mp4track.cpp

完整的RTP RTSP代码库

	if (m_chunkBufferSize == 0) {
		return;
	}

	u_int64_t chunkOffset = m_pFile->GetPosition();

	// write chunk buffer
	m_pFile->WriteBytes(m_pChunkBuffer, m_chunkBufferSize);

	VERBOSE_WRITE_SAMPLE(m_pFile->GetVerbosity(),
		printf("WriteChunk: track %u offset 0x"X64" size %u (0x%x) numSamples %u\n",
			m_trackId, chunkOffset, m_chunkBufferSize, 
			m_chunkBufferSize, m_chunkSamples));

	UpdateSampleToChunk(m_writeSampleId, 
		m_pChunkCountProperty->GetValue() + 1, 
		m_chunkSamples);

	UpdateChunkOffsets(chunkOffset);

	// clean up chunk buffer
	MP4Free(m_pChunkBuffer);
	m_pChunkBuffer = NULL;
	m_chunkBufferSize = 0;
	m_chunkSamples = 0;
	m_chunkDuration = 0;
}

void MP4Track::FinishWrite()
{
	// write out any remaining samples in chunk buffer
	WriteChunkBuffer();

	if (m_pStszFixedSampleSizeProperty == NULL &&
	    m_stsz_sample_bits == 4) {
	  if (m_have_stz2_4bit_sample) {
	    ((MP4Integer8Property *)m_pStszSampleSizeProperty)->AddValue(m_stz2_4bit_sample_value);
	    m_pStszSampleSizeProperty->IncrementValue();
	  }
	}

	// record buffer size and bitrates
	MP4BitfieldProperty* pBufferSizeProperty;

	if (m_pTrakAtom->FindProperty(
	  "trak.mdia.minf.stbl.stsd.*.esds.decConfigDescr.bufferSizeDB",
	  (MP4Property**)&pBufferSizeProperty)) {
		pBufferSizeProperty->SetValue(GetMaxSampleSize());
	}

	MP4Integer32Property* pBitrateProperty;

	if (m_pTrakAtom->FindProperty(
	  "trak.mdia.minf.stbl.stsd.*.esds.decConfigDescr.maxBitrate",
	  (MP4Property**)&pBitrateProperty)) {
		pBitrateProperty->SetValue(GetMaxBitrate());
	}

	if (m_pTrakAtom->FindProperty(
	  "trak.mdia.minf.stbl.stsd.*.esds.decConfigDescr.avgBitrate",
	  (MP4Property**)&pBitrateProperty)) {
		pBitrateProperty->SetValue(GetAvgBitrate());
	}
}

bool MP4Track::IsChunkFull(MP4SampleId sampleId)
{
	if (m_samplesPerChunk) {
		return m_chunkSamples >= m_samplesPerChunk;
	}

	ASSERT(m_durationPerChunk);
	return m_chunkDuration >= m_durationPerChunk;
}

u_int32_t MP4Track::GetNumberOfSamples()
{
	return m_pStszSampleCountProperty->GetValue();
}

u_int32_t MP4Track::GetSampleSize(MP4SampleId sampleId)
{
  if (m_pStszFixedSampleSizeProperty != NULL) {
	u_int32_t fixedSampleSize = 
		m_pStszFixedSampleSizeProperty->GetValue(); 

	if (fixedSampleSize != 0) {
	  return fixedSampleSize * m_bytesPerSample;
	}
  }
  // will have to check for 4 bit sample size here
  if (m_stsz_sample_bits == 4) {
    uint8_t value = m_pStszSampleSizeProperty->GetValue((sampleId - 1) / 2);
    if ((sampleId - 1) / 2 == 0) {
      value >>= 4;
    } else value &= 0xf;
    return m_bytesPerSample * value;
  }
  return m_bytesPerSample * 
    m_pStszSampleSizeProperty->GetValue(sampleId - 1);
}

u_int32_t MP4Track::GetMaxSampleSize()
{
  if (m_pStszFixedSampleSizeProperty != NULL) {
	u_int32_t fixedSampleSize = 
		m_pStszFixedSampleSizeProperty->GetValue(); 

