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  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
  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/channel_layout.h"
  36. #include "libavutil/intreadwrite.h"
  37. #include "avformat.h"
  38. #include "internal.h"
  39.  
  40. #define CHUNK_PREAMBLE_SIZE 4
  41. #define OPCODE_PREAMBLE_SIZE 4
  42.  
  43. #define CHUNK_INIT_AUDIO   0x0000
  44. #define CHUNK_AUDIO_ONLY   0x0001
  45. #define CHUNK_INIT_VIDEO   0x0002
  46. #define CHUNK_VIDEO        0x0003
  47. #define CHUNK_SHUTDOWN     0x0004
  48. #define CHUNK_END          0x0005
  49. /* these last types are used internally */
  50. #define CHUNK_DONE         0xFFFC
  51. #define CHUNK_NOMEM        0xFFFD
  52. #define CHUNK_EOF          0xFFFE
  53. #define CHUNK_BAD          0xFFFF
  54.  
  55. #define OPCODE_END_OF_STREAM           0x00
  56. #define OPCODE_END_OF_CHUNK            0x01
  57. #define OPCODE_CREATE_TIMER            0x02
  58. #define OPCODE_INIT_AUDIO_BUFFERS      0x03
  59. #define OPCODE_START_STOP_AUDIO        0x04
  60. #define OPCODE_INIT_VIDEO_BUFFERS      0x05
  61. #define OPCODE_UNKNOWN_06              0x06
  62. #define OPCODE_SEND_BUFFER             0x07
  63. #define OPCODE_AUDIO_FRAME             0x08
  64. #define OPCODE_SILENCE_FRAME           0x09
  65. #define OPCODE_INIT_VIDEO_MODE         0x0A
  66. #define OPCODE_CREATE_GRADIENT         0x0B
  67. #define OPCODE_SET_PALETTE             0x0C
  68. #define OPCODE_SET_PALETTE_COMPRESSED  0x0D
  69. #define OPCODE_UNKNOWN_0E              0x0E
  70. #define OPCODE_SET_DECODING_MAP        0x0F
  71. #define OPCODE_UNKNOWN_10              0x10
  72. #define OPCODE_VIDEO_DATA              0x11
  73. #define OPCODE_UNKNOWN_12              0x12
  74. #define OPCODE_UNKNOWN_13              0x13
  75. #define OPCODE_UNKNOWN_14              0x14
  76. #define OPCODE_UNKNOWN_15              0x15
  77.  
  78. #define PALETTE_COUNT 256
  79.  
  80. typedef struct IPMVEContext {
  81.  
  82.     unsigned char *buf;
  83.     int buf_size;
  84.  
  85.     uint64_t frame_pts_inc;
  86.  
  87.     unsigned int video_bpp;
  88.     unsigned int video_width;
  89.     unsigned int video_height;
  90.     int64_t video_pts;
  91.     uint32_t     palette[256];
  92.     int          has_palette;
  93.     int          changed;
  94.  
  95.     unsigned int audio_bits;
  96.     unsigned int audio_channels;
  97.     unsigned int audio_sample_rate;
  98.     enum AVCodecID audio_type;
  99.     unsigned int audio_frame_count;
  100.  
  101.     int video_stream_index;
  102.     int audio_stream_index;
  103.  
  104.     int64_t audio_chunk_offset;
  105.     int audio_chunk_size;
  106.     int64_t video_chunk_offset;
  107.     int video_chunk_size;
  108.     int64_t decode_map_chunk_offset;
  109.     int decode_map_chunk_size;
  110.  
  111.     int64_t next_chunk_offset;
  112.  
  113. } IPMVEContext;
  114.  
  115. static int load_ipmovie_packet(IPMVEContext *s, AVIOContext *pb,
  116.     AVPacket *pkt) {
  117.  
  118.     int chunk_type;
  119.  
  120.     if (s->audio_chunk_offset && s->audio_channels && s->audio_bits) {
  121.         if (s->audio_type == AV_CODEC_ID_NONE) {
  122.             av_log(NULL, AV_LOG_ERROR, "Can not read audio packet before"
  123.                    "audio codec is known\n");
  124.                 return CHUNK_BAD;
  125.         }
  126.  
