mp4track.cpp

完整的RTP RTSP代码库

	MP4SampleId firstSampleInChunk = 
		sampleId - ((sampleId - firstSample) % samplesPerChunk);

	// need cumulative samples sizes from firstSample to sampleId - 1
	u_int32_t sampleOffset = 0;
	for (MP4SampleId i = firstSampleInChunk; i < sampleId; i++) {
		sampleOffset += GetSampleSize(i);
	}

	return chunkOffset + sampleOffset;
}

void MP4Track::UpdateSampleToChunk(MP4SampleId sampleId,
	 MP4ChunkId chunkId, u_int32_t samplesPerChunk)
{
	u_int32_t numStsc = m_pStscCountProperty->GetValue();

	// if samplesPerChunk == samplesPerChunk of last entry
	if (numStsc && samplesPerChunk == 
	  m_pStscSamplesPerChunkProperty->GetValue(numStsc-1)) {

		// nothing to do

	} else {
		// add stsc entry
		m_pStscFirstChunkProperty->AddValue(chunkId);
		m_pStscSamplesPerChunkProperty->AddValue(samplesPerChunk);
		m_pStscSampleDescrIndexProperty->AddValue(1);
		m_pStscFirstSampleProperty->AddValue(sampleId - samplesPerChunk + 1);

		m_pStscCountProperty->IncrementValue();
	}
}

void MP4Track::UpdateChunkOffsets(u_int64_t chunkOffset)
{
	if (m_pChunkOffsetProperty->GetType() == Integer32Property) {
		((MP4Integer32Property*)m_pChunkOffsetProperty)->AddValue(chunkOffset);
	} else {
		((MP4Integer64Property*)m_pChunkOffsetProperty)->AddValue(chunkOffset);
	}
	m_pChunkCountProperty->IncrementValue();
}

MP4Duration MP4Track::GetFixedSampleDuration()
{
	u_int32_t numStts = m_pSttsCountProperty->GetValue();

	if (numStts == 0) {
		return m_fixedSampleDuration;
	}
	if (numStts != 1) {
		return MP4_INVALID_DURATION;	// sample duration is not fixed
	}
	return m_pSttsSampleDeltaProperty->GetValue(0);
}

void MP4Track::SetFixedSampleDuration(MP4Duration duration)
{
	u_int32_t numStts = m_pSttsCountProperty->GetValue();

	// setting this is only allowed before samples have been written
	if (numStts != 0) {
		return;
	}
	m_fixedSampleDuration = duration;
	return;
}

void MP4Track::GetSampleTimes(MP4SampleId sampleId,
	MP4Timestamp* pStartTime, MP4Duration* pDuration)
{
	u_int32_t numStts = m_pSttsCountProperty->GetValue();
	MP4SampleId sid;
	MP4Duration elapsed;
	
	
	if (m_cachedSttsSid != MP4_INVALID_SAMPLE_ID && sampleId >= m_cachedSttsSid) {
		sid	  = m_cachedSttsSid;
		elapsed	  = m_cachedSttsElapsed;
	} else {
		m_cachedSttsIndex = 0;
		sid	  = 1;
		elapsed	  = 0;
	}

	for (u_int32_t sttsIndex = m_cachedSttsIndex; sttsIndex < numStts; sttsIndex++) {
		u_int32_t sampleCount = 
			m_pSttsSampleCountProperty->GetValue(sttsIndex);
		u_int32_t sampleDelta = 
			m_pSttsSampleDeltaProperty->GetValue(sttsIndex);

		if (sampleId <= sid + sampleCount - 1) {
			if (pStartTime) {
			  *pStartTime = (sampleId - sid);
			  *pStartTime *= sampleDelta;
			  *pStartTime += elapsed;
			}
			if (pDuration) {
				*pDuration = sampleDelta;
			}

			m_cachedSttsIndex = sttsIndex;
			m_cachedSttsSid = sid;
			m_cachedSttsElapsed = elapsed;

