text: /*
   * FFM (ffserver live feed) demuxer
   * Copyright (c) 2001 Fabrice Bellard
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include <stdint.h>
  
  #include "libavutil/internal.h"
  #include "libavutil/intreadwrite.h"
  #include "libavutil/intfloat.h"
  #include "libavutil/opt.h"
  #include "libavutil/avassert.h"
  #include "libavutil/avstring.h"
  #include "avformat.h"
  #include "internal.h"
  #include "ffm.h"
  #include "avio_internal.h"
  
  static int ffm_is_avail_data(AVFormatContext *s, int size)
  {
      FFMContext *ffm = s->priv_data;
      int64_t pos, avail_size;
      int len;
  
      len = ffm->packet_end - ffm->packet_ptr;
      if (size <= len)
          return 1;
      pos = avio_tell(s->pb);
      if (!ffm->write_index) {
          if (pos == ffm->file_size)
              return AVERROR_EOF;
          avail_size = ffm->file_size - pos;
      } else {
      if (pos == ffm->write_index) {
          /* exactly at the end of stream */
          return AVERROR(EAGAIN);
      } else if (pos < ffm->write_index) {
          avail_size = ffm->write_index - pos;
      } else {
          avail_size = (ffm->file_size - pos) + (ffm->write_index - FFM_PACKET_SIZE);
      }
      }
      avail_size = (avail_size / ffm->packet_size) * (ffm->packet_size - FFM_HEADER_SIZE) + len;
      if (size <= avail_size)
          return 1;
      else
          return AVERROR(EAGAIN);
  }
  
  static int ffm_resync(AVFormatContext *s, int state)
  {
      av_log(s, AV_LOG_ERROR, "resyncing\n");
      while (state != PACKET_ID) {
          if (avio_feof(s->pb)) {
              av_log(s, AV_LOG_ERROR, "cannot find FFM syncword\n");
              return -1;
          }
          state = (state << 8) | avio_r8(s->pb);
      }
      return 0;
  }
  
  /* first is true if we read the frame header */
  static int ffm_read_data(AVFormatContext *s,
                           uint8_t *buf, int size, int header)
  {
      FFMContext *ffm = s->priv_data;
      AVIOContext *pb = s->pb;
      int len, fill_size, size1, frame_offset, id;
      int64_t last_pos = -1;
  
      size1 = size;
      while (size > 0) {
      redo:
          len = ffm->packet_end - ffm->packet_ptr;
          if (len < 0)
              return -1;
          if (len > size)
              len = size;
          if (len == 0) {
              if (avio_tell(pb) == ffm->file_size)
                  avio_seek(pb, ffm->packet_size, SEEK_SET);
      retry_read:
              if (pb->buffer_size != ffm->packet_size) {
                  int64_t tell = avio_tell(pb);
                  int ret = ffio_set_buf_size(pb, ffm->packet_size);
                  if (ret < 0)
                      return ret;
                  avio_seek(pb, tell, SEEK_SET);
              }
              id = avio_rb16(pb); /* PACKET_ID */
              if (id != PACKET_ID) {
                  if (ffm_resync(s, id) < 0)
                      return -1;
                  last_pos = avio_tell(pb);
              }
              fill_size = avio_rb16(pb);
              ffm->dts = avio_rb64(pb);
              frame_offset = avio_rb16(pb);
              avio_read(pb, ffm->packet, ffm->packet_size - FFM_HEADER_SIZE);
              ffm->packet_end = ffm->packet + (ffm->packet_size - FFM_HEADER_SIZE - fill_size);
              if (ffm->packet_end < ffm->packet || frame_offset < 0)
                  return -1;
              /* if first packet or resynchronization packet, we must
                 handle it specifically */
              if (ffm->first_packet || (frame_offset & 0x8000)) {
                  if (!frame_offset) {
                      /* This packet has no frame headers in it */
                      if (avio_tell(pb) >= ffm->packet_size * 3LL) {
                          int64_t seekback = FFMIN(ffm->packet_size * 2LL, avio_tell(pb) - last_pos);
                          seekback = FFMAX(seekback, 0);
                          avio_seek(pb, -seekback, SEEK_CUR);
                          goto retry_read;
                      }
                      /* This is bad, we cannot find a valid frame header */
                      return 0;
                  }
                  ffm->first_packet = 0;
                  if ((frame_offset & 0x7fff) < FFM_HEADER_SIZE)
                      return -1;
                  ffm->packet_ptr = ffm->packet + (frame_offset & 0x7fff) - FFM_HEADER_SIZE;
                  if (!header)
                      break;
              } else {
                  ffm->packet_ptr = ffm->packet;
              }
              goto redo;
          }
          memcpy(buf, ffm->packet_ptr, len);
          buf += len;
          ffm->packet_ptr += len;
          size -= len;
          header = 0;
      }
      return size1 - size;
  }
  