	if (fixedSampleSize != 0) {
		return fixedSampleSize * m_bytesPerSample;
	}
  }

	u_int32_t maxSampleSize = 0;
	u_int32_t numSamples = m_pStszSampleSizeProperty->GetCount();
	for (MP4SampleId sid = 1; sid <= numSamples; sid++) {
		u_int32_t sampleSize =
			m_pStszSampleSizeProperty->GetValue(sid - 1);
		if (sampleSize > maxSampleSize) {
			maxSampleSize = sampleSize;
		}
	}
	return maxSampleSize * m_bytesPerSample;
}

u_int64_t MP4Track::GetTotalOfSampleSizes()
{
  uint64_t retval;
  if (m_pStszFixedSampleSizeProperty != NULL) {
	u_int32_t fixedSampleSize = 
		m_pStszFixedSampleSizeProperty->GetValue(); 

	// if fixed sample size, just need to multiply by number of samples
	if (fixedSampleSize != 0) {
	  retval = m_bytesPerSample;
	  retval *= fixedSampleSize;
	  retval *= GetNumberOfSamples();
	  return retval;
	}
  }

	// else non-fixed sample size, sum them
	u_int64_t totalSampleSizes = 0;
	u_int32_t numSamples = m_pStszSampleSizeProperty->GetCount();
	for (MP4SampleId sid = 1; sid <= numSamples; sid++) {
		u_int32_t sampleSize =
			m_pStszSampleSizeProperty->GetValue(sid - 1);
		totalSampleSizes += sampleSize;
	}
	return totalSampleSizes * m_bytesPerSample;
}

void MP4Track::SampleSizePropertyAddValue (uint32_t size)
{
  // this has to deal with different sample size values
  switch (m_pStszSampleSizeProperty->GetType()) {
  case Integer32Property:
    ((MP4Integer32Property *)m_pStszSampleSizeProperty)->AddValue(size);
    break;
  case Integer16Property:
    ((MP4Integer16Property *)m_pStszSampleSizeProperty)->AddValue(size);
    break;
  case Integer8Property:
    if (m_stsz_sample_bits == 4) {
      if (m_have_stz2_4bit_sample == false) {
	m_have_stz2_4bit_sample = true;
	m_stz2_4bit_sample_value = size << 4;
	return;
      } else {
	m_have_stz2_4bit_sample = false;
	size &= 0xf;
	size |= m_stz2_4bit_sample_value;
      }
    }
    ((MP4Integer8Property *)m_pStszSampleSizeProperty)->AddValue(size);
    break;
  default: break;
  }


  //  m_pStszSampleSizeProperty->IncrementValue();
}

void MP4Track::UpdateSampleSizes(MP4SampleId sampleId, u_int32_t numBytes)
{
  if (m_bytesPerSample > 1) {
    if ((numBytes % m_bytesPerSample) != 0) {
      // error
      VERBOSE_ERROR(m_pFile->GetVerbosity(), 
		    printf("UpdateSampleSize: numBytes %u not divisible by bytesPerSample %u sampleId %u\n", 
			   numBytes, m_bytesPerSample, sampleId);
		    );
    }
    numBytes /= m_bytesPerSample;
  }
	// for first sample
	// wmay - if we are adding, we want to make sure that
	// we don't inadvertently set up the fixed size again.
	// so, we check the number of samples
	if (sampleId == 1 && GetNumberOfSamples() == 0) {
	  if (m_pStszFixedSampleSizeProperty == NULL ||
	      numBytes == 0) {
	    // special case of first sample is zero bytes in length
	    // leave m_pStszFixedSampleSizeProperty at 0
	    // start recording variable sample sizes
	    if (m_pStszFixedSampleSizeProperty != NULL)
	      m_pStszFixedSampleSizeProperty->SetValue(0); 
	    SampleSizePropertyAddValue(0);
	  } else {
	    // presume sample size is fixed
	    m_pStszFixedSampleSizeProperty->SetValue(numBytes); 
	  }
	} else { // sampleId > 1

	  u_int32_t fixedSampleSize = 0;
	  if (m_pStszFixedSampleSizeProperty != NULL) {
	    fixedSampleSize = m_pStszFixedSampleSizeProperty->GetValue(); 
	  }

