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https://github.com/FFmpeg/FFmpeg.git
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300 lines
11 KiB
C
300 lines
11 KiB
C
/*
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* MPEG-1 / MPEG-2 video parser
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* Copyright (c) 2000,2001 Fabrice Bellard
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* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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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 "parser.h"
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#include "mpeg12.h"
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#include "mpeg12data.h"
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#include "internal.h"
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struct MpvParseContext {
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ParseContext pc;
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AVRational frame_rate;
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int progressive_sequence;
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int width, height;
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};
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#if !FF_API_FLAG_TRUNCATED
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/**
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* Find the end of the current frame in the bitstream.
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* @return the position of the first byte of the next frame, or -1
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*/
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static int mpeg1_find_frame_end(ParseContext *pc, const uint8_t *buf,
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int buf_size, AVCodecParserContext *s)
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{
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int i;
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uint32_t state = pc->state;
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/* EOF considered as end of frame */
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if (buf_size == 0)
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return 0;
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/*
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0 frame start -> 1/4
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1 first_SEQEXT -> 0/2
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2 first field start -> 3/0
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3 second_SEQEXT -> 2/0
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4 searching end
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*/
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for (i = 0; i < buf_size; i++) {
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av_assert1(pc->frame_start_found >= 0 && pc->frame_start_found <= 4);
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if (pc->frame_start_found & 1) {
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if (state == EXT_START_CODE && (buf[i] & 0xF0) != 0x80)
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pc->frame_start_found--;
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else if (state == EXT_START_CODE + 2) {
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if ((buf[i] & 3) == 3)
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pc->frame_start_found = 0;
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else
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pc->frame_start_found = (pc->frame_start_found + 1) & 3;
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}
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state++;
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} else {
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i = avpriv_find_start_code(buf + i, buf + buf_size, &state) - buf - 1;
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if (pc->frame_start_found == 0 && state >= SLICE_MIN_START_CODE && state <= SLICE_MAX_START_CODE) {
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i++;
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pc->frame_start_found = 4;
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}
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if (state == SEQ_END_CODE) {
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pc->frame_start_found = 0;
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pc->state = -1;
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return i + 1;
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}
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if (pc->frame_start_found == 2 && state == SEQ_START_CODE)
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pc->frame_start_found = 0;
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if (pc->frame_start_found < 4 && state == EXT_START_CODE)
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pc->frame_start_found++;
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if (pc->frame_start_found == 4 && (state & 0xFFFFFF00) == 0x100) {
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if (state < SLICE_MIN_START_CODE || state > SLICE_MAX_START_CODE) {
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pc->frame_start_found = 0;
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pc->state = -1;
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return i - 3;
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}
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}
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if (pc->frame_start_found == 0 && s && state == PICTURE_START_CODE) {
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ff_fetch_timestamp(s, i - 3, 1, i > 3);
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}
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}
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}
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pc->state = state;
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return END_NOT_FOUND;
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}
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#endif
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static void mpegvideo_extract_headers(AVCodecParserContext *s,
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AVCodecContext *avctx,
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const uint8_t *buf, int buf_size)
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{
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struct MpvParseContext *pc = s->priv_data;
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const uint8_t *buf_end = buf + buf_size;
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uint32_t start_code;
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int frame_rate_index, ext_type, bytes_left;
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int frame_rate_ext_n, frame_rate_ext_d;
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int top_field_first, repeat_first_field, progressive_frame;
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int horiz_size_ext, vert_size_ext, bit_rate_ext;
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int did_set_size=0;
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int set_dim_ret = 0;
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int bit_rate = 0;
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int vbv_delay = 0;
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int chroma_format;
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enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
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//FIXME replace the crap with get_bits()
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s->repeat_pict = 0;
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while (buf < buf_end) {
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start_code= -1;
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buf= avpriv_find_start_code(buf, buf_end, &start_code);
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bytes_left = buf_end - buf;
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switch(start_code) {
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case PICTURE_START_CODE:
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if (bytes_left >= 2) {
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s->pict_type = (buf[1] >> 3) & 7;
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if (bytes_left >= 4)
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vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
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}
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break;
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case SEQ_START_CODE:
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if (bytes_left >= 7) {
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pc->width = (buf[0] << 4) | (buf[1] >> 4);
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pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
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if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
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set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
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did_set_size=1;
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}
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pix_fmt = AV_PIX_FMT_YUV420P;
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frame_rate_index = buf[3] & 0xf;
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pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
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bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
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avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
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avctx->ticks_per_frame = 1;
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}
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break;
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case EXT_START_CODE:
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if (bytes_left >= 1) {
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ext_type = (buf[0] >> 4);
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switch(ext_type) {
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case 0x1: /* sequence extension */