  /* ensure that actual seeking happens between FFM_PACKET_SIZE
     and file_size - FFM_PACKET_SIZE */
  static int64_t ffm_seek1(AVFormatContext *s, int64_t pos1)
  {
      FFMContext *ffm = s->priv_data;
      AVIOContext *pb = s->pb;
      int64_t pos;
  
      pos = FFMIN(pos1, ffm->file_size - FFM_PACKET_SIZE);
      pos = FFMAX(pos, FFM_PACKET_SIZE);
      ff_dlog(s, "seek to %"PRIx64" -> %"PRIx64"\n", pos1, pos);
      return avio_seek(pb, pos, SEEK_SET);
  }
  
  static int64_t get_dts(AVFormatContext *s, int64_t pos)
  {
      AVIOContext *pb = s->pb;
      int64_t dts;
  
      ffm_seek1(s, pos);
      avio_skip(pb, 4);
      dts = avio_rb64(pb);
      ff_dlog(s, "dts=%0.6f\n", dts / 1000000.0);
      return dts;
  }
  
  static void adjust_write_index(AVFormatContext *s)
  {
      FFMContext *ffm = s->priv_data;
      AVIOContext *pb = s->pb;
      int64_t pts;
      //int64_t orig_write_index = ffm->write_index;
      int64_t pos_min, pos_max;
      int64_t pts_start;
      int64_t ptr = avio_tell(pb);
  
  
      pos_min = 0;
      pos_max = ffm->file_size - 2 * FFM_PACKET_SIZE;
  
      pts_start = get_dts(s, pos_min);
  
      pts = get_dts(s, pos_max);
  
      if (pts - 100000 > pts_start)
          goto end;
  
      ffm->write_index = FFM_PACKET_SIZE;
  
      pts_start = get_dts(s, pos_min);
  
      pts = get_dts(s, pos_max);
  
      if (pts - 100000 <= pts_start) {
          while (1) {
              int64_t newpos;
              int64_t newpts;
  
              newpos = ((pos_max + pos_min) / (2 * FFM_PACKET_SIZE)) * FFM_PACKET_SIZE;
  
              if (newpos == pos_min)
                  break;
  
              newpts = get_dts(s, newpos);
  
              if (newpts - 100000 <= pts) {
                  pos_max = newpos;
                  pts = newpts;
              } else {
                  pos_min = newpos;
              }
          }
          ffm->write_index += pos_max;
      }
  
   end:
      avio_seek(pb, ptr, SEEK_SET);
  }
  
  
  static int ffm_close(AVFormatContext *s)
  {
      int i;
  
      for (i = 0; i < s->nb_streams; i++)
          av_freep(&s->streams[i]->codec->rc_eq);
  
