libavcodec/vc1_parser.c

   1 /*
   2  * VC-1 and WMV3 parser
   3  * Copyright (c) 2006-2007 Konstantin Shishkov
   4  * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 /**
  24  * @file
  25  * VC-1 and WMV3 parser
  26  */
  27
  28 #include "libavutil/attributes.h"
  29 #include "libavutil/avassert.h"
  30 #include "parser.h"
  31 #include "vc1.h"
  32 #include "get_bits.h"
  33 #include "vc1dsp.h"
  34
  35 /** The maximum number of bytes of a sequence, entry point or
  36  *  frame header whose values we pay any attention to */
  37 #define UNESCAPED_THRESHOLD 37
  38
  39 /** The maximum number of bytes of a sequence, entry point or
  40  *  frame header which must be valid memory (because they are
  41  *  used to update the bitstream cache in skip_bits() calls)
  42  */
  43 #define UNESCAPED_LIMIT 144
  44
  45 typedef enum {
  46     NO_MATCH,
  47     ONE_ZERO,
  48     TWO_ZEROS,
  49     ONE
  50 } VC1ParseSearchState;
  51
  52 typedef struct VC1ParseContext {
  53     ParseContext pc;
  54     VC1Context v;
  55     uint8_t prev_start_code;
  56     size_t bytes_to_skip;
  57     uint8_t unesc_buffer[UNESCAPED_LIMIT];
  58     size_t unesc_index;
  59     VC1ParseSearchState search_state;
  60 } VC1ParseContext;
  61
  62 static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
  63                                const uint8_t *buf, int buf_size)
  64 {
  65     /* Parse the header we just finished unescaping */
  66     VC1ParseContext *vpc = s->priv_data;
  67     GetBitContext gb;
  68     int ret;
  69     vpc->v.s.avctx = avctx;
  70     ret = init_get_bits8(&gb, buf, buf_size);
  71     av_assert1(ret >= 0); // buf_size is bounded by UNESCAPED_THRESHOLD
  72
  73     switch (vpc->prev_start_code) {
  74     case VC1_CODE_SEQHDR & 0xFF:
  75         ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
  76         break;
  77     case VC1_CODE_ENTRYPOINT & 0xFF:
  78         ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
  79         break;
  80     case VC1_CODE_FRAME & 0xFF:
  81         if(vpc->v.profile < PROFILE_ADVANCED)
  82             ret = ff_vc1_parse_frame_header    (&vpc->v, &gb);
  83         else
  84             ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
  85
  86         if (ret < 0)
  87             break;
  88
  89         /* keep AV_PICTURE_TYPE_BI internal to VC1 */
  90         if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
  91             s->pict_type = AV_PICTURE_TYPE_B;
  92         else
  93             s->pict_type = vpc->v.s.pict_type;
  94
  95         if (vpc->v.broadcast){
  96             // process pulldown flags
  97             s->repeat_pict = 1;
  98             // Pulldown flags are only valid when 'broadcast' has been set.
  99             if (vpc->v.rff){
 100                 // repeat field
 101                 s->repeat_pict = 2;
 102             }else if (vpc->v.rptfrm){
 103                 // repeat frames
 104                 s->repeat_pict = vpc->v.rptfrm * 2 + 1;
 105             }
 106         }else{
 107             s->repeat_pict = 0;
 108         }
 109
 110         if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
 111             s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
 112         else
 113             s->field_order = AV_FIELD_PROGRESSIVE;
 114
 115         break;
 116     }
 117     s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P
 118                                          : AV_PIX_FMT_NONE;
 119     if (avctx->width && avctx->height) {
 120         s->width        = avctx->width;
 121         s->height       = avctx->height;
 122         s->coded_width  = FFALIGN(avctx->coded_width,  16);
 123         s->coded_height = FFALIGN(avctx->coded_height, 16);
 124     }
 125 }
 126
 127 static int vc1_parse(AVCodecParserContext *s,
 128                            AVCodecContext *avctx,
 129                            const uint8_t **poutbuf, int *poutbuf_size,
 130                            const uint8_t *buf, int buf_size)
 131 {
 132     /* Here we do the searching for frame boundaries and headers at
 133      * the same time. Only a minimal amount at the start of each
 134      * header is unescaped. */
 135     VC1ParseContext *vpc = s->priv_data;
 136     int pic_found = vpc->pc.frame_start_found;
 137     uint8_t *unesc_buffer = vpc->unesc_buffer;
 138     size_t unesc_index = vpc->unesc_index;
 139     VC1ParseSearchState search_state = vpc->search_state;
 140     int start_code_found = 0;
 141     int next = END_NOT_FOUND;
 142     int i = vpc->bytes_to_skip;
 143
 144     if (pic_found && buf_size == 0) {
 145         /* EOF considered as end of frame */
 146         memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
 147         vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 148         next = 0;
 149     }
 150     while (i < buf_size) {
 151         uint8_t b;
 152         start_code_found = 0;
 153         while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
 154             b = buf[i++];
 155             unesc_buffer[unesc_index++] = b;