  127.         /* adjust for PCM audio by skipping chunk header */
  128.         if (s->audio_type != AV_CODEC_ID_INTERPLAY_DPCM) {
  129.             s->audio_chunk_offset += 6;
  130.             s->audio_chunk_size -= 6;
  131.         }
  132.  
  133.         avio_seek(pb, s->audio_chunk_offset, SEEK_SET);
  134.         s->audio_chunk_offset = 0;
  135.  
  136.         if (s->audio_chunk_size != av_get_packet(pb, pkt, s->audio_chunk_size))
  137.             return CHUNK_EOF;
  138.  
  139.         pkt->stream_index = s->audio_stream_index;
  140.         pkt->pts = s->audio_frame_count;
  141.  
  142.         /* audio frame maintenance */
  143.         if (s->audio_type != AV_CODEC_ID_INTERPLAY_DPCM)
  144.             s->audio_frame_count +=
  145.             (s->audio_chunk_size / s->audio_channels / (s->audio_bits / 8));
  146.         else
  147.             s->audio_frame_count +=
  148.                 (s->audio_chunk_size - 6 - s->audio_channels) / s->audio_channels;
  149.  
  150.         av_dlog(NULL, "sending audio frame with pts %"PRId64" (%d audio frames)\n",
  151.                 pkt->pts, s->audio_frame_count);
  152.  
  153.         chunk_type = CHUNK_VIDEO;
  154.  
  155.     } else if (s->decode_map_chunk_offset) {
  156.  
  157.         /* send both the decode map and the video data together */
  158.  
  159.         if (av_new_packet(pkt, s->decode_map_chunk_size + s->video_chunk_size))
  160.             return CHUNK_NOMEM;
  161.  
  162.         if (s->has_palette) {
  163.             uint8_t *pal;
  164.  
  165.             pal = av_packet_new_side_data(pkt, AV_PKT_DATA_PALETTE,
  166.                                           AVPALETTE_SIZE);
  167.             if (pal) {
  168.                 memcpy(pal, s->palette, AVPALETTE_SIZE);
  169.                 s->has_palette = 0;
  170.             }
  171.         }
  172.  
  173.         if (s->changed) {
  174.             ff_add_param_change(pkt, 0, 0, 0, s->video_width, s->video_height);
  175.             s->changed = 0;
  176.         }
  177.         pkt->pos= s->decode_map_chunk_offset;
  178.         avio_seek(pb, s->decode_map_chunk_offset, SEEK_SET);
  179.         s->decode_map_chunk_offset = 0;
  180.  
  181.         if (avio_read(pb, pkt->data, s->decode_map_chunk_size) !=
  182.             s->decode_map_chunk_size) {
  183.             av_free_packet(pkt);
  184.             return CHUNK_EOF;
  185.         }
  186.  
  187.         avio_seek(pb, s->video_chunk_offset, SEEK_SET);
  188.         s->video_chunk_offset = 0;
  189.  
  190.         if (avio_read(pb, pkt->data + s->decode_map_chunk_size,
  191.             s->video_chunk_size) != s->video_chunk_size) {
  192.             av_free_packet(pkt);
  193.             return CHUNK_EOF;
  194.         }
  195.  
  196.         pkt->stream_index = s->video_stream_index;
  197.         pkt->pts = s->video_pts;
  198.  
  199.         av_dlog(NULL, "sending video frame with pts %"PRId64"\n", pkt->pts);
  200.  
  201.         s->video_pts += s->frame_pts_inc;
  202.  
  203.         chunk_type = CHUNK_VIDEO;
  204.  
  205.     } else {
  206.  
  207.         avio_seek(pb, s->next_chunk_offset, SEEK_SET);
  208.         chunk_type = CHUNK_DONE;
  209.  
  210.     }
  211.  
  212.     return chunk_type;
  213. }
  214.  
  215. /* This function loads and processes a single chunk in an IP movie file.
