liveMedia/MediaSession.cpp

Go to the documentation of this file.

/**********
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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2008 Live Networks, Inc.  All rights reserved.
// A data structure that represents a session that consists of
// potentially multiple (audio and/or video) sub-sessions
// Implementation

#include "liveMedia.hh"
#include "Locale.hh"
#ifdef SUPPORT_REAL_RTSP
#include "../RealRTSP/include/RealRTSP.hh"
#endif
#include "GroupsockHelper.hh"
#include <ctype.h>


MediaSession* MediaSession::createNew(UsageEnvironment& env,
                                      char const* sdpDescription) {
  MediaSession* newSession = new MediaSession(env);
  if (newSession != NULL) {
    if (!newSession->initializeWithSDP(sdpDescription)) {
      delete newSession;
      return NULL;
    }
  }

  return newSession;
}

Boolean MediaSession::lookupByName(UsageEnvironment& env,
                                   char const* instanceName,
                                   MediaSession*& resultSession) {
  resultSession = NULL; // unless we succeed

  Medium* medium;
  if (!Medium::lookupByName(env, instanceName, medium)) return False;

  if (!medium->isMediaSession()) {
    env.setResultMsg(instanceName, " is not a 'MediaSession' object");
    return False;
  }

  resultSession = (MediaSession*)medium;
  return True;
}

MediaSession::MediaSession(UsageEnvironment& env)
  : Medium(env),
    fSubsessionsHead(NULL), fSubsessionsTail(NULL),
    fConnectionEndpointName(NULL), fMaxPlayStartTime(0.0f), fMaxPlayEndTime(0.0f),
    fScale(1.0f), fMediaSessionType(NULL), fSessionName(NULL), fSessionDescription(NULL),
    fControlPath(NULL) {
#ifdef SUPPORT_REAL_RTSP
  RealInitSDPAttributes(this);
#endif
  fSourceFilterAddr.s_addr = 0;

  // Get our host name, and use this for the RTCP CNAME:
  const unsigned maxCNAMElen = 100;
  char CNAME[maxCNAMElen+1];
#ifndef CRIS
  gethostname((char*)CNAME, maxCNAMElen);
#else
  // "gethostname()" isn't defined for this platform
  sprintf(CNAME, "unknown host %d", (unsigned)(our_random()*0x7FFFFFFF));
#endif
  CNAME[maxCNAMElen] = '\0'; // just in case
  fCNAME = strDup(CNAME);
}

MediaSession::~MediaSession() {
  delete fSubsessionsHead;
  delete[] fCNAME;
  delete[] fConnectionEndpointName;
  delete[] fMediaSessionType;
  delete[] fSessionName;
  delete[] fSessionDescription;
  delete[] fControlPath;
#ifdef SUPPORT_REAL_RTSP
  RealReclaimSDPAttributes(this);
#endif
}

Boolean MediaSession::isMediaSession() const {
  return True;
}

Boolean MediaSession::initializeWithSDP(char const* sdpDescription) {
  if (sdpDescription == NULL) return False;

  // Begin by processing all SDP lines until we see the first "m="
  char const* sdpLine = sdpDescription;
  char const* nextSDPLine;
  while (1) {
    if (!parseSDPLine(sdpLine, nextSDPLine)) return False;
    //##### We should really check for:
    // - "a=control:" attributes (to set the URL for aggregate control)
    // - the correct SDP version (v=0)
    if (sdpLine[0] == 'm') break;
    sdpLine = nextSDPLine;
    if (sdpLine == NULL) break; // there are no m= lines at all

    // Check for various special SDP lines that we understand:
    if (parseSDPLine_s(sdpLine)) continue;
    if (parseSDPLine_i(sdpLine)) continue;
    if (parseSDPLine_c(sdpLine)) continue;
    if (parseSDPAttribute_control(sdpLine)) continue;
    if (parseSDPAttribute_range(sdpLine)) continue;
    if (parseSDPAttribute_type(sdpLine)) continue;
    if (parseSDPAttribute_source_filter(sdpLine)) continue;
#ifdef SUPPORT_REAL_RTSP
    if (RealParseSDPAttributes(this, sdpLine)) continue;
#endif
  }

  while (sdpLine != NULL) {
    // We have a "m=" line, representing a new sub-session:
    MediaSubsession* subsession = new MediaSubsession(*this);
    if (subsession == NULL) {
      envir().setResultMsg("Unable to create new MediaSubsession");
      return False;
    }

