T140TextRTPSink.hh

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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
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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.
 
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// "liveMedia"
// Copyright (c) 1996-2024 Live Networks, Inc.  All rights reserved.
// RTP sink for T.140 text (RFC 2793)
// C++ header
 
#ifndef _T140_TEXT_RTP_SINK_HH
#define _T140_TEXT_RTP_SINK_HH
 
#ifndef _TEXT_RTP_SINK_HH
#include "TextRTPSink.hh"
#endif
#ifndef _FRAMED_FILTER_HH
#include "FramedFilter.hh"
#endif
 
class T140IdleFilter;
 
class T140TextRTPSink: public TextRTPSink {
public:
  static T140TextRTPSink* createNew(UsageEnvironment& env, Groupsock* RTPgs, unsigned char rtpPayloadFormat);
 
protected:
  T140TextRTPSink(UsageEnvironment& env, Groupsock* RTPgs, unsigned char rtpPayloadFormat);
        // called only by createNew()
 
  virtual ~T140TextRTPSink();
 
protected: // redefined virtual functions:
  virtual Boolean continuePlaying();
  virtual void doSpecialFrameHandling(unsigned fragmentationOffset,
                                      unsigned char* frameStart,
                                      unsigned numBytesInFrame,
                                      struct timeval framePresentationTime,
                                      unsigned numRemainingBytes);
  virtual Boolean frameCanAppearAfterPacketStart(unsigned char const* frameStart,
                                                 unsigned numBytesInFrame) const;
 
protected:
  T140IdleFilter* fOurIdleFilter;
  Boolean fAreInIdlePeriod;
};
 
 
 
// Because the T.140 text RTP payload format specification recommends that (empty) RTP packets be sent during 'idle periods'
// when no new text is available, we implement "T140TextRTPSink" using a separate "T140IdleFilter" class - sitting in front
// -  that delivers, to the "T140TextRTPSink", a continuous sequence of (possibly) empty frames.
// (Note: This class should be used only by "T140TextRTPSink", or a subclass.)
 
class T140IdleFilter: public FramedFilter {
public:
  T140IdleFilter(UsageEnvironment& env, FramedSource* inputSource);
  virtual ~T140IdleFilter();
 
private: // redefined virtual functions:
  virtual void doGetNextFrame();
  virtual void doStopGettingFrames();
 
private:
  static void afterGettingFrame(void* clientData, unsigned frameSize,
                                unsigned numTruncatedBytes,
                                struct timeval presentationTime,
                                unsigned durationInMicroseconds);
  void afterGettingFrame(unsigned frameSize,
                         unsigned numTruncatedBytes,
                         struct timeval presentationTime,
                         unsigned durationInMicroseconds);
 
  static void handleIdleTimeout(void* clientData);
  void handleIdleTimeout();
 
  void deliverFromBuffer();
  void deliverEmptyFrame();
 
  static void onSourceClosure(void* clientData);
  void onSourceClosure();
 
private:
  TaskToken fIdleTimerTask;
  unsigned fBufferSize, fNumBufferedBytes;
  char* fBuffer;
  unsigned fBufferedNumTruncatedBytes; // a count of truncated bytes from the upstream
  struct timeval fBufferedDataPresentationTime;
  unsigned fBufferedDataDurationInMicroseconds;
};
 
#endif