libavformat/ipmovie.c

   1 /*
   2  * Interplay MVE File Demuxer
   3  * Copyright (c) 2003 The ffmpeg Project
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file libavformat/ipmovie.c
  24  * Interplay MVE file demuxer
  25  * by Mike Melanson (melanson@pcisys.net)
  26  * For more information regarding the Interplay MVE file format, visit:
  27  *   http://www.pcisys.net/~melanson/codecs/
  28  * The aforementioned site also contains a command line utility for parsing
  29  * IP MVE files so that you can get a good idea of the typical structure of
  30  * such files. This demuxer is not the best example to use if you are trying
  31  * to write your own as it uses a rather roundabout approach for splitting
  32  * up and sending out the chunks.
  33  */
  34
  35 #include "libavutil/intreadwrite.h"
  36 #include "avformat.h"
  37
  38 /* debugging support: #define DEBUG_IPMOVIE as non-zero to see extremely
  39  * verbose information about the demux process */
  40 #define DEBUG_IPMOVIE 0
  41
  42 #if DEBUG_IPMOVIE
  43 #define debug_ipmovie printf
  44 #else
  45 static inline void debug_ipmovie(const char *format, ...) { }
  46 #endif
  47
  48 #define IPMOVIE_SIGNATURE "Interplay MVE File\x1A\0"
  49 #define IPMOVIE_SIGNATURE_SIZE 20
  50 #define CHUNK_PREAMBLE_SIZE 4
  51 #define OPCODE_PREAMBLE_SIZE 4
  52
  53 #define CHUNK_INIT_AUDIO   0x0000
  54 #define CHUNK_AUDIO_ONLY   0x0001
  55 #define CHUNK_INIT_VIDEO   0x0002
  56 #define CHUNK_VIDEO        0x0003
  57 #define CHUNK_SHUTDOWN     0x0004
  58 #define CHUNK_END          0x0005
  59 /* these last types are used internally */
  60 #define CHUNK_DONE         0xFFFC
  61 #define CHUNK_NOMEM        0xFFFD
  62 #define CHUNK_EOF          0xFFFE
  63 #define CHUNK_BAD          0xFFFF
  64
  65 #define OPCODE_END_OF_STREAM           0x00
  66 #define OPCODE_END_OF_CHUNK            0x01
  67 #define OPCODE_CREATE_TIMER            0x02
  68 #define OPCODE_INIT_AUDIO_BUFFERS      0x03
  69 #define OPCODE_START_STOP_AUDIO        0x04
  70 #define OPCODE_INIT_VIDEO_BUFFERS      0x05
  71 #define OPCODE_UNKNOWN_06              0x06
  72 #define OPCODE_SEND_BUFFER             0x07
  73 #define OPCODE_AUDIO_FRAME             0x08
  74 #define OPCODE_SILENCE_FRAME           0x09
  75 #define OPCODE_INIT_VIDEO_MODE         0x0A
  76 #define OPCODE_CREATE_GRADIENT         0x0B
  77 #define OPCODE_SET_PALETTE             0x0C
  78 #define OPCODE_SET_PALETTE_COMPRESSED  0x0D
  79 #define OPCODE_UNKNOWN_0E              0x0E
  80 #define OPCODE_SET_DECODING_MAP        0x0F
  81 #define OPCODE_UNKNOWN_10              0x10
  82 #define OPCODE_VIDEO_DATA              0x11
  83 #define OPCODE_UNKNOWN_12              0x12
  84 #define OPCODE_UNKNOWN_13              0x13
  85 #define OPCODE_UNKNOWN_14              0x14
  86 #define OPCODE_UNKNOWN_15              0x15
  87
  88 #define PALETTE_COUNT 256
  89
  90 typedef struct IPMVEContext {
  91
  92     unsigned char *buf;
  93     int buf_size;
  94
  95     float fps;
  96     int frame_pts_inc;
  97
  98     unsigned int video_width;
  99     unsigned int video_height;
 100     int64_t video_pts;
 101
 102     unsigned int audio_bits;
 103     unsigned int audio_channels;
 104     unsigned int audio_sample_rate;
 105     enum CodecID audio_type;
 106     unsigned int audio_frame_count;
 107
 108     int video_stream_index;
