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FFmpeg/libavformat/ffmdec.c

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  1. /*

  2.  * FFM (ffserver live feed) demuxer

  3.  * Copyright (c) 2001 Fabrice Bellard

  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. #include "libavutil/intreadwrite.h"

  23. #include "libavutil/intfloat.h"

  24. #include "avformat.h"

  25. #include "internal.h"

  26. #include "ffm.h"

  27. #include "avio_internal.h"

  28. 

  29. static int ffm_is_avail_data(AVFormatContext *s, int size)

  30. {

  31.     FFMContext *ffm = s->priv_data;

  32.     int64_t pos, avail_size;

  33.     int len;

  34. 

  35.     len = ffm->packet_end - ffm->packet_ptr;

  36.     if (size <= len)

  37.         return 1;

  38.     pos = avio_tell(s->pb);

  39.     if (!ffm->write_index) {

  40.         if (pos == ffm->file_size)

  41.             return AVERROR_EOF;

  42.         avail_size = ffm->file_size - pos;

  43.     } else {

  44.     if (pos == ffm->write_index) {

  45.         /* exactly at the end of stream */

  46.         return AVERROR(EAGAIN);

  47.     } else if (pos < ffm->write_index) {

  48.         avail_size = ffm->write_index - pos;

  49.     } else {

  50.         avail_size = (ffm->file_size - pos) + (ffm->write_index - FFM_PACKET_SIZE);

  51.     }

  52.     }

  53.     avail_size = (avail_size / ffm->packet_size) * (ffm->packet_size - FFM_HEADER_SIZE) + len;

  54.     if (size <= avail_size)

  55.         return 1;

  56.     else

  57.         return AVERROR(EAGAIN);

  58. }

  59. 

  60. static int ffm_resync(AVFormatContext *s, int state)

  61. {

  62.     av_log(s, AV_LOG_ERROR, "resyncing\n");

  63.     while (state != PACKET_ID) {

  64.         if (url_feof(s->pb)) {

  65.             av_log(s, AV_LOG_ERROR, "cannot find FFM syncword\n");

  66.             return -1;

  67.         }

  68.         state = (state << 8) | avio_r8(s->pb);

  69.     }

  70.     return 0;

  71. }

  72. 

  73. /* first is true if we read the frame header */

  74. static int ffm_read_data(AVFormatContext *s,

  75.                          uint8_t *buf, int size, int header)

  76. {

  77.     FFMContext *ffm = s->priv_data;

  78.     AVIOContext *pb = s->pb;

  79.     int len, fill_size, size1, frame_offset, id;

  80. 

  81.     size1 = size;

  82.     while (size > 0) {

  83.     redo:

  84.         len = ffm->packet_end - ffm->packet_ptr;

  85.         if (len < 0)

  86.             return -1;

  87.         if (len > size)

  88.             len = size;

  89.         if (len == 0) {

  90.             if (avio_tell(pb) == ffm->file_size)

  91.                 avio_seek(pb, ffm->packet_size, SEEK_SET);

  92.     retry_read:

  93.             if (pb->buffer_size != ffm->packet_size) {

  94.                 int64_t tell = avio_tell(pb);

  95.                 ffio_set_buf_size(pb, ffm->packet_size);

  96.                 avio_seek(pb, tell, SEEK_SET);

  97.             }

  98.             id = avio_rb16(pb); /* PACKET_ID */

  99.             if (id != PACKET_ID)

  100.                 if (ffm_resync(s, id) < 0)

  101.                     return -1;

  102.             fill_size = avio_rb16(pb);

  103.             ffm->dts = avio_rb64(pb);

  104.             frame_offset = avio_rb16(pb);

  105.             avio_read(pb, ffm->packet, ffm->packet_size - FFM_HEADER_SIZE);

  106.             ffm->packet_end = ffm->packet + (ffm->packet_size - FFM_HEADER_SIZE - fill_size);

  107.             if (ffm->packet_end < ffm->packet || frame_offset < 0)

  108.                 return -1;

