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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 <stdint.h>

  23. 

  24. #include "libavutil/intreadwrite.h"

  25. #include "libavutil/intfloat.h"

  26. #include "avformat.h"

  27. #include "internal.h"

  28. #include "ffm.h"

  29. #include "avio_internal.h"

  30. 

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

  32. {

  33.     FFMContext *ffm = s->priv_data;

  34.     int64_t pos, avail_size;

  35.     int len;

  36. 

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

  38.     if (size <= len)

  39.         return 1;

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

  41.     if (!ffm->write_index) {

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

  43.             return AVERROR_EOF;

  44.         avail_size = ffm->file_size - pos;

  45.     } else {

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

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

  48.         return AVERROR(EAGAIN);

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

  50.         avail_size = ffm->write_index - pos;

  51.     } else {

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

  53.     }

  54.     }

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

  56.     if (size <= avail_size)

  57.         return 1;

  58.     else

  59.         return AVERROR(EAGAIN);

  60. }

  61. 

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

  63. {

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

  65.     while (state != PACKET_ID) {

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

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

  68.             return -1;

  69.         }

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

  71.     }

  72.     return 0;

  73. }

  74. 

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

  76. static int ffm_read_data(AVFormatContext *s,

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

  78. {

  79.     FFMContext *ffm = s->priv_data;

  80.     AVIOContext *pb = s->pb;

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

  82. 

  83.     size1 = size;

  84.     while (size > 0) {

  85.     redo:

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

  87.         if (len < 0)

  88.             return -1;

  89.         if (len > size)

  90.             len = size;

  91.         if (len == 0) {

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

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

  94.     retry_read:

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

  96.                 int64_t tell = avio_tell(pb);

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

  98.                 avio_seek(pb, tell, SEEK_SET);

  99.             }

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

  101.             if (id != PACKET_ID)

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

  103.                     return -1;

  104.             fill_size = avio_rb16(pb);

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

  106.             frame_offset = avio_rb16(pb);

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

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

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

  110.                 return -1;

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

  112.                handle it specifically */

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

  114.                 if (!frame_offset) {

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

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

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

  118.                         goto retry_read;

  119.                     }

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

  121.                     return 0;

  122.                 }

  123.                 ffm->first_packet = 0;

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

  125.                     return -1;

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

  127.                 if (!header)

  128.                     break;

  129.             } else {

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

  131.             }

  132.             goto redo;

  133.         }

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

  135.         buf += len;

  136.         ffm->packet_ptr += len;

  137.         size -= len;

  138.         header = 0;

  139.     }

  140.     return size1 - size;

  141. }

  142. 

  143. /* ensure that acutal seeking happens between FFM_PACKET_SIZE

  144.    and file_size - FFM_PACKET_SIZE */

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

  146. {

  147.     FFMContext *ffm = s->priv_data;

  148.     AVIOContext *pb = s->pb;

  149.     int64_t pos;

  150. 

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

  152.     pos = FFMAX(pos, FFM_PACKET_SIZE);

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

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

  155. }

  156. 

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

  158. {

  159.     AVIOContext *pb = s->pb;

  160.     int64_t dts;

  161. 

  162.     ffm_seek1(s, pos);

  163.     avio_skip(pb, 4);

  164.     dts = avio_rb64(pb);

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

  166.     return dts;

  167. }

  168. 

  169. static void adjust_write_index(AVFormatContext *s)

  170. {

  171.     FFMContext *ffm = s->priv_data;

  172.     AVIOContext *pb = s->pb;

  173.     int64_t pts;

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

  175.     int64_t pos_min, pos_max;

  176.     int64_t pts_start;

  177.     int64_t ptr = avio_tell(pb);

  178. 

  179. 

  180.     pos_min = 0;

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

  182. 

  183.     pts_start = get_dts(s, pos_min);

  184. 

  185.     pts = get_dts(s, pos_max);

  186. 

  187.     if (pts - 100000 > pts_start)

  188.         goto end;

  189. 

  190.     ffm->write_index = FFM_PACKET_SIZE;

  191. 

  192.     pts_start = get_dts(s, pos_min);

  193. 

  194.     pts = get_dts(s, pos_max);

  195. 