    // Parse the line as "m=<medium_name> <client_portNum> RTP/AVP <fmt>"
    // or "m=<medium_name> <client_portNum>/<num_ports> RTP/AVP <fmt>"
    // (Should we be checking for >1 payload format number here?)#####
    char* mediumName = strDupSize(sdpLine); // ensures we have enough space
    char* protocolName = NULL;
    unsigned payloadFormat;
    if ((sscanf(sdpLine, "m=%s %hu RTP/AVP %u",
                mediumName, &subsession->fClientPortNum, &payloadFormat) == 3 ||
         sscanf(sdpLine, "m=%s %hu/%*u RTP/AVP %u",
                mediumName, &subsession->fClientPortNum, &payloadFormat) == 3)
        && payloadFormat <= 127) {
      protocolName = "RTP";
    } else if ((sscanf(sdpLine, "m=%s %hu UDP %u",
                       mediumName, &subsession->fClientPortNum, &payloadFormat) == 3 ||
                sscanf(sdpLine, "m=%s %hu udp %u",
                       mediumName, &subsession->fClientPortNum, &payloadFormat) == 3 ||
                sscanf(sdpLine, "m=%s %hu RAW/RAW/UDP %u",
                       mediumName, &subsession->fClientPortNum, &payloadFormat) == 3)
               && payloadFormat <= 127) {
      // This is a RAW UDP source
      protocolName = "UDP";
    } else {
      // This "m=" line is bad; output an error message saying so:
      char* sdpLineStr;
      if (nextSDPLine == NULL) {
        sdpLineStr = (char*)sdpLine;
      } else {
        sdpLineStr = strDup(sdpLine);
        sdpLineStr[nextSDPLine-sdpLine] = '\0';
      }
      envir() << "Bad SDP \"m=\" line: " <<  sdpLineStr << "\n";
      if (sdpLineStr != (char*)sdpLine) delete[] sdpLineStr;

      delete[] mediumName;
      delete subsession;

      // Skip the following SDP lines, up until the next "m=":
      while (1) {
        sdpLine = nextSDPLine;
        if (sdpLine == NULL) break; // we've reached the end
        if (!parseSDPLine(sdpLine, nextSDPLine)) return False;

        if (sdpLine[0] == 'm') break; // we've reached the next subsession
      }
      continue;
    }

    // Insert this subsession at the end of the list:
    if (fSubsessionsTail == NULL) {
      fSubsessionsHead = fSubsessionsTail = subsession;
    } else {
      fSubsessionsTail->setNext(subsession);
      fSubsessionsTail = subsession;
    }

    subsession->serverPortNum = subsession->fClientPortNum; // by default

    char const* mStart = sdpLine;
    subsession->fSavedSDPLines = strDup(mStart);

    subsession->fMediumName = strDup(mediumName);
    delete[] mediumName;
    subsession->fProtocolName = strDup(protocolName);
    subsession->fRTPPayloadFormat = payloadFormat;

    // Process the following SDP lines, up until the next "m=":
    while (1) {
      sdpLine = nextSDPLine;
      if (sdpLine == NULL) break; // we've reached the end
      if (!parseSDPLine(sdpLine, nextSDPLine)) return False;

      if (sdpLine[0] == 'm') break; // we've reached the next subsession

      // Check for various special SDP lines that we understand:
      if (subsession->parseSDPLine_c(sdpLine)) continue;
      if (subsession->parseSDPAttribute_rtpmap(sdpLine)) continue;
      if (subsession->parseSDPAttribute_control(sdpLine)) continue;
      if (subsession->parseSDPAttribute_range(sdpLine)) continue;
      if (subsession->parseSDPAttribute_fmtp(sdpLine)) continue;
      if (subsession->parseSDPAttribute_source_filter(sdpLine)) continue;
      if (subsession->parseSDPAttribute_x_dimensions(sdpLine)) continue;
      if (subsession->parseSDPAttribute_framerate(sdpLine)) continue;
#ifdef SUPPORT_REAL_RTSP
      if (RealParseSDPAttributes(subsession, sdpLine)) continue;
#endif

