atom_stsc.cpp

网络MPEG4IP流媒体开发源代码

/*
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is MPEG4IP.
 * 
 * The Initial Developer of the Original Code is Cisco Systems Inc.
 * Portions created by Cisco Systems Inc. are
 * Copyright (C) Cisco Systems Inc. 2001.  All Rights Reserved.
 * 
 * Contributor(s): 
 *		Dave Mackie		[e-mail]
 */

#include "mp4common.h"

MP4StscAtom::MP4StscAtom() 
	: MP4Atom("stsc")
{
	AddVersionAndFlags();

	MP4Integer32Property* pCount = 
		new MP4Integer32Property("entryCount"); 
	AddProperty(pCount);

	MP4TableProperty* pTable = new MP4TableProperty("entries", pCount);
	AddProperty(pTable);

	pTable->AddProperty(
		new MP4Integer32Property("firstChunk"));
	pTable->AddProperty(
		new MP4Integer32Property("samplesPerChunk"));
	pTable->AddProperty(
		new MP4Integer32Property("sampleDescriptionIndex"));

	// As an optimization we add an implicit property to this table,
	// "firstSample" that corresponds to the first sample of the firstChunk
	MP4Integer32Property* pSample =
		new MP4Integer32Property("firstSample");
	pSample->SetImplicit();
	pTable->AddProperty(pSample);
}

void MP4StscAtom::Read() 
{
	// Read as usual
	MP4Atom::Read();

	// Compute the firstSample values for later use
	u_int32_t count = 
		((MP4Integer32Property*)m_pProperties[2])->GetValue();

	MP4Integer32Property* pFirstChunk = (MP4Integer32Property*)
		((MP4TableProperty*)m_pProperties[3])->GetProperty(0);
	MP4Integer32Property* pSamplesPerChunk = (MP4Integer32Property*)
		((MP4TableProperty*)m_pProperties[3])->GetProperty(1);
	MP4Integer32Property* pFirstSample = (MP4Integer32Property*)
		((MP4TableProperty*)m_pProperties[3])->GetProperty(3);

	MP4SampleId sampleId = 1;

	for (u_int32_t i = 0; i < count; i++) {
		pFirstSample->SetValue(sampleId, i);

		if (i < count - 1) {
			sampleId +=
				(pFirstChunk->GetValue(i+1) - pFirstChunk->GetValue(i))
				 * pSamplesPerChunk->GetValue(i);
		}
	}
}