	  // if we don't have a fixed size, or the current sample size
	  // doesn't match our sample size, we need to write the current
	  // sample size into the table
	  if (fixedSampleSize == 0 || numBytes != fixedSampleSize) {
	    if (fixedSampleSize != 0) {
	      // fixed size was set; we need to clear fixed sample size
	      m_pStszFixedSampleSizeProperty->SetValue(0); 
	      
	      // and create sizes for all previous samples
	      // use GetNumberOfSamples due to needing the total number
	      // not just the appended part of the file
	      uint32_t samples = GetNumberOfSamples();
	      for (MP4SampleId sid = 1; sid <= samples; sid++) {
		SampleSizePropertyAddValue(fixedSampleSize);
	      }
	    }
	    // add size value for this sample
	    SampleSizePropertyAddValue(numBytes);
	  }
	}
	// either way, we increment the number of samples.
	m_pStszSampleCountProperty->IncrementValue();
#if 0
	printf("track %u sample id %u bytes %u fixed %u count %u prop %u\n", 
	       m_trackId, sampleId, numBytes,
	       m_pStszFixedSampleSizeProperty->GetValue(),
	       m_pStszSampleSizeProperty->GetCount(),
	       m_pStszSampleCountProperty->GetValue());
#endif
}

u_int32_t MP4Track::GetAvgBitrate()
{
	if (GetDuration() == 0) {
		return 0;
	}

	double calc = UINT64_TO_DOUBLE(GetTotalOfSampleSizes());
	// this is a bit better - we use the whole duration
	calc *= 8.0;
	calc *= GetTimeScale();
	calc /=	UINT64_TO_DOUBLE(GetDuration());
	// we might want to think about rounding to the next 100 or 1000
	return (uint32_t) ceil(calc);
}

u_int32_t MP4Track::GetMaxBitrate()
{
	u_int32_t timeScale = GetTimeScale();
	MP4SampleId numSamples = GetNumberOfSamples();
	u_int32_t maxBytesPerSec = 0;
	u_int32_t bytesThisSec = 0;
	MP4Timestamp thisSecStart = 0;
	MP4Timestamp lastSampleTime = 0;
	uint32_t lastSampleSize = 0;

	MP4SampleId thisSecStartSid = 1;
	for (MP4SampleId sid = 1; sid <= numSamples; sid++) {
	  uint32_t sampleSize;
	  MP4Timestamp sampleTime;

	  sampleSize = GetSampleSize(sid);
	  GetSampleTimes(sid, &sampleTime, NULL);
	  
	  if (sampleTime < thisSecStart + timeScale) {
	    bytesThisSec += sampleSize;
	    lastSampleSize = sampleSize;
	    lastSampleTime = sampleTime;
	  } else {
	    // we've already written the last sample and sampleSize.
	    // this means that we've probably overflowed the last second
	    // calculate the time we've overflowed
	    MP4Duration overflow_dur = 
	      (thisSecStart + timeScale) - lastSampleTime;
	    // calculate the duration of the last sample
	    MP4Duration lastSampleDur = sampleTime - lastSampleTime;
	    uint32_t overflow_bytes;
	    // now, calculate the number of bytes we overflowed.  Round up.
	    overflow_bytes = 
	      ((lastSampleSize * overflow_dur) + (lastSampleDur - 1)) / lastSampleDur;

	    if (bytesThisSec - overflow_bytes > maxBytesPerSec) {
	      maxBytesPerSec = bytesThisSec - overflow_bytes;
	    }

	    // now adjust the values for this sample.  Remove the bytes
	    // from the first sample in this time frame
	    lastSampleTime = sampleTime;
	    lastSampleSize = sampleSize;
	    bytesThisSec += sampleSize;
	    bytesThisSec -= GetSampleSize(thisSecStartSid);
	    thisSecStartSid++;
	    GetSampleTimes(thisSecStartSid, &thisSecStart, NULL);
	  }
	}

	return maxBytesPerSec * 8;
}

u_int32_t MP4Track::GetSampleStscIndex(MP4SampleId sampleId)
{
	u_int32_t stscIndex;
	u_int32_t numStscs = m_pStscCountProperty->GetValue();

	if (numStscs == 0) {
		throw new MP4Error("No data chunks exist", "GetSampleStscIndex");
	}

