FFmpeg: libavformat/ffmdec.c Source File

00001 /*
00002  * FFM (ffserver live feed) demuxer
00003  * Copyright (c) 2001 Fabrice Bellard
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "libavutil/intreadwrite.h"
00023 #include "libavutil/intfloat.h"
00024 #include "avformat.h"
00025 #include "internal.h"
00026 #include "ffm.h"
00027 #include "avio_internal.h"
00028 
00029 static int ffm_is_avail_data(AVFormatContext *s, int size)
00030 {
00031     FFMContext *ffm = s->priv_data;
00032     int64_t pos, avail_size;
00033     int len;
00034 
00035     len = ffm->packet_end - ffm->packet_ptr;
00036     if (size <= len)
00037         return 1;
00038     pos = avio_tell(s->pb);
00039     if (!ffm->write_index) {
00040         if (pos == ffm->file_size)
00041             return AVERROR_EOF;
00042         avail_size = ffm->file_size - pos;
00043     } else {
00044     if (pos == ffm->write_index) {
00045         /* exactly at the end of stream */
00046         return AVERROR(EAGAIN);
00047     } else if (pos < ffm->write_index) {
00048         avail_size = ffm->write_index - pos;
00049     } else {
00050         avail_size = (ffm->file_size - pos) + (ffm->write_index - FFM_PACKET_SIZE);
00051     }
00052     }
00053     avail_size = (avail_size / ffm->packet_size) * (ffm->packet_size - FFM_HEADER_SIZE) + len;
00054     if (size <= avail_size)
00055         return 1;
00056     else
00057         return AVERROR(EAGAIN);
00058 }
00059 
00060 static int ffm_resync(AVFormatContext *s, int state)
00061 {
00062     av_log(s, AV_LOG_ERROR, "resyncing\n");
00063     while (state != PACKET_ID) {
00064         if (url_feof(s->pb)) {
00065             av_log(s, AV_LOG_ERROR, "cannot find FFM syncword\n");
00066             return -1;
00067         }
00068         state = (state << 8) | avio_r8(s->pb);
00069     }
00070     return 0;
00071 }
00072 
00073 /* first is true if we read the frame header */
00074 static int ffm_read_data(AVFormatContext *s,
00075                          uint8_t *buf, int size, int header)
00076 {
00077     FFMContext *ffm = s->priv_data;
00078     AVIOContext *pb = s->pb;
00079     int len, fill_size, size1, frame_offset, id;
00080 
00081     size1 = size;
00082     while (size > 0) {
00083     redo:
00084         len = ffm->packet_end - ffm->packet_ptr;
00085         if (len < 0)
00086             return -1;
00087         if (len > size)
00088             len = size;
00089         if (len == 0) {
00090             if (avio_tell(pb) == ffm->file_size)
00091                 avio_seek(pb, ffm->packet_size, SEEK_SET);
00092     retry_read:
00093             if (pb->buffer_size != ffm->packet_size) {
00094                 int64_t tell = avio_tell(pb);
00095                 ffio_set_buf_size(pb, ffm->packet_size);
00096                 avio_seek(pb, tell, SEEK_SET);
00097             }
00098             id = avio_rb16(pb); /* PACKET_ID */
00099             if (id != PACKET_ID)
00100                 if (ffm_resync(s, id) < 0)
00101                     return -1;
00102             fill_size = avio_rb16(pb);
00103             ffm->dts = avio_rb64(pb);
00104             frame_offset = avio_rb16(pb);
00105             avio_read(pb, ffm->packet, ffm->packet_size - FFM_HEADER_SIZE);
00106             ffm->packet_end = ffm->packet + (ffm->packet_size - FFM_HEADER_SIZE - fill_size);
00107             if (ffm->packet_end < ffm->packet || frame_offset < 0)
00108                 return -1;
00109             /* if first packet or resynchronization packet, we must
00110                handle it specifically */
00111             if (ffm->first_packet || (frame_offset & 0x8000)) {
00112                 if (!frame_offset) {
00113                     /* This packet has no frame headers in it */
00114                     if (avio_tell(pb) >= ffm->packet_size * 3LL) {
00115                         avio_seek(pb, -ffm->packet_size * 2LL, SEEK_CUR);
00116                         goto retry_read;
00117                     }
00118                     /* This is bad, we cannot find a valid frame header */
