text: /*
   * Apple HTTP Live Streaming demuxer
   * Copyright (c) 2010 Martin Storsjo
   *
   * 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
   */
  
  /**
   * @file
   * Apple HTTP Live Streaming demuxer
   * http://tools.ietf.org/html/draft-pantos-http-live-streaming
   */
  
  #include "libavutil/avstring.h"
  #include "libavutil/intreadwrite.h"
  #include "libavutil/mathematics.h"
  #include "libavutil/opt.h"
  #include "libavutil/dict.h"
  #include "libavutil/time.h"
  #include "avformat.h"
  #include "internal.h"
  #include "avio_internal.h"
  #include "url.h"
  
  #define INITIAL_BUFFER_SIZE 32768
  
  /*
   * An apple http stream consists of a playlist with media segment files,
   * played sequentially. There may be several playlists with the same
   * video content, in different bandwidth variants, that are played in
   * parallel (preferably only one bandwidth variant at a time). In this case,
   * the user supplied the url to a main playlist that only lists the variant
   * playlists.
   *
   * If the main playlist doesn't point at any variants, we still create
   * one anonymous toplevel variant for this, to maintain the structure.
   */
  
  enum KeyType {
      KEY_NONE,
      KEY_AES_128,
  };
  
  struct segment {
      double duration;
      char url[MAX_URL_SIZE];
      char key[MAX_URL_SIZE];
      enum KeyType key_type;
      uint8_t iv[16];
  };
  
  /*
   * Each variant has its own demuxer. If it currently is active,
   * it has an open AVIOContext too, and potentially an AVPacket
   * containing the next packet from this stream.
   */
  struct variant {
      int bandwidth;
      char url[MAX_URL_SIZE];
      AVIOContext pb;
      uint8_t* read_buffer;
      URLContext *input;
      AVFormatContext *parent;
      int index;
      AVFormatContext *ctx;
      AVPacket pkt;
      int stream_offset;
  
      int finished;
      int target_duration;
      int start_seq_no;
      int n_segments;
      struct segment **segments;
      int needed, cur_needed;
      int cur_seq_no;
      int64_t last_load_time;
  
      char key_url[MAX_URL_SIZE];
      uint8_t key[16];
  };
  
  typedef struct HLSContext {
      int n_variants;
      struct variant **variants;
      int cur_seq_no;
      int end_of_segment;
      int first_packet;
      int64_t first_timestamp;
      int64_t seek_timestamp;
      int seek_flags;
      AVIOInterruptCB *interrupt_callback;
      char *user_agent;                    ///< holds HTTP user agent set as an AVOption to the HTTP protocol context
      char *cookies;                       ///< holds HTTP cookie values set in either the initial response or as an AVOption to the HTTP protocol context
  } HLSContext;
  
  static int read_chomp_line(AVIOContext *s, char *buf, int maxlen)
  {
      int len = ff_get_line(s, buf, maxlen);
      while (len > 0 && av_isspace(buf[len - 1]))
          buf[--len] = '\0';
      return len;
  }
  
  static void free_segment_list(struct variant *var)
  {
      int i;
      for (i = 0; i < var->n_segments; i++)
          av_free(var->segments[i]);
      av_freep(&var->segments);
      var->n_segments = 0;
  }
  
  static void free_variant_list(HLSContext *c)
  {
      int i;
      for (i = 0; i < c->n_variants; i++) {
          struct variant *var = c->variants[i];
          free_segment_list(var);
          av_free_packet(&var->pkt);
          av_free(var->pb.buffer);
          if (var->input)
              ffurl_close(var->input);
          if (var->ctx) {
              var->ctx->pb = NULL;
              avformat_close_input(&var->ctx);
          }
          av_free(var);
      }
      av_freep(&c->variants);
      av_freep(&c->cookies);
      av_freep(&c->user_agent);
      c->n_variants = 0;
  }
  