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

  197.         while (1) {

  198.             int64_t newpos;

  199.             int64_t newpts;

  200. 

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

  202. 

  203.             if (newpos == pos_min)

  204.                 break;

  205. 

  206.             newpts = get_dts(s, newpos);

  207. 

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

  209.                 pos_max = newpos;

  210.                 pts = newpts;

  211.             } else {

  212.                 pos_min = newpos;

  213.             }

  214.         }

  215.         ffm->write_index += pos_max;

  216.     }

  217. 

  218.  end:

  219.     avio_seek(pb, ptr, SEEK_SET);

  220. }

  221. 

  222. 

  223. static int ffm_close(AVFormatContext *s)

  224. {

  225.     int i;

  226. 

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

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

  229. 

  230.     return 0;

  231. }

  232. 

  233. static int ffm2_read_header(AVFormatContext *s)

  234. {

  235.     FFMContext *ffm = s->priv_data;

  236.     AVStream *st;

  237.     AVIOContext *pb = s->pb;

  238.     AVCodecContext *codec;

  239. 

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

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

  242.         goto fail;

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

  244.     /* get also filesize */

  245.     if (pb->seekable) {

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

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

  248.             adjust_write_index(s);

  249.     } else {

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

  251.     }

  252. 

  253.     while(!url_feof(pb)) {

  254.         unsigned id = avio_rb32(pb);

  255.         unsigned size = avio_rb32(pb);

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

  257.         char rc_eq_buf[128];

  258. 

  259.         if(!id)

  260.             break;

  261. 

  262.         switch(id) {

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

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

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

  266.             break;

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

  268.             st = avformat_new_stream(s, NULL);

  269.             if (!st)

  270.                 goto fail;

  271. 

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

  273. 

  274.             codec = st->codec;

  275.             /* generic info */

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

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

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

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

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

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

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

  283.                 if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)

  284.                     return AVERROR(ENOMEM);

  285.             }

  286.             avio_seek(pb, next, SEEK_SET);

  287.             id = avio_rb32(pb);

  288.             size = avio_rb32(pb);

  289.             next = avio_tell(pb) + size;

  290.             switch(id) {

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  336.                 break;

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

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

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

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

  341.                 break;

  342.             }

  343.             break;

  344.         }

  345.         avio_seek(pb, next, SEEK_SET);

  346.     }

  347. 

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

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

  350.         avio_r8(pb);

  351. 

  352.     /* init packet demux */

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

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

  355.     ffm->frame_offset = 0;

  356.     ffm->dts = 0;

  357.     ffm->read_state = READ_HEADER;

  358.     ffm->first_packet = 1;

  359.     return 0;

  360.  fail:

  361.     ffm_close(s);

  362.     return -1;

  363. }

  364. 

  365. static int ffm_read_header(AVFormatContext *s)

  366. {

  367.     FFMContext *ffm = s->priv_data;

  368.     AVStream *st;

  369.     AVIOContext *pb = s->pb;

  370.     AVCodecContext *codec;

  371.     int i, nb_streams;

  372.     uint32_t tag;

  373. 

  374.     /* header */

  375.     tag = avio_rl32(pb);

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

  377.         return ffm2_read_header(s);

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

  379.         goto fail;

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

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

  382.         goto fail;

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

  384.     /* get also filesize */

  385.     if (pb->seekable) {

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

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

  388.             adjust_write_index(s);

  389.     } else {

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

  391.     }

  392. 

  393.     nb_streams = avio_rb32(pb);

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

  395.     /* read each stream */

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

  397.         char rc_eq_buf[128];

  398. 

  399.         st = avformat_new_stream(s, NULL);

  400.         if (!st)

  401.             goto fail;

  402. 

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

  404. 

  405.         codec = st->codec;

  406.         /* generic info */

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

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

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

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

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

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

  413.         /* specific info */

  414.         switch(codec->codec_type) {

  415.         case AVMEDIA_TYPE_VIDEO:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  460.             break;

  461.         case AVMEDIA_TYPE_AUDIO:

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

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

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

  465.             break;

  466.         default:

  467.             goto fail;

  468.         }

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

  470.             if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)

  471.                 return AVERROR(ENOMEM);

  472.         }

  473.     }

  474. 

