceHeaderPresent = True;
} else if (startCode == PICTURE_START_CODE) {
// This is a picture header
// Record the parameters of this picture:
if (numBytesInFrame < 8) return; // shouldn't happen
unsigned next4Bytes = (frameStart[4]<<24) | (frameStart[5]<<16)
| (frameStart[6]<<8) | frameStart[7];
unsigned char byte8 = numBytesInFrame == 8 ? 0 : frameStart[8];
fPictureState.temporal_reference = (next4Bytes&0xFFC00000)>>(32-10);
fPictureState.picture_coding_type = (next4Bytes&0x00380000)>>(32-(10+3));
unsigned char FBV, BFC, FFV, FFC;
FBV = BFC = FFV = FFC = 0;
switch (fPictureState.picture_coding_type) {
case 3:
FBV = (byte8&0x40)>>6;
BFC = (byte8&0x38)>>3;
// fall through to:
case 2:
FFV = (next4Bytes&0x00000004)>>2;
FFC = ((next4Bytes&0x00000003)<<1) | ((byte8&0x80)>>7);
}
fPictureState.vector_code_bits = (FBV<<7) | (BFC<<4) | (FFV<<3) | FFC;
} else if ((startCode&0xFFFFFF00) == 0x00000100) {
unsigned char lastCodeByte = startCode&0xFF;
if (lastCodeByte <= 0xAF) {
// This is (the start of) a slice
thisFrameIsASlice = True;
} else {
// This is probably a GOP header; we don't do anything with this
}
} else {
// The first 4 bytes aren't a code that we recognize.
envir() << "Warning: MPEG1or2VideoRTPSink::doSpecialFrameHandling saw strange first 4 bytes "
<< (void*)startCode << ", but we're not a fragment\n";
}
} else {
// We're a fragment (other than the first) of a slice.
thisFrameIsASlice = True;
}
if (thisFrameIsASlice) {
// This packet begins a slice iff there's no fragmentation offset:
fPacketBeginsSlice = (fragmentationOffset == 0);
// This packet also ends a slice iff there are no fragments remaining:
fPacketEndsSlice = (numRemainingBytes == 0);
}
// Set the video-specific header based on the parameters that we've seen.
// Note that this may get done more than once, if several frames appear
// in the packet. That's OK, because this situation happens infrequently,
// and we want the video-specific header to reflect the most up-to-date
// information (in particular, from a Picture Header) anyway.
unsigned videoSpecificHeader =
// T == 0
(fPictureState.temporal_reference<<16) |
// AN == N == 0
(fSequenceHeaderPresent<<13) |
(fPacketBeginsSlice<<12) |
(fPacketEndsSlice<<11) |
(fPictureState.picture_coding_type<<8) |
fPictureState.vector_code_bits;
setSpecialHeaderWord(videoSpecificHeader);
// Also set the RTP timestamp. (As above, we do this for each frame
// in the packet.)
setTimestamp(frameTimestamp);
// Set the RTP 'M' (marker) bit iff this frame ends (i.e., is the last
// slice of) a picture (and there are no fragments remaining).
// This relies on the source being a "MPEG1or2VideoStreamFramer".
MPEG1or2VideoStreamFramer* framerSource = (MPEG1or2VideoStreamFramer*)fSource;
if (framerSource != NULL && framerSource->pictureEndMarker()
&& numRemainingBytes == 0) {
setMarkerBit();
framerSource->pictureEndMarker() = False;
}
fPreviousFrameWasSlice = thisFrameIsASlice;
}
unsigned MPEG1or2VideoRTPSink::specialHeaderSize() const {
// There's a 4 byte special audio header:
return 4;
}
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