  109.             /* if first packet or resynchronization packet, we must

  110.                handle it specifically */

  111.             if (ffm->first_packet || (frame_offset & 0x8000)) {

  112.                 if (!frame_offset) {

  113.                     /* This packet has no frame headers in it */

  114.                     if (avio_tell(pb) >= ffm->packet_size * 3LL) {

  115.                         avio_seek(pb, -ffm->packet_size * 2LL, SEEK_CUR);

  116.                         goto retry_read;

  117.                     }

  118.                     /* This is bad, we cannot find a valid frame header */

  119.                     return 0;

  120.                 }

  121.                 ffm->first_packet = 0;

  122.                 if ((frame_offset & 0x7fff) < FFM_HEADER_SIZE)

  123.                     return -1;

  124.                 ffm->packet_ptr = ffm->packet + (frame_offset & 0x7fff) - FFM_HEADER_SIZE;

  125.                 if (!header)

  126.                     break;

  127.             } else {

  128.                 ffm->packet_ptr = ffm->packet;

  129.             }

  130.             goto redo;

  131.         }

  132.         memcpy(buf, ffm->packet_ptr, len);

  133.         buf += len;

  134.         ffm->packet_ptr += len;

  135.         size -= len;

  136.         header = 0;

  137.     }

  138.     return size1 - size;

  139. }

  140. 

  141. /* ensure that acutal seeking happens between FFM_PACKET_SIZE

  142.    and file_size - FFM_PACKET_SIZE */

  143. static int64_t ffm_seek1(AVFormatContext *s, int64_t pos1)

  144. {

  145.     FFMContext *ffm = s->priv_data;

  146.     AVIOContext *pb = s->pb;

  147.     int64_t pos;

  148. 

  149.     pos = FFMIN(pos1, ffm->file_size - FFM_PACKET_SIZE);

  150.     pos = FFMAX(pos, FFM_PACKET_SIZE);

  151.     av_dlog(s, "seek to %"PRIx64" -> %"PRIx64"\n", pos1, pos);

  152.     return avio_seek(pb, pos, SEEK_SET);

  153. }

  154. 

  155. static int64_t get_dts(AVFormatContext *s, int64_t pos)

  156. {

  157.     AVIOContext *pb = s->pb;

  158.     int64_t dts;

  159. 

  160.     ffm_seek1(s, pos);

  161.     avio_skip(pb, 4);

  162.     dts = avio_rb64(pb);

  163.     av_dlog(s, "dts=%0.6f\n", dts / 1000000.0);

  164.     return dts;

  165. }

  166. 

  167. static void adjust_write_index(AVFormatContext *s)

  168. {

  169.     FFMContext *ffm = s->priv_data;

  170.     AVIOContext *pb = s->pb;

  171.     int64_t pts;

  172.     //int64_t orig_write_index = ffm->write_index;

  173.     int64_t pos_min, pos_max;

  174.     int64_t pts_start;

  175.     int64_t ptr = avio_tell(pb);

  176. 

  177. 

  178.     pos_min = 0;

  179.     pos_max = ffm->file_size - 2 * FFM_PACKET_SIZE;

  180. 

  181.     pts_start = get_dts(s, pos_min);

  182. 

  183.     pts = get_dts(s, pos_max);

  184. 

  185.     if (pts - 100000 > pts_start)

  186.         goto end;

  187. 

  188.     ffm->write_index = FFM_PACKET_SIZE;

  189. 

  190.     pts_start = get_dts(s, pos_min);

  191. 

  192.     pts = get_dts(s, pos_max);

  193. 

  194.     if (pts - 100000 <= pts_start) {

  195.         while (1) {

  196.             int64_t newpos;

  197.             int64_t newpts;

  198. 

  199.             newpos = ((pos_max + pos_min) / (2 * FFM_PACKET_SIZE)) * FFM_PACKET_SIZE;

  200. 

  201.             if (newpos == pos_min)

  202.                 break;

  203. 

  204.             newpts = get_dts(s, newpos);

  205. 