  /*
   * Used to reset a statically allocated AVPacket to a clean slate,
   * containing no data.
   */
  static void reset_packet(AVPacket *pkt)
  {
      av_init_packet(pkt);
      pkt->data = NULL;
  }
  
  static struct variant *new_variant(HLSContext *c, int bandwidth,
                                     const char *url, const char *base)
  {
      struct variant *var = av_mallocz(sizeof(struct variant));
      if (!var)
          return NULL;
      reset_packet(&var->pkt);
      var->bandwidth = bandwidth;
      ff_make_absolute_url(var->url, sizeof(var->url), base, url);
      dynarray_add(&c->variants, &c->n_variants, var);
      return var;
  }
  
  struct variant_info {
      char bandwidth[20];
  };
  
  static void handle_variant_args(struct variant_info *info, const char *key,
                                  int key_len, char **dest, int *dest_len)
  {
      if (!strncmp(key, "BANDWIDTH=", key_len)) {
          *dest     =        info->bandwidth;
          *dest_len = sizeof(info->bandwidth);
      }
  }
  
  struct key_info {
       char uri[MAX_URL_SIZE];
       char method[10];
       char iv[35];
  };
  
  static void handle_key_args(struct key_info *info, const char *key,
                              int key_len, char **dest, int *dest_len)
  {
      if (!strncmp(key, "METHOD=", key_len)) {
          *dest     =        info->method;
          *dest_len = sizeof(info->method);
      } else if (!strncmp(key, "URI=", key_len)) {
          *dest     =        info->uri;
          *dest_len = sizeof(info->uri);
      } else if (!strncmp(key, "IV=", key_len)) {
          *dest     =        info->iv;
          *dest_len = sizeof(info->iv);
      }
  }
  
  static int parse_playlist(HLSContext *c, const char *url,
                            struct variant *var, AVIOContext *in)
  {
      int ret = 0, is_segment = 0, is_variant = 0, bandwidth = 0;
      double duration = 0.0;
      enum KeyType key_type = KEY_NONE;
      uint8_t iv[16] = "";
      int has_iv = 0;
      char key[MAX_URL_SIZE] = "";
      char line[1024];
      const char *ptr;
      int close_in = 0;
  
      if (!in) {
          AVDictionary *opts = NULL;
          close_in = 1;
          /* Some HLS servers don't like being sent the range header */
          av_dict_set(&opts, "seekable", "0", 0);
  
          // broker prior HTTP options that should be consistent across requests
          av_dict_set(&opts, "user-agent", c->user_agent, 0);
          av_dict_set(&opts, "cookies", c->cookies, 0);
  
          ret = avio_open2(&in, url, AVIO_FLAG_READ,
                           c->interrupt_callback, &opts);
          av_dict_free(&opts);
          if (ret < 0)
              return ret;
      }
  
      read_chomp_line(in, line, sizeof(line));
      if (strcmp(line, "#EXTM3U")) {
          ret = AVERROR_INVALIDDATA;
          goto fail;
      }
  
