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/*
* H.264 encoder
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/common.h"
#include "bitstream.h"
#include "mpegvideo.h"
#include "h264data.h"
/**
* Write out the provided data into a NAL unit.
* @param nal_ref_idc NAL reference IDC
* @param nal_unit_type NAL unit payload type
* @param dest the target buffer, dst+1 == src is allowed as a special case
* @param destsize the length of the dst array
* @param b2 the data which should be escaped
* @returns pointer to current position in the output buffer or NULL if an error occurred
*/
static uint8_t *h264_write_nal_unit(int nal_ref_idc, int nal_unit_type, uint8_t *dest, int *destsize,
PutBitContext *b2)
{
PutBitContext b;
int i, destpos, rbsplen, escape_count;
uint8_t *rbsp;
if (nal_unit_type != NAL_END_STREAM)
put_bits(b2,1,1); // rbsp_stop_bit
// Align b2 on a byte boundary
align_put_bits(b2);
rbsplen = put_bits_count(b2)/8;
flush_put_bits(b2);
rbsp = b2->buf;
init_put_bits(&b,dest,*destsize);
put_bits(&b,16,0);
put_bits(&b,16,0x01);
put_bits(&b,1,0); // forbidden zero bit
put_bits(&b,2,nal_ref_idc); // nal_ref_idc
put_bits(&b,5,nal_unit_type); // nal_unit_type
flush_put_bits(&b);
destpos = 5;
escape_count= 0;
for (i=0; i<rbsplen; i+=2)
{
if (rbsp[i]) continue;
if (i>0 && rbsp[i-1]==0)
i--;
if (i+2<rbsplen && rbsp[i+1]==0 && rbsp[i+2]<=3)
{
escape_count++;
i+=2;
}
}
if(escape_count==0)
{
if(dest+destpos != rbsp)
{
memcpy(dest+destpos, rbsp, rbsplen);
*destsize -= (rbsplen+destpos);
}
return dest+rbsplen+destpos;
}
if(rbsplen + escape_count + 1> *destsize)
{
av_log(NULL, AV_LOG_ERROR, "Destination buffer too small!\n");
return NULL;
}
// this should be damn rare (hopefully)
for (i = 0 ; i < rbsplen ; i++)
{
if (i + 2 < rbsplen && (rbsp[i] == 0 && rbsp[i+1] == 0 && rbsp[i+2] < 4))
{
dest[destpos++] = rbsp[i++];
dest[destpos++] = rbsp[i];
dest[destpos++] = 0x03; // emulation prevention byte
}
else
dest[destpos++] = rbsp[i];
}
*destsize -= destpos;
return dest+destpos;
}
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