  206.             if (newpts - 100000 <= pts) {

  207.                 pos_max = newpos;

  208.                 pts = newpts;

  209.             } else {

  210.                 pos_min = newpos;

  211.             }

  212.         }

  213.         ffm->write_index += pos_max;

  214.     }

  215. 

  216.  end:

  217.     avio_seek(pb, ptr, SEEK_SET);

  218. }

  219. 

  220. 

  221. static int ffm_close(AVFormatContext *s)

  222. {

  223.     int i;

  224. 

  225.     for (i = 0; i < s->nb_streams; i++)

  226.         av_freep(&s->streams[i]->codec->rc_eq);

  227. 

  228.     return 0;

  229. }

  230. 

  231. static int ffm2_read_header(AVFormatContext *s)

  232. {

  233.     FFMContext *ffm = s->priv_data;

  234.     AVStream *st;

  235.     AVIOContext *pb = s->pb;

  236.     AVCodecContext *codec;

  237. 

  238.     ffm->packet_size = avio_rb32(pb);

  239.     if (ffm->packet_size != FFM_PACKET_SIZE)

  240.         goto fail;

  241.     ffm->write_index = avio_rb64(pb);

  242.     /* get also filesize */

  243.     if (pb->seekable) {

  244.         ffm->file_size = avio_size(pb);

  245.         if (ffm->write_index && 0)

  246.             adjust_write_index(s);

  247.     } else {

  248.         ffm->file_size = (UINT64_C(1) << 63) - 1;

  249.     }

  250. 

  251.     while(!url_feof(pb)) {

  252.         unsigned id = avio_rb32(pb);

  253.         unsigned size = avio_rb32(pb);

  254.         int64_t next = avio_tell(pb) + size;

  255.         char rc_eq_buf[128];

  256. 

  257.         if(!id)

  258.             break;

  259. 

  260.         switch(id) {

  261.         case MKBETAG('M', 'A', 'I', 'N'):

  262.             avio_rb32(pb); /* nb_streams */

  263.             avio_rb32(pb); /* total bitrate */

  264.             break;

  265.         case MKBETAG('C', 'O', 'M', 'M'):

  266.             st = avformat_new_stream(s, NULL);

  267.             if (!st)

  268.                 goto fail;

  269. 

  270.             avpriv_set_pts_info(st, 64, 1, 1000000);

  271. 

  272.             codec = st->codec;

  273.             /* generic info */

  274.             codec->codec_id = avio_rb32(pb);

  275.             codec->codec_type = avio_r8(pb);

  276.             codec->bit_rate = avio_rb32(pb);

  277.             codec->flags = avio_rb32(pb);

  278.             codec->flags2 = avio_rb32(pb);

  279.             codec->debug = avio_rb32(pb);

  280.             if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {

  281.                 codec->extradata_size = avio_rb32(pb);

  282.                 codec->extradata = av_malloc(codec->extradata_size);

  283.                 if (!codec->extradata)

  284.                     return AVERROR(ENOMEM);

  285.                 avio_read(pb, codec->extradata, codec->extradata_size);

  286.             }

  287.             avio_seek(pb, next, SEEK_SET);

  288.             id = avio_rb32(pb);

  289.             size = avio_rb32(pb);

  290.             next = avio_tell(pb) + size;

  291.             switch(id) {

  292.             case MKBETAG('S', 'T', 'V', 'I'):

  293.                 codec->time_base.num = avio_rb32(pb);

  294.                 codec->time_base.den = avio_rb32(pb);

  295.                 codec->width = avio_rb16(pb);

  296.                 codec->height = avio_rb16(pb);

  297.                 codec->gop_size = avio_rb16(pb);

  298.                 codec->pix_fmt = avio_rb32(pb);

  299.                 codec->qmin = avio_r8(pb);

  300.                 codec->qmax = avio_r8(pb);

  301.                 codec->max_qdiff = avio_r8(pb);

  302.                 codec->qcompress = avio_rb16(pb) / 10000.0;

  303.                 codec->qblur = avio_rb16(pb) / 10000.0;

  304.                 codec->bit_rate_tolerance = avio_rb32(pb);