00119                     return 0;
00120                 }
00121                 ffm->first_packet = 0;
00122                 if ((frame_offset & 0x7fff) < FFM_HEADER_SIZE)
00123                     return -1;
00124                 ffm->packet_ptr = ffm->packet + (frame_offset & 0x7fff) - FFM_HEADER_SIZE;
00125                 if (!header)
00126                     break;
00127             } else {
00128                 ffm->packet_ptr = ffm->packet;
00129             }
00130             goto redo;
00131         }
00132         memcpy(buf, ffm->packet_ptr, len);
00133         buf += len;
00134         ffm->packet_ptr += len;
00135         size -= len;
00136         header = 0;
00137     }
00138     return size1 - size;
00139 }
00140 
00141 /* ensure that acutal seeking happens between FFM_PACKET_SIZE
00142    and file_size - FFM_PACKET_SIZE */
00143 static int64_t ffm_seek1(AVFormatContext *s, int64_t pos1)
00144 {
00145     FFMContext *ffm = s->priv_data;
00146     AVIOContext *pb = s->pb;
00147     int64_t pos;
00148 
00149     pos = FFMIN(pos1, ffm->file_size - FFM_PACKET_SIZE);
00150     pos = FFMAX(pos, FFM_PACKET_SIZE);
00151     av_dlog(s, "seek to %"PRIx64" -> %"PRIx64"\n", pos1, pos);
00152     return avio_seek(pb, pos, SEEK_SET);
00153 }
00154 
00155 static int64_t get_dts(AVFormatContext *s, int64_t pos)
00156 {
00157     AVIOContext *pb = s->pb;
00158     int64_t dts;
00159 
00160     ffm_seek1(s, pos);
00161     avio_skip(pb, 4);
00162     dts = avio_rb64(pb);
00163     av_dlog(s, "dts=%0.6f\n", dts / 1000000.0);
00164     return dts;
00165 }
00166 
00167 static void adjust_write_index(AVFormatContext *s)
00168 {
00169     FFMContext *ffm = s->priv_data;
00170     AVIOContext *pb = s->pb;
00171     int64_t pts;
00172     //int64_t orig_write_index = ffm->write_index;
00173     int64_t pos_min, pos_max;
00174     int64_t pts_start;
00175     int64_t ptr = avio_tell(pb);
00176 
00177 
00178     pos_min = 0;
00179     pos_max = ffm->file_size - 2 * FFM_PACKET_SIZE;
00180 
00181     pts_start = get_dts(s, pos_min);
00182 
00183     pts = get_dts(s, pos_max);
00184 
00185     if (pts - 100000 > pts_start)
00186         goto end;
00187 
00188     ffm->write_index = FFM_PACKET_SIZE;
00189 
00190     pts_start = get_dts(s, pos_min);
00191 
00192     pts = get_dts(s, pos_max);
00193 
00194     if (pts - 100000 <= pts_start) {
00195         while (1) {
00196             int64_t newpos;
00197             int64_t newpts;
00198 
00199             newpos = ((pos_max + pos_min) / (2 * FFM_PACKET_SIZE)) * FFM_PACKET_SIZE;
00200 
00201             if (newpos == pos_min)
00202                 break;
00203 
00204             newpts = get_dts(s, newpos);
00205 
00206             if (newpts - 100000 <= pts) {
00207                 pos_max = newpos;
00208                 pts = newpts;
00209             } else {
00210                 pos_min = newpos;
00211             }
00212         }
00213         ffm->write_index += pos_max;
00214     }
00215 
00216  end:
00217     avio_seek(pb, ptr, SEEK_SET);
00218 }
00219 
00220 
00221 static int ffm_close(AVFormatContext *s)
00222 {
00223     int i;
00224 
00225     for (i = 0; i < s->nb_streams; i++)
00226         av_freep(&s->streams[i]->codec->rc_eq);
00227 
00228     return 0;
00229 }
00230 
00231 static int ffm2_read_header(AVFormatContext *s)
00232 {
00233     FFMContext *ffm = s->priv_data;
00234     AVStream *st;
00235     AVIOContext *pb = s->pb;
00236     AVCodecContext *codec;
00237 
00238     ffm->packet_size = avio_rb32(pb);
00239     if (ffm->packet_size != FFM_PACKET_SIZE)
00240         goto fail;
00241     ffm->write_index = avio_rb64(pb);
00242     /* get also filesize */
00243     if (pb->seekable) {
00244         ffm->file_size = avio_size(pb);
00245         if (ffm->write_index && 0)
00246             adjust_write_index(s);
00247     } else {
00248         ffm->file_size = (UINT64_C(1) << 63) - 1;
00249     }
00250 
00251     while(!url_feof(pb)) {
00252         unsigned id = avio_rb32(pb);
00253         unsigned size = avio_rb32(pb);