			return;
		}
		sid += sampleCount;
		elapsed += sampleCount * sampleDelta;
	}

	throw new MP4Error("sample id out of range", 
		"MP4Track::GetSampleTimes");
}

MP4SampleId MP4Track::GetSampleIdFromTime(
	MP4Timestamp when, 
	bool wantSyncSample) 
{
	u_int32_t numStts = m_pSttsCountProperty->GetValue();
	MP4SampleId sid = 1;
	MP4Duration elapsed = 0;

	for (u_int32_t sttsIndex = 0; sttsIndex < numStts; sttsIndex++) {
		u_int32_t sampleCount = 
			m_pSttsSampleCountProperty->GetValue(sttsIndex);
		u_int32_t sampleDelta = 
			m_pSttsSampleDeltaProperty->GetValue(sttsIndex);

		if (sampleDelta == 0 && sttsIndex < numStts - 1) {
			VERBOSE_READ(m_pFile->GetVerbosity(),
				printf("Warning: Zero sample duration, stts entry %u\n",
				sttsIndex));
		}

		MP4Duration d = when - elapsed;

		if (d <= sampleCount * sampleDelta) {
			MP4SampleId sampleId = sid;
			if (sampleDelta) {
				sampleId += (d / sampleDelta);
			}

			if (wantSyncSample) {
				return GetNextSyncSample(sampleId);
			}
			return sampleId;
		}

		sid += sampleCount;
		elapsed += sampleCount * sampleDelta;
	}

	throw new MP4Error("time out of range", 
		"MP4Track::GetSampleIdFromTime");

	return 0; // satisfy MS compiler
}

void MP4Track::UpdateSampleTimes(MP4Duration duration)
{
	u_int32_t numStts = m_pSttsCountProperty->GetValue();

	// if duration == duration of last entry
	if (numStts 
	  && duration == m_pSttsSampleDeltaProperty->GetValue(numStts-1)) {
		// increment last entry sampleCount
		m_pSttsSampleCountProperty->IncrementValue(1, numStts-1);

	} else {
		// add stts entry, sampleCount = 1, sampleDuration = duration
		m_pSttsSampleCountProperty->AddValue(1);
		m_pSttsSampleDeltaProperty->AddValue(duration);
		m_pSttsCountProperty->IncrementValue();;
	}
}

u_int32_t MP4Track::GetSampleCttsIndex(MP4SampleId sampleId, 
	MP4SampleId* pFirstSampleId)
{
	u_int32_t numCtts = m_pCttsCountProperty->GetValue();

	MP4SampleId sid = 1;
	
	for (u_int32_t cttsIndex = 0; cttsIndex < numCtts; cttsIndex++) {
		u_int32_t sampleCount = 
			m_pCttsSampleCountProperty->GetValue(cttsIndex);

		if (sampleId <= sid + sampleCount - 1) {
			if (pFirstSampleId) {
				*pFirstSampleId = sid;
			}
			return cttsIndex;
		}
		sid += sampleCount;
	}

	throw new MP4Error("sample id out of range", 
		"MP4Track::GetSampleCttsIndex");
	return 0; // satisfy MS compiler
}

MP4Duration MP4Track::GetSampleRenderingOffset(MP4SampleId sampleId)
{
	if (m_pCttsCountProperty == NULL) {
		return 0;
	}
	if (m_pCttsCountProperty->GetValue() == 0) {
		return 0;
	}

	u_int32_t cttsIndex = GetSampleCttsIndex(sampleId);

	return m_pCttsSampleOffsetProperty->GetValue(cttsIndex);
}

void MP4Track::UpdateRenderingOffsets(MP4SampleId sampleId, 
	MP4Duration renderingOffset)
{
	// if ctts atom doesn't exist
	if (m_pCttsCountProperty == NULL) {

		// no rendering offset, so nothing to do
		if (renderingOffset == 0) {
			return;
		}