  305.                 avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));

  306.                 codec->rc_eq = av_strdup(rc_eq_buf);

  307.                 codec->rc_max_rate = avio_rb32(pb);

  308.                 codec->rc_min_rate = avio_rb32(pb);

  309.                 codec->rc_buffer_size = avio_rb32(pb);

  310.                 codec->i_quant_factor = av_int2double(avio_rb64(pb));

  311.                 codec->b_quant_factor = av_int2double(avio_rb64(pb));

  312.                 codec->i_quant_offset = av_int2double(avio_rb64(pb));

  313.                 codec->b_quant_offset = av_int2double(avio_rb64(pb));

  314.                 codec->dct_algo = avio_rb32(pb);

  315.                 codec->strict_std_compliance = avio_rb32(pb);

  316.                 codec->max_b_frames = avio_rb32(pb);

  317.                 codec->mpeg_quant = avio_rb32(pb);

  318.                 codec->intra_dc_precision = avio_rb32(pb);

  319.                 codec->me_method = avio_rb32(pb);

  320.                 codec->mb_decision = avio_rb32(pb);

  321.                 codec->nsse_weight = avio_rb32(pb);

  322.                 codec->frame_skip_cmp = avio_rb32(pb);

  323.                 codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));

  324.                 codec->codec_tag = avio_rb32(pb);

  325.                 codec->thread_count = avio_r8(pb);

  326.                 codec->coder_type = avio_rb32(pb);

  327.                 codec->me_cmp = avio_rb32(pb);

  328.                 codec->me_subpel_quality = avio_rb32(pb);

  329.                 codec->me_range = avio_rb32(pb);

  330.                 codec->keyint_min = avio_rb32(pb);

  331.                 codec->scenechange_threshold = avio_rb32(pb);

  332.                 codec->b_frame_strategy = avio_rb32(pb);

  333.                 codec->qcompress = av_int2double(avio_rb64(pb));

  334.                 codec->qblur = av_int2double(avio_rb64(pb));

  335.                 codec->max_qdiff = avio_rb32(pb);

  336.                 codec->refs = avio_rb32(pb);

  337.                 break;

  338.             case MKBETAG('S', 'T', 'A', 'U'):

  339.                 codec->sample_rate = avio_rb32(pb);

  340.                 codec->channels = avio_rl16(pb);

  341.                 codec->frame_size = avio_rl16(pb);

  342.                 break;

  343.             }

  344.             break;

  345.         }

  346.         avio_seek(pb, next, SEEK_SET);

  347.     }

  348. 

  349.     /* get until end of block reached */

  350.     while ((avio_tell(pb) % ffm->packet_size) != 0)

  351.         avio_r8(pb);

  352. 

  353.     /* init packet demux */

  354.     ffm->packet_ptr = ffm->packet;

  355.     ffm->packet_end = ffm->packet;

  356.     ffm->frame_offset = 0;

  357.     ffm->dts = 0;

  358.     ffm->read_state = READ_HEADER;

  359.     ffm->first_packet = 1;

  360.     return 0;

  361.  fail:

  362.     ffm_close(s);

  363.     return -1;

  364. }

  365. 

  366. static int ffm_read_header(AVFormatContext *s)

  367. {

  368.     FFMContext *ffm = s->priv_data;

  369.     AVStream *st;

  370.     AVIOContext *pb = s->pb;

  371.     AVCodecContext *codec;

  372.     int i, nb_streams;

  373.     uint32_t tag;

  374. 

  375.     /* header */

  376.     tag = avio_rl32(pb);

  377.     if (tag == MKTAG('F', 'F', 'M', '2'))

  378.         return ffm2_read_header(s);

  379.     if (tag != MKTAG('F', 'F', 'M', '1'))

  380.         goto fail;

  381.     ffm->packet_size = avio_rb32(pb);

  382.     if (ffm->packet_size != FFM_PACKET_SIZE)

  383.         goto fail;

  384.     ffm->write_index = avio_rb64(pb);

  385.     /* get also filesize */

  386.     if (pb->seekable) {

  387.         ffm->file_size = avio_size(pb);

  388.         if (ffm->write_index && 0)

  389.             adjust_write_index(s);

  390.     } else {

  391.         ffm->file_size = (UINT64_C(1) << 63) - 1;

  392.     }

  393. 