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

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

  477.         avio_r8(pb);

  478. 

  479.     /* init packet demux */

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

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

  482.     ffm->frame_offset = 0;

  483.     ffm->dts = 0;

  484.     ffm->read_state = READ_HEADER;

  485.     ffm->first_packet = 1;

  486.     return 0;

  487.  fail:

  488.     ffm_close(s);

  489.     return -1;

  490. }

  491. 

  492. /* return < 0 if eof */

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

  494. {

  495.     int size;

  496.     FFMContext *ffm = s->priv_data;

  497.     int duration, ret;

  498. 

  499.     switch(ffm->read_state) {

  500.     case READ_HEADER:

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

  502.             return ret;

  503. 

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

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

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

  507.             FRAME_HEADER_SIZE)

  508.             return -1;

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

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

  511.                 return -1;

  512.         ffm->read_state = READ_DATA;

  513.         /* fall through */

  514.     case READ_DATA:

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

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

  517.             return ret;

  518. 

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

  520. 

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

  522.             return AVERROR(ENOMEM);

  523.         }

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

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

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

  527.             av_free_packet(pkt);

  528.             ffm->read_state = READ_HEADER;

  529.             return -1;

  530.         }

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

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

  533.             pkt->flags |= AV_PKT_FLAG_KEY;

  534. 

  535.         ffm->read_state = READ_HEADER;

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

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

  538.             av_free_packet(pkt);

  539.             return -1;

  540.         }

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

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

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

  544.         else

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

  546.         pkt->duration = duration;

  547.         break;

  548.     }

  549.     return 0;

  550. }

  551. 

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

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

  554.    approximative */

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

  556. {

  557.     FFMContext *ffm = s->priv_data;

  558.     int64_t pos_min, pos_max, pos;

  559.     int64_t pts_min, pts_max, pts;

  560.     double pos1;

  561. 

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

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

  564.        dichotomy in typical cases) */

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

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

  567.             pos_min = FFM_PACKET_SIZE;

  568.             pos_max = ffm->write_index - FFM_PACKET_SIZE;

  569.         } else {

  570.             pos_min = ffm->write_index;

  571.             pos_max = ffm->file_size - FFM_PACKET_SIZE;

  572.         }

  573.     } else {

  574.         pos_min = FFM_PACKET_SIZE;

  575.         pos_max = ffm->file_size - FFM_PACKET_SIZE;

  576.     }

  577.     while (pos_min <= pos_max) {

  578.         pts_min = get_dts(s, pos_min);

  579.         pts_max = get_dts(s, pos_max);

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

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

  582.             goto found;

  583.         }

  584.         /* linear interpolation */

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

  586.             (double)(pts_max - pts_min);

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

  588.         if (pos <= pos_min)

  589.             pos = pos_min;

  590.         else if (pos >= pos_max)

  591.             pos = pos_max;

  592.         pts = get_dts(s, pos);

  593.         /* check if we are lucky */

  594.         if (pts == wanted_pts) {

  595.             goto found;

  596.         } else if (pts > wanted_pts) {

  597.             pos_max = pos - FFM_PACKET_SIZE;

  598.         } else {

  599.             pos_min = pos + FFM_PACKET_SIZE;

  600.         }

  601.     }

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

  603. 

  604.  found:

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

  606.         return -1;

  607. 

  608.     /* reset read state */

  609.     ffm->read_state = READ_HEADER;

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

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

  612.     ffm->first_packet = 1;

  613. 

  614.     return 0;

  615. }

  616. 

  617. static int ffm_probe(AVProbeData *p)

  618. {

  619.     if (

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

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

  622.         return AVPROBE_SCORE_MAX + 1;

  623.     return 0;

  624. }

  625. 

  626. AVInputFormat ff_ffm_demuxer = {

  627.     .name           = "ffm",

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

  629.     .priv_data_size = sizeof(FFMContext),

  630.     .read_probe     = ffm_probe,

  631.     .read_header    = ffm_read_header,

  632.     .read_packet    = ffm_read_packet,

  633.     .read_close     = ffm_close,

  634.     .read_seek      = ffm_seek,

  635. };