00254         int64_t next = avio_tell(pb) + size;
00255         char rc_eq_buf[128];
00256 
00257         if(!id)
00258             break;
00259 
00260         switch(id) {
00261         case MKBETAG('M', 'A', 'I', 'N'):
00262             avio_rb32(pb); /* nb_streams */
00263             avio_rb32(pb); /* total bitrate */
00264             break;
00265         case MKBETAG('C', 'O', 'M', 'M'):
00266             st = avformat_new_stream(s, NULL);
00267             if (!st)
00268                 goto fail;
00269 
00270             avpriv_set_pts_info(st, 64, 1, 1000000);
00271 
00272             codec = st->codec;
00273             /* generic info */
00274             codec->codec_id = avio_rb32(pb);
00275             codec->codec_type = avio_r8(pb);
00276             codec->bit_rate = avio_rb32(pb);
00277             codec->flags = avio_rb32(pb);
00278             codec->flags2 = avio_rb32(pb);
00279             codec->debug = avio_rb32(pb);
00280             if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {
00281                 codec->extradata_size = avio_rb32(pb);
00282                 codec->extradata = av_malloc(codec->extradata_size);
00283                 if (!codec->extradata)
00284                     return AVERROR(ENOMEM);
00285                 avio_read(pb, codec->extradata, codec->extradata_size);
00286             }
00287             avio_seek(pb, next, SEEK_SET);
00288             id = avio_rb32(pb);
00289             size = avio_rb32(pb);
00290             next = avio_tell(pb) + size;
00291             switch(id) {
00292             case MKBETAG('S', 'T', 'V', 'I'):
00293                 codec->time_base.num = avio_rb32(pb);
00294                 codec->time_base.den = avio_rb32(pb);
00295                 codec->width = avio_rb16(pb);
00296                 codec->height = avio_rb16(pb);
00297                 codec->gop_size = avio_rb16(pb);
00298                 codec->pix_fmt = avio_rb32(pb);
00299                 codec->qmin = avio_r8(pb);
00300                 codec->qmax = avio_r8(pb);
00301                 codec->max_qdiff = avio_r8(pb);
00302                 codec->qcompress = avio_rb16(pb) / 10000.0;
00303                 codec->qblur = avio_rb16(pb) / 10000.0;
00304                 codec->bit_rate_tolerance = avio_rb32(pb);
00305                 avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
00306                 codec->rc_eq = av_strdup(rc_eq_buf);
00307                 codec->rc_max_rate = avio_rb32(pb);
00308                 codec->rc_min_rate = avio_rb32(pb);
00309                 codec->rc_buffer_size = avio_rb32(pb);
00310                 codec->i_quant_factor = av_int2double(avio_rb64(pb));
00311                 codec->b_quant_factor = av_int2double(avio_rb64(pb));
00312                 codec->i_quant_offset = av_int2double(avio_rb64(pb));
00313                 codec->b_quant_offset = av_int2double(avio_rb64(pb));
00314                 codec->dct_algo = avio_rb32(pb);
00315                 codec->strict_std_compliance = avio_rb32(pb);
00316                 codec->max_b_frames = avio_rb32(pb);
00317                 codec->mpeg_quant = avio_rb32(pb);
00318                 codec->intra_dc_precision = avio_rb32(pb);
00319                 codec->me_method = avio_rb32(pb);
00320                 codec->mb_decision = avio_rb32(pb);
00321                 codec->nsse_weight = avio_rb32(pb);
00322                 codec->frame_skip_cmp = avio_rb32(pb);
00323                 codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));
00324                 codec->codec_tag = avio_rb32(pb);
00325                 codec->thread_count = avio_r8(pb);
00326                 codec->coder_type = avio_rb32(pb);
00327                 codec->me_cmp = avio_rb32(pb);
00328                 codec->me_subpel_quality = avio_rb32(pb);
00329                 codec->me_range = avio_rb32(pb);
00330                 codec->keyint_min = avio_rb32(pb);
00331                 codec->scenechange_threshold = avio_rb32(pb);
00332                 codec->b_frame_strategy = avio_rb32(pb);
