/**********
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 3 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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2020 Live Networks, Inc.  All rights reserved.
// H.265 Video RTP Sources
// Implementation

#include "H265VideoRTPSource.hh"

////////// H265BufferedPacket and H265BufferedPacketFactory //////////

class H265BufferedPacket: public BufferedPacket {
public:
  H265BufferedPacket(H265VideoRTPSource& ourSource);
  virtual ~H265BufferedPacket();

private: // redefined virtual functions
  virtual unsigned nextEnclosedFrameSize(unsigned char*& framePtr,
					 unsigned dataSize);
private:
  H265VideoRTPSource& fOurSource;
};

class H265BufferedPacketFactory: public BufferedPacketFactory {
private: // redefined virtual functions
  virtual BufferedPacket* createNewPacket(MultiFramedRTPSource* ourSource);
};


///////// H265VideoRTPSource implementation ////////

H265VideoRTPSource*
H265VideoRTPSource::createNew(UsageEnvironment& env, Groupsock* RTPgs,
			      unsigned char rtpPayloadFormat,
			      Boolean expectDONFields,		     
			      unsigned rtpTimestampFrequency) {
  return new H265VideoRTPSource(env, RTPgs, rtpPayloadFormat,
				expectDONFields, rtpTimestampFrequency);
}

H265VideoRTPSource
::H265VideoRTPSource(UsageEnvironment& env, Groupsock* RTPgs,
		     unsigned char rtpPayloadFormat,
		     Boolean expectDONFields,		     
		     unsigned rtpTimestampFrequency)
  : MultiFramedRTPSource(env, RTPgs, rtpPayloadFormat, rtpTimestampFrequency,
			 new H265BufferedPacketFactory),
    fExpectDONFields(expectDONFields),
    fPreviousNALUnitDON(0), fCurrentNALUnitAbsDon((u_int64_t)(~0)) {
}

H265VideoRTPSource::~H265VideoRTPSource() {
}

Boolean H265VideoRTPSource
::processSpecialHeader(BufferedPacket* packet,
                       unsigned& resultSpecialHeaderSize) {
  unsigned char* headerStart = packet->data();
  unsigned packetSize = packet->dataSize();
  u_int16_t DONL = 0;
  unsigned numBytesToSkip;

  // Check the Payload Header's 'nal_unit_type' for special aggregation or fragmentation packets:
  if (packetSize < 2) return False;
  fCurPacketNALUnitType = (headerStart[0]&0x7E)>>1;
  switch (fCurPacketNALUnitType) {
  case 48: { // Aggregation Packet (AP)
    // We skip over the 2-byte Payload Header, and the DONL header (if any).
    if (fExpectDONFields) {
      if (packetSize < 4) return False;
      DONL = (headerStart[2]<<8)|headerStart[3];
      numBytesToSkip = 4;
    } else {
      numBytesToSkip = 2;
    }
    break;
  }
  case 49: { // Fragmentation Unit (FU)
    // This NALU begins with the 2-byte Payload Header, the 1-byte FU header, and (optionally)
    // the 2-byte DONL header.
    // If the start bit is set, we reconstruct the original NAL header at the end of these
    // 3 (or 5) bytes, and skip over the first 1 (or 3) bytes.
    if (packetSize < 3) return False;
    u_int8_t startBit = headerStart[2]&0x80; // from the FU header
    u_int8_t endBit = headerStart[2]&0x40; // from the FU header
    if (startBit) {
      fCurrentPacketBeginsFrame = True;

      u_int8_t nal_unit_type = headerStart[2]&0x3F; // the last 6 bits of the FU header
      u_int8_t newNALHeader[2];
      newNALHeader[0] = (headerStart[0]&0x81)|(nal_unit_type<<1);
      newNALHeader[1] = headerStart[1];