 109     int audio_stream_index;
 110
 111     int64_t audio_chunk_offset;
 112     int audio_chunk_size;
 113     int64_t video_chunk_offset;
 114     int video_chunk_size;
 115     int64_t decode_map_chunk_offset;
 116     int decode_map_chunk_size;
 117
 118     int64_t next_chunk_offset;
 119
 120     AVPaletteControl palette_control;
 121
 122 } IPMVEContext;
 123
 124 static int load_ipmovie_packet(IPMVEContext *s, ByteIOContext *pb,
 125     AVPacket *pkt) {
 126
 127     int chunk_type;
 128     int64_t audio_pts = 0;
 129
 130     if (s->audio_chunk_offset) {
 131
 132         /* adjust for PCM audio by skipping chunk header */
 133         if (s->audio_type != CODEC_ID_INTERPLAY_DPCM) {
 134             s->audio_chunk_offset += 6;
 135             s->audio_chunk_size -= 6;
 136         }
 137
 138         url_fseek(pb, s->audio_chunk_offset, SEEK_SET);
 139         s->audio_chunk_offset = 0;
 140
 141         /* figure out the audio pts */
 142         audio_pts = 90000;
 143         audio_pts *= s->audio_frame_count;
 144         audio_pts /= s->audio_sample_rate;
 145
 146         if (s->audio_chunk_size != av_get_packet(pb, pkt, s->audio_chunk_size))
 147             return CHUNK_EOF;
 148
 149         pkt->stream_index = s->audio_stream_index;
 150         pkt->pts = audio_pts;
 151
 152         /* audio frame maintenance */
 153         if (s->audio_type != CODEC_ID_INTERPLAY_DPCM)
 154             s->audio_frame_count +=
 155             (s->audio_chunk_size / s->audio_channels / (s->audio_bits / 8));
 156         else
 157             s->audio_frame_count +=
 158                 (s->audio_chunk_size - 6) / s->audio_channels;
 159
 160         debug_ipmovie("sending audio frame with pts %"PRId64" (%d audio frames)\n",
 161             audio_pts, s->audio_frame_count);
 162
 163         chunk_type = CHUNK_VIDEO;
 164
 165     } else if (s->decode_map_chunk_offset) {
 166
 167         /* send both the decode map and the video data together */
 168
 169         if (av_new_packet(pkt, s->decode_map_chunk_size + s->video_chunk_size))
 170             return CHUNK_NOMEM;
 171
 172         pkt->pos= s->decode_map_chunk_offset;
 173         url_fseek(pb, s->decode_map_chunk_offset, SEEK_SET);
 174         s->decode_map_chunk_offset = 0;
 175
 176         if (get_buffer(pb, pkt->data, s->decode_map_chunk_size) !=
 177             s->decode_map_chunk_size) {
 178             av_free_packet(pkt);
 179             return CHUNK_EOF;
 180         }
 181
 182         url_fseek(pb, s->video_chunk_offset, SEEK_SET);
 183         s->video_chunk_offset = 0;
 184
 185         if (get_buffer(pb, pkt->data + s->decode_map_chunk_size,
 186             s->video_chunk_size) != s->video_chunk_size) {
 187             av_free_packet(pkt);
 188             return CHUNK_EOF;
 189         }
 190
 191         pkt->stream_index = s->video_stream_index;
 192         pkt->pts = s->video_pts;
 193
 194         debug_ipmovie("sending video frame with pts %"PRId64"\n",
 195             pkt->pts);
 196
 197         s->video_pts += s->frame_pts_inc;
 198
 199         chunk_type = CHUNK_VIDEO;
 200
 201     } else {
 202
 203         url_fseek(pb, s->next_chunk_offset, SEEK_SET);
 204         chunk_type = CHUNK_DONE;
 205
 206     }
 207
 208     return chunk_type;
 209 }
 210
 211 /* This function loads and processes a single chunk in an IP movie file.
