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Ap4Processor.cpp：源码内容
							/*****************************************************************
|
|    AP4 - File Processor
|
|    Copyright 2003-2005 Gilles Boccon-Gibod & Julien Boeuf
|
|
|    This file is part of Bento4/AP4 (MP4 Atom Processing Library).
|
|    Unless you have obtained Bento4 under a difference license,
|    this version of Bento4 is Bento4|GPL.
|    Bento4|GPL is free software; you can redistribute it and/or modify
|    it under the terms of the GNU General Public License as published by
|    the Free Software Foundation; either version 2, or (at your option)
|    any later version.
|
|    Bento4|GPL 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 General Public License for more details.
|
|    You should have received a copy of the GNU General Public License
|    along with Bento4|GPL; see the file COPYING.  If not, write to the
|    Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
|    02111-1307, USA.
|
****************************************************************/
/*----------------------------------------------------------------------
|       includes
+---------------------------------------------------------------------*/
#include "Ap4Processor.h"
#include "Ap4AtomSampleTable.h"
#include "Ap4AtomFactory.h"
#include "Ap4MoovAtom.h"
#include "Ap4Array.h"
#include "Ap4Debug.h"
/*----------------------------------------------------------------------
|       types
+---------------------------------------------------------------------*/
class AP4_SampleLocator {
public:
    AP4_SampleLocator() : 
        m_TrakIndex(0), 
        m_SampleTable(NULL), 
        m_SampleIndex(0), 
        m_Chunk(0) {}
    AP4_Ordinal          m_TrakIndex;
    AP4_AtomSampleTable* m_SampleTable;
    AP4_Ordinal          m_SampleIndex;
    AP4_Sample           m_Sample;
    AP4_Ordinal          m_Chunk;
};
struct AP4_SampleCursor {
    AP4_SampleLocator m_Locator;
};
/*----------------------------------------------------------------------
|       AP4_Processor::Process
+---------------------------------------------------------------------*/
AP4_Result
AP4_Processor::Process(AP4_ByteStream&  input, 
                       AP4_ByteStream&  output,
                       AP4_AtomFactory& atom_factory)
{
    // read all atoms 
    AP4_AtomParent top_level;
    AP4_Atom* atom;
    while (AP4_SUCCEEDED(atom_factory.CreateAtomFromStream(input, atom))) {
        top_level.AddChild(atom);
    }
    // remove the [mdat] and [free] atoms, keep a ref to [moov]
    AP4_MoovAtom* moov = NULL;
    AP4_List<AP4_Atom>::Item* atom_item = top_level.GetChildren().FirstItem();
    while (atom_item) {
        atom = atom_item->GetData();
        AP4_List<AP4_Atom>::Item* next = atom_item->GetNext();
        if (//atom->GetType() == AP4_ATOM_TYPE_FREE ||
            atom->GetType() == AP4_ATOM_TYPE_MDAT) {
            atom->Detach();
            delete atom;
        } else if (atom->GetType() == AP4_ATOM_TYPE_MOOV) {
            moov = (AP4_MoovAtom*)atom;
        }
        atom_item = next;
    }
    // check that we have a moov atom
    if (moov == NULL) return AP4_FAILURE;
    // initialize the processor
    AP4_Result result = Initialize(top_level);
    if (AP4_FAILED(result)) return result;
    // build an array of track sample cursors
    AP4_List<AP4_TrakAtom>& trak_atoms = moov->GetTrakAtoms();
    AP4_Cardinal track_count = trak_atoms.ItemCount();
    AP4_SampleCursor* cursors = new AP4_SampleCursor[track_count];
    TrackHandler** handlers = new TrackHandler*[track_count];
    AP4_List<AP4_TrakAtom>::Item* item = trak_atoms.FirstItem();
    unsigned int index = 0;
    while (item) {
        // create the track handler    // find the stsd atom
        AP4_ContainerAtom* stbl = dynamic_cast<AP4_ContainerAtom*>(
            item->GetData()->FindChild("mdia/minf/stbl"));
        if (stbl == NULL) continue;
        handlers[index] = CreateTrackHandler(item->GetData());
        cursors[index].m_Locator.m_TrakIndex = index;
        cursors[index].m_Locator.m_SampleTable = new AP4_AtomSampleTable(stbl, input);
        cursors[index].m_Locator.m_SampleIndex = 0;
        cursors[index].m_Locator.m_SampleTable->GetSample(0, cursors[index].m_Locator.m_Sample);
        cursors[index].m_Locator.m_Chunk = 1;
        index++;
        item = item->GetNext();
    }
    // figure out the layout of the chunks
    AP4_Array<AP4_SampleLocator> locators;
    for (;;) {
        // see which is the next sample to write
        unsigned int min_offset = 0xFFFFFFFF;
        int cursor = -1;
        for (unsigned int i=0; i<track_count; i++) {
            if (cursors[i].m_Locator.m_SampleTable &&
                cursors[i].m_Locator.m_Sample.GetOffset() <= min_offset) {
                    min_offset = cursors[i].m_Locator.m_Sample.GetOffset();
                    cursor = i;
            }
        }
        // stop if all cursors are exhausted
        if (cursor == -1) break;
        // append this locator to the layout list
        AP4_SampleLocator& locator = cursors[cursor].m_Locator;
        locators.Append(locator);
        //AP4_Debug("NEXT: track %d, sample %d:%d: offset=%d, size=%dn",
