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|
/*****************************************************************
|
| AP4 - AVC Parser
|
| Copyright 2002-2008 Axiomatic Systems, LLC
|
|
| 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 "Ap4AvcParser.h"
#include "Ap4Utils.h"
/*----------------------------------------------------------------------
| AP4_NalParser::AP4_NalParser
+---------------------------------------------------------------------*/
AP4_NalParser::AP4_NalParser() :
m_State(STATE_RESET),
m_ZeroTrail(0)
{
}
/*----------------------------------------------------------------------
| AP4_NalParser::Unescape
+---------------------------------------------------------------------*/
void
AP4_NalParser::Unescape(AP4_DataBuffer &data)
{
unsigned int zero_count = 0;
unsigned int bytes_removed = 0;
AP4_UI08* out = data.UseData();
const AP4_UI08* in = data.GetData();
AP4_Size in_size = data.GetDataSize();
for (unsigned int i=0; i<in_size; i++) {
if (zero_count >= 2 && in[i] == 3 && i+1 < in_size && in[i+1] <= 3) {
++bytes_removed;
zero_count = 0;
} else {
out[i-bytes_removed] = in[i];
if (in[i] == 0) {
++zero_count;
}
}
}
data.SetDataSize(in_size-bytes_removed);
}
/*----------------------------------------------------------------------
| AP4_NalParser::Feed
+---------------------------------------------------------------------*/
AP4_Result
AP4_NalParser::Feed(const void* data,
AP4_Size data_size,
AP4_Size& bytes_consumed,
const AP4_DataBuffer*& nalu,
bool is_eos)
{
// default return values
nalu = NULL;
bytes_consumed = 0;
// iterate the state machine
unsigned int data_offset;
unsigned int payload_start = 0;
unsigned int payload_end = 0;
bool found_nalu = false;
for (data_offset=0; data_offset<data_size && !found_nalu; data_offset++) {
unsigned char byte = ((const unsigned char*)data)[data_offset];
switch (m_State) {
case STATE_RESET:
if (byte == 0) {
m_State = STATE_START_CODE_1;
}
break;
case STATE_START_CODE_1:
if (byte == 0) {
m_State = STATE_START_CODE_2;
} else {
m_State = STATE_RESET;
}
break;
case STATE_START_CODE_2:
if (byte == 0) break;
if (byte == 1) {
m_State = STATE_START_NALU;
} else {
m_State = STATE_RESET;
}
break;
case STATE_START_NALU:
m_Buffer.SetDataSize(0);
m_ZeroTrail = 0;
payload_start = payload_end = data_offset;
m_State = STATE_IN_NALU;
// FALLTHROUGH
case STATE_IN_NALU:
if (byte == 0) {
++m_ZeroTrail;
++payload_end;
break;
}
if (m_ZeroTrail >= 2) {
if (byte == 1) {
found_nalu = true;
m_State = STATE_START_NALU;
break;
} else {
++payload_end;
}
} else {
++payload_end;
}
m_ZeroTrail = 0;
break;
}
}
if (is_eos && m_State == STATE_IN_NALU && data_offset == data_size) {
found_nalu = true;
m_ZeroTrail = 0;
m_State = STATE_RESET;
}
if (payload_end > payload_start) {
AP4_Size current_payload_size = m_Buffer.GetDataSize();
m_Buffer.SetDataSize(m_Buffer.GetDataSize()+(payload_end-payload_start));
AP4_CopyMemory(((unsigned char *)m_Buffer.UseData())+current_payload_size,
((const unsigned char*)data)+payload_start,
payload_end-payload_start);
}
// compute how many bytes we have consumed
bytes_consumed = data_offset;
// return the NALU if we found one
if (found_nalu) {
// trim zero bytes that are part of the next start code
if (m_ZeroTrail >= 3 && m_Buffer.GetDataSize() >= 3) {
// 4 byte start code
m_Buffer.SetDataSize(m_Buffer.GetDataSize()-3);
} else if (m_ZeroTrail >= 2 && m_Buffer.GetDataSize() >= 2) {
// 3 byte start code
m_Buffer.SetDataSize(m_Buffer.GetDataSize()-2);
}
m_ZeroTrail = 0;
nalu = &m_Buffer;
}
return AP4_SUCCESS;
}
/*----------------------------------------------------------------------
| AP4_NalParser::Reset
+---------------------------------------------------------------------*/
AP4_Result
AP4_NalParser::Reset()
{
m_State = STATE_RESET;
m_ZeroTrail = 0;
m_Buffer.SetDataSize(0);
return AP4_SUCCESS;
}
|
