git.sesse.net Git - ffmpeg/blob - libavformat/nutdec.c

   1 /*
   2  * "NUT" Container Format demuxer
   3  * Copyright (c) 2004-2006 Michael Niedermayer
   4  * Copyright (c) 2003 Alex Beregszaszi
   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 #include "tree.h"
  25 #include "nut.h"
  26
  27 #undef NDEBUG
  28 #include <assert.h>
  29
  30 static uint64_t get_v(ByteIOContext *bc){
  31     uint64_t val = 0;
  32     int tmp;
  33
  34     do{
  35         tmp = get_byte(bc);
  36         val= (val<<7) + (tmp&127);
  37     }while(tmp&128);
  38     return val;
  39 }
  40
  41 static int get_str(ByteIOContext *bc, char *string, unsigned int maxlen){
  42     unsigned int len= get_v(bc);
  43
  44     if(len && maxlen)
  45         get_buffer(bc, string, FFMIN(len, maxlen));
  46     while(len > maxlen){
  47         get_byte(bc);
  48         len--;
  49     }
  50
  51     if(maxlen)
  52         string[FFMIN(len, maxlen-1)]= 0;
  53
  54     if(maxlen == len)
  55         return -1;
  56     else
  57         return 0;
  58 }
  59
  60 static int64_t get_s(ByteIOContext *bc){
  61     int64_t v = get_v(bc) + 1;
  62
  63     if (v&1) return -(v>>1);
  64     else     return  (v>>1);
  65 }
  66
  67 static uint64_t get_fourcc(ByteIOContext *bc){
  68     unsigned int len= get_v(bc);
  69
  70     if     (len==2) return get_le16(bc);
  71     else if(len==4) return get_le32(bc);
  72     else            return -1;
  73 }
  74
  75 #ifdef TRACE
  76 static inline uint64_t get_v_trace(ByteIOContext *bc, char *file, char *func, int line){
  77     uint64_t v= get_v(bc);
  78
  79     printf("get_v %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);
  80     return v;
  81 }
  82
  83 static inline int64_t get_s_trace(ByteIOContext *bc, char *file, char *func, int line){
  84     int64_t v= get_s(bc);
  85
  86     printf("get_s %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);
  87     return v;
  88 }
  89
  90 static inline uint64_t get_vb_trace(ByteIOContext *bc, char *file, char *func, int line){
  91     uint64_t v= get_vb(bc);
  92
  93     printf("get_vb %5"PRId64" / %"PRIX64" in %s %s:%d\n", v, v, file, func, line);
  94     return v;
  95 }
  96 #define get_v(bc)  get_v_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  97 #define get_s(bc)  get_s_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  98 #define get_vb(bc)  get_vb_trace(bc, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  99 #endif
 100
 101 static int get_packetheader(NUTContext *nut, ByteIOContext *bc, int calculate_checksum)
 102 {
 103     int64_t start, size;
 104 //    start= url_ftell(bc) - 8;
 105
 106     size= get_v(bc);
 107     if(size > 4096)
 108         get_be32(bc); //FIXME check this
 109
 110     init_checksum(bc, calculate_checksum ? av_crc04C11DB7_update : NULL, 0);
 111
 112 //    nut->packet_start[2] = start;
 113 //    nut->written_packet_size= size;
 114
 115     return size;
 116 }
 117
 118 static uint64_t find_any_startcode(ByteIOContext *bc, int64_t pos){
 119     uint64_t state=0;
 120
 121     if(pos >= 0)
 122         url_fseek(bc, pos, SEEK_SET); //note, this may fail if the stream isnt seekable, but that shouldnt matter, as in this case we simply start where we are currently
 123
 124     while(!url_feof(bc)){
 125         state= (state<<8) | get_byte(bc);
 126         if((state>>56) != 'N')
 127             continue;
 128         switch(state){
 129         case MAIN_STARTCODE:
 130         case STREAM_STARTCODE:
 131         case SYNCPOINT_STARTCODE:
 132         case INFO_STARTCODE:
 133         case INDEX_STARTCODE:
 134             return state;
 135         }
 136     }
 137
 138     return 0;
 139 }
 140
 141 /**
 142  * find the given startcode.