      // (Later, check for malformed lines, and other valid SDP lines#####)
    }
    if (sdpLine != NULL) subsession->fSavedSDPLines[sdpLine-mStart] = '\0';

    // If we don't yet know the codec name, try looking it up from the
    // list of static payload types:
    if (subsession->fCodecName == NULL) {
      subsession->fCodecName
        = lookupPayloadFormat(subsession->fRTPPayloadFormat,
                              subsession->fRTPTimestampFrequency,
                              subsession->fNumChannels);
      if (subsession->fCodecName == NULL) {
        char typeStr[20];
        sprintf(typeStr, "%d", subsession->fRTPPayloadFormat);
        envir().setResultMsg("Unknown codec name for RTP payload type ",
                             typeStr);
        return False;
      }
    }

    // If we don't yet know this subsession's RTP timestamp frequency
    // (because it uses a dynamic payload type and the corresponding
    // SDP "rtpmap" attribute erroneously didn't specify it),
    // then guess it now:
    if (subsession->fRTPTimestampFrequency == 0) {
      subsession->fRTPTimestampFrequency
        = guessRTPTimestampFrequency(subsession->fMediumName,
                                     subsession->fCodecName);
    }
  }

  return True;
}

Boolean MediaSession::parseSDPLine(char const* inputLine,
                                   char const*& nextLine){
  // Begin by finding the start of the next line (if any):
  nextLine = NULL;
  for (char const* ptr = inputLine; *ptr != '\0'; ++ptr) {
    if (*ptr == '\r' || *ptr == '\n') {
      // We found the end of the line
      ++ptr;
      while (*ptr == '\r' || *ptr == '\n') ++ptr;
      nextLine = ptr;
      if (nextLine[0] == '\0') nextLine = NULL; // special case for end
      break;
    }
  }

  // Then, check that this line is a SDP line of the form <char>=<etc>
  // (However, we also accept blank lines in the input.)
  if (inputLine[0] == '\r' || inputLine[0] == '\n') return True;
  if (strlen(inputLine) < 2 || inputLine[1] != '='
      || inputLine[0] < 'a' || inputLine[0] > 'z') {
    envir().setResultMsg("Invalid SDP line: ", inputLine);
    return False;
  }

  return True;
}

static char* parseCLine(char const* sdpLine) {
  char* resultStr = NULL;
  char* buffer = strDupSize(sdpLine); // ensures we have enough space
  if (sscanf(sdpLine, "c=IN IP4 %[^/ ]", buffer) == 1) {
    // Later, handle the optional /<ttl> and /<numAddresses> #####
    resultStr = strDup(buffer);
  }
  delete[] buffer;

  return resultStr;
}

Boolean MediaSession::parseSDPLine_s(char const* sdpLine) {
  // Check for "s=<session name>" line
  char* buffer = strDupSize(sdpLine);
  Boolean parseSuccess = False;

  if (sscanf(sdpLine, "s=%[^\r\n]", buffer) == 1) {
    delete[] fSessionName; fSessionName = strDup(buffer);
    parseSuccess = True;
  }
  delete[] buffer;

  return parseSuccess;
}

Boolean MediaSession::parseSDPLine_i(char const* sdpLine) {
  // Check for "i=<session description>" line
  char* buffer = strDupSize(sdpLine);
  Boolean parseSuccess = False;

  if (sscanf(sdpLine, "i=%[^\r\n]", buffer) == 1) {
    delete[] fSessionDescription; fSessionDescription = strDup(buffer);
    parseSuccess = True;
  }
  delete[] buffer;

  return parseSuccess;
}

Boolean MediaSession::parseSDPLine_c(char const* sdpLine) {
  // Check for "c=IN IP4 <connection-endpoint>"
  // or "c=IN IP4 <connection-endpoint>/<ttl+numAddresses>"
  // (Later, do something with <ttl+numAddresses> also #####)
  char* connectionEndpointName = parseCLine(sdpLine);
  if (connectionEndpointName != NULL) {
    delete[] fConnectionEndpointName;
    fConnectionEndpointName = connectionEndpointName;
    return True;
  }