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if (bytes_left >= 6) {
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horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
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vert_size_ext = (buf[2] >> 5) & 3;
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bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
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frame_rate_ext_n = (buf[5] >> 5) & 3;
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frame_rate_ext_d = (buf[5] & 0x1f);
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pc->progressive_sequence = buf[1] & (1 << 3);
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avctx->has_b_frames= !(buf[5] >> 7);
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chroma_format = (buf[1] >> 1) & 3;
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switch (chroma_format) {
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case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
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case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
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case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
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}
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pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
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pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
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bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
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if(did_set_size)
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set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
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avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
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avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
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avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
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avctx->ticks_per_frame = 2;
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}
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break;
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case 0x8: /* picture coding extension */
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if (bytes_left >= 5) {
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top_field_first = buf[3] & (1 << 7);
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repeat_first_field = buf[3] & (1 << 1);
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progressive_frame = buf[4] & (1 << 7);
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/* check if we must repeat the frame */
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s->repeat_pict = 1;
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if (repeat_first_field) {
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if (pc->progressive_sequence) {
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if (top_field_first)
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s->repeat_pict = 5;
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else
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s->repeat_pict = 3;
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} else if (progressive_frame) {
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s->repeat_pict = 2;
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}
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}
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if (!pc->progressive_sequence && !progressive_frame) {
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if (top_field_first)
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s->field_order = AV_FIELD_TT;
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else
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s->field_order = AV_FIELD_BB;
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} else
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s->field_order = AV_FIELD_PROGRESSIVE;
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}
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break;
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}
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}
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break;
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case -1:
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goto the_end;
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default:
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/* we stop parsing when we encounter a slice. It ensures
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that this function takes a negligible amount of time */
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if (start_code >= SLICE_MIN_START_CODE &&
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start_code <= SLICE_MAX_START_CODE)
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goto the_end;
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break;
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}
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}
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the_end:
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if (set_dim_ret < 0)
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av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
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if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
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avctx->rc_max_rate = 400LL*bit_rate;
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}
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if (bit_rate &&
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((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
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avctx->bit_rate = 400LL*bit_rate;
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}
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if (pix_fmt != AV_PIX_FMT_NONE) {
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s->format = pix_fmt;
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s->width = pc->width;
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s->height = pc->height;
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s->coded_width = FFALIGN(pc->width, 16);
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s->coded_height = FFALIGN(pc->height, 16);
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}
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#if FF_API_AVCTX_TIMEBASE
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if (avctx->framerate.num)
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avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
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#endif
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}
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static int mpegvideo_parse(AVCodecParserContext *s,
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AVCodecContext *avctx,
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const uint8_t **poutbuf, int *poutbuf_size,
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const uint8_t *buf, int buf_size)
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{
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struct MpvParseContext *pc1 = s->priv_data;
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ParseContext *pc= &pc1->pc;
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int next;
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if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
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next= buf_size;
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}else{
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#if FF_API_FLAG_TRUNCATED
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next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
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#else
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next = mpeg1_find_frame_end(pc, buf, buf_size, s);
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#endif
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if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
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*poutbuf = NULL;
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*poutbuf_size = 0;
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return buf_size;
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}
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}
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/* we have a full frame : we just parse the first few MPEG headers
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to have the full timing information. The time take by this
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function should be negligible for uncorrupted streams */
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mpegvideo_extract_headers(s, avctx, buf, buf_size);
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ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
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s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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return next;
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}
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static int mpegvideo_parse_init(AVCodecParserContext *s)
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{
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s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
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return 0;
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}
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const AVCodecParser ff_mpegvideo_parser = {
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.codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
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.priv_data_size = sizeof(struct MpvParseContext),
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.parser_init = mpegvideo_parse_init,
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.parser_parse = mpegvideo_parse,
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.parser_close = ff_parse_close,
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};
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