  394.     nb_streams = avio_rb32(pb);

  395.     avio_rb32(pb); /* total bitrate */

  396.     /* read each stream */

  397.     for(i=0;i<nb_streams;i++) {

  398.         char rc_eq_buf[128];

  399. 

  400.         st = avformat_new_stream(s, NULL);

  401.         if (!st)

  402.             goto fail;

  403. 

  404.         avpriv_set_pts_info(st, 64, 1, 1000000);

  405. 

  406.         codec = st->codec;

  407.         /* generic info */

  408.         codec->codec_id = avio_rb32(pb);

  409.         codec->codec_type = avio_r8(pb); /* codec_type */

  410.         codec->bit_rate = avio_rb32(pb);

  411.         codec->flags = avio_rb32(pb);

  412.         codec->flags2 = avio_rb32(pb);

  413.         codec->debug = avio_rb32(pb);

  414.         /* specific info */

  415.         switch(codec->codec_type) {

  416.         case AVMEDIA_TYPE_VIDEO:

  417.             codec->time_base.num = avio_rb32(pb);

  418.             codec->time_base.den = avio_rb32(pb);

  419.             codec->width = avio_rb16(pb);

  420.             codec->height = avio_rb16(pb);

  421.             codec->gop_size = avio_rb16(pb);

  422.             codec->pix_fmt = avio_rb32(pb);

  423.             codec->qmin = avio_r8(pb);

  424.             codec->qmax = avio_r8(pb);

  425.             codec->max_qdiff = avio_r8(pb);

  426.             codec->qcompress = avio_rb16(pb) / 10000.0;

  427.             codec->qblur = avio_rb16(pb) / 10000.0;

  428.             codec->bit_rate_tolerance = avio_rb32(pb);

  429.             avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));

  430.             codec->rc_eq = av_strdup(rc_eq_buf);

  431.             codec->rc_max_rate = avio_rb32(pb);

  432.             codec->rc_min_rate = avio_rb32(pb);

  433.             codec->rc_buffer_size = avio_rb32(pb);

  434.             codec->i_quant_factor = av_int2double(avio_rb64(pb));

  435.             codec->b_quant_factor = av_int2double(avio_rb64(pb));

  436.             codec->i_quant_offset = av_int2double(avio_rb64(pb));

  437.             codec->b_quant_offset = av_int2double(avio_rb64(pb));

  438.             codec->dct_algo = avio_rb32(pb);

  439.             codec->strict_std_compliance = avio_rb32(pb);

  440.             codec->max_b_frames = avio_rb32(pb);

  441.             codec->mpeg_quant = avio_rb32(pb);

  442.             codec->intra_dc_precision = avio_rb32(pb);

  443.             codec->me_method = avio_rb32(pb);

  444.             codec->mb_decision = avio_rb32(pb);

  445.             codec->nsse_weight = avio_rb32(pb);

  446.             codec->frame_skip_cmp = avio_rb32(pb);

  447.             codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));

  448.             codec->codec_tag = avio_rb32(pb);

  449.             codec->thread_count = avio_r8(pb);

  450.             codec->coder_type = avio_rb32(pb);

  451.             codec->me_cmp = avio_rb32(pb);

  452.             codec->me_subpel_quality = avio_rb32(pb);

  453.             codec->me_range = avio_rb32(pb);

  454.             codec->keyint_min = avio_rb32(pb);

  455.             codec->scenechange_threshold = avio_rb32(pb);

  456.             codec->b_frame_strategy = avio_rb32(pb);

  457.             codec->qcompress = av_int2double(avio_rb64(pb));

  458.             codec->qblur = av_int2double(avio_rb64(pb));

  459.             codec->max_qdiff = avio_rb32(pb);

  460.             codec->refs = avio_rb32(pb);

  461.             break;