 143  * @param code the startcode
 144  * @param pos the start position of the search, or -1 if the current position
 145  * @returns the position of the startcode or -1 if not found
 146  */
 147 static int64_t find_startcode(ByteIOContext *bc, uint64_t code, int64_t pos){
 148     for(;;){
 149         uint64_t startcode= find_any_startcode(bc, pos);
 150         if(startcode == code)
 151             return url_ftell(bc) - 8;
 152         else if(startcode == 0)
 153             return -1;
 154         pos=-1;
 155     }
 156 }
 157
 158 static int64_t lsb2full(StreamContext *stream, int64_t lsb){
 159     int64_t mask = (1<<stream->msb_pts_shift)-1;
 160     int64_t delta= stream->last_pts - mask/2;
 161     return  ((lsb - delta)&mask) + delta;
 162 }
 163
 164 static int nut_probe(AVProbeData *p){
 165     int i;
 166     uint64_t code= 0;
 167
 168     for (i = 0; i < p->buf_size; i++) {
 169         code = (code << 8) | p->buf[i];
 170         if (code == MAIN_STARTCODE)
 171             return AVPROBE_SCORE_MAX;
 172     }
 173     return 0;
 174 }
 175
 176 #define GET_V(dst, check) \
 177     tmp= get_v(bc);\
 178     if(!(check)){\
 179         av_log(s, AV_LOG_ERROR, "Error " #dst " is (%"PRId64")\n", tmp);\
 180         return -1;\
 181     }\
 182     dst= tmp;
 183
 184 static int skip_reserved(ByteIOContext *bc, int64_t pos){
 185     pos -= url_ftell(bc);
 186     if(pos<0){
 187         url_fseek(bc, pos, SEEK_CUR);
 188         return -1;
 189     }else{
 190         while(pos--)
 191             get_byte(bc);
 192         return 0;
 193     }
 194 }
 195
 196 static int decode_main_header(NUTContext *nut){
 197     AVFormatContext *s= nut->avf;
 198     ByteIOContext *bc = &s->pb;
 199     uint64_t tmp, end;
 200     unsigned int stream_count;
 201     int i, j, tmp_stream, tmp_mul, tmp_pts, tmp_size, count, tmp_res;
 202
 203     end= get_packetheader(nut, bc, 1);
 204     end += url_ftell(bc);
 205
 206     GET_V(tmp              , tmp >=2 && tmp <= 3)
 207     GET_V(stream_count     , tmp > 0 && tmp <=MAX_STREAMS)
 208
 209     nut->max_distance = get_v(bc);
 210     if(nut->max_distance > 65536){
 211         av_log(s, AV_LOG_DEBUG, "max_distance %d\n", nut->max_distance);
 212         nut->max_distance= 65536;
 213     }
 214
 215     GET_V(nut->time_base_count, tmp>0 && tmp<INT_MAX / sizeof(AVRational))
 216     nut->time_base= av_malloc(nut->time_base_count * sizeof(AVRational));
 217
 218     for(i=0; i<nut->time_base_count; i++){
 219         GET_V(nut->time_base[i].num, tmp>0 && tmp<(1ULL<<31))
 220         GET_V(nut->time_base[i].den, tmp>0 && tmp<(1ULL<<31))
 221         if(ff_gcd(nut->time_base[i].num, nut->time_base[i].den) != 1){
 222             av_log(s, AV_LOG_ERROR, "time base invalid\n");
 223             return -1;
 224         }
 225     }
 226     tmp_pts=0;
 227     tmp_mul=1;
 228     tmp_stream=0;
 229     for(i=0; i<256;){
 230         int tmp_flags = get_v(bc);
 231         int tmp_fields= get_v(bc);
 232         if(tmp_fields>0) tmp_pts   = get_s(bc);
 233         if(tmp_fields>1) tmp_mul   = get_v(bc);
 234         if(tmp_fields>2) tmp_stream= get_v(bc);
 235         if(tmp_fields>3) tmp_size  = get_v(bc);
 236         else             tmp_size  = 0;
 237         if(tmp_fields>4) tmp_res   = get_v(bc);
 238         else             tmp_res   = 0;
 239         if(tmp_fields>5) count     = get_v(bc);
 240         else             count     = tmp_mul - tmp_size;
 241
 242         while(tmp_fields-- > 6)
 243            get_v(bc);
 244
 245         if(count == 0 || i+count > 256){
 246             av_log(s, AV_LOG_ERROR, "illegal count %d at %d\n", count, i);
 247             return -1;
 248         }
 249         if(tmp_stream >= stream_count){
 250             av_log(s, AV_LOG_ERROR, "illegal stream number\n");
 251             return -1;
 252         }
 253
 254         for(j=0; j<count; j++,i++){
 255             if (i == 'N') {
 256                 nut->frame_code[i].flags= FLAG_INVALID;
 257                 j--;
 258                 continue;