  216.  * It returns the type of chunk that was processed. */
  217. static int process_ipmovie_chunk(IPMVEContext *s, AVIOContext *pb,
  218.     AVPacket *pkt)
  219. {
  220.     unsigned char chunk_preamble[CHUNK_PREAMBLE_SIZE];
  221.     int chunk_type;
  222.     int chunk_size;
  223.     unsigned char opcode_preamble[OPCODE_PREAMBLE_SIZE];
  224.     unsigned char opcode_type;
  225.     unsigned char opcode_version;
  226.     int opcode_size;
  227.     unsigned char scratch[1024];
  228.     int i, j;
  229.     int first_color, last_color;
  230.     int audio_flags;
  231.     unsigned char r, g, b;
  232.     unsigned int width, height;
  233.  
  234.     /* see if there are any pending packets */
  235.     chunk_type = load_ipmovie_packet(s, pb, pkt);
  236.     if (chunk_type != CHUNK_DONE)
  237.         return chunk_type;
  238.  
  239.     /* read the next chunk, wherever the file happens to be pointing */
  240.     if (url_feof(pb))
  241.         return CHUNK_EOF;
  242.     if (avio_read(pb, chunk_preamble, CHUNK_PREAMBLE_SIZE) !=
  243.         CHUNK_PREAMBLE_SIZE)
  244.         return CHUNK_BAD;
  245.     chunk_size = AV_RL16(&chunk_preamble[0]);
  246.     chunk_type = AV_RL16(&chunk_preamble[2]);
  247.  
  248.     av_dlog(NULL, "chunk type 0x%04X, 0x%04X bytes: ", chunk_type, chunk_size);
  249.  
  250.     switch (chunk_type) {
  251.  
  252.     case CHUNK_INIT_AUDIO:
  253.         av_dlog(NULL, "initialize audio\n");
  254.         break;
  255.  
  256.     case CHUNK_AUDIO_ONLY:
  257.         av_dlog(NULL, "audio only\n");
  258.         break;
  259.  
  260.     case CHUNK_INIT_VIDEO:
  261.         av_dlog(NULL, "initialize video\n");
  262.         break;
  263.  
  264.     case CHUNK_VIDEO:
  265.         av_dlog(NULL, "video (and audio)\n");
  266.         break;
  267.  
  268.     case CHUNK_SHUTDOWN:
  269.         av_dlog(NULL, "shutdown\n");
  270.         break;
  271.  
  272.     case CHUNK_END:
  273.         av_dlog(NULL, "end\n");
  274.         break;
  275.  
  276.     default:
  277.         av_dlog(NULL, "invalid chunk\n");
  278.         chunk_type = CHUNK_BAD;
  279.         break;
  280.  
  281.     }
  282.  
  283.     while ((chunk_size > 0) && (chunk_type != CHUNK_BAD)) {
  284.  
  285.         /* read the next chunk, wherever the file happens to be pointing */
  286.         if (url_feof(pb)) {
  287.             chunk_type = CHUNK_EOF;
  288.             break;
  289.         }
  290.         if (avio_read(pb, opcode_preamble, CHUNK_PREAMBLE_SIZE) !=
  291.             CHUNK_PREAMBLE_SIZE) {
  292.             chunk_type = CHUNK_BAD;
  293.             break;
  294.         }
  295.  
  296.         opcode_size = AV_RL16(&opcode_preamble[0]);
  297.         opcode_type = opcode_preamble[2];
  298.         opcode_version = opcode_preamble[3];
  299.  
  300.         chunk_size -= OPCODE_PREAMBLE_SIZE;
  301.         chunk_size -= opcode_size;
  302.         if (chunk_size < 0) {
  303.             av_dlog(NULL, "chunk_size countdown just went negative\n");
  304.             chunk_type = CHUNK_BAD;
  305.             break;
  306.         }
  307.  
  308.         av_dlog(NULL, "  opcode type %02X, version %d, 0x%04X bytes: ",
  309.                 opcode_type, opcode_version, opcode_size);
  310.         switch (opcode_type) {
  311.  
  312.         case OPCODE_END_OF_STREAM:
  313.             av_dlog(NULL, "end of stream\n");
  314.             avio_skip(pb, opcode_size);
  315.             break;
  316.  