      return 0;
  }
  
  static int ffm_append_recommended_configuration(AVStream *st, char **conf)
  {
      int ret;
      size_t newsize;
      av_assert0(conf && st);
      if (!*conf)
          return 0;
      if (!st->recommended_encoder_configuration) {
          st->recommended_encoder_configuration = *conf;
          *conf = 0;
          return 0;
      }
      newsize = strlen(*conf) + strlen(st->recommended_encoder_configuration) + 2;
      if ((ret = av_reallocp(&st->recommended_encoder_configuration, newsize)) < 0)
          return ret;
      av_strlcat(st->recommended_encoder_configuration, ",", newsize);
      av_strlcat(st->recommended_encoder_configuration, *conf, newsize);
      av_freep(conf);
      return 0;
  }
  
  static int ffm2_read_header(AVFormatContext *s)
  {
      FFMContext *ffm = s->priv_data;
      AVStream *st;
      AVIOContext *pb = s->pb;
      AVCodecContext *codec;
      int ret;
      int f_main = 0, f_cprv = -1, f_stvi = -1, f_stau = -1;
      AVCodec *enc;
      char *buffer;
  
      ffm->packet_size = avio_rb32(pb);
      if (ffm->packet_size != FFM_PACKET_SIZE) {
          av_log(s, AV_LOG_ERROR, "Invalid packet size %d, expected size was %d\n",
                 ffm->packet_size, FFM_PACKET_SIZE);
          ret = AVERROR_INVALIDDATA;
          goto fail;
      }
  
      ffm->write_index = avio_rb64(pb);
      /* get also filesize */
      if (pb->seekable) {
          ffm->file_size = avio_size(pb);
          if (ffm->write_index && 0)
              adjust_write_index(s);
      } else {
          ffm->file_size = (UINT64_C(1) << 63) - 1;
      }
  
      while(!avio_feof(pb)) {
          unsigned id = avio_rb32(pb);
          unsigned size = avio_rb32(pb);
          int64_t next = avio_tell(pb) + size;
          char rc_eq_buf[128];
  
          if(!id)
              break;
  
          switch(id) {
          case MKBETAG('M', 'A', 'I', 'N'):
              if (f_main++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              avio_rb32(pb); /* nb_streams */
              avio_rb32(pb); /* total bitrate */
              break;
          case MKBETAG('C', 'O', 'M', 'M'):
              f_cprv = f_stvi = f_stau = 0;
              st = avformat_new_stream(s, NULL);
              if (!st) {
                  ret = AVERROR(ENOMEM);
                  goto fail;
              }
  
              avpriv_set_pts_info(st, 64, 1, 1000000);
  