 259             }
 260             nut->frame_code[i].flags           = tmp_flags ;
 261             nut->frame_code[i].pts_delta       = tmp_pts   ;
 262             nut->frame_code[i].stream_id       = tmp_stream;
 263             nut->frame_code[i].size_mul        = tmp_mul   ;
 264             nut->frame_code[i].size_lsb        = tmp_size+j;
 265             nut->frame_code[i].reserved_count  = tmp_res   ;
 266         }
 267     }
 268     assert(nut->frame_code['N'].flags == FLAG_INVALID);
 269
 270     if(skip_reserved(bc, end) || get_checksum(bc)){
 271         av_log(s, AV_LOG_ERROR, "Main header checksum mismatch\n");
 272         return -1;
 273     }
 274
 275     nut->stream = av_mallocz(sizeof(StreamContext)*stream_count);
 276     for(i=0; i<stream_count; i++){
 277         av_new_stream(s, i);
 278     }
 279
 280     return 0;
 281 }
 282
 283 static int decode_stream_header(NUTContext *nut){
 284     AVFormatContext *s= nut->avf;
 285     ByteIOContext *bc = &s->pb;
 286     StreamContext *stc;
 287     int class, stream_id;
 288     uint64_t tmp, end;
 289     AVStream *st;
 290
 291     end= get_packetheader(nut, bc, 1);
 292     end += url_ftell(bc);
 293
 294     GET_V(stream_id, tmp < s->nb_streams && !nut->stream[tmp].time_base.num);
 295     stc= &nut->stream[stream_id];
 296
 297     st = s->streams[stream_id];
 298     if (!st)
 299         return AVERROR_NOMEM;
 300
 301     class = get_v(bc);
 302     tmp = get_fourcc(bc);
 303     st->codec->codec_tag= tmp;
 304     switch(class)
 305     {
 306         case 0:
 307             st->codec->codec_type = CODEC_TYPE_VIDEO;
 308             st->codec->codec_id = codec_get_bmp_id(tmp);
 309             if (st->codec->codec_id == CODEC_ID_NONE)
 310                 av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
 311             break;
 312         case 1:
 313             st->codec->codec_type = CODEC_TYPE_AUDIO;
 314             st->codec->codec_id = codec_get_wav_id(tmp);
 315             if (st->codec->codec_id == CODEC_ID_NONE)
 316                 av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
 317             break;
 318         case 2:
 319 //            st->codec->codec_type = CODEC_TYPE_TEXT;
 320 //            break;
 321         case 3:
 322             st->codec->codec_type = CODEC_TYPE_DATA;
 323             break;
 324         default:
 325             av_log(s, AV_LOG_ERROR, "Unknown stream class (%d)\n", class);
 326             return -1;
 327     }
 328     GET_V(stc->time_base_id    , tmp < nut->time_base_count);
 329     GET_V(stc->msb_pts_shift   , tmp < 16);
 330     stc->max_pts_distance= get_v(bc);
 331     GET_V(stc->decode_delay    , tmp < 1000); //sanity limit, raise this if moors law is true
 332     st->codec->has_b_frames= stc->decode_delay;
 333     get_v(bc); //stream flags
 334
 335     GET_V(st->codec->extradata_size, tmp < (1<<30));
 336     if(st->codec->extradata_size){
 337         st->codec->extradata= av_mallocz(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
 338         get_buffer(bc, st->codec->extradata, st->codec->extradata_size);
 339     }
 340
 341     if (st->codec->codec_type == CODEC_TYPE_VIDEO){
 342         GET_V(st->codec->width , tmp > 0)
 343         GET_V(st->codec->height, tmp > 0)
 344         st->codec->sample_aspect_ratio.num= get_v(bc);
 345         st->codec->sample_aspect_ratio.den= get_v(bc);
 346         if((!st->codec->sample_aspect_ratio.num) != (!st->codec->sample_aspect_ratio.den)){
 347             av_log(s, AV_LOG_ERROR, "invalid aspect ratio\n");
 348             return -1;
 349         }
 350         get_v(bc); /* csp type */
 351     }else if (st->codec->codec_type == CODEC_TYPE_AUDIO){
 352         GET_V(st->codec->sample_rate , tmp > 0)
 353         tmp= get_v(bc); // samplerate_den
 354         if(tmp > st->codec->sample_rate){
 355             av_log(s, AV_LOG_ERROR, "bleh, libnut muxed this ;)\n");
 356             st->codec->sample_rate= tmp;
 357         }
 358         GET_V(st->codec->channels, tmp > 0)
 359     }
