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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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 "parser.h"
  30 #include "vc1.h"
  31 #include "get_bits.h"
  32
  33 /** The maximum number of bytes of a sequence, entry point or
  34  *  frame header whose values we pay any attention to */
  35 #define UNESCAPED_THRESHOLD 37
  36
  37 /** The maximum number of bytes of a sequence, entry point or
  38  *  frame header which must be valid memory (because they are
  39  *  used to update the bitstream cache in skip_bits() calls)
  40  */
  41 #define UNESCAPED_LIMIT 144
  42
  43 typedef enum {
  44     NO_MATCH,
  45     ONE_ZERO,
  46     TWO_ZEROS,
  47     ONE
  48 } VC1ParseSearchState;
  49
  50 typedef struct VC1ParseContext {
  51     ParseContext pc;
  52     VC1Context v;
  53     uint8_t prev_start_code;
  54     size_t bytes_to_skip;
  55     uint8_t unesc_buffer[UNESCAPED_LIMIT];
  56     size_t unesc_index;
  57     VC1ParseSearchState search_state;
  58 } VC1ParseContext;
  59
  60 static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
  61                                const uint8_t *buf, int buf_size)
  62 {
  63     /* Parse the header we just finished unescaping */
  64     VC1ParseContext *vpc = s->priv_data;
  65     GetBitContext gb;
  66     vpc->v.s.avctx = avctx;
  67     vpc->v.parse_only = 1;
  68     init_get_bits(&gb, buf, buf_size * 8);
  69     switch (vpc->prev_start_code) {
  70     case VC1_CODE_SEQHDR & 0xFF:
  71         ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
  72         break;
  73     case VC1_CODE_ENTRYPOINT & 0xFF:
  74         ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
  75         break;
  76     case VC1_CODE_FRAME & 0xFF:
  77         if(vpc->v.profile < PROFILE_ADVANCED)
  78             ff_vc1_parse_frame_header    (&vpc->v, &gb);
  79         else
  80             ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
  81
  82         /* keep AV_PICTURE_TYPE_BI internal to VC1 */
  83         if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
  84             s->pict_type = AV_PICTURE_TYPE_B;
  85         else
  86             s->pict_type = vpc->v.s.pict_type;
  87
  88         if (avctx->ticks_per_frame > 1){
  89             // process pulldown flags
  90             s->repeat_pict = 1;
  91             // Pulldown flags are only valid when 'broadcast' has been set.
  92             // So ticks_per_frame will be 2
  93             if (vpc->v.rff){
  94                 // repeat field
  95                 s->repeat_pict = 2;
  96             }else if (vpc->v.rptfrm){
  97                 // repeat frames
  98                 s->repeat_pict = vpc->v.rptfrm * 2 + 1;
  99             }
 100         }else{
 101             s->repeat_pict = 0;
 102         }
 103
 104         if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
 105             s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
 106         else
 107             s->field_order = AV_FIELD_PROGRESSIVE;
 108
 109         break;
 110     }
 111     s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P
 112                                          : AV_PIX_FMT_NONE;
 113     if (avctx->width && avctx->height) {
 114         s->width        = avctx->width;
 115         s->height       = avctx->height;
 116         s->coded_width  = FFALIGN(avctx->coded_width,  16);
 117         s->coded_height = FFALIGN(avctx->coded_height, 16);
 118     }
 119 }
 120
 121 static int vc1_parse(AVCodecParserContext *s,
 122                            AVCodecContext *avctx,
 123                            const uint8_t **poutbuf, int *poutbuf_size,
 124                            const uint8_t *buf, int buf_size)
 125 {
 126     /* Here we do the searching for frame boundaries and headers at
 127      * the same time. Only a minimal amount at the start of each
 128      * header is unescaped. */
 129     VC1ParseContext *vpc = s->priv_data;
 130     int pic_found = vpc->pc.frame_start_found;
 131     uint8_t *unesc_buffer = vpc->unesc_buffer;
 132     size_t unesc_index = vpc->unesc_index;
 133     VC1ParseSearchState search_state = vpc->search_state;
 134     int start_code_found = 0;
 135     int next = END_NOT_FOUND;
 136     int i = vpc->bytes_to_skip;
 137
 138     if (pic_found && buf_size == 0) {
 139         /* EOF considered as end of frame */
 140         memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
 141         vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 142         next = 0;
 143     }
 144     while (i < buf_size) {
 145         uint8_t b;
 146         start_code_found = 0;
 147         while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
 148             b = buf[i++];
 149             unesc_buffer[unesc_index++] = b;
 150             if (search_state <= ONE_ZERO)
 151                 search_state = b ? NO_MATCH : search_state + 1;
 152             else if (search_state == TWO_ZEROS) {
 153                 if (b == 1)
 154                     search_state = ONE;
 155                 else if (b > 1) {
 156                     if (b == 3)