      if (fExpectDONFields) {
	if (packetSize < 5) return False;
	DONL = (headerStart[3]<<8)|headerStart[4];
	headerStart[3] = newNALHeader[0];
	headerStart[4] = newNALHeader[1];
	numBytesToSkip = 3;
      } else {
	headerStart[1] = newNALHeader[0];
	headerStart[2] = newNALHeader[1];
	numBytesToSkip = 1;
      }
    } else {
      // The start bit is not set, so we skip over all headers:
      fCurrentPacketBeginsFrame = False;
      if (fExpectDONFields) {
	if (packetSize < 5) return False;
	DONL = (headerStart[3]<<8)|headerStart[4];
	numBytesToSkip = 5;
      } else {
	numBytesToSkip = 3;
      }
    }
    fCurrentPacketCompletesFrame = (endBit != 0);
    break;
  }
  default: {
    // This packet contains one complete NAL unit:
    fCurrentPacketBeginsFrame = fCurrentPacketCompletesFrame = True;
    numBytesToSkip = 0;
    break;
  }
  }

  computeAbsDonFromDON(DONL);
  resultSpecialHeaderSize = numBytesToSkip;
  return True;
}

char const* H265VideoRTPSource::MIMEtype() const {
  return "video/H265";
}

void H265VideoRTPSource::computeAbsDonFromDON(u_int16_t DON) {
  if (!fExpectDONFields) {
    // Without DON fields in the input stream, we just increment our "AbsDon" count each time:
    ++fCurrentNALUnitAbsDon;
  } else {
    if (fCurrentNALUnitAbsDon == (u_int64_t)(~0)) {
      // This is the very first NAL unit, so "AbsDon" is just "DON":
      fCurrentNALUnitAbsDon = (u_int64_t)DON;
    } else {
      // Use the previous NAL unit's DON and the current DON to compute "AbsDon":
      //     AbsDon[n] = AbsDon[n-1] + (DON[n] - DON[n-1]) mod 2^16
      short signedDiff16 = (short)(DON - fPreviousNALUnitDON);
      int64_t signedDiff64 = (int64_t)signedDiff16;
      fCurrentNALUnitAbsDon += signedDiff64;
    }

    fPreviousNALUnitDON = DON; // for next time
  }
}


////////// H265BufferedPacket and H265BufferedPacketFactory implementation //////////

H265BufferedPacket::H265BufferedPacket(H265VideoRTPSource& ourSource)
  : fOurSource(ourSource) {
}

H265BufferedPacket::~H265BufferedPacket() {
}

unsigned H265BufferedPacket
::nextEnclosedFrameSize(unsigned char*& framePtr, unsigned dataSize) {
  unsigned resultNALUSize = 0; // if an error occurs

  switch (fOurSource.fCurPacketNALUnitType) {
  case 48: { // Aggregation Packet (AP)
    if (useCount() > 0) {
      // We're other than the first NAL unit inside this Aggregation Packet.
      // Update our 'decoding order number':
      u_int16_t DONL = 0;
      if (fOurSource.fExpectDONFields) {
	// There's a 1-byte DOND field next:
	if (dataSize < 1) break;
	u_int8_t DOND = framePtr[0];
	DONL = fOurSource.fPreviousNALUnitDON + (u_int16_t)(DOND + 1);
	++framePtr;
	--dataSize;
      }
      fOurSource.computeAbsDonFromDON(DONL);
    }

    // The next 2 bytes are the NAL unit size:
    if (dataSize < 2) break;
    resultNALUSize = (framePtr[0]<<8)|framePtr[1];
    framePtr += 2;
    break;
  }
  default: {
    // Common case: We use the entire packet data:
    return dataSize;
  }
  }

  return (resultNALUSize <= dataSize) ? resultNALUSize : dataSize;
}

BufferedPacket* H265BufferedPacketFactory
::createNewPacket(MultiFramedRTPSource* ourSource) {
  return new H265BufferedPacket((H265VideoRTPSource&)(*ourSource));
}