00333                 codec->qcompress = av_int2double(avio_rb64(pb));
00334                 codec->qblur = av_int2double(avio_rb64(pb));
00335                 codec->max_qdiff = avio_rb32(pb);
00336                 codec->refs = avio_rb32(pb);
00337                 break;
00338             case MKBETAG('S', 'T', 'A', 'U'):
00339                 codec->sample_rate = avio_rb32(pb);
00340                 codec->channels = avio_rl16(pb);
00341                 codec->frame_size = avio_rl16(pb);
00342                 break;
00343             }
00344             break;
00345         }
00346         avio_seek(pb, next, SEEK_SET);
00347     }
00348 
00349     /* get until end of block reached */
00350     while ((avio_tell(pb) % ffm->packet_size) != 0)
00351         avio_r8(pb);
00352 
00353     /* init packet demux */
00354     ffm->packet_ptr = ffm->packet;
00355     ffm->packet_end = ffm->packet;
00356     ffm->frame_offset = 0;
00357     ffm->dts = 0;
00358     ffm->read_state = READ_HEADER;
00359     ffm->first_packet = 1;
00360     return 0;
00361  fail:
00362     ffm_close(s);
00363     return -1;
00364 }
00365 
00366 static int ffm_read_header(AVFormatContext *s)
00367 {
00368     FFMContext *ffm = s->priv_data;
00369     AVStream *st;
00370     AVIOContext *pb = s->pb;
00371     AVCodecContext *codec;
00372     int i, nb_streams;
00373     uint32_t tag;
00374 
00375     /* header */
00376     tag = avio_rl32(pb);
00377     if (tag == MKTAG('F', 'F', 'M', '2'))
00378         return ffm2_read_header(s);
00379     if (tag != MKTAG('F', 'F', 'M', '1'))
00380         goto fail;
00381     ffm->packet_size = avio_rb32(pb);
00382     if (ffm->packet_size != FFM_PACKET_SIZE)
00383         goto fail;
00384     ffm->write_index = avio_rb64(pb);
00385     /* get also filesize */
00386     if (pb->seekable) {
00387         ffm->file_size = avio_size(pb);
00388         if (ffm->write_index && 0)
00389             adjust_write_index(s);
00390     } else {
00391         ffm->file_size = (UINT64_C(1) << 63) - 1;
00392     }
00393 
00394     nb_streams = avio_rb32(pb);
00395     avio_rb32(pb); /* total bitrate */
00396     /* read each stream */
00397     for(i=0;i<nb_streams;i++) {
00398         char rc_eq_buf[128];
00399 
00400         st = avformat_new_stream(s, NULL);
00401         if (!st)
00402             goto fail;
00403 
00404         avpriv_set_pts_info(st, 64, 1, 1000000);
00405 
00406         codec = st->codec;
00407         /* generic info */
00408         codec->codec_id = avio_rb32(pb);
00409         codec->codec_type = avio_r8(pb); /* codec_type */
00410         codec->bit_rate = avio_rb32(pb);
00411         codec->flags = avio_rb32(pb);
00412         codec->flags2 = avio_rb32(pb);
00413         codec->debug = avio_rb32(pb);
00414         /* specific info */
00415         switch(codec->codec_type) {
00416         case AVMEDIA_TYPE_VIDEO:
00417             codec->time_base.num = avio_rb32(pb);
00418             codec->time_base.den = avio_rb32(pb);
00419             codec->width = avio_rb16(pb);
00420             codec->height = avio_rb16(pb);
00421             codec->gop_size = avio_rb16(pb);
00422             codec->pix_fmt = avio_rb32(pb);
00423             codec->qmin = avio_r8(pb);
00424             codec->qmax = avio_r8(pb);
00425             codec->max_qdiff = avio_r8(pb);
00426             codec->qcompress = avio_rb16(pb) / 10000.0;
00427             codec->qblur = avio_rb16(pb) / 10000.0;
00428             codec->bit_rate_tolerance = avio_rb32(pb);
00429             avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
00430             codec->rc_eq = av_strdup(rc_eq_buf);
00431             codec->rc_max_rate = avio_rb32(pb);
00432             codec->rc_min_rate = avio_rb32(pb);
00433             codec->rc_buffer_size = avio_rb32(pb);
00434             codec->i_quant_factor = av_int2double(avio_rb64(pb));
00435             codec->b_quant_factor = av_int2double(avio_rb64(pb));
00436             codec->i_quant_offset = av_int2double(avio_rb64(pb));