 360     if(skip_reserved(bc, end) || get_checksum(bc)){
 361         av_log(s, AV_LOG_ERROR, "Stream header %d checksum mismatch\n", stream_id);
 362         return -1;
 363     }
 364     stc->time_base= nut->time_base[stc->time_base_id];
 365     av_set_pts_info(s->streams[stream_id], 63, stc->time_base.num, stc->time_base.den);
 366     return 0;
 367 }
 368
 369 static int decode_info_header(NUTContext *nut){
 370     AVFormatContext *s= nut->avf;
 371     ByteIOContext *bc = &s->pb;
 372     uint64_t tmp;
 373     unsigned int stream_id_plus1, chapter_start, chapter_len, count;
 374     int chapter_id, i;
 375     int64_t value, end;
 376     char name[256], str_value[1024], type_str[256], *type= type_str;
 377
 378     end= get_packetheader(nut, bc, 1);
 379     end += url_ftell(bc);
 380
 381     GET_V(stream_id_plus1, tmp <= s->nb_streams)
 382     chapter_id   = get_s(bc);
 383     chapter_start= get_v(bc);
 384     chapter_len  = get_v(bc);
 385     count        = get_v(bc);
 386     for(i=0; i<count; i++){
 387         get_str(bc, name, sizeof(name));
 388         value= get_s(bc);
 389         if(value == -1){
 390             type= "UTF-8";
 391             get_str(bc, str_value, sizeof(str_value));
 392         }else if(value == -2){
 393             get_str(bc, type, sizeof(type));
 394             get_str(bc, str_value, sizeof(str_value));
 395         }else if(value == -3){
 396             type= "s";
 397             value= get_s(bc);
 398         }else if(value == -4){
 399             type= "t";
 400             value= get_v(bc);
 401         }else if(value < -4){
 402             type= "r";
 403             get_s(bc);
 404         }else{
 405             type= "v";
 406         }
 407
 408         if(chapter_id==0 && !strcmp(type, "UTF-8")){
 409             if     (!strcmp(name, "Author"))
 410                 pstrcpy(s->author   , sizeof(s->author)   , str_value);
 411             else if(!strcmp(name, "Title"))
 412                 pstrcpy(s->title    , sizeof(s->title)    , str_value);
 413             else if(!strcmp(name, "Copyright"))
 414                 pstrcpy(s->copyright, sizeof(s->copyright), str_value);
 415             else if(!strcmp(name, "Description"))
 416                 pstrcpy(s->comment  , sizeof(s->comment)  , str_value);
 417         }
 418     }
 419
 420     if(skip_reserved(bc, end) || get_checksum(bc)){
 421         av_log(s, AV_LOG_ERROR, "Info header checksum mismatch\n");
 422         return -1;
 423     }
 424     return 0;
 425 }
 426
 427 int sp_pos_cmp(syncpoint_t *a, syncpoint_t *b){
 428     return (a->pos - b->pos>>32) - (b->pos - a->pos>>32);
 429 }
 430
 431 int sp_pts_cmp(syncpoint_t *a, syncpoint_t *b){
 432     return (a->ts - b->ts>>32) - (b->ts - a->ts>>32);
 433 }
 434
 435 static void add_sp(NUTContext *nut, int64_t pos, int64_t back_ptr, int64_t ts){
 436     syncpoint_t *sp2, *sp= av_mallocz(sizeof(syncpoint_t));
 437
 438     sp->pos= pos;
 439     sp->back_ptr= back_ptr;
 440     sp->ts= ts;
 441     sp2= av_tree_insert(&nut->syncpoints, sp, sp_pos_cmp);
 442     if(sp2 && sp2 != sp)
 443         av_free(sp);
 444 }
 445
 446 static int decode_syncpoint(NUTContext *nut, int64_t *ts, int64_t *back_ptr){
 447     AVFormatContext *s= nut->avf;
 448     ByteIOContext *bc = &s->pb;
 449     int64_t end, tmp;
 450     int i;
 451     AVRational time_base;
 452
 453     nut->last_syncpoint_pos= url_ftell(bc)-8;
 454
 455     end= get_packetheader(nut, bc, 1);
 456     end += url_ftell(bc);
 457
 458     tmp= get_v(bc);
 459     *back_ptr= nut->last_syncpoint_pos - 16*get_v(bc);
 460     if(*back_ptr < 0)
 461         return -1;
 462
 463     time_base= nut->time_base[tmp % nut->time_base_count];
 464     for(i=0; i<s->nb_streams; i++){
 465         nut->stream[i].last_pts= av_rescale_rnd(
 466             tmp / nut->time_base_count,
 467             time_base.num * (int64_t)nut->stream[i].time_base.den,
 468             time_base.den * (int64_t)nut->stream[i].time_base.num,
 469             AV_ROUND_DOWN);
 470         //last_key_frame ?