      if (var) {
          free_segment_list(var);
          var->finished = 0;
      }
      while (!url_feof(in)) {
          read_chomp_line(in, line, sizeof(line));
          if (av_strstart(line, "#EXT-X-STREAM-INF:", &ptr)) {
              struct variant_info info = {{0}};
              is_variant = 1;
              ff_parse_key_value(ptr, (ff_parse_key_val_cb) handle_variant_args,
                                 &info);
              bandwidth = atoi(info.bandwidth);
          } else if (av_strstart(line, "#EXT-X-KEY:", &ptr)) {
              struct key_info info = {{0}};
              ff_parse_key_value(ptr, (ff_parse_key_val_cb) handle_key_args,
                                 &info);
              key_type = KEY_NONE;
              has_iv = 0;
              if (!strcmp(info.method, "AES-128"))
                  key_type = KEY_AES_128;
              if (!strncmp(info.iv, "0x", 2) || !strncmp(info.iv, "0X", 2)) {
                  ff_hex_to_data(iv, info.iv + 2);
                  has_iv = 1;
              }
              av_strlcpy(key, info.uri, sizeof(key));
          } else if (av_strstart(line, "#EXT-X-TARGETDURATION:", &ptr)) {
              if (!var) {
                  var = new_variant(c, 0, url, NULL);
                  if (!var) {
                      ret = AVERROR(ENOMEM);
                      goto fail;
                  }
              }
              var->target_duration = atoi(ptr);
          } else if (av_strstart(line, "#EXT-X-MEDIA-SEQUENCE:", &ptr)) {
              if (!var) {
                  var = new_variant(c, 0, url, NULL);
                  if (!var) {
                      ret = AVERROR(ENOMEM);
                      goto fail;
                  }
              }
              var->start_seq_no = atoi(ptr);
          } else if (av_strstart(line, "#EXT-X-ENDLIST", &ptr)) {
              if (var)
                  var->finished = 1;
          } else if (av_strstart(line, "#EXTINF:", &ptr)) {
              is_segment = 1;
              duration   = atof(ptr);
          } else if (av_strstart(line, "#", NULL)) {
              continue;
          } else if (line[0]) {
              if (is_variant) {
                  if (!new_variant(c, bandwidth, line, url)) {
                      ret = AVERROR(ENOMEM);
                      goto fail;
                  }
                  is_variant = 0;
                  bandwidth  = 0;
              }
              if (is_segment) {
                  struct segment *seg;
                  if (!var) {
                      var = new_variant(c, 0, url, NULL);
                      if (!var) {
                          ret = AVERROR(ENOMEM);
                          goto fail;
                      }
                  }
                  seg = av_malloc(sizeof(struct segment));
                  if (!seg) {
                      ret = AVERROR(ENOMEM);
                      goto fail;
                  }
                  seg->duration = duration;
                  seg->key_type = key_type;
                  if (has_iv) {
                      memcpy(seg->iv, iv, sizeof(iv));
                  } else {
                      int seq = var->start_seq_no + var->n_segments;
                      memset(seg->iv, 0, sizeof(seg->iv));
                      AV_WB32(seg->iv + 12, seq);
                  }
                  ff_make_absolute_url(seg->key, sizeof(seg->key), url, key);
                  ff_make_absolute_url(seg->url, sizeof(seg->url), url, line);
                  dynarray_add(&var->segments, &var->n_segments, seg);
                  is_segment = 0;
              }
          }
      }
      if (var)
          var->last_load_time = av_gettime();
  
  fail:
      if (close_in)
          avio_close(in);
      return ret;
  }
  
  static int open_input(HLSContext *c, struct variant *var)
  {
      AVDictionary *opts = NULL;
      int ret;
      struct segment *seg = var->segments[var->cur_seq_no - var->start_seq_no];
  
      // broker prior HTTP options that should be consistent across requests
      av_dict_set(&opts, "user-agent", c->user_agent, 0);
      av_dict_set(&opts, "cookies", c->cookies, 0);
      av_dict_set(&opts, "seekable", "0", 0);
  