 212  * It returns the type of chunk that was processed. */
 213 static int process_ipmovie_chunk(IPMVEContext *s, ByteIOContext *pb,
 214     AVPacket *pkt)
 215 {
 216     unsigned char chunk_preamble[CHUNK_PREAMBLE_SIZE];
 217     int chunk_type;
 218     int chunk_size;
 219     unsigned char opcode_preamble[OPCODE_PREAMBLE_SIZE];
 220     unsigned char opcode_type;
 221     unsigned char opcode_version;
 222     int opcode_size;
 223     unsigned char scratch[1024];
 224     int i, j;
 225     int first_color, last_color;
 226     int audio_flags;
 227     unsigned char r, g, b;
 228
 229     /* see if there are any pending packets */
 230     chunk_type = load_ipmovie_packet(s, pb, pkt);
 231     if (chunk_type != CHUNK_DONE)
 232         return chunk_type;
 233
 234     /* read the next chunk, wherever the file happens to be pointing */
 235     if (url_feof(pb))
 236         return CHUNK_EOF;
 237     if (get_buffer(pb, chunk_preamble, CHUNK_PREAMBLE_SIZE) !=
 238         CHUNK_PREAMBLE_SIZE)
 239         return CHUNK_BAD;
 240     chunk_size = AV_RL16(&chunk_preamble[0]);
 241     chunk_type = AV_RL16(&chunk_preamble[2]);
 242
 243     debug_ipmovie("chunk type 0x%04X, 0x%04X bytes: ", chunk_type, chunk_size);
 244
 245     switch (chunk_type) {
 246
 247     case CHUNK_INIT_AUDIO:
 248         debug_ipmovie("initialize audio\n");
 249         break;
 250
 251     case CHUNK_AUDIO_ONLY:
 252         debug_ipmovie("audio only\n");
 253         break;
 254
 255     case CHUNK_INIT_VIDEO:
 256         debug_ipmovie("initialize video\n");
 257         break;
 258
 259     case CHUNK_VIDEO:
 260         debug_ipmovie("video (and audio)\n");
 261         break;
 262
 263     case CHUNK_SHUTDOWN:
 264         debug_ipmovie("shutdown\n");
 265         break;
 266
 267     case CHUNK_END:
 268         debug_ipmovie("end\n");
 269         break;
 270
 271     default:
 272         debug_ipmovie("invalid chunk\n");
 273         chunk_type = CHUNK_BAD;
 274         break;
 275
 276     }
 277
 278     while ((chunk_size > 0) && (chunk_type != CHUNK_BAD)) {
 279
 280         /* read the next chunk, wherever the file happens to be pointing */
 281        if (url_feof(pb)) {
 282             chunk_type = CHUNK_EOF;
 283             break;
 284         }
 285         if (get_buffer(pb, opcode_preamble, CHUNK_PREAMBLE_SIZE) !=
 286             CHUNK_PREAMBLE_SIZE) {
 287             chunk_type = CHUNK_BAD;
 288             break;
 289         }
 290
 291         opcode_size = AV_RL16(&opcode_preamble[0]);
 292         opcode_type = opcode_preamble[2];
 293         opcode_version = opcode_preamble[3];
 294
 295         chunk_size -= OPCODE_PREAMBLE_SIZE;
 296         chunk_size -= opcode_size;
 297         if (chunk_size < 0) {
 298             debug_ipmovie("chunk_size countdown just went negative\n");
 299             chunk_type = CHUNK_BAD;
 300             break;
 301         }
 302
 303         debug_ipmovie("  opcode type %02X, version %d, 0x%04X bytes: ",
 304             opcode_type, opcode_version, opcode_size);
 305         switch (opcode_type) {
 306
 307         case OPCODE_END_OF_STREAM:
 308             debug_ipmovie("end of stream\n");
 309             url_fseek(pb, opcode_size, SEEK_CUR);
 310             break;
 311
 312         case OPCODE_END_OF_CHUNK:
 313             debug_ipmovie("end of chunk\n");
 314             url_fseek(pb, opcode_size, SEEK_CUR);
 315             break;
 316
 317         case OPCODE_CREATE_TIMER:
 318             debug_ipmovie("create timer\n");
 319             if ((opcode_version > 0) || (opcode_size > 6)) {
 320                 debug_ipmovie("bad create_timer opcode\n");
 321                 chunk_type = CHUNK_BAD;
 322                 break;
 323             }
 324             if (get_buffer(pb, scratch, opcode_size) !=
 325                 opcode_size) {
 326                 chunk_type = CHUNK_BAD;
 327                 break;
 328             }