 157                         unesc_index--; // swallow emulation prevention byte
 158                     search_state = NO_MATCH;
 159                 }
 160             }
 161             else { // search_state == ONE
 162                 // Header unescaping terminates early due to detection of next start code
 163                 search_state = NO_MATCH;
 164                 start_code_found = 1;
 165                 break;
 166             }
 167         }
 168         if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
 169                 unesc_index >= UNESCAPED_THRESHOLD &&
 170                 vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
 171         {
 172             // No need to keep scanning the rest of the buffer for
 173             // start codes if we know it contains a complete frame and
 174             // we've already unescaped all we need of the frame header
 175             vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 176             break;
 177         }
 178         if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
 179             while (i < buf_size) {
 180                 if (search_state == NO_MATCH) {
 181                     i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
 182                     if (i < buf_size) {
 183                         search_state = ONE_ZERO;
 184                     }
 185                     i++;
 186                 } else {
 187                     b = buf[i++];
 188                     if (search_state == ONE_ZERO)
 189                         search_state = b ? NO_MATCH : TWO_ZEROS;
 190                     else if (search_state == TWO_ZEROS) {
 191                         if (b >= 1)
 192                             search_state = b == 1 ? ONE : NO_MATCH;
 193                     }
 194                     else { // search_state == ONE
 195                         search_state = NO_MATCH;
 196                         start_code_found = 1;
 197                         break;
 198                     }
 199                 }
 200             }
 201         }
 202         if (start_code_found) {
 203             vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
 204
 205             vpc->prev_start_code = b;
 206             unesc_index = 0;
 207
 208             if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
 209                 if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
 210                     pic_found = 1;
 211                 }
 212                 else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
 213                     next = i - 4;
 214                     pic_found = b == (VC1_CODE_FRAME & 0xFF);
 215                     break;
 216                 }
 217             }
 218         }
 219     }
 220
 221     vpc->pc.frame_start_found = pic_found;
 222     vpc->unesc_index = unesc_index;
 223     vpc->search_state = search_state;
 224
 225     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
 226         next = buf_size;
 227     } else {
 228         if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
 229             vpc->bytes_to_skip = 0;
 230             *poutbuf = NULL;
 231             *poutbuf_size = 0;
 232             return buf_size;
 233         }
 234     }
 235
 236     /* If we return with a valid pointer to a combined frame buffer
 237      * then on the next call then we'll have been unhelpfully rewound
 238      * by up to 4 bytes (depending upon whether the start code
 239      * overlapped the input buffer, and if so by how much). We don't
 240      * want this: it will either cause spurious second detections of
 241      * the start code we've already seen, or cause extra bytes to be
 242      * inserted at the start of the unescaped buffer. */
 243     vpc->bytes_to_skip = 4;
 244     if (next < 0 && start_code_found)
 245         vpc->bytes_to_skip += next;
 246
 247     *poutbuf = buf;
 248     *poutbuf_size = buf_size;
 249     return next;
 250 }
 251
 252 static int vc1_split(AVCodecContext *avctx,
 253                            const uint8_t *buf, int buf_size)
 254 {
 255     int i;
 256     uint32_t state= -1;
 257     int charged=0;
 258
 259     for(i=0; i<buf_size; i++){
 260         state= (state<<8) | buf[i];
 261         if(IS_MARKER(state)){
 262             if(state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT){
 263                 charged=1;
 264             }else if(charged){
 265                 return i-3;
 266             }
 267         }
 268     }
 269     return 0;
 270 }
 271
 272 static av_cold int vc1_parse_init(AVCodecParserContext *s)
 273 {
 274     VC1ParseContext *vpc = s->priv_data;
 275     vpc->v.s.slice_context_count = 1;
 276     vpc->prev_start_code = 0;
 277     vpc->bytes_to_skip = 0;
 278     vpc->unesc_index = 0;
 279     vpc->search_state = NO_MATCH;
 280     return ff_vc1_init_common(&vpc->v);
 281 }
 282
 283 AVCodecParser ff_vc1_parser = {
 284     .codec_ids      = { AV_CODEC_ID_VC1 },
 285     .priv_data_size = sizeof(VC1ParseContext),
 286     .parser_init    = vc1_parse_init,
 287     .parser_parse   = vc1_parse,
 288     .parser_close   = ff_parse_close,
 289     .split          = vc1_split,
 290 };