(转载)H264字节流拆包和RTP封包方法

UINT MediaStreamH264::TransportData(PBYTE pData, UINT dataSize, int pts)
{
PBYTE p_buffer = pData;
int i_buffer = dataSize;

UINT writeSize = 0;

while( i_buffer > 4 && ( p_buffer[0] != 0 || p_buffer[1] != 0 || p_buffer[2] != 1 ) )
{
i_buffer--;
p_buffer++;
}

/* Split nal units */
while( i_buffer > 4 )
{
int i_offset;
int i_size = i_buffer;
int i_skip = i_buffer;

/* search nal end */
for( i_offset = 4; i_offset+2 < i_buffer ; i_offset++)
{
if( p_buffer[i_offset] == 0 && p_buffer[i_offset+1] == 0 && p_buffer[i_offset+2] == 1 )
{
/* we found another startcode */
i_size = i_offset - ( p_buffer[i_offset-1] == 0 ? 1 : 0);
i_skip = i_offset;
break;
}
}
/* TODO add STAP-A to remove a lot of overhead with small slice/sei/... */
UINT iWrite = TransportH264Nal(p_buffer, i_size, pts, (i_size >= i_buffer) );
if (iWrite > 0 )
writeSize += iWrite;

i_buffer -= i_skip;
p_buffer += i_skip;
}
return writeSize;
}

UINT MediaStreamH264::TransportH264Nal(const PBYTE pNal, UINT nalSize, INT32 pts, BOOL isLast)
{
ATLock atlock(&m_tlockRun);

if (m_bRun == FALSE)
return 0;

if( nalSize < 5 )
return 0;

UINT mtu = m_nMTU;

const int i_max = mtu - RTP_HEADER_SIZE; /* payload max in one packet */
int i_nal_hdr;
int i_nal_type;

i_nal_hdr = pNal[3];
i_nal_type = i_nal_hdr&0x1f;

string sps;
string pps;

if( i_nal_type == 7 || i_nal_type == 8 )
{
/* XXX Why do you want to remove them ? It will break streaming with
* SPS/PPS change (broadcast) ? */
return 0;
}

/* Skip start code */
PBYTE p_data = pNal;
int i_data = nalSize;

p_data += 3;
i_data -= 3;

int writeSize = 0;

if( i_data <= i_max )
{
/* Single NAL unit packet */
//writeSize = m_pRtpTransport->SetRtpData(p_data, i_data, pts, isLast);
writeSize = m_pRtpTransport->Write(p_data, i_data, m_nRtpPayloadType, pts, 0, isLast);
if (writeSize <= 0)
return 0;
return writeSize;
}
else
{
/* FU-A Fragmentation Unit without interleaving */
const int i_count = ( i_data-1 + i_max-2 - 1 ) / (i_max-2);
int i;

p_data++;
i_data--;

for( i = 0; i < i_count; i++ )
{
const int i_payload =  (i_data < (i_max-2)) ? i_data : (i_max-2);
const int nalSize = 2 + i_payload;

m_Packet.ExtendBuffer(nalSize);

/* FU indicator */
m_Packet.m_pData[0] = 0x00 | (i_nal_hdr & 0x60) | 28;
/* FU header */
m_Packet.m_pData[1] = ( i == 0 ? 0x80 : 0x00 ) | ( (i == i_count-1) ? 0x40 : 0x00 )  | i_nal_type;

/* FU payload */
memcpy( &m_Packet.m_pData[2], p_data, i_payload );

m_Packet.m_DataSize = nalSize;

//int iWrite = m_pRtpTransport->SetRtpData(m_Packet.m_pData, m_Packet.m_DataSize, pts, isLast && (i == i_count-1));
int iWrite = m_pRtpTransport->Write(m_Packet.m_pData, m_Packet.m_DataSize, m_nRtpPayloadType, pts, 0, isLast && (i == i_count-1));
if (iWrite > 0)
writeSize += iWrite;

i_data -= i_payload;
p_data += i_payload;
}
}
return writeSize;
}