 329             s->fps = 1000000.0 / (AV_RL32(&scratch[0]) * AV_RL16(&scratch[4]));
 330             s->frame_pts_inc = 90000 / s->fps;
 331             debug_ipmovie("  %.2f frames/second (timer div = %d, subdiv = %d)\n",
 332                 s->fps, AV_RL32(&scratch[0]), AV_RL16(&scratch[4]));
 333             break;
 334
 335         case OPCODE_INIT_AUDIO_BUFFERS:
 336             debug_ipmovie("initialize audio buffers\n");
 337             if ((opcode_version > 1) || (opcode_size > 10)) {
 338                 debug_ipmovie("bad init_audio_buffers opcode\n");
 339                 chunk_type = CHUNK_BAD;
 340                 break;
 341             }
 342             if (get_buffer(pb, scratch, opcode_size) !=
 343                 opcode_size) {
 344                 chunk_type = CHUNK_BAD;
 345                 break;
 346             }
 347             s->audio_sample_rate = AV_RL16(&scratch[4]);
 348             audio_flags = AV_RL16(&scratch[2]);
 349             /* bit 0 of the flags: 0 = mono, 1 = stereo */
 350             s->audio_channels = (audio_flags & 1) + 1;
 351             /* bit 1 of the flags: 0 = 8 bit, 1 = 16 bit */
 352             s->audio_bits = (((audio_flags >> 1) & 1) + 1) * 8;
 353             /* bit 2 indicates compressed audio in version 1 opcode */
 354             if ((opcode_version == 1) && (audio_flags & 0x4))
 355                 s->audio_type = CODEC_ID_INTERPLAY_DPCM;
 356             else if (s->audio_bits == 16)
 357                 s->audio_type = CODEC_ID_PCM_S16LE;
 358             else
 359                 s->audio_type = CODEC_ID_PCM_U8;
 360             debug_ipmovie("audio: %d bits, %d Hz, %s, %s format\n",
 361                 s->audio_bits,
 362                 s->audio_sample_rate,
 363                 (s->audio_channels == 2) ? "stereo" : "mono",
 364                 (s->audio_type == CODEC_ID_INTERPLAY_DPCM) ?
 365                 "Interplay audio" : "PCM");
 366             break;
 367
 368         case OPCODE_START_STOP_AUDIO:
 369             debug_ipmovie("start/stop audio\n");
 370             url_fseek(pb, opcode_size, SEEK_CUR);
 371             break;
 372
 373         case OPCODE_INIT_VIDEO_BUFFERS:
 374             debug_ipmovie("initialize video buffers\n");
 375             if ((opcode_version > 2) || (opcode_size > 8)) {
 376                 debug_ipmovie("bad init_video_buffers opcode\n");
 377                 chunk_type = CHUNK_BAD;
 378                 break;
 379             }
 380             if (get_buffer(pb, scratch, opcode_size) !=
 381                 opcode_size) {
 382                 chunk_type = CHUNK_BAD;
 383                 break;
 384             }
 385             s->video_width = AV_RL16(&scratch[0]) * 8;
 386             s->video_height = AV_RL16(&scratch[2]) * 8;
 387             debug_ipmovie("video resolution: %d x %d\n",
 388                 s->video_width, s->video_height);
 389             break;
 390
 391         case OPCODE_UNKNOWN_06:
 392         case OPCODE_UNKNOWN_0E:
 393         case OPCODE_UNKNOWN_10:
 394         case OPCODE_UNKNOWN_12:
 395         case OPCODE_UNKNOWN_13:
 396         case OPCODE_UNKNOWN_14:
 397         case OPCODE_UNKNOWN_15:
 398             debug_ipmovie("unknown (but documented) opcode %02X\n", opcode_type);
 399             url_fseek(pb, opcode_size, SEEK_CUR);
 400             break;
 401
 402         case OPCODE_SEND_BUFFER:
 403             debug_ipmovie("send buffer\n");
 404             url_fseek(pb, opcode_size, SEEK_CUR);
 405             break;
 406
 407         case OPCODE_AUDIO_FRAME:
 408             debug_ipmovie("audio frame\n");
 409
 410             /* log position and move on for now */
 411             s->audio_chunk_offset = url_ftell(pb);
 412             s->audio_chunk_size = opcode_size;
 413             url_fseek(pb, opcode_size, SEEK_CUR);
 414             break;
 415
 416         case OPCODE_SILENCE_FRAME:
