mirror of
https://github.com/FFmpeg/FFmpeg.git
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110 lines
3.0 KiB
C
110 lines
3.0 KiB
C
/*
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* H.264 encoder
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "libavutil/common.h"
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#include "bitstream.h"
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#include "mpegvideo.h"
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#include "h264data.h"
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/**
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* Write out the provided data into a NAL unit.
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* @param nal_ref_idc NAL reference IDC
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* @param nal_unit_type NAL unit payload type
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* @param dest the target buffer, dst+1 == src is allowed as a special case
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* @param destsize the length of the dst array
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* @param b2 the data which should be escaped
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* @returns pointer to current position in the output buffer or NULL if an error occurred
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*/
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static uint8_t *h264_write_nal_unit(int nal_ref_idc, int nal_unit_type, uint8_t *dest, int *destsize,
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PutBitContext *b2)
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{
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PutBitContext b;
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int i, destpos, rbsplen, escape_count;
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uint8_t *rbsp;
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if (nal_unit_type != NAL_END_STREAM)
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put_bits(b2,1,1); // rbsp_stop_bit
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// Align b2 on a byte boundary
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align_put_bits(b2);
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rbsplen = put_bits_count(b2)/8;
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flush_put_bits(b2);
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rbsp = b2->buf;
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init_put_bits(&b,dest,*destsize);
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put_bits(&b,16,0);
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put_bits(&b,16,0x01);
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put_bits(&b,1,0); // forbidden zero bit
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put_bits(&b,2,nal_ref_idc); // nal_ref_idc
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put_bits(&b,5,nal_unit_type); // nal_unit_type
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flush_put_bits(&b);
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destpos = 5;
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escape_count= 0;
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for (i=0; i<rbsplen; i+=2)
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{
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if (rbsp[i]) continue;
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if (i>0 && rbsp[i-1]==0)
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i--;
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if (i+2<rbsplen && rbsp[i+1]==0 && rbsp[i+2]<=3)
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{
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escape_count++;
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i+=2;
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}
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}
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if(escape_count==0)
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{
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if(dest+destpos != rbsp)
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{
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memcpy(dest+destpos, rbsp, rbsplen);
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*destsize -= (rbsplen+destpos);
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}
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return dest+rbsplen+destpos;
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}
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if(rbsplen + escape_count + 1> *destsize)
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{
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av_log(NULL, AV_LOG_ERROR, "Destination buffer too small!\n");
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return NULL;
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}
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// this should be damn rare (hopefully)
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for (i = 0 ; i < rbsplen ; i++)
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{
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if (i + 2 < rbsplen && (rbsp[i] == 0 && rbsp[i+1] == 0 && rbsp[i+2] < 4))
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{
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dest[destpos++] = rbsp[i++];
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dest[destpos++] = rbsp[i];
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dest[destpos++] = 0x03; // emulation prevention byte
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}
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else
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dest[destpos++] = rbsp[i];
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}
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*destsize -= destpos;
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return dest+destpos;
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}
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