  return False;
}

Boolean MediaSession::parseSDPAttribute_type(char const* sdpLine) {
  // Check for a "a=type:broadcast|meeting|moderated|test|H.332|recvonly" line:
  Boolean parseSuccess = False;

  char* buffer = strDupSize(sdpLine);
  if (sscanf(sdpLine, "a=type: %[^ ]", buffer) == 1) {
    delete[] fMediaSessionType;
    fMediaSessionType = strDup(buffer);
    parseSuccess = True;
  }
  delete[] buffer;

  return parseSuccess;
}

static Boolean parseRangeAttribute(char const* sdpLine, float& startTime, float& endTime) {
  return sscanf(sdpLine, "a=range: npt = %g - %g", &startTime, &endTime) == 2;
}

Boolean MediaSession::parseSDPAttribute_control(char const* sdpLine) {
  // Check for a "a=control:<control-path>" line:
  Boolean parseSuccess = False;

  char* controlPath = strDupSize(sdpLine); // ensures we have enough space
  if (sscanf(sdpLine, "a=control: %s", controlPath) == 1) {
    parseSuccess = True;
    delete[] fControlPath; fControlPath = strDup(controlPath);
  }
  delete[] controlPath;

  return parseSuccess;
}

Boolean MediaSession::parseSDPAttribute_range(char const* sdpLine) {
  // Check for a "a=range:npt=<startTime>-<endTime>" line:
  // (Later handle other kinds of "a=range" attributes also???#####)
  Boolean parseSuccess = False;

  float playStartTime;
  float playEndTime;
  if (parseRangeAttribute(sdpLine, playStartTime, playEndTime)) {
    parseSuccess = True;
    if (playStartTime > fMaxPlayStartTime) {
      fMaxPlayStartTime = playStartTime;
    }
    if (playEndTime > fMaxPlayEndTime) {
      fMaxPlayEndTime = playEndTime;
    }
  }

  return parseSuccess;
}

static Boolean parseSourceFilterAttribute(char const* sdpLine,
                                          struct in_addr& sourceAddr) {
  // Check for a "a=source-filter:incl IN IP4 <something> <source>" line.
  // Note: At present, we don't check that <something> really matches
  // one of our multicast addresses.  We also don't support more than
  // one <source> #####
  Boolean result = False; // until we succeed
  char* sourceName = strDupSize(sdpLine); // ensures we have enough space
  do {
    if (sscanf(sdpLine, "a=source-filter: incl IN IP4 %*s %s",
               sourceName) != 1) break;

    // Now, convert this name to an address, if we can:
    NetAddressList addresses(sourceName);
    if (addresses.numAddresses() == 0) break;

    netAddressBits sourceAddrBits
      = *(netAddressBits*)(addresses.firstAddress()->data());
    if (sourceAddrBits == 0) break;

    sourceAddr.s_addr = sourceAddrBits;
    result = True;
  } while (0);

  delete[] sourceName;
  return result;
}

Boolean MediaSession
::parseSDPAttribute_source_filter(char const* sdpLine) {
  return parseSourceFilterAttribute(sdpLine, fSourceFilterAddr);
}

