stbl_read.c

一个用于智能手机的多媒体库适合S60 WinCE的跨平台开发库

/*
 *			GPAC - Multimedia Framework C SDK
 *
 *			Copyright (c) Jean Le Feuvre 2000-2005
 *					All rights reserved
 *
 *  This file is part of GPAC / ISO Media File Format sub-project
 *
 *  GPAC 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, or (at your option)
 *  any later version.
 *   
 *  GPAC 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; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */

#include <gpac/internal/isomedia_dev.h>

//Get the sample number
GF_Err findEntryForTime(GF_SampleTableBox *stbl, u64 DTS, u8 useCTS, u32 *sampleNumber, u32 *prevSampleNumber)
{
	u32 i, j, curSampNum, CTSOffset, count;
	u64 curDTS;
	GF_SttsEntry *ent;
	(*sampleNumber) = 0;
	(*prevSampleNumber) = 0;

	if (!stbl->CompositionOffset) useCTS = 0;
	/*FIXME: CTS is ALWAYS disabled for now to make sure samples are fetched in 
	decoding order. */
	useCTS = 0;

	//our cache
	if (stbl->TimeToSample->r_FirstSampleInEntry &&
		(DTS >= stbl->TimeToSample->r_CurrentDTS) ) {
		//if we're using CTS, we don't really know whether we're in the good entry or not
		//(eg, the real DTS of the sample could be in a previous entry
		i = stbl->TimeToSample->r_currentEntryIndex;
		curDTS = stbl->TimeToSample->r_CurrentDTS;
		curSampNum = stbl->TimeToSample->r_FirstSampleInEntry;
	} else {
		i = 0;
		curDTS = stbl->TimeToSample->r_CurrentDTS = 0;
		curSampNum = stbl->TimeToSample->r_FirstSampleInEntry = 1;
		stbl->TimeToSample->r_currentEntryIndex = 0;
	}

	//we need to validate our cache if we are using CTS because of B-frames and co...
	if (i && useCTS) {
		while (1) {
			stbl_GetSampleCTS(stbl->CompositionOffset, curSampNum, &CTSOffset);
			//we're too far, rewind
			if ( i && (curDTS + CTSOffset > DTS) ) {
				ent = (GF_SttsEntry*)gf_list_get(stbl->TimeToSample->entryList, i);
				curSampNum -= ent->sampleCount;
				curDTS -= ent->sampleDelta * ent->sampleCount;
				i --;
			} else if (!i) {
				//begining of the table, no choice
				curDTS = stbl->TimeToSample->r_CurrentDTS = 0;
				curSampNum = stbl->TimeToSample->r_FirstSampleInEntry = 1;
				stbl->TimeToSample->r_currentEntryIndex = 0;
				break;
			} else {
				//OK now we're good
				break;
			}
		}
	}

	//look for the DTS from this entry
	count = gf_list_count(stbl->TimeToSample->entryList);
	for (; i<count; i++) {
		ent = (GF_SttsEntry*)gf_list_get(stbl->TimeToSample->entryList, i);
		if (useCTS) {
			stbl_GetSampleCTS(stbl->CompositionOffset, curSampNum, &CTSOffset);
		} else {
			CTSOffset = 0;
		}
		for (j=0; j<ent->sampleCount; j++) {
			if (curDTS + CTSOffset >= DTS) goto entry_found;
			curSampNum += 1;
			curDTS += ent->sampleDelta;
		}
		//we're switching to the next entry, update the cache!
		stbl->TimeToSample->r_CurrentDTS += ent->sampleCount * ent->sampleDelta;
		stbl->TimeToSample->r_currentEntryIndex += 1;
		stbl->TimeToSample->r_FirstSampleInEntry += ent->sampleCount;
	}
	//return as is
	return GF_OK;

entry_found:
	//do we have the exact time ?
	if (curDTS + CTSOffset == DTS) {
		(*sampleNumber) = curSampNum;
	}
	//if we match the exact DTS also select this sample 
	else if (curDTS == DTS) {
		(*sampleNumber) = curSampNum;
	} else {
		//exception for the first sample (we need to "load" the playback)
		if (curSampNum != 1) {
			(*prevSampleNumber) = curSampNum - 1;
		} else {
			(*prevSampleNumber) = 1;
		}
	}
	return GF_OK;
}

//Get the Size of a given sample
GF_Err stbl_GetSampleSize(GF_SampleSizeBox *stsz, u32 SampleNumber, u32 *Size)
{
	if (!stsz || !SampleNumber || SampleNumber > stsz->sampleCount) return GF_BAD_PARAM;

	(*Size) = 0;

	if (stsz->sampleSize && (stsz->type != GF_ISOM_BOX_TYPE_STZ2)) {
		(*Size) = stsz->sampleSize;
	} else {
		(*Size) = stsz->sizes[SampleNumber - 1];
	}
	return GF_OK;
}