  317.         case OPCODE_END_OF_CHUNK:
  318.             av_dlog(NULL, "end of chunk\n");
  319.             avio_skip(pb, opcode_size);
  320.             break;
  321.  
  322.         case OPCODE_CREATE_TIMER:
  323.             av_dlog(NULL, "create timer\n");
  324.             if ((opcode_version > 0) || (opcode_size > 6)) {
  325.                 av_dlog(NULL, "bad create_timer opcode\n");
  326.                 chunk_type = CHUNK_BAD;
  327.                 break;
  328.             }
  329.             if (avio_read(pb, scratch, opcode_size) !=
  330.                 opcode_size) {
  331.                 chunk_type = CHUNK_BAD;
  332.                 break;
  333.             }
  334.             s->frame_pts_inc = ((uint64_t)AV_RL32(&scratch[0])) * AV_RL16(&scratch[4]);
  335.             av_dlog(NULL, "  %.2f frames/second (timer div = %d, subdiv = %d)\n",
  336.                     1000000.0 / s->frame_pts_inc, AV_RL32(&scratch[0]),
  337.                     AV_RL16(&scratch[4]));
  338.             break;
  339.  
  340.         case OPCODE_INIT_AUDIO_BUFFERS:
  341.             av_dlog(NULL, "initialize audio buffers\n");
  342.             if ((opcode_version > 1) || (opcode_size > 10)) {
  343.                 av_dlog(NULL, "bad init_audio_buffers opcode\n");
  344.                 chunk_type = CHUNK_BAD;
  345.                 break;
  346.             }
  347.             if (avio_read(pb, scratch, opcode_size) !=
  348.                 opcode_size) {
  349.                 chunk_type = CHUNK_BAD;
  350.                 break;
  351.             }
  352.             s->audio_sample_rate = AV_RL16(&scratch[4]);
  353.             audio_flags = AV_RL16(&scratch[2]);
  354.             /* bit 0 of the flags: 0 = mono, 1 = stereo */
  355.             s->audio_channels = (audio_flags & 1) + 1;
  356.             /* bit 1 of the flags: 0 = 8 bit, 1 = 16 bit */
  357.             s->audio_bits = (((audio_flags >> 1) & 1) + 1) * 8;
  358.             /* bit 2 indicates compressed audio in version 1 opcode */
  359.             if ((opcode_version == 1) && (audio_flags & 0x4))
  360.                 s->audio_type = AV_CODEC_ID_INTERPLAY_DPCM;
  361.             else if (s->audio_bits == 16)
  362.                 s->audio_type = AV_CODEC_ID_PCM_S16LE;
  363.             else
  364.                 s->audio_type = AV_CODEC_ID_PCM_U8;
  365.             av_dlog(NULL, "audio: %d bits, %d Hz, %s, %s format\n",
  366.                     s->audio_bits, s->audio_sample_rate,
  367.                     (s->audio_channels == 2) ? "stereo" : "mono",
  368.                     (s->audio_type == AV_CODEC_ID_INTERPLAY_DPCM) ?
  369.                     "Interplay audio" : "PCM");
  370.             break;
  371.  
  372.         case OPCODE_START_STOP_AUDIO:
  373.             av_dlog(NULL, "start/stop audio\n");
  374.             avio_skip(pb, opcode_size);
  375.             break;
  376.  
  377.         case OPCODE_INIT_VIDEO_BUFFERS:
  378.             av_dlog(NULL, "initialize video buffers\n");
  379.             if ((opcode_version > 2) || (opcode_size > 8)) {
  380.                 av_dlog(NULL, "bad init_video_buffers opcode\n");
  381.                 chunk_type = CHUNK_BAD;
  382.                 break;
  383.             }
  384.             if (avio_read(pb, scratch, opcode_size) !=
  385.                 opcode_size) {
  386.                 chunk_type = CHUNK_BAD;
  387.                 break;
  388.             }
  389.             width  = AV_RL16(&scratch[0]) * 8;
  390.             height = AV_RL16(&scratch[2]) * 8;
  391.             if (width != s->video_width) {
  392.                 s->video_width = width;
  393.                 s->changed++;
  394.             }
  395.             if (height != s->video_height) {
  396.                 s->video_height = height;
  397.                 s->changed++;
  398.             }
  399.             if (opcode_version < 2 || !AV_RL16(&scratch[6])) {
  400.                 s->video_bpp = 8;
  401.             } else {
  402.                 s->video_bpp = 16;
  403.             }
  404.             av_dlog(NULL, "video resolution: %d x %d\n",
  405.                     s->video_width, s->video_height);
  406.             break;
  407.  