char* MediaSession::lookupPayloadFormat(unsigned char rtpPayloadType,
                                        unsigned& freq, unsigned& nCh) {
  // Look up the codec name and timestamp frequency for known (static)
  // RTP payload formats.
  char* temp = NULL;
  switch (rtpPayloadType) {
  case 0: {temp = "PCMU"; freq = 8000; nCh = 1; break;}
  case 2: {temp = "G726-32"; freq = 8000; nCh = 1; break;}
  case 3: {temp = "GSM"; freq = 8000; nCh = 1; break;}
  case 4: {temp = "G723"; freq = 8000; nCh = 1; break;}
  case 5: {temp = "DVI4"; freq = 8000; nCh = 1; break;}
  case 6: {temp = "DVI4"; freq = 16000; nCh = 1; break;}
  case 7: {temp = "LPC"; freq = 8000; nCh = 1; break;}
  case 8: {temp = "PCMA"; freq = 8000; nCh = 1; break;}
  case 9: {temp = "G722"; freq = 8000; nCh = 1; break;}
  case 10: {temp = "L16"; freq = 44100; nCh = 2; break;}
  case 11: {temp = "L16"; freq = 44100; nCh = 1; break;}
  case 12: {temp = "QCELP"; freq = 8000; nCh = 1; break;}
  case 14: {temp = "MPA"; freq = 90000; nCh = 1; break;}
    // 'number of channels' is actually encoded in the media stream
  case 15: {temp = "G728"; freq = 8000; nCh = 1; break;}
  case 16: {temp = "DVI4"; freq = 11025; nCh = 1; break;}
  case 17: {temp = "DVI4"; freq = 22050; nCh = 1; break;}
  case 18: {temp = "G729"; freq = 8000; nCh = 1; break;}
  case 25: {temp = "CELB"; freq = 90000; nCh = 1; break;}
  case 26: {temp = "JPEG"; freq = 90000; nCh = 1; break;}
  case 28: {temp = "NV"; freq = 90000; nCh = 1; break;}
  case 31: {temp = "H261"; freq = 90000; nCh = 1; break;}
  case 32: {temp = "MPV"; freq = 90000; nCh = 1; break;}
  case 33: {temp = "MP2T"; freq = 90000; nCh = 1; break;}
  case 34: {temp = "H263"; freq = 90000; nCh = 1; break;}
  };

  return strDup(temp);
}

unsigned MediaSession::guessRTPTimestampFrequency(char const* mediumName,
                                                  char const* codecName) {
  // By default, we assume that audio sessions use a frequency of 8000,
  // and that video sessions use a frequency of 90000.
  // Begin by checking for known exceptions to this rule
  // (where the frequency is known unambiguously (e.g., not like "DVI4"))
  if (strcmp(codecName, "L16") == 0) return 44100;
  if (strcmp(codecName, "MPA") == 0
      || strcmp(codecName, "MPA-ROBUST") == 0
      || strcmp(codecName, "X-MP3-DRAFT-00")) return 90000;

  // Now, guess default values:
  if (strcmp(mediumName, "video") == 0) return 90000;
  return 8000; // for "audio", and any other medium
}

Boolean MediaSession
::initiateByMediaType(char const* mimeType,
                      MediaSubsession*& resultSubsession,
                      int useSpecialRTPoffset) {
  // Look through this session's subsessions for media that match "mimeType"
  resultSubsession = NULL;
  MediaSubsessionIterator iter(*this);
  MediaSubsession* subsession;
  while ((subsession = iter.next()) != NULL) {
    Boolean wasAlreadyInitiated = subsession->readSource() != NULL;
    if (!wasAlreadyInitiated) {
      // Try to create a source for this subsession:
      if (!subsession->initiate(useSpecialRTPoffset)) return False;
    }

    // Make sure the source's MIME type is one that we handle:
    if (strcmp(subsession->readSource()->MIMEtype(), mimeType) != 0) {
      if (!wasAlreadyInitiated) subsession->deInitiate();
      continue;
    }

    resultSubsession = subsession;
    break; // use this
  }

  if (resultSubsession == NULL) {
    envir().setResultMsg("Session has no usable media subsession");
    return False;
  }

  return True;
}



MediaSubsessionIterator::MediaSubsessionIterator(MediaSession& session)
  : fOurSession(session) {
  reset();
}

MediaSubsessionIterator::~MediaSubsessionIterator() {
}

MediaSubsession* MediaSubsessionIterator::next() {
  MediaSubsession* result = fNextPtr;

  if (fNextPtr != NULL) fNextPtr = fNextPtr->fNext;

  return result;
}

void MediaSubsessionIterator::reset() {
  fNextPtr = fOurSession.fSubsessionsHead;
}