 471     }
 472     //FIXME put this in a reset func maybe
 473
 474     if(skip_reserved(bc, end) || get_checksum(bc)){
 475         av_log(s, AV_LOG_ERROR, "sync point checksum mismatch\n");
 476         return -1;
 477     }
 478
 479     *ts= tmp / s->nb_streams * av_q2d(nut->time_base[tmp % s->nb_streams])*AV_TIME_BASE;
 480     add_sp(nut, nut->last_syncpoint_pos, *back_ptr, *ts);
 481
 482     return 0;
 483 }
 484
 485 static int find_and_decode_index(NUTContext *nut){
 486     AVFormatContext *s= nut->avf;
 487     ByteIOContext *bc = &s->pb;
 488     uint64_t tmp, end;
 489     int i, j, syncpoint_count;
 490     int64_t filesize= url_fsize(bc);
 491     int64_t *syncpoints;
 492     int8_t *has_keyframe;
 493
 494     url_fseek(bc, filesize-12, SEEK_SET);
 495     url_fseek(bc, filesize-get_be64(bc), SEEK_SET);
 496     if(get_be64(bc) != INDEX_STARTCODE){
 497         av_log(s, AV_LOG_ERROR, "no index at the end\n");
 498         return -1;
 499     }
 500
 501     end= get_packetheader(nut, bc, 1);
 502     end += url_ftell(bc);
 503
 504     get_v(bc); //max_pts
 505     GET_V(syncpoint_count, tmp < INT_MAX/8 && tmp > 0)
 506     syncpoints= av_malloc(sizeof(int64_t)*syncpoint_count);
 507     has_keyframe= av_malloc(sizeof(int8_t)*(syncpoint_count+1));
 508     for(i=0; i<syncpoint_count; i++){
 509         GET_V(syncpoints[i], tmp>0)
 510         if(i)
 511             syncpoints[i] += syncpoints[i-1];
 512     }
 513
 514     for(i=0; i<s->nb_streams; i++){
 515         int64_t last_pts= -1;
 516         for(j=0; j<syncpoint_count;){
 517             uint64_t x= get_v(bc);
 518             int type= x&1;
 519             int n= j;
 520             x>>=1;
 521             if(type){
 522                 int flag= x&1;
 523                 x>>=1;
 524                 if(n+x >= syncpoint_count + 1){
 525                     av_log(s, AV_LOG_ERROR, "index overflow A\n");
 526                     return -1;
 527                 }
 528                 while(x--)
 529                     has_keyframe[n++]= flag;
 530                 has_keyframe[n++]= !flag;
 531             }else{
 532                 while(x != 1){
 533                     if(n>=syncpoint_count + 1){
 534                         av_log(s, AV_LOG_ERROR, "index overflow B\n");
 535                         return -1;
 536                     }
 537                     has_keyframe[n++]= x&1;
 538                     x>>=1;
 539                 }
 540             }
 541             if(has_keyframe[0]){
 542                 av_log(s, AV_LOG_ERROR, "keyframe before first syncpoint in index\n");
 543                 return -1;
 544             }
 545             assert(n<=syncpoint_count+1);
 546             for(; j<n; j++){
 547                 if(has_keyframe[j]){
 548                     uint64_t B, A= get_v(bc);
 549                     if(!A){
 550                         A= get_v(bc);
 551                         B= get_v(bc);
 552                         //eor_pts[j][i] = last_pts + A + B
 553                     }else
 554                         B= 0;
 555                     av_add_index_entry(
 556                         s->streams[i],
 557                         16*syncpoints[j-1],
 558                         last_pts + A,
 559                         0,
 560                         0,
 561                         AVINDEX_KEYFRAME);
 562                     last_pts += A + B;
 563                 }