  408.         case OPCODE_UNKNOWN_06:
  409.         case OPCODE_UNKNOWN_0E:
  410.         case OPCODE_UNKNOWN_10:
  411.         case OPCODE_UNKNOWN_12:
  412.         case OPCODE_UNKNOWN_13:
  413.         case OPCODE_UNKNOWN_14:
  414.         case OPCODE_UNKNOWN_15:
  415.             av_dlog(NULL, "unknown (but documented) opcode %02X\n", opcode_type);
  416.             avio_skip(pb, opcode_size);
  417.             break;
  418.  
  419.         case OPCODE_SEND_BUFFER:
  420.             av_dlog(NULL, "send buffer\n");
  421.             avio_skip(pb, opcode_size);
  422.             break;
  423.  
  424.         case OPCODE_AUDIO_FRAME:
  425.             av_dlog(NULL, "audio frame\n");
  426.  
  427.             /* log position and move on for now */
  428.             s->audio_chunk_offset = avio_tell(pb);
  429.             s->audio_chunk_size = opcode_size;
  430.             avio_skip(pb, opcode_size);
  431.             break;
  432.  
  433.         case OPCODE_SILENCE_FRAME:
  434.             av_dlog(NULL, "silence frame\n");
  435.             avio_skip(pb, opcode_size);
  436.             break;
  437.  
  438.         case OPCODE_INIT_VIDEO_MODE:
  439.             av_dlog(NULL, "initialize video mode\n");
  440.             avio_skip(pb, opcode_size);
  441.             break;
  442.  
  443.         case OPCODE_CREATE_GRADIENT:
  444.             av_dlog(NULL, "create gradient\n");
  445.             avio_skip(pb, opcode_size);
  446.             break;
  447.  
  448.         case OPCODE_SET_PALETTE:
  449.             av_dlog(NULL, "set palette\n");
  450.             /* check for the logical maximum palette size
  451.              * (3 * 256 + 4 bytes) */
  452.             if (opcode_size > 0x304) {
  453.                 av_dlog(NULL, "demux_ipmovie: set_palette opcode too large\n");
  454.                 chunk_type = CHUNK_BAD;
  455.                 break;
  456.             }
  457.             if (avio_read(pb, scratch, opcode_size) != opcode_size) {
  458.                 chunk_type = CHUNK_BAD;
  459.                 break;
  460.             }
  461.  
  462.             /* load the palette into internal data structure */
  463.             first_color = AV_RL16(&scratch[0]);
  464.             last_color = first_color + AV_RL16(&scratch[2]) - 1;
  465.             /* sanity check (since they are 16 bit values) */
  466.             if ((first_color > 0xFF) || (last_color > 0xFF)) {
  467.                 av_dlog(NULL, "demux_ipmovie: set_palette indexes out of range (%d -> %d)\n",
  468.                     first_color, last_color);
  469.                 chunk_type = CHUNK_BAD;
  470.                 break;
  471.             }
  472.             j = 4;  /* offset of first palette data */
  473.             for (i = first_color; i <= last_color; i++) {
  474.                 /* the palette is stored as a 6-bit VGA palette, thus each
  475.                  * component is shifted up to a 8-bit range */
  476.                 r = scratch[j++] * 4;
  477.                 g = scratch[j++] * 4;
  478.                 b = scratch[j++] * 4;
  479.                 s->palette[i] = (0xFFU << 24) | (r << 16) | (g << 8) | (b);
  480.                 s->palette[i] |= s->palette[i] >> 6 & 0x30303;
  481.             }
  482.             s->has_palette = 1;
  483.             break;
  484.  
  485.         case OPCODE_SET_PALETTE_COMPRESSED:
  486.             av_dlog(NULL, "set palette compressed\n");
  487.             avio_skip(pb, opcode_size);
  488.             break;
  489.  