MediaSubsession::MediaSubsession(MediaSession& parent)
  : sessionId(NULL), serverPortNum(0), sink(NULL), miscPtr(NULL),
    fParent(parent), fNext(NULL),
    fConnectionEndpointName(NULL),
    fClientPortNum(0), fRTPPayloadFormat(0xFF),
    fSavedSDPLines(NULL), fMediumName(NULL), fCodecName(NULL), fProtocolName(NULL),
    fRTPTimestampFrequency(0), fControlPath(NULL),
    fSourceFilterAddr(parent.sourceFilterAddr()),
    fAuxiliarydatasizelength(0), fConstantduration(0), fConstantsize(0),
    fCRC(0), fCtsdeltalength(0), fDe_interleavebuffersize(0), fDtsdeltalength(0),
    fIndexdeltalength(0), fIndexlength(0), fInterleaving(0), fMaxdisplacement(0),
    fObjecttype(0), fOctetalign(0), fProfile_level_id(0), fRobustsorting(0),
    fSizelength(0), fStreamstateindication(0), fStreamtype(0),
    fCpresent(False), fRandomaccessindication(False),
    fConfig(NULL), fMode(NULL), fSpropParameterSets(NULL),
    fPlayStartTime(0.0), fPlayEndTime(0.0),
    fVideoWidth(0), fVideoHeight(0), fVideoFPS(0), fNumChannels(1), fScale(1.0f), fNPT_PTS_Offset(0.0f),
    fRTPSocket(NULL), fRTCPSocket(NULL),
    fRTPSource(NULL), fRTCPInstance(NULL), fReadSource(NULL) {
  rtpInfo.seqNum = 0; rtpInfo.timestamp = 0; rtpInfo.infoIsNew = False;
#ifdef SUPPORT_REAL_RTSP
  RealInitSDPAttributes(this);
#endif
}

MediaSubsession::~MediaSubsession() {
  deInitiate();

  delete[] fConnectionEndpointName; delete[] fSavedSDPLines;
  delete[] fMediumName; delete[] fCodecName; delete[] fProtocolName;
  delete[] fControlPath; delete[] fConfig; delete[] fMode; delete[] fSpropParameterSets;

  delete fNext;
#ifdef SUPPORT_REAL_RTSP
  RealReclaimSDPAttributes(this);
#endif
}

float MediaSubsession::playStartTime() const {
  if (fPlayStartTime > 0) return fPlayStartTime;

  return fParent.playStartTime();
}

float MediaSubsession::playEndTime() const {
  if (fPlayEndTime > 0) return fPlayEndTime;

  return fParent.playEndTime();
}

Boolean MediaSubsession::initiate(int useSpecialRTPoffset) {
  if (fReadSource != NULL) return True; // has already been initiated

  do {
    if (fCodecName == NULL) {
      env().setResultMsg("Codec is unspecified");
      break;
    }

    // Create RTP and RTCP 'Groupsocks' on which to receive incoming data.
    // (Groupsocks will work even for unicast addresses)
    Groupsock* oldGroupsock = NULL;
    Boolean success = False;
    struct in_addr tempAddr;
    tempAddr.s_addr = connectionEndpointAddress();
        // This could get changed later, as a result of a RTSP "SETUP"
    while (1) {
      unsigned short rtpPortNum = fClientPortNum&~1;
      if (isSSM()) {
        fRTPSocket = new Groupsock(env(), tempAddr, fSourceFilterAddr,
                                   rtpPortNum);
      } else {
        fRTPSocket = new Groupsock(env(), tempAddr, rtpPortNum, 255);
      }
      if (fRTPSocket == NULL) {
        env().setResultMsg("Failed to create RTP socket");
        break;
      }

      // Get the client port number, to make sure that it's even (for RTP):
      Port clientPort(0);
      if (!getSourcePort(env(), fRTPSocket->socketNum(), clientPort)) {
        break;
      }
      fClientPortNum = ntohs(clientPort.num());

      // If the port number's not even, try again:
      if ((fClientPortNum&1) == 0) {
        success = True;
        break;
      }
      // Try again:
      delete oldGroupsock;
      oldGroupsock = fRTPSocket;
      fClientPortNum = 0;
    }
    delete oldGroupsock;
    if (!success) break;