		// else create a ctts atom
		MP4Atom* pCttsAtom = AddAtom("trak.mdia.minf.stbl", "ctts");

		// and get handles on the properties
		ASSERT(pCttsAtom->FindProperty(
			"ctts.entryCount",
			(MP4Property**)&m_pCttsCountProperty));

		ASSERT(pCttsAtom->FindProperty(
			"ctts.entries.sampleCount",
			(MP4Property**)&m_pCttsSampleCountProperty));

		ASSERT(pCttsAtom->FindProperty(
			"ctts.entries.sampleOffset",
			(MP4Property**)&m_pCttsSampleOffsetProperty));

		// if this is not the first sample
		if (sampleId > 1) {
			// add a ctts entry for all previous samples
			// with rendering offset equal to zero
			m_pCttsSampleCountProperty->AddValue(sampleId - 1);
			m_pCttsSampleOffsetProperty->AddValue(0);
			m_pCttsCountProperty->IncrementValue();;
		}
	}

	// ctts atom exists (now)

	u_int32_t numCtts = m_pCttsCountProperty->GetValue();

	// if renderingOffset == renderingOffset of last entry
	if (numCtts && renderingOffset
	   == m_pCttsSampleOffsetProperty->GetValue(numCtts-1)) {

		// increment last entry sampleCount
		m_pCttsSampleCountProperty->IncrementValue(1, numCtts-1);

	} else {
		// add ctts entry, sampleCount = 1, sampleOffset = renderingOffset
		m_pCttsSampleCountProperty->AddValue(1);
		m_pCttsSampleOffsetProperty->AddValue(renderingOffset);
		m_pCttsCountProperty->IncrementValue();
	}
}

void MP4Track::SetSampleRenderingOffset(MP4SampleId sampleId,
	 MP4Duration renderingOffset)
{
	// check if any ctts entries exist
	if (m_pCttsCountProperty == NULL
	  || m_pCttsCountProperty->GetValue() == 0) {
		// if not then Update routine can be used 
		// to create a ctts entry for samples before this one
		// and a ctts entry for this sample 
		UpdateRenderingOffsets(sampleId, renderingOffset);

		// but we also need a ctts entry 
		// for all samples after this one
		u_int32_t afterSamples = GetNumberOfSamples() - sampleId;

		if (afterSamples) {
			m_pCttsSampleCountProperty->AddValue(afterSamples);
			m_pCttsSampleOffsetProperty->AddValue(0);
			m_pCttsCountProperty->IncrementValue();;
		}

		return;
	}

	MP4SampleId firstSampleId;
	u_int32_t cttsIndex = GetSampleCttsIndex(sampleId, &firstSampleId);

	// do nothing in the degenerate case
	if (renderingOffset == 
	  m_pCttsSampleOffsetProperty->GetValue(cttsIndex)) {
		return;
	}

	u_int32_t sampleCount =
		m_pCttsSampleCountProperty->GetValue(cttsIndex);

	// if this sample has it's own ctts entry
	if (sampleCount == 1) {
		// then just set the value, 
		// note we don't attempt to collapse entries
		m_pCttsSampleOffsetProperty->SetValue(renderingOffset, cttsIndex);
		return;
	}

	MP4SampleId lastSampleId = firstSampleId + sampleCount - 1;

	// else we share this entry with other samples
	// we need to insert our own entry
	if (sampleId == firstSampleId) {
		// our sample is the first one
		m_pCttsSampleCountProperty->
			InsertValue(1, cttsIndex);
		m_pCttsSampleOffsetProperty->
			InsertValue(renderingOffset, cttsIndex);

		m_pCttsSampleCountProperty->
			SetValue(sampleCount - 1, cttsIndex + 1);

		m_pCttsCountProperty->IncrementValue();

	} else if (sampleId == lastSampleId) {
		// our sample is the last one
		m_pCttsSampleCountProperty->
			InsertValue(1, cttsIndex + 1);
		m_pCttsSampleOffsetProperty->
			InsertValue(renderingOffset, cttsIndex + 1);

		m_pCttsSampleCountProperty->
			SetValue(sampleCount - 1, cttsIndex);

		m_pCttsCountProperty->IncrementValue();

	} else {
		// our sample is in the middle, UGH!