              codec = st->codec;
              /* generic info */
              codec->codec_id = avio_rb32(pb);
              codec->codec_type = avio_r8(pb);
              codec->bit_rate = avio_rb32(pb);
              codec->flags = avio_rb32(pb);
              codec->flags2 = avio_rb32(pb);
              codec->debug = avio_rb32(pb);
              if (codec->flags & AV_CODEC_FLAG_GLOBAL_HEADER) {
                  if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)
                      return AVERROR(ENOMEM);
              }
              break;
          case MKBETAG('S', 'T', 'V', 'I'):
              if (f_stvi++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              codec->time_base.num = avio_rb32(pb);
              codec->time_base.den = avio_rb32(pb);
              if (codec->time_base.num <= 0 || codec->time_base.den <= 0) {
                  av_log(s, AV_LOG_ERROR, "Invalid time base %d/%d\n",
                         codec->time_base.num, codec->time_base.den);
                  ret = AVERROR_INVALIDDATA;
                  goto fail;
              }
              codec->width = avio_rb16(pb);
              codec->height = avio_rb16(pb);
              codec->gop_size = avio_rb16(pb);
              codec->pix_fmt = avio_rb32(pb);
              codec->qmin = avio_r8(pb);
              codec->qmax = avio_r8(pb);
              codec->max_qdiff = avio_r8(pb);
              codec->qcompress = avio_rb16(pb) / 10000.0;
              codec->qblur = avio_rb16(pb) / 10000.0;
              codec->bit_rate_tolerance = avio_rb32(pb);
              avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
              codec->rc_eq = av_strdup(rc_eq_buf);
              codec->rc_max_rate = avio_rb32(pb);
              codec->rc_min_rate = avio_rb32(pb);
              codec->rc_buffer_size = avio_rb32(pb);
              codec->i_quant_factor = av_int2double(avio_rb64(pb));
              codec->b_quant_factor = av_int2double(avio_rb64(pb));
              codec->i_quant_offset = av_int2double(avio_rb64(pb));
              codec->b_quant_offset = av_int2double(avio_rb64(pb));
              codec->dct_algo = avio_rb32(pb);
              codec->strict_std_compliance = avio_rb32(pb);
              codec->max_b_frames = avio_rb32(pb);
              codec->mpeg_quant = avio_rb32(pb);
              codec->intra_dc_precision = avio_rb32(pb);
              codec->me_method = avio_rb32(pb);
              codec->mb_decision = avio_rb32(pb);
              codec->nsse_weight = avio_rb32(pb);
              codec->frame_skip_cmp = avio_rb32(pb);
              codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));
              codec->codec_tag = avio_rb32(pb);
              codec->thread_count = avio_r8(pb);
              codec->coder_type = avio_rb32(pb);
              codec->me_cmp = avio_rb32(pb);
              codec->me_subpel_quality = avio_rb32(pb);
              codec->me_range = avio_rb32(pb);
              codec->keyint_min = avio_rb32(pb);
              codec->scenechange_threshold = avio_rb32(pb);
              codec->b_frame_strategy = avio_rb32(pb);
              codec->qcompress = av_int2double(avio_rb64(pb));
              codec->qblur = av_int2double(avio_rb64(pb));
              codec->max_qdiff = avio_rb32(pb);
              codec->refs = avio_rb32(pb);
              break;
          case MKBETAG('S', 'T', 'A', 'U'):
              if (f_stau++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              codec->sample_rate = avio_rb32(pb);
              codec->channels = avio_rl16(pb);
              codec->frame_size = avio_rl16(pb);
              break;
          case MKBETAG('C', 'P', 'R', 'V'):
              if (f_cprv++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              enc = avcodec_find_encoder(codec->codec_id);
              if (enc && enc->priv_data_size && enc->priv_class) {
                  buffer = av_malloc(size + 1);
                  if (!buffer) {
                      ret = AVERROR(ENOMEM);
                      goto fail;
                  }
                  avio_get_str(pb, size, buffer, size + 1);
                  if ((ret = ffm_append_recommended_configuration(st, &buffer)) < 0)
                      goto fail;
              }
              break;
          case MKBETAG('S', '2', 'V', 'I'):
              if (f_stvi++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              buffer = av_malloc(size);
              if (!buffer) {
                  ret = AVERROR(ENOMEM);
                  goto fail;
              }
              avio_get_str(pb, INT_MAX, buffer, size);
              av_set_options_string(codec, buffer, "=", ",");
              if ((ret = ffm_append_recommended_configuration(st, &buffer)) < 0)
                  goto fail;
              break;
          case MKBETAG('S', '2', 'A', 'U'):
              if (f_stau++) {
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              buffer = av_malloc(size);
              if (!buffer) {
                  ret = AVERROR(ENOMEM);
                  goto fail;
              }
              avio_get_str(pb, INT_MAX, buffer, size);
              av_set_options_string(codec, buffer, "=", ",");
              if ((ret = ffm_append_recommended_configuration(st, &buffer)) < 0)
                  goto fail;
              break;
          }
          avio_seek(pb, next, SEEK_SET);
      }
  
      /* get until end of block reached */
      while ((avio_tell(pb) % ffm->packet_size) != 0 && !pb->eof_reached)
          avio_r8(pb);
  