00437             codec->b_quant_offset = av_int2double(avio_rb64(pb));
00438             codec->dct_algo = avio_rb32(pb);
00439             codec->strict_std_compliance = avio_rb32(pb);
00440             codec->max_b_frames = avio_rb32(pb);
00441             codec->mpeg_quant = avio_rb32(pb);
00442             codec->intra_dc_precision = avio_rb32(pb);
00443             codec->me_method = avio_rb32(pb);
00444             codec->mb_decision = avio_rb32(pb);
00445             codec->nsse_weight = avio_rb32(pb);
00446             codec->frame_skip_cmp = avio_rb32(pb);
00447             codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));
00448             codec->codec_tag = avio_rb32(pb);
00449             codec->thread_count = avio_r8(pb);
00450             codec->coder_type = avio_rb32(pb);
00451             codec->me_cmp = avio_rb32(pb);
00452             codec->me_subpel_quality = avio_rb32(pb);
00453             codec->me_range = avio_rb32(pb);
00454             codec->keyint_min = avio_rb32(pb);
00455             codec->scenechange_threshold = avio_rb32(pb);
00456             codec->b_frame_strategy = avio_rb32(pb);
00457             codec->qcompress = av_int2double(avio_rb64(pb));
00458             codec->qblur = av_int2double(avio_rb64(pb));
00459             codec->max_qdiff = avio_rb32(pb);
00460             codec->refs = avio_rb32(pb);
00461             break;
00462         case AVMEDIA_TYPE_AUDIO:
00463             codec->sample_rate = avio_rb32(pb);
00464             codec->channels = avio_rl16(pb);
00465             codec->frame_size = avio_rl16(pb);
00466             break;
00467         default:
00468             goto fail;
00469         }
00470         if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {
00471             codec->extradata_size = avio_rb32(pb);
00472             codec->extradata = av_malloc(codec->extradata_size);
00473             if (!codec->extradata)
00474                 return AVERROR(ENOMEM);
00475             avio_read(pb, codec->extradata, codec->extradata_size);
00476         }
00477     }
00478 
00479     /* get until end of block reached */
00480     while ((avio_tell(pb) % ffm->packet_size) != 0)
00481         avio_r8(pb);
00482 
00483     /* init packet demux */
00484     ffm->packet_ptr = ffm->packet;
00485     ffm->packet_end = ffm->packet;
00486     ffm->frame_offset = 0;
00487     ffm->dts = 0;
00488     ffm->read_state = READ_HEADER;
00489     ffm->first_packet = 1;
00490     return 0;
00491  fail:
00492     ffm_close(s);
00493     return -1;
00494 }
00495 
00496 /* return < 0 if eof */
00497 static int ffm_read_packet(AVFormatContext *s, AVPacket *pkt)
00498 {
00499     int size;
00500     FFMContext *ffm = s->priv_data;
00501     int duration, ret;
00502 
00503     switch(ffm->read_state) {
00504     case READ_HEADER:
00505         if ((ret = ffm_is_avail_data(s, FRAME_HEADER_SIZE+4)) < 0)
00506             return ret;
00507 
00508         av_dlog(s, "pos=%08"PRIx64" spos=%"PRIx64", write_index=%"PRIx64" size=%"PRIx64"\n",
00509                avio_tell(s->pb), s->pb->pos, ffm->write_index, ffm->file_size);
00510         if (ffm_read_data(s, ffm->header, FRAME_HEADER_SIZE, 1) !=
00511             FRAME_HEADER_SIZE)
00512             return -1;
00513         if (ffm->header[1] & FLAG_DTS)
00514             if (ffm_read_data(s, ffm->header+16, 4, 1) != 4)
00515                 return -1;
00516         ffm->read_state = READ_DATA;
00517         /* fall thru */
00518     case READ_DATA:
00519         size = AV_RB24(ffm->header + 2);
00520         if ((ret = ffm_is_avail_data(s, size)) < 0)
00521             return ret;
00522 
00523         duration = AV_RB24(ffm->header + 5);
00524 
00525         if (av_new_packet(pkt, size) < 0) {
00526             return AVERROR(ENOMEM);
00527         }
00528         pkt->stream_index = ffm->header[0];
00529         if ((unsigned)pkt->stream_index >= s->nb_streams) {
00530             av_log(s, AV_LOG_ERROR, "invalid stream index %d\n", pkt->stream_index);
00531             av_free_packet(pkt);
00532             ffm->read_state = READ_HEADER;