      if (seg->key_type == KEY_NONE) {
          ret = ffurl_open(&var->input, seg->url, AVIO_FLAG_READ,
                            &var->parent->interrupt_callback, &opts);
          goto cleanup;
      } else if (seg->key_type == KEY_AES_128) {
          char iv[33], key[33], url[MAX_URL_SIZE];
          if (strcmp(seg->key, var->key_url)) {
              URLContext *uc;
              if (ffurl_open(&uc, seg->key, AVIO_FLAG_READ,
                             &var->parent->interrupt_callback, &opts) == 0) {
                  if (ffurl_read_complete(uc, var->key, sizeof(var->key))
                      != sizeof(var->key)) {
                      av_log(NULL, AV_LOG_ERROR, "Unable to read key file %s\n",
                             seg->key);
                  }
                  ffurl_close(uc);
              } else {
                  av_log(NULL, AV_LOG_ERROR, "Unable to open key file %s\n",
                         seg->key);
              }
              av_strlcpy(var->key_url, seg->key, sizeof(var->key_url));
          }
          ff_data_to_hex(iv, seg->iv, sizeof(seg->iv), 0);
          ff_data_to_hex(key, var->key, sizeof(var->key), 0);
          iv[32] = key[32] = '\0';
          if (strstr(seg->url, "://"))
              snprintf(url, sizeof(url), "crypto+%s", seg->url);
          else
              snprintf(url, sizeof(url), "crypto:%s", seg->url);
          if ((ret = ffurl_alloc(&var->input, url, AVIO_FLAG_READ,
                                 &var->parent->interrupt_callback)) < 0)
              goto cleanup;
          av_opt_set(var->input->priv_data, "key", key, 0);
          av_opt_set(var->input->priv_data, "iv", iv, 0);
          /* Need to repopulate options */
          av_dict_free(&opts);
          av_dict_set(&opts, "seekable", "0", 0);
          if ((ret = ffurl_connect(var->input, &opts)) < 0) {
              ffurl_close(var->input);
              var->input = NULL;
              goto cleanup;
          }
          ret = 0;
      }
      else
        ret = AVERROR(ENOSYS);
  
  cleanup:
      av_dict_free(&opts);
      return ret;
  }
  
  static int read_data(void *opaque, uint8_t *buf, int buf_size)
  {
      struct variant *v = opaque;
      HLSContext *c = v->parent->priv_data;
      int ret, i;
  
  restart:
      if (!v->input) {
          /* If this is a live stream and the reload interval has elapsed since
           * the last playlist reload, reload the variant playlists now. */
          int64_t reload_interval = v->n_segments > 0 ?
                                    v->segments[v->n_segments - 1]->duration :
                                    v->target_duration;
          reload_interval *= 1000000;
  
  reload:
          if (!v->finished &&
              av_gettime() - v->last_load_time >= reload_interval) {
              if ((ret = parse_playlist(c, v->url, v, NULL)) < 0)
                  return ret;
              /* If we need to reload the playlist again below (if
               * there's still no more segments), switch to a reload
               * interval of half the target duration. */
              reload_interval = v->target_duration * 500000LL;
          }
          if (v->cur_seq_no < v->start_seq_no) {
              av_log(NULL, AV_LOG_WARNING,
                     "skipping %d segments ahead, expired from playlists\n",
                     v->start_seq_no - v->cur_seq_no);
              v->cur_seq_no = v->start_seq_no;
          }
          if (v->cur_seq_no >= v->start_seq_no + v->n_segments) {
              if (v->finished)
                  return AVERROR_EOF;
              while (av_gettime() - v->last_load_time < reload_interval) {
                  if (ff_check_interrupt(c->interrupt_callback))
                      return AVERROR_EXIT;
                  av_usleep(100*1000);
              }
              /* Enough time has elapsed since the last reload */
              goto reload;
          }
  
          ret = open_input(c, v);
          if (ret < 0)
              return ret;
      }
      ret = ffurl_read(v->input, buf, buf_size);
      if (ret > 0)
          return ret;
      ffurl_close(v->input);
      v->input = NULL;
      v->cur_seq_no++;
  
      c->end_of_segment = 1;
      c->cur_seq_no = v->cur_seq_no;
  
      if (v->ctx && v->ctx->nb_streams && v->parent->nb_streams >= v->stream_offset + v->ctx->nb_streams) {
          v->needed = 0;
          for (i = v->stream_offset; i < v->stream_offset + v->ctx->nb_streams;
               i++) {
              if (v->parent->streams[i]->discard < AVDISCARD_ALL)
                  v->needed = 1;
          }
      }
      if (!v->needed) {
          av_log(v->parent, AV_LOG_INFO, "No longer receiving variant %d\n",
                 v->index);
          return AVERROR_EOF;
      }
      goto restart;
  }
  
  static int hls_read_header(AVFormatContext *s)
  {
      URLContext *u = (s->flags & AVFMT_FLAG_CUSTOM_IO) ? NULL : s->pb->opaque;
      HLSContext *c = s->priv_data;
      int ret = 0, i, j, stream_offset = 0;
  
      c->interrupt_callback = &s->interrupt_callback;
  