    // Set our RTCP port to be the RTP port +1
    unsigned short const rtcpPortNum = fClientPortNum|1;
    if (isSSM()) {
      fRTCPSocket = new Groupsock(env(), tempAddr, fSourceFilterAddr,
                                  rtcpPortNum);
      // Also, send RTCP packets back to the source via unicast:
      if (fRTCPSocket != NULL) {
        fRTCPSocket->changeDestinationParameters(fSourceFilterAddr,0,~0);
      }
    } else {
      fRTCPSocket = new Groupsock(env(), tempAddr, rtcpPortNum, 255);
    }
    if (fRTCPSocket == NULL) {
      char tmpBuf[100];
      sprintf(tmpBuf, "Failed to create RTCP socket (port %d)",
              rtcpPortNum);
      env().setResultMsg(tmpBuf);
      break;
    }

    // Check "fProtocolName"
    if (strcmp(fProtocolName, "UDP") == 0) {
      // A UDP-packetized stream (*not* a RTP stream)
      fReadSource = BasicUDPSource::createNew(env(), fRTPSocket);
      fRTPSource = NULL; // Note!

      if (strcmp(fCodecName, "MP2T") == 0) { // MPEG-2 Transport Stream
        fReadSource = MPEG2TransportStreamFramer::createNew(env(), fReadSource);
            // this sets "durationInMicroseconds" correctly, based on the PCR values
      }
    } else {
      // Check "fCodecName" against the set of codecs that we support,
      // and create our RTP source accordingly
      // (Later make this code more efficient, as this set grows #####)
      // (Also, add more fmts that can be implemented by SimpleRTPSource#####)
      Boolean createSimpleRTPSource = False;
      Boolean doNormalMBitRule = False; // used if "createSimpleRTPSource"
      if (strcmp(fCodecName, "QCELP") == 0) { // QCELP audio
        fReadSource =
          QCELPAudioRTPSource::createNew(env(), fRTPSocket, fRTPSource,
                                         fRTPPayloadFormat,
                                         fRTPTimestampFrequency);
        // Note that fReadSource will differ from fRTPSource in this case
      } else if (strcmp(fCodecName, "AMR") == 0) { // AMR audio (narrowband)
        fReadSource =
          AMRAudioRTPSource::createNew(env(), fRTPSocket, fRTPSource,
                                       fRTPPayloadFormat, 0 /*isWideband*/,
                                       fNumChannels, fOctetalign, fInterleaving,
                                       fRobustsorting, fCRC);
        // Note that fReadSource will differ from fRTPSource in this case
      } else if (strcmp(fCodecName, "AMR-WB") == 0) { // AMR audio (wideband)
        fReadSource =
          AMRAudioRTPSource::createNew(env(), fRTPSocket, fRTPSource,
                                       fRTPPayloadFormat, 1 /*isWideband*/,
                                       fNumChannels, fOctetalign, fInterleaving,
                                       fRobustsorting, fCRC);
        // Note that fReadSource will differ from fRTPSource in this case
      } else if (strcmp(fCodecName, "MPA") == 0) { // MPEG-1 or 2 audio
        fReadSource = fRTPSource
          = MPEG1or2AudioRTPSource::createNew(env(), fRTPSocket,
                                              fRTPPayloadFormat,
                                              fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "MPA-ROBUST") == 0) { // robust MP3 audio
        fRTPSource
          = MP3ADURTPSource::createNew(env(), fRTPSocket, fRTPPayloadFormat,
                                       fRTPTimestampFrequency);
        if (fRTPSource == NULL) break;

        // Add a filter that deinterleaves the ADUs after depacketizing them:
        MP3ADUdeinterleaver* deinterleaver
          = MP3ADUdeinterleaver::createNew(env(), fRTPSource);
        if (deinterleaver == NULL) break;

        // Add another filter that converts these ADUs to MP3 frames:
        fReadSource = MP3FromADUSource::createNew(env(), deinterleaver);
      } else if (strcmp(fCodecName, "X-MP3-DRAFT-00") == 0) {
        // a non-standard variant of "MPA-ROBUST" used by RealNetworks
        // (one 'ADU'ized MP3 frame per packet; no headers)
        fRTPSource
          = SimpleRTPSource::createNew(env(), fRTPSocket, fRTPPayloadFormat,
                                       fRTPTimestampFrequency,
                                       "audio/MPA-ROBUST" /*hack*/);
        if (fRTPSource == NULL) break;

