2013년 12월 26일 목요일

RTP Header Parsing

< RTPHeader.h >

#ifndef __RTP_HEADER_H__
#define __RTP_HEADER_H__

typedef unsigned short      WORD;
typedef unsigned long       DWORD;

typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
typedef unsigned int uint32_t;

typedef unsigned int u_int32_t;
typedef unsigned short u_int16_t;
typedef unsigned char u_int8_t;

typedef struct
{
WORD    cc:     4;      /* csrc count */
WORD    ext:    1;      /* header extension flag */
WORD    pad:    1;      /* padding flag - for encryption */
WORD    ver:    2;      /* protocal version */
WORD    pt:     7;      /* payload type */
WORD    mk:     1;      /* marker bit - for profile */
WORD seq; /* sequence number of this packet */
DWORD ts; /* timestamp of this packet */
DWORD ssrc; /* source of packet */
} RTP_HEADER;

class RtpHeader {
public:
RtpHeader(uint8_t *buf, int len);
virtual ~RtpHeader();

uint8_t* payload();
int length() { return fLength; }
int payloadLen();

uint16_t version() { return fVersion; }
uint16_t padding() { return fPadding; }
uint16_t extension() { return fExtension; }
uint16_t csrcCount() { return fCSRCCount; }
uint16_t markerBit() { return fMarkerBit; }
uint16_t payloadType() { return fPayloadType; }
uint16_t sequenceNum() { return fSequenceNum; }
uint32_t timestamp() { return fTimestamp; }
uint32_t ssrc() { return fSSRC; }

private:
uint8_t* fBuf;
int fLength;
uint16_t fVersion;
uint16_t fPadding;
uint16_t fExtension;
uint16_t fCSRCCount;
uint16_t fMarkerBit;
uint16_t fPayloadType;
uint16_t fSequenceNum;
uint32_t fTimestamp;
uint32_t fSSRC;

uint8_t *fCurPtr;
};

#endif


< RTPHeader.cpp >

#include <Winsock2.h>
#include "RTPHeader.h"

RtpHeader::RtpHeader(uint8_t *buf, int len) : fBuf(NULL), fLength(0), fVersion(0), fPadding(0), fExtension(0), fCSRCCount(0),
fMarkerBit(0), fPayloadType(0), fSequenceNum(0), fTimestamp(0), fSSRC(0)
{
if (len < sizeof(RTP_HEADER))
return;

fBuf = fCurPtr = buf;
fLength = len;

RTP_HEADER *p = (RTP_HEADER *)buf;
fCSRCCount = p->cc;
fExtension = p->ext;
fPadding = p->pad;
fVersion = p->ver;
fPayloadType = p->pt;
fMarkerBit = p->mk;
fSequenceNum = ntohs(p->seq);
fTimestamp = ntohl(p->ts);
fSSRC = ntohl(p->ssrc);

fCurPtr += sizeof(RTP_HEADER);

// check RTP version (it must be 2)
if (fVersion != 2)
DPRINTF("invalid rtp version %u\n", fVersion);

// skip CSRC
if (fCSRCCount > 0) {
if (payloadLen() <= fCSRCCount*4) {
DPRINTF("invalid rtp header, CSRC count error %u\n", fCSRCCount);
} else {
fCurPtr += (fCSRCCount*4);
}
}

// skip Extension field
if (fExtension) {
if (payloadLen() <= 4) {
DPRINTF("invalid rtp header, extension length error\n");
} else {
unsigned extHdr = ntohl(*(unsigned *)fCurPtr); fCurPtr += 4;
unsigned remExtSize = 4*(extHdr&0xFFFF);
if (payloadLen() <= remExtSize) {
DPRINTF("invalid rtp header, extension size error %u\n", remExtSize);
} else {
fCurPtr += remExtSize;
}
}
}

// remove padding
if (fPadding) {
if (payloadLen() <= 0) {
DPRINTF("invalid rtp header, padding error\n");
} else {
unsigned numPaddingBytes = (unsigned)fBuf[fLength-1];
if (payloadLen() <= numPaddingBytes) {
DPRINTF("invalid rtp header, padding number error\n");
} else {
fLength -= numPaddingBytes;
    fPadding = p->pad = 0;
}
}
}
}

RtpHeader::~RtpHeader()
{
}

uint8_t* RtpHeader::payload()
{
return fCurPtr;
}

int RtpHeader::payloadLen()
{
uint8_t *ptrLast = &fBuf[fLength-1];
return ptrLast-fCurPtr+1;
}


< 사용 >
...
RtpHeader *rtp = new RtpHeader((uint8_t*)buf, len);

unsigned short pt = rtp->payloadType();
unsigned short mk = rtp->markerBit();
unsigned short seqnum = rtp->sequenceNum();
unsigned int ts = rtp->timestamp();
unsigned int rtpSSRC = rtp->ssrc();

 delete rtp;

2013년 12월 18일 수요일

vc++에서 ffmpeg dll 로드실패 처리 - avcodec_register_all 실행시 crash

vc++ 에서 ffmpeg dll (--enable-shared 옵션) 링크에 성공한 후 실행하면 첫번째

avcodec_register_all 함수에서 죽는 현상 발생한다.(다른 함수들도 마찬가지)

vc++ property -> Linker -> Optimization -> References 를 Keep Unreferenced Data (/OPT:NOREF)

로 변경해서 적용할것.