      /* init packet demux */
      ffm->packet_ptr = ffm->packet;
      ffm->packet_end = ffm->packet;
      ffm->frame_offset = 0;
      ffm->dts = 0;
      ffm->read_state = READ_HEADER;
      ffm->first_packet = 1;
      return 0;
   fail:
      ffm_close(s);
      return ret;
  }
  
  static int ffm_read_header(AVFormatContext *s)
  {
      FFMContext *ffm = s->priv_data;
      AVStream *st;
      AVIOContext *pb = s->pb;
      AVCodecContext *codec;
      int i, nb_streams;
      uint32_t tag;
  
      /* header */
      tag = avio_rl32(pb);
      if (tag == MKTAG('F', 'F', 'M', '2'))
          return ffm2_read_header(s);
      if (tag != MKTAG('F', 'F', 'M', '1'))
          goto fail;
      ffm->packet_size = avio_rb32(pb);
      if (ffm->packet_size != FFM_PACKET_SIZE)
          goto fail;
      ffm->write_index = avio_rb64(pb);
      /* get also filesize */
      if (pb->seekable) {
          ffm->file_size = avio_size(pb);
          if (ffm->write_index && 0)
              adjust_write_index(s);
      } else {
          ffm->file_size = (UINT64_C(1) << 63) - 1;
      }
  
      nb_streams = avio_rb32(pb);
      avio_rb32(pb); /* total bitrate */
      /* read each stream */
      for(i=0;i<nb_streams;i++) {
          char rc_eq_buf[128];
  
          st = avformat_new_stream(s, NULL);
          if (!st)
              goto fail;
  
          avpriv_set_pts_info(st, 64, 1, 1000000);
  
          codec = st->codec;
          /* generic info */
          codec->codec_id = avio_rb32(pb);
          codec->codec_type = avio_r8(pb); /* codec_type */
          codec->bit_rate = avio_rb32(pb);
          codec->flags = avio_rb32(pb);
          codec->flags2 = avio_rb32(pb);
          codec->debug = avio_rb32(pb);
          /* specific info */
          switch(codec->codec_type) {
          case AVMEDIA_TYPE_VIDEO:
              codec->time_base.num = avio_rb32(pb);
              codec->time_base.den = avio_rb32(pb);
              if (codec->time_base.num <= 0 || codec->time_base.den <= 0) {
                  av_log(s, AV_LOG_ERROR, "Invalid time base %d/%d\n",
                         codec->time_base.num, codec->time_base.den);
                  goto fail;
              }
              codec->width = avio_rb16(pb);
              codec->height = avio_rb16(pb);
              codec->gop_size = avio_rb16(pb);
              codec->pix_fmt = avio_rb32(pb);
              codec->qmin = avio_r8(pb);
              codec->qmax = avio_r8(pb);
              codec->max_qdiff = avio_r8(pb);
              codec->qcompress = avio_rb16(pb) / 10000.0;
              codec->qblur = avio_rb16(pb) / 10000.0;
              codec->bit_rate_tolerance = avio_rb32(pb);
              avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
              codec->rc_eq = av_strdup(rc_eq_buf);
              codec->rc_max_rate = avio_rb32(pb);
              codec->rc_min_rate = avio_rb32(pb);
              codec->rc_buffer_size = avio_rb32(pb);
              codec->i_quant_factor = av_int2double(avio_rb64(pb));
              codec->b_quant_factor = av_int2double(avio_rb64(pb));
              codec->i_quant_offset = av_int2double(avio_rb64(pb));
              codec->b_quant_offset = av_int2double(avio_rb64(pb));
              codec->dct_algo = avio_rb32(pb);
              codec->strict_std_compliance = avio_rb32(pb);
              codec->max_b_frames = avio_rb32(pb);
              codec->mpeg_quant = avio_rb32(pb);
              codec->intra_dc_precision = avio_rb32(pb);
              codec->me_method = avio_rb32(pb);
              codec->mb_decision = avio_rb32(pb);
              codec->nsse_weight = avio_rb32(pb);
              codec->frame_skip_cmp = avio_rb32(pb);
              codec->rc_buffer_aggressivity = av_int2double(avio_rb64(pb));
              codec->codec_tag = avio_rb32(pb);
              codec->thread_count = avio_r8(pb);
              codec->coder_type = avio_rb32(pb);
              codec->me_cmp = avio_rb32(pb);
              codec->me_subpel_quality = avio_rb32(pb);
              codec->me_range = avio_rb32(pb);
              codec->keyint_min = avio_rb32(pb);
              codec->scenechange_threshold = avio_rb32(pb);
              codec->b_frame_strategy = avio_rb32(pb);
              codec->qcompress = av_int2double(avio_rb64(pb));
              codec->qblur = av_int2double(avio_rb64(pb));
              codec->max_qdiff = avio_rb32(pb);
              codec->refs = avio_rb32(pb);
              break;
          case AVMEDIA_TYPE_AUDIO:
              codec->sample_rate = avio_rb32(pb);
              codec->channels = avio_rl16(pb);
              codec->frame_size = avio_rl16(pb);
              break;
          default:
              goto fail;
          }
          if (codec->flags & AV_CODEC_FLAG_GLOBAL_HEADER) {
              if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)
                  return AVERROR(ENOMEM);
          }
      }
  