 417             debug_ipmovie("silence frame\n");
 418             url_fseek(pb, opcode_size, SEEK_CUR);
 419             break;
 420
 421         case OPCODE_INIT_VIDEO_MODE:
 422             debug_ipmovie("initialize video mode\n");
 423             url_fseek(pb, opcode_size, SEEK_CUR);
 424             break;
 425
 426         case OPCODE_CREATE_GRADIENT:
 427             debug_ipmovie("create gradient\n");
 428             url_fseek(pb, opcode_size, SEEK_CUR);
 429             break;
 430
 431         case OPCODE_SET_PALETTE:
 432             debug_ipmovie("set palette\n");
 433             /* check for the logical maximum palette size
 434              * (3 * 256 + 4 bytes) */
 435             if (opcode_size > 0x304) {
 436                 debug_ipmovie("demux_ipmovie: set_palette opcode too large\n");
 437                 chunk_type = CHUNK_BAD;
 438                 break;
 439             }
 440             if (get_buffer(pb, scratch, opcode_size) != opcode_size) {
 441                 chunk_type = CHUNK_BAD;
 442                 break;
 443             }
 444
 445             /* load the palette into internal data structure */
 446             first_color = AV_RL16(&scratch[0]);
 447             last_color = first_color + AV_RL16(&scratch[2]) - 1;
 448             /* sanity check (since they are 16 bit values) */
 449             if ((first_color > 0xFF) || (last_color > 0xFF)) {
 450                 debug_ipmovie("demux_ipmovie: set_palette indexes out of range (%d -> %d)\n",
 451                     first_color, last_color);
 452                 chunk_type = CHUNK_BAD;
 453                 break;
 454             }
 455             j = 4;  /* offset of first palette data */
 456             for (i = first_color; i <= last_color; i++) {
 457                 /* the palette is stored as a 6-bit VGA palette, thus each
 458                  * component is shifted up to a 8-bit range */
 459                 r = scratch[j++] * 4;
 460                 g = scratch[j++] * 4;
 461                 b = scratch[j++] * 4;
 462                 s->palette_control.palette[i] = (r << 16) | (g << 8) | (b);
 463             }
 464             /* indicate a palette change */
 465             s->palette_control.palette_changed = 1;
 466             break;
 467
 468         case OPCODE_SET_PALETTE_COMPRESSED:
 469             debug_ipmovie("set palette compressed\n");
 470             url_fseek(pb, opcode_size, SEEK_CUR);
 471             break;
 472
 473         case OPCODE_SET_DECODING_MAP:
 474             debug_ipmovie("set decoding map\n");
 475
 476             /* log position and move on for now */
 477             s->decode_map_chunk_offset = url_ftell(pb);
 478             s->decode_map_chunk_size = opcode_size;
 479             url_fseek(pb, opcode_size, SEEK_CUR);
 480             break;
 481
 482         case OPCODE_VIDEO_DATA:
 483             debug_ipmovie("set video data\n");
 484
 485             /* log position and move on for now */
 486             s->video_chunk_offset = url_ftell(pb);
 487             s->video_chunk_size = opcode_size;
 488             url_fseek(pb, opcode_size, SEEK_CUR);
 489             break;
 490
 491         default:
 492             debug_ipmovie("*** unknown opcode type\n");
 493             chunk_type = CHUNK_BAD;
 494             break;
 495
 496         }
 497     }
 498
 499     /* make a note of where the stream is sitting */
 500     s->next_chunk_offset = url_ftell(pb);
 501
 502     /* dispatch the first of any pending packets */
 503     if ((chunk_type == CHUNK_VIDEO) || (chunk_type == CHUNK_AUDIO_ONLY))
 504         chunk_type = load_ipmovie_packet(s, pb, pkt);
 505
 506     return chunk_type;
 507 }
 508
 509 static int ipmovie_probe(AVProbeData *p)
 510 {
 511     if (strncmp(p->buf, IPMOVIE_SIGNATURE, IPMOVIE_SIGNATURE_SIZE) != 0)
 512         return 0;
 513
 514     return AVPROBE_SCORE_MAX;
 515 }
 516
 517 static int ipmovie_read_header(AVFormatContext *s,