  462.         case AVMEDIA_TYPE_AUDIO:

  463.             codec->sample_rate = avio_rb32(pb);

  464.             codec->channels = avio_rl16(pb);

  465.             codec->frame_size = avio_rl16(pb);

  466.             break;

  467.         default:

  468.             goto fail;

  469.         }

  470.         if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {

  471.             codec->extradata_size = avio_rb32(pb);

  472.             codec->extradata = av_malloc(codec->extradata_size);

  473.             if (!codec->extradata)

  474.                 return AVERROR(ENOMEM);

  475.             avio_read(pb, codec->extradata, codec->extradata_size);

  476.         }

  477.     }

  478. 

  479.     /* get until end of block reached */

  480.     while ((avio_tell(pb) % ffm->packet_size) != 0)

  481.         avio_r8(pb);

  482. 

  483.     /* init packet demux */

  484.     ffm->packet_ptr = ffm->packet;

  485.     ffm->packet_end = ffm->packet;

  486.     ffm->frame_offset = 0;

  487.     ffm->dts = 0;

  488.     ffm->read_state = READ_HEADER;

  489.     ffm->first_packet = 1;

  490.     return 0;

  491.  fail:

  492.     ffm_close(s);

  493.     return -1;

  494. }

  495. 

  496. /* return < 0 if eof */

  497. static int ffm_read_packet(AVFormatContext *s, AVPacket *pkt)

  498. {

  499.     int size;

  500.     FFMContext *ffm = s->priv_data;

  501.     int duration, ret;

  502. 

  503.     switch(ffm->read_state) {

  504.     case READ_HEADER:

  505.         if ((ret = ffm_is_avail_data(s, FRAME_HEADER_SIZE+4)) < 0)

  506.             return ret;

  507. 

  508.         av_dlog(s, "pos=%08"PRIx64" spos=%"PRIx64", write_index=%"PRIx64" size=%"PRIx64"\n",

  509.                avio_tell(s->pb), s->pb->pos, ffm->write_index, ffm->file_size);

  510.         if (ffm_read_data(s, ffm->header, FRAME_HEADER_SIZE, 1) !=

  511.             FRAME_HEADER_SIZE)

  512.             return -1;

  513.         if (ffm->header[1] & FLAG_DTS)

  514.             if (ffm_read_data(s, ffm->header+16, 4, 1) != 4)

  515.                 return -1;

  516.         ffm->read_state = READ_DATA;

  517.         /* fall thru */

  518.     case READ_DATA:

  519.         size = AV_RB24(ffm->header + 2);

  520.         if ((ret = ffm_is_avail_data(s, size)) < 0)

  521.             return ret;

  522. 

  523.         duration = AV_RB24(ffm->header + 5);

  524. 

  525.         if (av_new_packet(pkt, size) < 0) {

  526.             return AVERROR(ENOMEM);

  527.         }

  528.         pkt->stream_index = ffm->header[0];

  529.         if ((unsigned)pkt->stream_index >= s->nb_streams) {

  530.             av_log(s, AV_LOG_ERROR, "invalid stream index %d\n", pkt->stream_index);

  531.             av_free_packet(pkt);

  532.             ffm->read_state = READ_HEADER;

  533.             return -1;

  534.         }

  535.         pkt->pos = avio_tell(s->pb);

  536.         if (ffm->header[1] & FLAG_KEY_FRAME)

  537.             pkt->flags |= AV_PKT_FLAG_KEY;

  538. 

  539.         ffm->read_state = READ_HEADER;

  540.         if (ffm_read_data(s, pkt->data, size, 0) != size) {

  541.             /* bad case: desynchronized packet. we cancel all the packet loading */

  542.             av_free_packet(pkt);

  543.             return -1;

  544.         }

  545.         pkt->pts = AV_RB64(ffm->header+8);

  546.         if (ffm->header[1] & FLAG_DTS)

  547.             pkt->dts = pkt->pts - AV_RB32(ffm->header+16);

  548.         else

  549.             pkt->dts = pkt->pts;

  550.         pkt->duration = duration;

  551.         break;

  552.     }

  553.     return 0;

  554. }

  555. 