      /* get until end of block reached */
      while ((avio_tell(pb) % ffm->packet_size) != 0 && !pb->eof_reached)
          avio_r8(pb);
  
      /* init packet demux */
      ffm->packet_ptr = ffm->packet;
      ffm->packet_end = ffm->packet;
      ffm->frame_offset = 0;
      ffm->dts = 0;
      ffm->read_state = READ_HEADER;
      ffm->first_packet = 1;
      return 0;
   fail:
      ffm_close(s);
      return -1;
  }
  
  /* return < 0 if eof */
  static int ffm_read_packet(AVFormatContext *s, AVPacket *pkt)
  {
      int size;
      FFMContext *ffm = s->priv_data;
      int duration, ret;
  
      switch(ffm->read_state) {
      case READ_HEADER:
          if ((ret = ffm_is_avail_data(s, FRAME_HEADER_SIZE+4)) < 0)
              return ret;
  
          ff_dlog(s, "pos=%08"PRIx64" spos=%"PRIx64", write_index=%"PRIx64" size=%"PRIx64"\n",
                 avio_tell(s->pb), s->pb->pos, ffm->write_index, ffm->file_size);
          if (ffm_read_data(s, ffm->header, FRAME_HEADER_SIZE, 1) !=
              FRAME_HEADER_SIZE)
              return -1;
          if (ffm->header[1] & FLAG_DTS)
              if (ffm_read_data(s, ffm->header+16, 4, 1) != 4)
                  return -1;
          ffm->read_state = READ_DATA;
          /* fall through */
      case READ_DATA:
          size = AV_RB24(ffm->header + 2);
          if ((ret = ffm_is_avail_data(s, size)) < 0)
              return ret;
  
          duration = AV_RB24(ffm->header + 5);
  
          if (av_new_packet(pkt, size) < 0) {
              return AVERROR(ENOMEM);
          }
          pkt->stream_index = ffm->header[0];
          if ((unsigned)pkt->stream_index >= s->nb_streams) {
              av_log(s, AV_LOG_ERROR, "invalid stream index %d\n", pkt->stream_index);
              av_free_packet(pkt);
              ffm->read_state = READ_HEADER;
              return -1;
          }
          pkt->pos = avio_tell(s->pb);
          if (ffm->header[1] & FLAG_KEY_FRAME)
              pkt->flags |= AV_PKT_FLAG_KEY;
  
          ffm->read_state = READ_HEADER;
          if (ffm_read_data(s, pkt->data, size, 0) != size) {
              /* bad case: desynchronized packet. we cancel all the packet loading */
              av_free_packet(pkt);
              return -1;
          }
          pkt->pts = AV_RB64(ffm->header+8);
          if (ffm->header[1] & FLAG_DTS)
              pkt->dts = pkt->pts - AV_RB32(ffm->header+16);
          else
              pkt->dts = pkt->pts;
          pkt->duration = duration;
          break;
      }
      return 0;
  }
  