 518                                AVFormatParameters *ap)
 519 {
 520     IPMVEContext *ipmovie = s->priv_data;
 521     ByteIOContext *pb = s->pb;
 522     AVPacket pkt;
 523     AVStream *st;
 524     unsigned char chunk_preamble[CHUNK_PREAMBLE_SIZE];
 525     int chunk_type;
 526
 527     /* initialize private context members */
 528     ipmovie->video_pts = ipmovie->audio_frame_count = 0;
 529     ipmovie->audio_chunk_offset = ipmovie->video_chunk_offset =
 530     ipmovie->decode_map_chunk_offset = 0;
 531
 532     /* on the first read, this will position the stream at the first chunk */
 533     ipmovie->next_chunk_offset = IPMOVIE_SIGNATURE_SIZE + 6;
 534
 535     /* process the first chunk which should be CHUNK_INIT_VIDEO */
 536     if (process_ipmovie_chunk(ipmovie, pb, &pkt) != CHUNK_INIT_VIDEO)
 537         return AVERROR_INVALIDDATA;
 538
 539     /* peek ahead to the next chunk-- if it is an init audio chunk, process
 540      * it; if it is the first video chunk, this is a silent file */
 541     if (get_buffer(pb, chunk_preamble, CHUNK_PREAMBLE_SIZE) !=
 542         CHUNK_PREAMBLE_SIZE)
 543         return AVERROR(EIO);
 544     chunk_type = AV_RL16(&chunk_preamble[2]);
 545     url_fseek(pb, -CHUNK_PREAMBLE_SIZE, SEEK_CUR);
 546
 547     if (chunk_type == CHUNK_VIDEO)
 548         ipmovie->audio_type = CODEC_ID_NONE;  /* no audio */
 549     else if (process_ipmovie_chunk(ipmovie, pb, &pkt) != CHUNK_INIT_AUDIO)
 550         return AVERROR_INVALIDDATA;
 551
 552     /* initialize the stream decoders */
 553     st = av_new_stream(s, 0);
 554     if (!st)
 555         return AVERROR(ENOMEM);
 556     av_set_pts_info(st, 33, 1, 90000);
 557     ipmovie->video_stream_index = st->index;
 558     st->codec->codec_type = CODEC_TYPE_VIDEO;
 559     st->codec->codec_id = CODEC_ID_INTERPLAY_VIDEO;
 560     st->codec->codec_tag = 0;  /* no fourcc */
 561     st->codec->width = ipmovie->video_width;
 562     st->codec->height = ipmovie->video_height;
 563
 564     /* palette considerations */
 565     st->codec->palctrl = &ipmovie->palette_control;
 566
 567     if (ipmovie->audio_type) {
 568         st = av_new_stream(s, 0);
 569         if (!st)
 570             return AVERROR(ENOMEM);
 571         av_set_pts_info(st, 33, 1, 90000);
 572         ipmovie->audio_stream_index = st->index;
 573         st->codec->codec_type = CODEC_TYPE_AUDIO;
 574         st->codec->codec_id = ipmovie->audio_type;
 575         st->codec->codec_tag = 0;  /* no tag */
 576         st->codec->channels = ipmovie->audio_channels;
 577         st->codec->sample_rate = ipmovie->audio_sample_rate;
 578         st->codec->bits_per_coded_sample = ipmovie->audio_bits;
 579         st->codec->bit_rate = st->codec->channels * st->codec->sample_rate *
 580             st->codec->bits_per_coded_sample;
 581         if (st->codec->codec_id == CODEC_ID_INTERPLAY_DPCM)
 582             st->codec->bit_rate /= 2;
 583         st->codec->block_align = st->codec->channels * st->codec->bits_per_coded_sample;
 584     }
 585
 586     return 0;
 587 }
 588
 589 static int ipmovie_read_packet(AVFormatContext *s,
 590                                AVPacket *pkt)
 591 {
 592     IPMVEContext *ipmovie = s->priv_data;
 593     ByteIOContext *pb = s->pb;
 594     int ret;
 595
 596     ret = process_ipmovie_chunk(ipmovie, pb, pkt);
 597     if (ret == CHUNK_BAD)
 598         ret = AVERROR_INVALIDDATA;
 599     else if (ret == CHUNK_EOF)
 600         ret = AVERROR(EIO);
 601     else if (ret == CHUNK_NOMEM)
 602         ret = AVERROR(ENOMEM);
 603     else if (ret == CHUNK_VIDEO)
 604         ret = 0;
 605     else
 606         ret = -1;
 607
 608     return ret;
 609 }
 610
 611 AVInputFormat ipmovie_demuxer = {
 612     "ipmovie",
 613     NULL_IF_CONFIG_SMALL("Interplay MVE format"),
 614     sizeof(IPMVEContext),
 615     ipmovie_probe,
 616     ipmovie_read_header,
 617     ipmovie_read_packet,
 618 };