  490.         case OPCODE_SET_DECODING_MAP:
  491.             av_dlog(NULL, "set decoding map\n");
  492.  
  493.             /* log position and move on for now */
  494.             s->decode_map_chunk_offset = avio_tell(pb);
  495.             s->decode_map_chunk_size = opcode_size;
  496.             avio_skip(pb, opcode_size);
  497.             break;
  498.  
  499.         case OPCODE_VIDEO_DATA:
  500.             av_dlog(NULL, "set video data\n");
  501.  
  502.             /* log position and move on for now */
  503.             s->video_chunk_offset = avio_tell(pb);
  504.             s->video_chunk_size = opcode_size;
  505.             avio_skip(pb, opcode_size);
  506.             break;
  507.  
  508.         default:
  509.             av_dlog(NULL, "*** unknown opcode type\n");
  510.             chunk_type = CHUNK_BAD;
  511.             break;
  512.  
  513.         }
  514.     }
  515.  
  516.     /* make a note of where the stream is sitting */
  517.     s->next_chunk_offset = avio_tell(pb);
  518.  
  519.     /* dispatch the first of any pending packets */
  520.     if ((chunk_type == CHUNK_VIDEO) || (chunk_type == CHUNK_AUDIO_ONLY))
  521.         chunk_type = load_ipmovie_packet(s, pb, pkt);
  522.  
  523.     return chunk_type;
  524. }
  525.  
  526. static const char signature[] = "Interplay MVE File\x1A\0\x1A";
  527.  
  528. static int ipmovie_probe(AVProbeData *p)
  529. {
  530.     const uint8_t *b = p->buf;
  531.     const uint8_t *b_end = p->buf + p->buf_size - sizeof(signature);
  532.     do {
  533.         if (b[0] == signature[0] && memcmp(b, signature, sizeof(signature)) == 0)
  534.             return AVPROBE_SCORE_MAX;
  535.         b++;
  536.     } while (b < b_end);
  537.  
  538.     return 0;
  539. }
  540.  
  541. static int ipmovie_read_header(AVFormatContext *s)
  542. {
  543.     IPMVEContext *ipmovie = s->priv_data;
  544.     AVIOContext *pb = s->pb;
  545.     AVPacket pkt;
  546.     AVStream *st;
  547.     unsigned char chunk_preamble[CHUNK_PREAMBLE_SIZE];
  548.     int chunk_type, i;
  549.     uint8_t signature_buffer[sizeof(signature)];
  550.  
  551.     avio_read(pb, signature_buffer, sizeof(signature_buffer));
  552.     while (memcmp(signature_buffer, signature, sizeof(signature))) {
  553.         memmove(signature_buffer, signature_buffer + 1, sizeof(signature_buffer) - 1);
  554.         signature_buffer[sizeof(signature_buffer) - 1] = avio_r8(pb);
  555.         if (url_feof(pb))
  556.             return AVERROR_EOF;
  557.     }
  558.     /* initialize private context members */
  559.     ipmovie->video_pts = ipmovie->audio_frame_count = 0;
  560.     ipmovie->audio_chunk_offset = ipmovie->video_chunk_offset =
  561.     ipmovie->decode_map_chunk_offset = 0;
  562.  
  563.     /* on the first read, this will position the stream at the first chunk */
  564.     ipmovie->next_chunk_offset = avio_tell(pb) + 4;
  565.  
  566.     for (i = 0; i < 256; i++)
  567.         ipmovie->palette[i] = 0xFFU << 24;
  568.  
  569.     /* process the first chunk which should be CHUNK_INIT_VIDEO */
  570.     if (process_ipmovie_chunk(ipmovie, pb, &pkt) != CHUNK_INIT_VIDEO)
  571.         return AVERROR_INVALIDDATA;
  572.  
  573.     /* peek ahead to the next chunk-- if it is an init audio chunk, process
  574.      * it; if it is the first video chunk, this is a silent file */
  575.     if (avio_read(pb, chunk_preamble, CHUNK_PREAMBLE_SIZE) !=
  576.         CHUNK_PREAMBLE_SIZE)
  577.         return AVERROR(EIO);
  578.     chunk_type = AV_RL16(&chunk_preamble[2]);
  579.     avio_seek(pb, -CHUNK_PREAMBLE_SIZE, SEEK_CUR);
  580.  