        // Add a filter that converts these ADUs to MP3 frames:
        fReadSource = MP3FromADUSource::createNew(env(), fRTPSource,
                                                  False /*no ADU header*/);
      } else if (strcmp(fCodecName, "MP4A-LATM") == 0) { // MPEG-4 LATM audio
        fReadSource = fRTPSource
          = MPEG4LATMAudioRTPSource::createNew(env(), fRTPSocket,
                                               fRTPPayloadFormat,
                                               fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "AC3") == 0) { // AC3 audio
        fReadSource = fRTPSource
          = AC3AudioRTPSource::createNew(env(), fRTPSocket,
                                         fRTPPayloadFormat,
                                         fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "MP4V-ES") == 0) { // MPEG-4 Elem Str vid
        fReadSource = fRTPSource
          = MPEG4ESVideoRTPSource::createNew(env(), fRTPSocket,
                                             fRTPPayloadFormat,
                                             fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "MPEG4-GENERIC") == 0) {
        fReadSource = fRTPSource
          = MPEG4GenericRTPSource::createNew(env(), fRTPSocket,
                                             fRTPPayloadFormat,
                                             fRTPTimestampFrequency,
                                             fMediumName, fMode,
                                             fSizelength, fIndexlength,
                                             fIndexdeltalength);
      } else if (strcmp(fCodecName, "MPV") == 0) { // MPEG-1 or 2 video
        fReadSource = fRTPSource
          = MPEG1or2VideoRTPSource::createNew(env(), fRTPSocket,
                                              fRTPPayloadFormat,
                                              fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "MP2T") == 0) { // MPEG-2 Transport Stream
        fRTPSource = SimpleRTPSource::createNew(env(), fRTPSocket, fRTPPayloadFormat,
                                                fRTPTimestampFrequency, "video/MP2T",
                                                0, False);
        fReadSource = MPEG2TransportStreamFramer::createNew(env(), fRTPSource);
            // this sets "durationInMicroseconds" correctly, based on the PCR values
      } else if (strcmp(fCodecName, "H261") == 0) { // H.261
        fReadSource = fRTPSource
          = H261VideoRTPSource::createNew(env(), fRTPSocket,
                                          fRTPPayloadFormat,
                                          fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "H263-1998") == 0 ||
                 strcmp(fCodecName, "H263-2000") == 0) { // H.263+
        fReadSource = fRTPSource
          = H263plusVideoRTPSource::createNew(env(), fRTPSocket,
                                              fRTPPayloadFormat,
                                              fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "H264") == 0) {
        fReadSource = fRTPSource
          = H264VideoRTPSource::createNew(env(), fRTPSocket,
                                          fRTPPayloadFormat,
                                          fRTPTimestampFrequency);
      } else if (strcmp(fCodecName, "JPEG") == 0) { // motion JPEG
        fReadSource = fRTPSource
          = JPEGVideoRTPSource::createNew(env(), fRTPSocket,
                                          fRTPPayloadFormat,
                                          fRTPTimestampFrequency,
                                          videoWidth(),
                                          videoHeight());
      } else if (strcmp(fCodecName, "X-QT") == 0
                 || strcmp(fCodecName, "X-QUICKTIME") == 0) {
        // Generic QuickTime streams, as defined in
        // <http://developer.apple.com/quicktime/icefloe/dispatch026.html>
        char* mimeType
          = new char[strlen(mediumName()) + strlen(codecName()) + 2] ;
        sprintf(mimeType, "%s/%s", mediumName(), codecName());
        fReadSource = fRTPSource
          = QuickTimeGenericRTPSource::createNew(env(), fRTPSocket,
                                                 fRTPPayloadFormat,
                                                 fRTPTimestampFrequency,
                                                 mimeType);
        delete[] mimeType;
#ifdef SUPPORT_REAL_RTSP
      } else if (strcmp(fCodecName, "X-PN-REALAUDIO") == 0 ||
                 strcmp(fCodecName, "X-PN-MULTIRATE-REALAUDIO-LIVE") == 0 ||
                 strcmp(fCodecName, "X-PN-REALVIDEO") == 0 ||
                 strcmp(fCodecName, "X-PN-MULTIRATE-REALVIDEO-LIVE") == 0) {
        // A RealNetworks 'RDT' stream (*not* a RTP stream)
        fReadSource = RealRDTSource::createNew(