 564             }
 565         }
 566     }
 567
 568     if(skip_reserved(bc, end) || get_checksum(bc)){
 569         av_log(s, AV_LOG_ERROR, "Index checksum mismatch\n");
 570         return -1;
 571     }
 572     return 0;
 573 }
 574
 575 static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
 576 {
 577     NUTContext *nut = s->priv_data;
 578     ByteIOContext *bc = &s->pb;
 579     int64_t pos;
 580     int inited_stream_count;
 581
 582     nut->avf= s;
 583
 584     /* main header */
 585     pos=0;
 586     do{
 587         pos= find_startcode(bc, MAIN_STARTCODE, pos)+1;
 588         if (pos<0+1){
 589             av_log(s, AV_LOG_ERROR, "no main startcode found\n");
 590             return -1;
 591         }
 592     }while(decode_main_header(nut) < 0);
 593
 594     /* stream headers */
 595     pos=0;
 596     for(inited_stream_count=0; inited_stream_count < s->nb_streams;){
 597         pos= find_startcode(bc, STREAM_STARTCODE, pos)+1;
 598         if (pos<0+1){
 599             av_log(s, AV_LOG_ERROR, "not all stream headers found\n");
 600             return -1;
 601         }
 602         if(decode_stream_header(nut) >= 0)
 603             inited_stream_count++;
 604     }
 605
 606     /* info headers */
 607     pos=0;
 608     for(;;){
 609         uint64_t startcode= find_any_startcode(bc, pos);
 610         pos= url_ftell(bc);
 611
 612         if(startcode==0){
 613             av_log(s, AV_LOG_ERROR, "EOF before video frames\n");
 614             return -1;
 615         }else if(startcode == SYNCPOINT_STARTCODE){
 616             nut->next_startcode= startcode;
 617             break;
 618         }else if(startcode != INFO_STARTCODE){
 619             continue;
 620         }
 621
 622         decode_info_header(nut);
 623     }
 624
 625     s->data_offset= pos-8;
 626
 627     if(!url_is_streamed(bc)){
 628         int64_t orig_pos= url_ftell(bc);
 629         find_and_decode_index(nut);
 630         url_fseek(bc, orig_pos, SEEK_SET);
 631     }
 632     assert(nut->next_startcode == SYNCPOINT_STARTCODE);
 633
 634     return 0;
 635 }
 636
 637 static int decode_frame_header(NUTContext *nut, int64_t *pts, int *stream_id, int frame_code){
 638     AVFormatContext *s= nut->avf;
 639     ByteIOContext *bc = &s->pb;
 640     StreamContext *stc;
 641     int size, flags, size_mul, pts_delta, i, reserved_count;
 642     uint64_t tmp;
 643
 644     if(url_ftell(bc) > nut->last_syncpoint_pos + nut->max_distance){
 645         av_log(s, AV_LOG_ERROR, "last frame must have been damaged %Ld > %Ld + %d\n", url_ftell(bc), nut->last_syncpoint_pos, nut->max_distance);
 646         return -1;
 647     }
 648
 649     flags          = nut->frame_code[frame_code].flags;
 650     size_mul       = nut->frame_code[frame_code].size_mul;
 651     size           = nut->frame_code[frame_code].size_lsb;
 652     *stream_id     = nut->frame_code[frame_code].stream_id;
 653     pts_delta      = nut->frame_code[frame_code].pts_delta;
 654     reserved_count = nut->frame_code[frame_code].reserved_count;
 655
 656     if(flags & FLAG_INVALID)
 657         return -1;
 658     if(flags & FLAG_CODED)
 659         flags ^= get_v(bc);
 660     if(flags & FLAG_STREAM_ID){
 661         GET_V(*stream_id, tmp < s->nb_streams)
 662     }
 663     stc= &nut->stream[*stream_id];
 664     if(flags&FLAG_CODED_PTS){
 665         int coded_pts= get_v(bc);
 666 //FIXME check last_pts validity?