  581.     if (chunk_type == CHUNK_VIDEO)
  582.         ipmovie->audio_type = AV_CODEC_ID_NONE;  /* no audio */
  583.     else if (process_ipmovie_chunk(ipmovie, pb, &pkt) != CHUNK_INIT_AUDIO)
  584.         return AVERROR_INVALIDDATA;
  585.  
  586.     /* initialize the stream decoders */
  587.     st = avformat_new_stream(s, NULL);
  588.     if (!st)
  589.         return AVERROR(ENOMEM);
  590.     avpriv_set_pts_info(st, 63, 1, 1000000);
  591.     ipmovie->video_stream_index = st->index;
  592.     st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
  593.     st->codec->codec_id = AV_CODEC_ID_INTERPLAY_VIDEO;
  594.     st->codec->codec_tag = 0;  /* no fourcc */
  595.     st->codec->width = ipmovie->video_width;
  596.     st->codec->height = ipmovie->video_height;
  597.     st->codec->bits_per_coded_sample = ipmovie->video_bpp;
  598.  
  599.     if (ipmovie->audio_type) {
  600.         st = avformat_new_stream(s, NULL);
  601.         if (!st)
  602.             return AVERROR(ENOMEM);
  603.         avpriv_set_pts_info(st, 32, 1, ipmovie->audio_sample_rate);
  604.         ipmovie->audio_stream_index = st->index;
  605.         st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  606.         st->codec->codec_id = ipmovie->audio_type;
  607.         st->codec->codec_tag = 0;  /* no tag */
  608.         st->codec->channels = ipmovie->audio_channels;
  609.         st->codec->channel_layout = st->codec->channels == 1 ? AV_CH_LAYOUT_MONO :
  610.                                                                AV_CH_LAYOUT_STEREO;
  611.         st->codec->sample_rate = ipmovie->audio_sample_rate;
  612.         st->codec->bits_per_coded_sample = ipmovie->audio_bits;
  613.         st->codec->bit_rate = st->codec->channels * st->codec->sample_rate *
  614.             st->codec->bits_per_coded_sample;
  615.         if (st->codec->codec_id == AV_CODEC_ID_INTERPLAY_DPCM)
  616.             st->codec->bit_rate /= 2;
  617.         st->codec->block_align = st->codec->channels * st->codec->bits_per_coded_sample;
  618.     }
  619.  
  620.     return 0;
  621. }
  622.  
  623. static int ipmovie_read_packet(AVFormatContext *s,
  624.                                AVPacket *pkt)
  625. {
  626.     IPMVEContext *ipmovie = s->priv_data;
  627.     AVIOContext *pb = s->pb;
  628.     int ret;
  629.  
  630.     for (;;) {
  631.     ret = process_ipmovie_chunk(ipmovie, pb, pkt);
  632.     if (ret == CHUNK_BAD)
  633.         ret = AVERROR_INVALIDDATA;
  634.     else if (ret == CHUNK_EOF)
  635.         ret = AVERROR(EIO);
  636.     else if (ret == CHUNK_NOMEM)
  637.         ret = AVERROR(ENOMEM);
  638.     else if (ret == CHUNK_VIDEO)
  639.         ret = 0;
  640.     else if (ret == CHUNK_INIT_VIDEO || ret == CHUNK_INIT_AUDIO)
  641.         continue;
  642.     else
  643.         ret = -1;
  644.  
  645.     return ret;
  646.     }
  647. }
  648.  
  649. AVInputFormat ff_ipmovie_demuxer = {
  650.     .name           = "ipmovie",
  651.     .long_name      = NULL_IF_CONFIG_SMALL("Interplay MVE"),
  652.     .priv_data_size = sizeof(IPMVEContext),
  653.     .read_probe     = ipmovie_probe,
  654.     .read_header    = ipmovie_read_header,
  655.     .read_packet    = ipmovie_read_packet,
  656. };
  657.