	for (stscIndex = 0; stscIndex < numStscs; stscIndex++) {
		if (sampleId < m_pStscFirstSampleProperty->GetValue(stscIndex)) {
			ASSERT(stscIndex != 0);
			stscIndex -= 1;
			break;
		}
	}
	if (stscIndex == numStscs) {
		ASSERT(stscIndex != 0);
		stscIndex -= 1;
	}

	return stscIndex;
}

FILE* MP4Track::GetSampleFile(MP4SampleId sampleId)
{
	u_int32_t stscIndex =
		GetSampleStscIndex(sampleId);

	u_int32_t stsdIndex = 
		m_pStscSampleDescrIndexProperty->GetValue(stscIndex);

	// check if the answer will be the same as last time
	if (m_lastStsdIndex && stsdIndex == m_lastStsdIndex) {
		return m_lastSampleFile;
	}

	MP4Atom* pStsdAtom = 
		m_pTrakAtom->FindAtom("trak.mdia.minf.stbl.stsd");
	ASSERT(pStsdAtom);

	MP4Atom* pStsdEntryAtom = 
		pStsdAtom->GetChildAtom(stsdIndex - 1);
	ASSERT(pStsdEntryAtom);

	MP4Integer16Property* pDrefIndexProperty = NULL;
	if (!pStsdEntryAtom->FindProperty(
					 "*.dataReferenceIndex",
					 (MP4Property**)&pDrefIndexProperty) ||
	
	    pDrefIndexProperty == NULL) {
		throw new MP4Error("invalid stsd entry", "GetSampleFile");
	}

	u_int32_t drefIndex =
		pDrefIndexProperty->GetValue();

	MP4Atom* pDrefAtom =
		m_pTrakAtom->FindAtom("trak.mdia.minf.dinf.dref");
	ASSERT(pDrefAtom);

	MP4Atom* pUrlAtom =
		pDrefAtom->GetChildAtom(drefIndex - 1);
	ASSERT(pUrlAtom);

	FILE* pFile;

	if (pUrlAtom->GetFlags() & 1) {
		pFile = NULL;	// self-contained
	} else {
		MP4StringProperty* pLocationProperty = NULL;
		ASSERT(pUrlAtom->FindProperty(
					      "*.location", 
					      (MP4Property**)&pLocationProperty));
		ASSERT(pLocationProperty);

		const char* url = pLocationProperty->GetValue();

		VERBOSE_READ_SAMPLE(m_pFile->GetVerbosity(),
			printf("dref url = %s\n", url));

		pFile = (FILE*)-1;

		// attempt to open url if it's a file url 
		// currently this is the only thing we understand
		if (!strncmp(url, "file:", 5)) {
			const char* fileName = url + 5;
			if (!strncmp(fileName, "//", 2)) {
				fileName = strchr(fileName + 2, '/');
			}
			if (fileName) {
				pFile = fopen(fileName, "rb");
				if (!pFile) {
					pFile = (FILE*)-1;
				}
			}
		} 
	}

	if (m_lastSampleFile) {
		fclose(m_lastSampleFile);
	}

	// cache the answer
	m_lastStsdIndex = stsdIndex;
	m_lastSampleFile = pFile;

	return pFile;
}

u_int64_t MP4Track::GetSampleFileOffset(MP4SampleId sampleId)
{
	u_int32_t stscIndex =
		GetSampleStscIndex(sampleId);

	// firstChunk is the chunk index of the first chunk with 
	// samplesPerChunk samples in the chunk.  There may be multiples -
	// ie: several chunks with the same number of samples per chunk.
	u_int32_t firstChunk = 
		m_pStscFirstChunkProperty->GetValue(stscIndex);

	MP4SampleId firstSample = 
		m_pStscFirstSampleProperty->GetValue(stscIndex);

	u_int32_t samplesPerChunk = 
		m_pStscSamplesPerChunkProperty->GetValue(stscIndex);

	// chunkId tells which is the absolute chunk number that this sample
	// is stored in.
	MP4ChunkId chunkId = firstChunk +
		((sampleId - firstSample) / samplesPerChunk);

	// chunkOffset is the file offset (absolute) for the start of the chunk
	u_int64_t chunkOffset = m_pChunkOffsetProperty->GetValue(chunkId - 1);