		// insert our new entry
		m_pCttsSampleCountProperty->
			InsertValue(1, cttsIndex + 1);
		m_pCttsSampleOffsetProperty->
			InsertValue(renderingOffset, cttsIndex + 1);

		// adjust count of previous entry
		m_pCttsSampleCountProperty->
			SetValue(sampleId - firstSampleId, cttsIndex);

		// insert new entry for those samples beyond our sample
		m_pCttsSampleCountProperty->
			InsertValue(lastSampleId - sampleId, cttsIndex + 2);
		u_int32_t oldRenderingOffset =
			m_pCttsSampleOffsetProperty->GetValue(cttsIndex);
		m_pCttsSampleOffsetProperty->
			InsertValue(oldRenderingOffset, cttsIndex + 2);

		m_pCttsCountProperty->IncrementValue(2);
	}
}

bool MP4Track::IsSyncSample(MP4SampleId sampleId)
{
	if (m_pStssCountProperty == NULL) {
		return true;
	}

	u_int32_t numStss = m_pStssCountProperty->GetValue();
	u_int32_t stssLIndex = 0;
	u_int32_t stssRIndex = numStss - 1;
	
	while (stssRIndex >= stssLIndex){
		u_int32_t stssIndex = (stssRIndex + stssLIndex) >> 1;
		MP4SampleId syncSampleId = 
			m_pStssSampleProperty->GetValue(stssIndex);

		if (sampleId == syncSampleId) {
			return true;
		} 

		if (sampleId > syncSampleId) {
			stssLIndex = stssIndex + 1;
		} else {
			stssRIndex = stssIndex - 1;
		}
	}

	return false;
}

// N.B. "next" is inclusive of this sample id
MP4SampleId MP4Track::GetNextSyncSample(MP4SampleId sampleId)
{
	if (m_pStssCountProperty == NULL) {
		return sampleId;
	}

	u_int32_t numStss = m_pStssCountProperty->GetValue();
	
	for (u_int32_t stssIndex = 0; stssIndex < numStss; stssIndex++) {
		MP4SampleId syncSampleId = 
			m_pStssSampleProperty->GetValue(stssIndex);

		if (sampleId > syncSampleId) {
			continue;
		}
		return syncSampleId;
	}

	// LATER check stsh for alternate sample

	return MP4_INVALID_SAMPLE_ID;
}

void MP4Track::UpdateSyncSamples(MP4SampleId sampleId, bool isSyncSample)
{
  if (isSyncSample) {
    // if stss atom exists, add entry
    if (m_pStssCountProperty) {
      m_pStssSampleProperty->AddValue(sampleId);
      m_pStssCountProperty->IncrementValue();
    } // else nothing to do (yet)

  } else { // !isSyncSample
    // if stss atom doesn't exist, create one
    if (m_pStssCountProperty == NULL) {

      MP4Atom* pStssAtom = AddAtom("trak.mdia.minf.stbl", "stss");

      ASSERT(pStssAtom->FindProperty(
			      "stss.entryCount",
			      (MP4Property**)&m_pStssCountProperty));
		  
      ASSERT(pStssAtom->FindProperty(
			      "stss.entries.sampleNumber",
			      (MP4Property**)&m_pStssSampleProperty));

      // set values for all samples that came before this one
      uint32_t samples = GetNumberOfSamples();
      for (MP4SampleId sid = 1; sid < samples; sid++) {
	m_pStssSampleProperty->AddValue(sid);
	m_pStssCountProperty->IncrementValue();
      }
    } // else nothing to do