00533             return -1;
00534         }
00535         pkt->pos = avio_tell(s->pb);
00536         if (ffm->header[1] & FLAG_KEY_FRAME)
00537             pkt->flags |= AV_PKT_FLAG_KEY;
00538 
00539         ffm->read_state = READ_HEADER;
00540         if (ffm_read_data(s, pkt->data, size, 0) != size) {
00541             /* bad case: desynchronized packet. we cancel all the packet loading */
00542             av_free_packet(pkt);
00543             return -1;
00544         }
00545         pkt->pts = AV_RB64(ffm->header+8);
00546         if (ffm->header[1] & FLAG_DTS)
00547             pkt->dts = pkt->pts - AV_RB32(ffm->header+16);
00548         else
00549             pkt->dts = pkt->pts;
00550         pkt->duration = duration;
00551         break;
00552     }
00553     return 0;
00554 }
00555 
00556 /* seek to a given time in the file. The file read pointer is
00557    positioned at or before pts. XXX: the following code is quite
00558    approximative */
00559 static int ffm_seek(AVFormatContext *s, int stream_index, int64_t wanted_pts, int flags)
00560 {
00561     FFMContext *ffm = s->priv_data;
00562     int64_t pos_min, pos_max, pos;
00563     int64_t pts_min, pts_max, pts;
00564     double pos1;
00565 
00566     av_dlog(s, "wanted_pts=%0.6f\n", wanted_pts / 1000000.0);
00567     /* find the position using linear interpolation (better than
00568        dichotomy in typical cases) */
00569     if (ffm->write_index && ffm->write_index < ffm->file_size) {
00570         if (get_dts(s, FFM_PACKET_SIZE) < wanted_pts) {
00571             pos_min = FFM_PACKET_SIZE;
00572             pos_max = ffm->write_index - FFM_PACKET_SIZE;
00573         } else {
00574             pos_min = ffm->write_index;
00575             pos_max = ffm->file_size - FFM_PACKET_SIZE;
00576         }
00577     } else {
00578         pos_min = FFM_PACKET_SIZE;
00579         pos_max = ffm->file_size - FFM_PACKET_SIZE;
00580     }
00581     while (pos_min <= pos_max) {
00582         pts_min = get_dts(s, pos_min);
00583         pts_max = get_dts(s, pos_max);
00584         if (pts_min > wanted_pts || pts_max <= wanted_pts) {
00585             pos = pts_min > wanted_pts ? pos_min : pos_max;
00586             goto found;
00587         }
00588         /* linear interpolation */
00589         pos1 = (double)(pos_max - pos_min) * (double)(wanted_pts - pts_min) /
00590             (double)(pts_max - pts_min);
00591         pos = (((int64_t)pos1) / FFM_PACKET_SIZE) * FFM_PACKET_SIZE;
00592         if (pos <= pos_min)
00593             pos = pos_min;
00594         else if (pos >= pos_max)
00595             pos = pos_max;
00596         pts = get_dts(s, pos);
00597         /* check if we are lucky */
00598         if (pts == wanted_pts) {
00599             goto found;
00600         } else if (pts > wanted_pts) {
00601             pos_max = pos - FFM_PACKET_SIZE;
00602         } else {
00603             pos_min = pos + FFM_PACKET_SIZE;
00604         }
00605     }
00606     pos = (flags & AVSEEK_FLAG_BACKWARD) ? pos_min : pos_max;
00607 
00608  found:
00609     if (ffm_seek1(s, pos) < 0)
00610         return -1;
00611 
00612     /* reset read state */
00613     ffm->read_state = READ_HEADER;
00614     ffm->packet_ptr = ffm->packet;
00615     ffm->packet_end = ffm->packet;
00616     ffm->first_packet = 1;
00617 
00618     return 0;
00619 }
00620 
00621 static int ffm_probe(AVProbeData *p)
00622 {
00623     if (
00624         p->buf[0] == 'F' && p->buf[1] == 'F' && p->buf[2] == 'M' &&
00625         (p->buf[3] == '1' || p->buf[3] == '2'))
00626         return AVPROBE_SCORE_MAX + 1;
00627     return 0;
00628 }
00629 
00630 AVInputFormat ff_ffm_demuxer = {
00631     .name           = "ffm",
00632     .long_name      = NULL_IF_CONFIG_SMALL("FFM (FFserver live feed)"),
00633     .priv_data_size = sizeof(FFMContext),
00634     .read_probe     = ffm_probe,
00635     .read_header    = ffm_read_header,
00636     .read_packet    = ffm_read_packet,
00637     .read_close     = ffm_close,
00638     .read_seek      = ffm_seek,
00639 };