 156             if (search_state <= ONE_ZERO)
 157                 search_state = b ? NO_MATCH : search_state + 1;
 158             else if (search_state == TWO_ZEROS) {
 159                 if (b == 1)
 160                     search_state = ONE;
 161                 else if (b > 1) {
 162                     if (b == 3)
 163                         unesc_index--; // swallow emulation prevention byte
 164                     search_state = NO_MATCH;
 165                 }
 166             }
 167             else { // search_state == ONE
 168                 // Header unescaping terminates early due to detection of next start code
 169                 search_state = NO_MATCH;
 170                 start_code_found = 1;
 171                 break;
 172             }
 173         }
 174         if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
 175                 unesc_index >= UNESCAPED_THRESHOLD &&
 176                 vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
 177         {
 178             // No need to keep scanning the rest of the buffer for
 179             // start codes if we know it contains a complete frame and
 180             // we've already unescaped all we need of the frame header
 181             vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 182             break;
 183         }
 184         if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
 185             while (i < buf_size) {
 186                 if (search_state == NO_MATCH) {
 187                     i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
 188                     if (i < buf_size) {
 189                         search_state = ONE_ZERO;
 190                     }
 191                     i++;
 192                 } else {
 193                     b = buf[i++];
 194                     if (search_state == ONE_ZERO)
 195                         search_state = b ? NO_MATCH : TWO_ZEROS;
 196                     else if (search_state == TWO_ZEROS) {
 197                         if (b >= 1)
 198                             search_state = b == 1 ? ONE : NO_MATCH;
 199                     }
 200                     else { // search_state == ONE
 201                         search_state = NO_MATCH;
 202                         start_code_found = 1;
 203                         break;
 204                     }
 205                 }
 206             }
 207         }
 208         if (start_code_found) {
 209             vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 210
 211             vpc->prev_start_code = b;
 212             unesc_index = 0;
 213
 214             if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
 215                 if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
 216                     pic_found = 1;
 217                 }
 218                 else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
 219                     next = i - 4;
 220                     pic_found = b == (VC1_CODE_FRAME & 0xFF);
 221                     break;
 222                 }
 223             }
 224         }
 225     }
 226
 227     vpc->pc.frame_start_found = pic_found;
 228     vpc->unesc_index = unesc_index;
 229     vpc->search_state = search_state;
 230
 231     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 232         next = buf_size;
 233     } else {
 234         if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
 235             vpc->bytes_to_skip = 0;
 236             *poutbuf = NULL;
 237             *poutbuf_size = 0;
 238             return buf_size;
 239         }
 240     }
 241
 242     /* If we return with a valid pointer to a combined frame buffer
 243      * then on the next call then we'll have been unhelpfully rewound
 244      * by up to 4 bytes (depending upon whether the start code
 245      * overlapped the input buffer, and if so by how much). We don't
 246      * want this: it will either cause spurious second detections of
 247      * the start code we've already seen, or cause extra bytes to be
 248      * inserted at the start of the unescaped buffer. */
 249     vpc->bytes_to_skip = 4;
 250     if (next < 0 && next != END_NOT_FOUND)
 251         vpc->bytes_to_skip += next;
 252
 253     *poutbuf = buf;
 254     *poutbuf_size = buf_size;
 255     return next;
 256 }
 257
 258 static av_cold int vc1_parse_init(AVCodecParserContext *s)
 259 {
 260     VC1ParseContext *vpc = s->priv_data;
 261     vpc->v.s.slice_context_count = 1;
 262     vpc->v.first_pic_header_flag = 1;
 263     vpc->v.parse_only = 1;
 264     vpc->prev_start_code = 0;
 265     vpc->bytes_to_skip = 0;
 266     vpc->unesc_index = 0;
 267     vpc->search_state = NO_MATCH;
 268     ff_vc1dsp_init(&vpc->v.vc1dsp); /* startcode_find_candidate */
 269     return 0;
 270 }
 271
 272 const AVCodecParser ff_vc1_parser = {
 273     .codec_ids      = { AV_CODEC_ID_VC1 },
 274     .priv_data_size = sizeof(VC1ParseContext),
 275     .parser_init    = vc1_parse_init,
 276     .parser_parse   = vc1_parse,
 277     .parser_close   = ff_parse_close,
 278 };