      // if the URL context is good, read important options we must broker later
      if (u && u->prot->priv_data_class) {
          // get the previous user agent & set back to null if string size is zero
          av_freep(&c->user_agent);
          av_opt_get(u->priv_data, "user-agent", 0, (uint8_t**)&(c->user_agent));
          if (c->user_agent && !strlen(c->user_agent))
              av_freep(&c->user_agent);
  
          // get the previous cookies & set back to null if string size is zero
          av_freep(&c->cookies);
          av_opt_get(u->priv_data, "cookies", 0, (uint8_t**)&(c->cookies));
          if (c->cookies && !strlen(c->cookies))
              av_freep(&c->cookies);
      }
  
      if ((ret = parse_playlist(c, s->filename, NULL, s->pb)) < 0)
          goto fail;
  
      if (c->n_variants == 0) {
          av_log(NULL, AV_LOG_WARNING, "Empty playlist\n");
          ret = AVERROR_EOF;
          goto fail;
      }
      /* If the playlist only contained variants, parse each individual
       * variant playlist. */
      if (c->n_variants > 1 || c->variants[0]->n_segments == 0) {
          for (i = 0; i < c->n_variants; i++) {
              struct variant *v = c->variants[i];
              if ((ret = parse_playlist(c, v->url, v, NULL)) < 0)
                  goto fail;
          }
      }
  
      if (c->variants[0]->n_segments == 0) {
          av_log(NULL, AV_LOG_WARNING, "Empty playlist\n");
          ret = AVERROR_EOF;
          goto fail;
      }
  
      /* If this isn't a live stream, calculate the total duration of the
       * stream. */
      if (c->variants[0]->finished) {
          int64_t duration = 0;
          for (i = 0; i < c->variants[0]->n_segments; i++)
              duration += round(c->variants[0]->segments[i]->duration * AV_TIME_BASE);
          s->duration = duration;
      }
  
      /* Open the demuxer for each variant */
      for (i = 0; i < c->n_variants; i++) {
          struct variant *v = c->variants[i];
          AVInputFormat *in_fmt = NULL;
          char bitrate_str[20];
          AVProgram *program = NULL;
          if (v->n_segments == 0)
              continue;
  
          if (!(v->ctx = avformat_alloc_context())) {
              ret = AVERROR(ENOMEM);
              goto fail;
          }
  
          v->index  = i;
          v->needed = 1;
          v->parent = s;
  
          /* If this is a live stream with more than 3 segments, start at the
           * third last segment. */
          v->cur_seq_no = v->start_seq_no;
          if (!v->finished && v->n_segments > 3)
              v->cur_seq_no = v->start_seq_no + v->n_segments - 3;
  
          v->read_buffer = av_malloc(INITIAL_BUFFER_SIZE);
          ffio_init_context(&v->pb, v->read_buffer, INITIAL_BUFFER_SIZE, 0, v,
                            read_data, NULL, NULL);
          v->pb.seekable = 0;
          ret = av_probe_input_buffer(&v->pb, &in_fmt, v->segments[0]->url,
                                      NULL, 0, 0);
          if (ret < 0) {
              /* Free the ctx - it isn't initialized properly at this point,
               * so avformat_close_input shouldn't be called. If
               * avformat_open_input fails below, it frees and zeros the
               * context, so it doesn't need any special treatment like this. */
              av_log(s, AV_LOG_ERROR, "Error when loading first segment '%s'\n", v->segments[0]->url);
              avformat_free_context(v->ctx);
              v->ctx = NULL;
              goto fail;
          }
          v->ctx->pb       = &v->pb;
          ret = avformat_open_input(&v->ctx, v->segments[0]->url, in_fmt, NULL);
          if (ret < 0)
              goto fail;
  