  /* seek to a given time in the file. The file read pointer is
     positioned at or before pts. XXX: the following code is quite
     approximative */
  static int ffm_seek(AVFormatContext *s, int stream_index, int64_t wanted_pts, int flags)
  {
      FFMContext *ffm = s->priv_data;
      int64_t pos_min, pos_max, pos;
      int64_t pts_min, pts_max, pts;
      double pos1;
  
      ff_dlog(s, "wanted_pts=%0.6f\n", wanted_pts / 1000000.0);
      /* find the position using linear interpolation (better than
         dichotomy in typical cases) */
      if (ffm->write_index && ffm->write_index < ffm->file_size) {
          if (get_dts(s, FFM_PACKET_SIZE) < wanted_pts) {
              pos_min = FFM_PACKET_SIZE;
              pos_max = ffm->write_index - FFM_PACKET_SIZE;
          } else {
              pos_min = ffm->write_index;
              pos_max = ffm->file_size - FFM_PACKET_SIZE;
          }
      } else {
          pos_min = FFM_PACKET_SIZE;
          pos_max = ffm->file_size - FFM_PACKET_SIZE;
      }
      while (pos_min <= pos_max) {
          pts_min = get_dts(s, pos_min);
          pts_max = get_dts(s, pos_max);
          if (pts_min > wanted_pts || pts_max <= wanted_pts) {
              pos = pts_min > wanted_pts ? pos_min : pos_max;
              goto found;
          }
          /* linear interpolation */
          pos1 = (double)(pos_max - pos_min) * (double)(wanted_pts - pts_min) /
              (double)(pts_max - pts_min);
          pos = (((int64_t)pos1) / FFM_PACKET_SIZE) * FFM_PACKET_SIZE;
          if (pos <= pos_min)
              pos = pos_min;
          else if (pos >= pos_max)
              pos = pos_max;
          pts = get_dts(s, pos);
          /* check if we are lucky */
          if (pts == wanted_pts) {
              goto found;
          } else if (pts > wanted_pts) {
              pos_max = pos - FFM_PACKET_SIZE;
          } else {
              pos_min = pos + FFM_PACKET_SIZE;
          }
      }
      pos = (flags & AVSEEK_FLAG_BACKWARD) ? pos_min : pos_max;
  
   found:
      if (ffm_seek1(s, pos) < 0)
          return -1;
  
      /* reset read state */
      ffm->read_state = READ_HEADER;
      ffm->packet_ptr = ffm->packet;
      ffm->packet_end = ffm->packet;
      ffm->first_packet = 1;
  
      return 0;
  }
  
  static int ffm_probe(AVProbeData *p)
  {
      if (
          p->buf[0] == 'F' && p->buf[1] == 'F' && p->buf[2] == 'M' &&
          (p->buf[3] == '1' || p->buf[3] == '2'))
          return AVPROBE_SCORE_MAX + 1;
      return 0;
  }
  
  AVInputFormat ff_ffm_demuxer = {
      .name           = "ffm",
      .long_name      = NULL_IF_CONFIG_SMALL("FFM (FFserver live feed)"),
      .priv_data_size = sizeof(FFMContext),
      .read_probe     = ffm_probe,
      .read_header    = ffm_read_header,
      .read_packet    = ffm_read_packet,
      .read_close     = ffm_close,
      .read_seek      = ffm_seek,
  };
  