Libav
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00001 /* 00002 * MPEG1 / MPEG2 video parser 00003 * Copyright (c) 2000,2001 Fabrice Bellard 00004 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at> 00005 * 00006 * This file is part of FFmpeg. 00007 * 00008 * FFmpeg is free software; you can redistribute it and/or 00009 * modify it under the terms of the GNU Lesser General Public 00010 * License as published by the Free Software Foundation; either 00011 * version 2.1 of the License, or (at your option) any later version. 00012 * 00013 * FFmpeg is distributed in the hope that it will be useful, 00014 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00016 * Lesser General Public License for more details. 00017 * 00018 * You should have received a copy of the GNU Lesser General Public 00019 * License along with FFmpeg; if not, write to the Free Software 00020 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00021 */ 00022 00023 #include "parser.h" 00024 #include "mpegvideo.h" 00025 00026 static void mpegvideo_extract_headers(AVCodecParserContext *s, 00027 AVCodecContext *avctx, 00028 const uint8_t *buf, int buf_size) 00029 { 00030 ParseContext1 *pc = s->priv_data; 00031 const uint8_t *buf_end = buf + buf_size; 00032 uint32_t start_code; 00033 int frame_rate_index, ext_type, bytes_left; 00034 int frame_rate_ext_n, frame_rate_ext_d; 00035 int picture_structure, top_field_first, repeat_first_field, progressive_frame; 00036 int horiz_size_ext, vert_size_ext, bit_rate_ext; 00037 int did_set_size=0; 00038 //FIXME replace the crap with get_bits() 00039 s->repeat_pict = 0; 00040 00041 while (buf < buf_end) { 00042 start_code= -1; 00043 buf= ff_find_start_code(buf, buf_end, &start_code); 00044 bytes_left = buf_end - buf; 00045 switch(start_code) { 00046 case PICTURE_START_CODE: 00047 if (bytes_left >= 2) { 00048 s->pict_type = (buf[1] >> 3) & 7; 00049 } 00050 break; 00051 case SEQ_START_CODE: 00052 if (bytes_left >= 7) { 00053 pc->width = (buf[0] << 4) | (buf[1] >> 4); 00054 pc->height = ((buf[1] & 0x0f) << 8) | buf[2]; 00055 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){ 00056 avcodec_set_dimensions(avctx, pc->width, pc->height); 00057 did_set_size=1; 00058 } 00059 frame_rate_index = buf[3] & 0xf; 00060 pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num; 00061 pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den; 00062 avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400; 00063 avctx->codec_id = CODEC_ID_MPEG1VIDEO; 00064 avctx->sub_id = 1; 00065 } 00066 break; 00067 case EXT_START_CODE: 00068 if (bytes_left >= 1) { 00069 ext_type = (buf[0] >> 4); 00070 switch(ext_type) { 00071 case 0x1: /* sequence extension */ 00072 if (bytes_left >= 6) { 00073 horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7); 00074 vert_size_ext = (buf[2] >> 5) & 3; 00075 bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1); 00076 frame_rate_ext_n = (buf[5] >> 5) & 3; 00077 frame_rate_ext_d = (buf[5] & 0x1f); 00078 pc->progressive_sequence = buf[1] & (1 << 3); 00079 avctx->has_b_frames= !(buf[5] >> 7); 00080 00081 pc->width |=(horiz_size_ext << 12); 00082 pc->height |=( vert_size_ext << 12); 00083 avctx->bit_rate += (bit_rate_ext << 18) * 400; 00084 if(did_set_size) 00085 avcodec_set_dimensions(avctx, pc->width, pc->height); 00086 avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2; 00087 avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1); 00088 avctx->codec_id = CODEC_ID_MPEG2VIDEO; 00089 avctx->sub_id = 2; /* forces MPEG2 */ 00090 } 00091 break; 00092 case 0x8: /* picture coding extension */ 00093 if (bytes_left >= 5) { 00094 picture_structure = buf[2]&3; 00095 top_field_first = buf[3] & (1 << 7); 00096 repeat_first_field = buf[3] & (1 << 1); 00097 progressive_frame = buf[4] & (1 << 7); 00098 00099 /* check if we must repeat the frame */ 00100 s->repeat_pict = 1; 00101 if (repeat_first_field) { 00102 if (pc->progressive_sequence) { 00103 if (top_field_first) 00104 s->repeat_pict = 5; 00105 else 00106 s->repeat_pict = 3; 00107 } else if (progressive_frame) { 00108 s->repeat_pict = 2; 00109 } 00110 } 00111 } 00112 break; 00113 } 00114 } 00115 break; 00116 case -1: 00117 goto the_end; 00118 default: 00119 /* we stop parsing when we encounter a slice. It ensures 00120 that this function takes a negligible amount of time */ 00121 if (start_code >= SLICE_MIN_START_CODE && 00122 start_code <= SLICE_MAX_START_CODE) 00123 goto the_end; 00124 break; 00125 } 00126 } 00127 the_end: ; 00128 } 00129 00130 static int mpegvideo_parse(AVCodecParserContext *s, 00131 AVCodecContext *avctx, 00132 const uint8_t **poutbuf, int *poutbuf_size, 00133 const uint8_t *buf, int buf_size) 00134 { 00135 ParseContext1 *pc1 = s->priv_data; 00136 ParseContext *pc= &pc1->pc; 00137 int next; 00138 00139 if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){ 00140 next= buf_size; 00141 }else{ 00142 next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s); 00143 00144 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { 00145 *poutbuf = NULL; 00146 *poutbuf_size = 0; 00147 return buf_size; 00148 } 00149 00150 } 00151 /* we have a full frame : we just parse the first few MPEG headers 00152 to have the full timing information. The time take by this 00153 function should be negligible for uncorrupted streams */ 00154 mpegvideo_extract_headers(s, avctx, buf, buf_size); 00155 #if 0 00156 printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n", 00157 s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict); 00158 #endif 00159 00160 *poutbuf = buf; 00161 *poutbuf_size = buf_size; 00162 return next; 00163 } 00164 00165 static int mpegvideo_split(AVCodecContext *avctx, 00166 const uint8_t *buf, int buf_size) 00167 { 00168 int i; 00169 uint32_t state= -1; 00170 00171 for(i=0; i<buf_size; i++){ 00172 state= (state<<8) | buf[i]; 00173 if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100) 00174 return i-3; 00175 } 00176 return 0; 00177 } 00178 00179 AVCodecParser mpegvideo_parser = { 00180 { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO }, 00181 sizeof(ParseContext1), 00182 NULL, 00183 mpegvideo_parse, 00184 ff_parse1_close, 00185 mpegvideo_split, 00186 };