www.pudn.com > jm74.zip > annexb.c
/*!
*************************************************************************************
* \file annexb.c
*
* \brief
* Annex B Byte Stream format
*
* \author
* Main contributors (see contributors.h for copyright, address and affiliation details)
* - Stephan Wenger
*************************************************************************************
*/
#include
#include
#include "global.h"
#include "annexb.h"
#include "memalloc.h"
FILE *bits = NULL; //!< the bit stream file
static int FindStartCode (unsigned char *Buf, int zeros_in_startcode);
/*!
************************************************************************
* \brief
* Returns the size of the NALU (bits between start codes in case of
* Annex B. nalu->buf and nalu->len are filled. Other field in
* nalu-> remain uninitialized (will be taken care of by NALUtoRBSP.
*
* \return
* 0 if there is nothing any more to read (EOF)
* -1 in case of any error
*
* \note Side-effect: Returns length of start-code in bytes.
*
* \note
* GetAnnexbNALU expects start codes at byte aligned positions in the file
*
************************************************************************
*/
int GetAnnexbNALU (NALU_t *nalu)
{
int info2, info3, pos = 0;
int StartCodeFound, rewind;
char *Buf;
if ((Buf = (char*)calloc (nalu->max_size , sizeof(char))) == NULL) no_mem_exit("GetAnnexbNALU: Buf");
nalu->startcodeprefix_len=3;
info2 = 0;
info3 = 0;
if (3 != fread (Buf, 1, 3, bits))
{
free(Buf);
return 0;
}
info2 = FindStartCode (Buf, 2);
if(info2 != 1) {
if(1 != fread(Buf+3, 1, 1, bits))
{
free(Buf);
return 0;
}
info3 = FindStartCode (Buf, 3);
}
if (info2 != 1 && info3 != 1)
{
printf ("GetAnnexbNALU: no Start Code at the begin of the NALU, return -1\n");
free(Buf);
return -1;
}
if( info2 == 1) {
nalu->startcodeprefix_len = 3;
pos = 3;
}
else if(info3 ==1 ) {
pos = 4;
nalu->startcodeprefix_len = 4;
}
else
printf( " Panic: Error \n");
StartCodeFound = 0;
info2 = 0;
info3 = 0;
while (!StartCodeFound)
{
if (feof (bits))
{
nalu->len = (pos-1)-nalu->startcodeprefix_len;
memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);
nalu->forbidden_bit = (nalu->buf[0]>>7) & 1;
nalu->nal_reference_idc = (nalu->buf[0]>>5) & 3;
nalu->nal_unit_type = (nalu->buf[0]) & 0x1f;
// printf ("GetAnnexbNALU, eof case: pos %d nalu->len %d, nalu->reference_idc %d, nal_unit_type %d \n", pos, nalu->len, nalu->nal_reference_idc, nalu->nal_unit_type);
#if TRACE
fprintf (p_trace, "\n\nLast NALU in File\n\n");
fprintf (p_trace, "Annex B NALU w/ %s startcode, len %d, forbidden_bit %d, nal_reference_idc %d, nal_unit_type %d\n\n",
nalu->startcodeprefix_len == 4?"long":"short", nalu->len, nalu->forbidden_bit, nalu->nal_reference_idc, nalu->nal_unit_type);
fflush (p_trace);
#endif
free(Buf);
return pos-1;
}
Buf[pos++] = fgetc (bits);
info3 = FindStartCode(&Buf[pos-4], 3);
if(info3 != 1)
info2 = FindStartCode(&Buf[pos-3], 2);
StartCodeFound = (info2 == 1 || info3 == 1);
}
// Here, we have found another start code (and read length of startcode bytes more than we should
// have. Hence, go back in the file
rewind = 0;
if(info3 == 1)
rewind = -4;
else if (info2 == 1)
rewind = -3;
else
printf(" Panic: Error in next start code search \n");
if (0 != fseek (bits, rewind, SEEK_CUR))
{
snprintf (errortext, ET_SIZE, "GetAnnexbNALU: Cannot fseek %d in the bit stream file", rewind);
free(Buf);
error(errortext, 600);
}
// Here the Start code, the complete NALU, and the next start code is in the Buf.
// The size of Buf is pos, pos+rewind are the number of bytes excluding the next
// start code, and (pos+rewind)-startcodeprefix_len is the size of the NALU
nalu->len = (pos+rewind)-nalu->startcodeprefix_len;
memcpy (nalu->buf, &Buf[nalu->startcodeprefix_len], nalu->len);
nalu->forbidden_bit = (nalu->buf[0]>>7) & 1;
nalu->nal_reference_idc = (nalu->buf[0]>>5) & 3;
nalu->nal_unit_type = (nalu->buf[0]) & 0x1f;
//printf ("GetAnnexbNALU, regular case: pos %d nalu->len %d, nalu->reference_idc %d, nal_unit_type %d \n", pos, nalu->len, nalu->nal_reference_idc, nalu->nal_unit_type);
#if TRACE
fprintf (p_trace, "\n\nAnnex B NALU w/ %s startcode, len %d, forbidden_bit %d, nal_reference_idc %d, nal_unit_type %d\n\n",
nalu->startcodeprefix_len == 4?"long":"short", nalu->len, nalu->forbidden_bit, nalu->nal_reference_idc, nalu->nal_unit_type);
fflush (p_trace);
#endif
free(Buf);
return (pos+rewind);
}
/*!
************************************************************************
* \brief
* Opens the bit stream file named fn
* \return
* none
************************************************************************
*/
void OpenBitstreamFile (char *fn)
{
if (NULL == (bits=fopen(fn, "rb")))
{
snprintf (errortext, ET_SIZE, "Cannot open Annex B ByteStream file '%s'", input->infile);
error(errortext,500);
}
}
/*!
************************************************************************
* \brief
* Closes the bit stream file
************************************************************************
*/
void CloseBitstreamFile()
{
fclose (bits);
}
/*!
************************************************************************
* \brief
* returns if new start code is found at byte aligned position buf.
* new-startcode is of form N 0x00 bytes, followed by a 0x01 byte.
*
* \return
* 1 if start-code is found or \n
* 0, indicating that there is no start code
*
* \param Buf
* pointer to byte-stream
* \param zeros_in_startcode
* indicates number of 0x00 bytes in start-code.
************************************************************************
*/
static int FindStartCode (unsigned char *Buf, int zeros_in_startcode)
{
int info;
int i;
info = 1;
for (i = 0; i < zeros_in_startcode; i++)
if(Buf[i] != 0)
info = 0;
if(Buf[i] != 1)
info = 0;
return info;
}