 667         if(coded_pts < (1<<stc->msb_pts_shift)){
 668             *pts=lsb2full(stc, coded_pts);
 669         }else
 670             *pts=coded_pts - (1<<stc->msb_pts_shift);
 671     }else
 672         *pts= stc->last_pts + pts_delta;
 673     if(flags&FLAG_SIZE_MSB){
 674         size += size_mul*get_v(bc);
 675     }
 676     if(flags&FLAG_RESERVED)
 677         reserved_count= get_v(bc);
 678     for(i=0; i<reserved_count; i++)
 679         get_v(bc);
 680     if(flags&FLAG_CHECKSUM){
 681         get_be32(bc); //FIXME check this
 682     }else if(size > 2*nut->max_distance || FFABS(stc->last_pts - *pts) > stc->max_pts_distance){
 683         av_log(s, AV_LOG_ERROR, "frame size > 2max_distance and no checksum\n");
 684         return -1;
 685     }
 686
 687     stc->last_pts= *pts;
 688     stc->last_flags= flags;
 689
 690     return size;
 691 }
 692
 693 static int decode_frame(NUTContext *nut, AVPacket *pkt, int frame_code){
 694     AVFormatContext *s= nut->avf;
 695     ByteIOContext *bc = &s->pb;
 696     int size, stream_id, discard;
 697     int64_t pts, last_IP_pts;
 698     StreamContext *stc;
 699
 700     size= decode_frame_header(nut, &pts, &stream_id, frame_code);
 701     if(size < 0)
 702         return -1;
 703
 704     stc= &nut->stream[stream_id];
 705
 706     if (stc->last_flags & FLAG_KEY)
 707         stc->skip_until_key_frame=0;
 708
 709     discard= s->streams[ stream_id ]->discard;
 710     last_IP_pts= s->streams[ stream_id ]->last_IP_pts;
 711     if(  (discard >= AVDISCARD_NONKEY && !(stc->last_flags & FLAG_KEY))
 712        ||(discard >= AVDISCARD_BIDIR && last_IP_pts != AV_NOPTS_VALUE && last_IP_pts > pts)
 713        || discard >= AVDISCARD_ALL
 714        || stc->skip_until_key_frame){
 715         url_fskip(bc, size);
 716         return 1;
 717     }
 718
 719     av_get_packet(bc, pkt, size);
 720     pkt->stream_index = stream_id;
 721     if (stc->last_flags & FLAG_KEY)
 722         pkt->flags |= PKT_FLAG_KEY;
 723     pkt->pts = pts;
 724
 725     return 0;
 726 }
 727
 728 static int nut_read_packet(AVFormatContext *s, AVPacket *pkt)
 729 {
 730     NUTContext *nut = s->priv_data;
 731     ByteIOContext *bc = &s->pb;
 732     int i, frame_code=0, ret, skip;
 733     int64_t ts, back_ptr;
 734
 735     for(;;){
 736         int64_t pos= url_ftell(bc);
 737         uint64_t tmp= nut->next_startcode;
 738         nut->next_startcode=0;
 739
 740         if(tmp){
 741             pos-=8;
 742         }else{
 743             frame_code = get_byte(bc);
 744             if(url_feof(bc))
 745                 return -1;
 746             if(frame_code == 'N'){
 747                 tmp= frame_code;
 748                 for(i=1; i<8; i++)
 749                     tmp = (tmp<<8) + get_byte(bc);
 750             }
 751         }
 752         switch(tmp){
 753         case MAIN_STARTCODE:
 754         case STREAM_STARTCODE:
 755         case INDEX_STARTCODE:
 756             skip= get_packetheader(nut, bc, 0);
 757             url_fseek(bc, skip, SEEK_CUR);
 758             break;
 759         case INFO_STARTCODE:
 760             if(decode_info_header(nut)<0)
 761                 goto resync;
 762             break;
 763         case SYNCPOINT_STARTCODE:
 764             if(decode_syncpoint(nut, &ts, &back_ptr)<0)
 765                 goto resync;
 766             frame_code = get_byte(bc);
 767         case 0:
 768             ret= decode_frame(nut, pkt, frame_code);
 769             if(ret==0)
 770                 return 0;
 771             else if(ret==1) //ok but discard packet
 772                 break;
 773         default:
 774 resync:
 775 av_log(s, AV_LOG_DEBUG, "syncing from %"PRId64"\n", pos);
 776             tmp= find_any_startcode(bc, nut->last_syncpoint_pos+1);
 777             if(tmp==0)
 778                 return -1;
 779 av_log(s, AV_LOG_DEBUG, "sync\n");
 780             nut->next_startcode= tmp;
 781         }
 782     }
 783 }
 784