//Get the CTS offset of a given sample
GF_Err stbl_GetSampleCTS(GF_CompositionOffsetBox *ctts, u32 SampleNumber, u32 *CTSoffset)
{
	u32 i, count;
	GF_DttsEntry *ent;

	(*CTSoffset) = 0;
	ent = NULL;
	//test on SampleNumber is done before
	if (!ctts || !SampleNumber) return GF_BAD_PARAM;

	if (ctts->r_FirstSampleInEntry && (ctts->r_FirstSampleInEntry < SampleNumber) ) {
		i = ctts->r_currentEntryIndex;
	} else {
		ctts->r_FirstSampleInEntry = 1;
		ctts->r_currentEntryIndex = 0;
		i = 0;
	}
	count = gf_list_count(ctts->entryList);
	for (; i< count; i++) {
		ent = (GF_DttsEntry*)gf_list_get(ctts->entryList, i);
		if (SampleNumber < ctts->r_FirstSampleInEntry + ent->sampleCount) break;
		//update our cache
		ctts->r_currentEntryIndex += 1;
		ctts->r_FirstSampleInEntry += ent->sampleCount;
	}
	//no ent, set everything to 0...
	if (!ent) return GF_OK;
	/*asked for a sample not in table - this means CTTS is 0 (that's due to out internal packing construction of CTTS)*/
	if (SampleNumber >= ctts->r_FirstSampleInEntry + ent->sampleCount) return GF_OK;
	(*CTSoffset) = ent->decodingOffset;
	return GF_OK;
}

//Get the DTS of a sample
GF_Err stbl_GetSampleDTS(GF_TimeToSampleBox *stts, u32 SampleNumber, u64 *DTS)
{
	u32 i, j, count;
	GF_SttsEntry *ent;

	(*DTS) = 0;
	if (!stts || !SampleNumber) return GF_BAD_PARAM;

	ent = NULL;
	//use our cache
	count = gf_list_count(stts->entryList);
	if (stts->r_FirstSampleInEntry 
		&& (stts->r_FirstSampleInEntry <= SampleNumber)
		//this is for read/write access
		&& (stts->r_currentEntryIndex < count) ) {

		i = stts->r_currentEntryIndex;
	} else {
		i = stts->r_currentEntryIndex = 0;
		stts->r_FirstSampleInEntry = 1;
		stts->r_CurrentDTS = 0;
	}

	for (; i < count; i++) {
		ent = (GF_SttsEntry*)gf_list_get(stts->entryList, i);

		//in our entry
		if (ent->sampleCount + stts->r_FirstSampleInEntry >= 1 + SampleNumber) {
			j = SampleNumber - stts->r_FirstSampleInEntry;
			goto found;
		}
			
		//update our cache
		stts->r_CurrentDTS += ent->sampleCount * ent->sampleDelta;
		stts->r_currentEntryIndex += 1;
		stts->r_FirstSampleInEntry += ent->sampleCount;
	}
//	if (SampleNumber >= stts->r_FirstSampleInEntry + ent->sampleCount) return GF_BAD_PARAM;

	//no ent, this is really weird. Let's assume the DTS is then what is written in the table
	if (!ent || (i == count)) (*DTS) = stts->r_CurrentDTS;
	return GF_OK;

found:
	(*DTS) = stts->r_CurrentDTS + j * (u64) ent->sampleDelta;

	if (stts->r_FirstSampleInEntry == 1)
		stts->r_FirstSampleInEntry = 1;

	
	
	return GF_OK;
}

//Set the RAP flag of a sample
GF_Err stbl_GetSampleRAP(GF_SyncSampleBox *stss, u32 SampleNumber, u8 *IsRAP, u32 *prevRAP, u32 *nextRAP)
{
	u32 i;

	if (prevRAP) *prevRAP = 0;
	if (nextRAP) *nextRAP = 0;

	(*IsRAP) = 0;
	if (!stss || !SampleNumber) return GF_BAD_PARAM;

	if (stss->r_LastSyncSample && (stss->r_LastSyncSample < SampleNumber) ) {
		i = stss->r_LastSampleIndex;
	} else {
		i = 0;
	}
	for (; i < stss->entryCount; i++) {
		//get the entry
		if (stss->sampleNumbers[i] == SampleNumber) {
			//update the cache
			stss->r_LastSyncSample = SampleNumber;
			stss->r_LastSampleIndex = i;
			(*IsRAP) = 1;
		}
		else if (stss->sampleNumbers[i] > SampleNumber) {
			if (nextRAP) *nextRAP = stss->sampleNumbers[i];
			return GF_OK;
		}
		if (prevRAP) *prevRAP = stss->sampleNumbers[i];
	}
	return GF_OK;
}

//get the number of "ghost chunk" (implicit chunks described by an entry)
void GetGhostNum(GF_StscEntry *ent, u32 EntryIndex, u32 count, GF_SampleTableBox *stbl)
{