          v->stream_offset = stream_offset;
          v->ctx->ctx_flags &= ~AVFMTCTX_NOHEADER;
          ret = avformat_find_stream_info(v->ctx, NULL);
          if (ret < 0)
              goto fail;
          snprintf(bitrate_str, sizeof(bitrate_str), "%d", v->bandwidth);
  
          /* Create new AVprogram for variant i */
          program = av_new_program(s, i);
          if (!program)
              goto fail;
          av_dict_set(&program->metadata, "variant_bitrate", bitrate_str, 0);
  
          /* Create new AVStreams for each stream in this variant */
          for (j = 0; j < v->ctx->nb_streams; j++) {
              AVStream *st = avformat_new_stream(s, NULL);
              AVStream *ist = v->ctx->streams[j];
              if (!st) {
                  ret = AVERROR(ENOMEM);
                  goto fail;
              }
              ff_program_add_stream_index(s, i, stream_offset + j);
              st->id = i;
              avpriv_set_pts_info(st, ist->pts_wrap_bits, ist->time_base.num, ist->time_base.den);
              avcodec_copy_context(st->codec, v->ctx->streams[j]->codec);
              if (v->bandwidth)
                  av_dict_set(&st->metadata, "variant_bitrate", bitrate_str,
                                   0);
          }
          stream_offset += v->ctx->nb_streams;
      }
  
      c->first_packet = 1;
      c->first_timestamp = AV_NOPTS_VALUE;
      c->seek_timestamp  = AV_NOPTS_VALUE;
  
      return 0;
  fail:
      free_variant_list(c);
      return ret;
  }
  
  static int recheck_discard_flags(AVFormatContext *s, int first)
  {
      HLSContext *c = s->priv_data;
      int i, changed = 0;
  
      /* Check if any new streams are needed */
      for (i = 0; i < c->n_variants; i++)
          c->variants[i]->cur_needed = 0;
  
      for (i = 0; i < s->nb_streams; i++) {
          AVStream *st = s->streams[i];
          struct variant *var = c->variants[s->streams[i]->id];
          if (st->discard < AVDISCARD_ALL)
              var->cur_needed = 1;
      }
      for (i = 0; i < c->n_variants; i++) {
          struct variant *v = c->variants[i];
          if (v->cur_needed && !v->needed) {
              v->needed = 1;
              changed = 1;
              v->cur_seq_no = c->cur_seq_no;
              v->pb.eof_reached = 0;
              av_log(s, AV_LOG_INFO, "Now receiving variant %d\n", i);
          } else if (first && !v->cur_needed && v->needed) {
              if (v->input)
                  ffurl_close(v->input);
              v->input = NULL;
              v->needed = 0;
              changed = 1;
              av_log(s, AV_LOG_INFO, "No longer receiving variant %d\n", i);
          }
      }
      return changed;
  }
  
  static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
  {
      HLSContext *c = s->priv_data;
      int ret, i, minvariant = -1;
  
      if (c->first_packet) {
          recheck_discard_flags(s, 1);
          c->first_packet = 0;
      }
  
  start:
      c->end_of_segment = 0;
      for (i = 0; i < c->n_variants; i++) {
          struct variant *var = c->variants[i];
          /* Make sure we've got one buffered packet from each open variant
           * stream */
          if (var->needed && !var->pkt.data) {
              while (1) {
                  int64_t ts_diff;
                  AVStream *st;
                  ret = av_read_frame(var->ctx, &var->pkt);
                  if (ret < 0) {
                      if (!url_feof(&var->pb) && ret != AVERROR_EOF)
                          return ret;
                      reset_packet(&var->pkt);
                      break;
                  } else {
                      if (c->first_timestamp == AV_NOPTS_VALUE)
                          c->first_timestamp = var->pkt.dts;
                  }
  