 785 static int64_t nut_read_timestamp(AVFormatContext *s, int stream_index, int64_t *pos_arg, int64_t pos_limit){
 786     NUTContext *nut = s->priv_data;
 787     ByteIOContext *bc = &s->pb;
 788     int64_t pos, pts, back_ptr;
 789 av_log(s, AV_LOG_DEBUG, "read_timestamp(X,%d,%"PRId64",%"PRId64")\n", stream_index, *pos_arg, pos_limit);
 790
 791     pos= *pos_arg;
 792 resync:
 793     do{
 794         pos= find_startcode(bc, SYNCPOINT_STARTCODE, pos)+1;
 795         if(pos < 1){
 796             assert(nut->next_startcode == 0);
 797             av_log(s, AV_LOG_ERROR, "read_timestamp failed\n");
 798             return AV_NOPTS_VALUE;
 799         }
 800     }while(decode_syncpoint(nut, &pts, &back_ptr) < 0);
 801     *pos_arg = pos-1;
 802     assert(nut->last_syncpoint_pos == *pos_arg);
 803
 804     av_log(s, AV_LOG_DEBUG, "return %Ld %Ld\n", pts,back_ptr );
 805     if     (stream_index == -1) return pts;
 806     else if(stream_index == -2) return back_ptr;
 807
 808 assert(0);
 809 }
 810
 811 static int read_seek(AVFormatContext *s, int stream_index, int64_t pts, int flags){
 812     NUTContext *nut = s->priv_data;
 813     AVStream *st= s->streams[stream_index];
 814     syncpoint_t dummy={.ts= pts*av_q2d(st->time_base)*AV_TIME_BASE};
 815     syncpoint_t nopts_sp= {.ts= AV_NOPTS_VALUE, .back_ptr= AV_NOPTS_VALUE};
 816     syncpoint_t *sp, *next_node[2]= {&nopts_sp, &nopts_sp};
 817     int64_t pos, pos2, ts;
 818     int i;
 819
 820     if(st->index_entries){
 821         int index= av_index_search_timestamp(st, pts, flags);
 822         if(index<0)
 823             return -1;
 824
 825         pos2= st->index_entries[index].pos;
 826         ts  = st->index_entries[index].timestamp;
 827     }else{
 828         av_tree_find(nut->syncpoints, &dummy, sp_pts_cmp, next_node);
 829         av_log(s, AV_LOG_DEBUG, "%Ld-%Ld %Ld-%Ld\n", next_node[0]->pos, next_node[1]->pos,
 830                                                     next_node[0]->ts , next_node[1]->ts);
 831         pos= av_gen_search(s, -1, dummy.ts, next_node[0]->pos, next_node[1]->pos, next_node[1]->pos,
 832                                             next_node[0]->ts , next_node[1]->ts, AVSEEK_FLAG_BACKWARD, &ts, nut_read_timestamp);
 833
 834         if(!(flags & AVSEEK_FLAG_BACKWARD)){
 835             dummy.pos= pos+16;
 836             next_node[1]= &nopts_sp;
 837             av_tree_find(nut->syncpoints, &dummy, sp_pos_cmp, next_node);
 838             pos2= av_gen_search(s, -2, dummy.pos, next_node[0]->pos     , next_node[1]->pos, next_node[1]->pos,
 839                                                 next_node[0]->back_ptr, next_node[1]->back_ptr, flags, &ts, nut_read_timestamp);
 840             if(pos2>=0)
 841                 pos= pos2;
 842             //FIXME dir but i think it doesnt matter
 843         }
 844         dummy.pos= pos;
 845         sp= av_tree_find(nut->syncpoints, &dummy, sp_pos_cmp, NULL);
 846
 847         assert(sp);
 848         pos2= sp->back_ptr  - 15;
 849     }
 850     av_log(NULL, AV_LOG_DEBUG, "SEEKTO: %"PRId64"\n", pos2);
 851     pos= find_startcode(&s->pb, SYNCPOINT_STARTCODE, pos2);
 852     url_fseek(&s->pb, pos, SEEK_SET);
 853     av_log(NULL, AV_LOG_DEBUG, "SP: %"PRId64"\n", pos);
 854     if(pos2 > pos || pos2 + 15 < pos){
 855         av_log(NULL, AV_LOG_ERROR, "no syncpoint at backptr pos\n");
 856     }
 857     for(i=0; i<s->nb_streams; i++)
 858         nut->stream[i].skip_until_key_frame=1;
 859
 860     return 0;
 861 }
 862
 863 static int nut_read_close(AVFormatContext *s)
 864 {
 865     NUTContext *nut = s->priv_data;
 866
 867     av_freep(&nut->time_base);
 868     av_freep(&nut->stream);
 869
 870     return 0;
 871 }
 872
 873 #ifdef CONFIG_NUT_DEMUXER
 874 AVInputFormat nut_demuxer = {
 875     "nut",
 876     "nut format",
 877     sizeof(NUTContext),
 878     nut_probe,
 879     nut_read_header,
 880     nut_read_packet,
 881     nut_read_close,
 882     read_seek,
 883     .extensions = "nut",
 884 };
 885 #endif