  556. /* seek to a given time in the file. The file read pointer is

  557.    positioned at or before pts. XXX: the following code is quite

  558.    approximative */

  559. static int ffm_seek(AVFormatContext *s, int stream_index, int64_t wanted_pts, int flags)

  560. {

  561.     FFMContext *ffm = s->priv_data;

  562.     int64_t pos_min, pos_max, pos;

  563.     int64_t pts_min, pts_max, pts;

  564.     double pos1;

  565. 

  566.     av_dlog(s, "wanted_pts=%0.6f\n", wanted_pts / 1000000.0);

  567.     /* find the position using linear interpolation (better than

  568.        dichotomy in typical cases) */

  569.     if (ffm->write_index && ffm->write_index < ffm->file_size) {

  570.         if (get_dts(s, FFM_PACKET_SIZE) < wanted_pts) {

  571.             pos_min = FFM_PACKET_SIZE;

  572.             pos_max = ffm->write_index - FFM_PACKET_SIZE;

  573.         } else {

  574.             pos_min = ffm->write_index;

  575.             pos_max = ffm->file_size - FFM_PACKET_SIZE;

  576.         }

  577.     } else {

  578.         pos_min = FFM_PACKET_SIZE;

  579.         pos_max = ffm->file_size - FFM_PACKET_SIZE;

  580.     }

  581.     while (pos_min <= pos_max) {

  582.         pts_min = get_dts(s, pos_min);

  583.         pts_max = get_dts(s, pos_max);

  584.         if (pts_min > wanted_pts || pts_max <= wanted_pts) {

  585.             pos = pts_min > wanted_pts ? pos_min : pos_max;

  586.             goto found;

  587.         }

  588.         /* linear interpolation */

  589.         pos1 = (double)(pos_max - pos_min) * (double)(wanted_pts - pts_min) /

  590.             (double)(pts_max - pts_min);

  591.         pos = (((int64_t)pos1) / FFM_PACKET_SIZE) * FFM_PACKET_SIZE;

  592.         if (pos <= pos_min)

  593.             pos = pos_min;

  594.         else if (pos >= pos_max)

  595.             pos = pos_max;

  596.         pts = get_dts(s, pos);

  597.         /* check if we are lucky */

  598.         if (pts == wanted_pts) {

  599.             goto found;

  600.         } else if (pts > wanted_pts) {

  601.             pos_max = pos - FFM_PACKET_SIZE;

  602.         } else {

  603.             pos_min = pos + FFM_PACKET_SIZE;

  604.         }

  605.     }

  606.     pos = (flags & AVSEEK_FLAG_BACKWARD) ? pos_min : pos_max;

  607. 

  608.  found:

  609.     if (ffm_seek1(s, pos) < 0)

  610.         return -1;

  611. 

  612.     /* reset read state */

  613.     ffm->read_state = READ_HEADER;

  614.     ffm->packet_ptr = ffm->packet;

  615.     ffm->packet_end = ffm->packet;

  616.     ffm->first_packet = 1;

  617. 

  618.     return 0;

  619. }

  620. 

  621. static int ffm_probe(AVProbeData *p)

  622. {

  623.     if (

  624.         p->buf[0] == 'F' && p->buf[1] == 'F' && p->buf[2] == 'M' &&

  625.         (p->buf[3] == '1' || p->buf[3] == '2'))

  626.         return AVPROBE_SCORE_MAX + 1;

  627.     return 0;

  628. }

  629. 

  630. AVInputFormat ff_ffm_demuxer = {

  631.     .name           = "ffm",

  632.     .long_name      = NULL_IF_CONFIG_SMALL("FFM (FFserver live feed)"),

  633.     .priv_data_size = sizeof(FFMContext),

  634.     .read_probe     = ffm_probe,

  635.     .read_header    = ffm_read_header,

  636.     .read_packet    = ffm_read_packet,

  637.     .read_close     = ffm_close,

  638.     .read_seek      = ffm_seek,

  639. };