        //    locator.m_TrakIndex, 
        //    locator.m_Chunk,
        //    locator.m_SampleIndex,
        //    locator.m_Sample.GetOffset(),
        //    locator.m_Sample.GetSize());
        // move the cursor to the next sample
        locator.m_SampleIndex++;
        if (locator.m_SampleIndex == locator.m_SampleTable->GetSampleCount()) {
            // mark this track as completed
            locator.m_SampleTable = NULL;
        } else {
            // get the next sample info
            locator.m_SampleTable->GetSample(locator.m_SampleIndex, 
                locator.m_Sample);
            AP4_Ordinal skip, sdesc;
            locator.m_SampleTable->GetChunkForSample(locator.m_SampleIndex+1, // the internal API is 1-based
                locator.m_Chunk,
                skip, sdesc);
        }
    }
    // update the stbl atoms and compute the mdat size
    AP4_Size mdat_size = 0;
    int current_track  = -1;
    int current_chunk  = -1;
    AP4_Offset current_chunk_offset = 0;
    AP4_Size current_chunk_size = 0;
    for (AP4_Ordinal i=0; i<locators.ItemCount(); i++) {
        AP4_SampleLocator& locator = locators[i];
        if ((int)locator.m_TrakIndex != current_track ||
            (int)locator.m_Chunk     != current_chunk) {
            // start a new chunk for this track
            current_chunk_offset += current_chunk_size;
            current_chunk_size = 0;
            current_track = locator.m_TrakIndex;
            current_chunk = locator.m_Chunk;
            locator.m_SampleTable->SetChunkOffset(locator.m_Chunk, 
                current_chunk_offset);
        } 
        AP4_Size sample_size;
        TrackHandler* handler = handlers[locator.m_TrakIndex];
        if (handler) {
            sample_size = handler->GetProcessedSampleSize(locator.m_Sample);
            locator.m_SampleTable->SetSampleSize(locator.m_SampleIndex+1, sample_size);
        } else {
            sample_size = locator.m_Sample.GetSize();
        }
        current_chunk_size += sample_size;
        mdat_size += sample_size;
    }
    // process the tracks (ex: sample descriptions processing)
    for (AP4_Ordinal i=0; i<track_count; i++) {
        TrackHandler* handler = handlers[i];
        if (handler) handler->ProcessTrack();
    }
    // initialize the processor
    Finalize(top_level);
    // calculate the size of all atoms combined
    AP4_Size atoms_size = 0;
    top_level.GetChildren().Apply(AP4_AtomSizeAdder(atoms_size));
    // adjust the chunk offsets
    for (AP4_Ordinal i=0; i<track_count; i++) {
        AP4_TrakAtom* trak;
        trak_atoms.Get(i, trak);
        trak->AdjustChunkOffsets(atoms_size+AP4_ATOM_HEADER_SIZE);
    }
    // write all atoms
    top_level.GetChildren().Apply(AP4_AtomListWriter(output));
    // write mdat header
    output.WriteUI32(mdat_size+AP4_ATOM_HEADER_SIZE);
    output.WriteUI32(AP4_ATOM_TYPE_MDAT);
#if defined(AP4_DEBUG)
    AP4_Offset before;
    output.Tell(before);
#endif
    // write the samples
    AP4_Sample sample;
    AP4_DataBuffer data_in;
    AP4_DataBuffer data_out;
    for (unsigned int i=0; i<locators.ItemCount(); i++) {
        AP4_SampleLocator& locator = locators[i];
        locator.m_Sample.ReadData(data_in);
        TrackHandler* handler = handlers[locator.m_TrakIndex];
        if (handler) {
            handler->ProcessSample(data_in, data_out);
            output.Write(data_out.GetData(), data_out.GetDataSize());
        } else {
            output.Write(data_in.GetData(), data_in.GetDataSize());            
        }
    }
#if defined(AP4_DEBUG)
    AP4_Offset after;
    output.Tell(after);
    AP4_ASSERT(after-before == mdat_size);
#endif
    // cleanup
    delete[] cursors;
    for (unsigned int i=0; i<track_count; i++) {
        delete handlers[i];
    }
    delete[] handlers;
    return AP4_SUCCESS;
}
/*----------------------------------------------------------------------
|       AP4_Processor:Initialize
+---------------------------------------------------------------------*/
AP4_Result 
AP4_Processor::Initialize(AP4_AtomParent& top_level)
{
    // default implementation: do nothing
    return AP4_SUCCESS;
}
/*----------------------------------------------------------------------
|       AP4_Processor:Finalize
+---------------------------------------------------------------------*/
AP4_Result 
AP4_Processor::Finalize(AP4_AtomParent& top_level)
{
    // default implementation: do nothing
    return AP4_SUCCESS;
}
/*----------------------------------------------------------------------
|       AP4_Processor:CreateTrackHandler
+---------------------------------------------------------------------*/
AP4_Processor::TrackHandler* 
AP4_Processor::CreateTrackHandler(AP4_TrakAtom* /* trak */)
{
    // default implementation: no handler
    return NULL;
}
/*----------------------------------------------------------------------
|       AP4_Processor::TrackHandler::GetProcessedSampleSize
+---------------------------------------------------------------------*/
AP4_Size   
AP4_Processor::TrackHandler::GetProcessedSampleSize(AP4_Sample& sample)
{
    // default implementation: do no change the sample size
    return sample.GetSize();
}

						