                  if (c->seek_timestamp == AV_NOPTS_VALUE)
                      break;
  
                  if (var->pkt.dts == AV_NOPTS_VALUE) {
                      c->seek_timestamp = AV_NOPTS_VALUE;
                      break;
                  }
  
                  st = var->ctx->streams[var->pkt.stream_index];
                  ts_diff = av_rescale_rnd(var->pkt.dts, AV_TIME_BASE,
                                           st->time_base.den, AV_ROUND_DOWN) -
                            c->seek_timestamp;
                  if (ts_diff >= 0 && (c->seek_flags  & AVSEEK_FLAG_ANY ||
                                       var->pkt.flags & AV_PKT_FLAG_KEY)) {
                      c->seek_timestamp = AV_NOPTS_VALUE;
                      break;
                  }
              }
          }
          /* Check if this stream has the packet with the lowest dts */
          if (var->pkt.data) {
              if(minvariant < 0) {
                  minvariant = i;
              } else {
                  struct variant *minvar = c->variants[minvariant];
                  int64_t dts    =    var->pkt.dts;
                  int64_t mindts = minvar->pkt.dts;
                  AVStream *st   =    var->ctx->streams[   var->pkt.stream_index];
                  AVStream *minst= minvar->ctx->streams[minvar->pkt.stream_index];
  
                  if(   st->start_time != AV_NOPTS_VALUE)    dts -=    st->start_time;
                  if(minst->start_time != AV_NOPTS_VALUE) mindts -= minst->start_time;
  
                  if (av_compare_ts(dts, st->time_base, mindts, minst->time_base) < 0)
                      minvariant = i;
              }
          }
      }
      if (c->end_of_segment) {
          if (recheck_discard_flags(s, 0))
              goto start;
      }
      /* If we got a packet, return it */
      if (minvariant >= 0) {
          *pkt = c->variants[minvariant]->pkt;
          pkt->stream_index += c->variants[minvariant]->stream_offset;
          reset_packet(&c->variants[minvariant]->pkt);
          return 0;
      }
      return AVERROR_EOF;
  }
  
  static int hls_close(AVFormatContext *s)
  {
      HLSContext *c = s->priv_data;
  
      free_variant_list(c);
      return 0;
  }
  
  static int hls_read_seek(AVFormatContext *s, int stream_index,
                                 int64_t timestamp, int flags)
  {
      HLSContext *c = s->priv_data;
      int i, j, ret;
  
      if ((flags & AVSEEK_FLAG_BYTE) || !c->variants[0]->finished)
          return AVERROR(ENOSYS);
  
      c->seek_flags     = flags;
      c->seek_timestamp = stream_index < 0 ? timestamp :
                          av_rescale_rnd(timestamp, AV_TIME_BASE,
                                         s->streams[stream_index]->time_base.den,
                                         flags & AVSEEK_FLAG_BACKWARD ?
                                         AV_ROUND_DOWN : AV_ROUND_UP);
      timestamp = av_rescale_rnd(timestamp, 1, stream_index >= 0 ?
                                 s->streams[stream_index]->time_base.den :
                                 AV_TIME_BASE, flags & AVSEEK_FLAG_BACKWARD ?
                                 AV_ROUND_DOWN : AV_ROUND_UP);
      if (s->duration < c->seek_timestamp) {
          c->seek_timestamp = AV_NOPTS_VALUE;
          return AVERROR(EIO);
      }
  
      ret = AVERROR(EIO);
      for (i = 0; i < c->n_variants; i++) {
          /* Reset reading */
          struct variant *var = c->variants[i];
          int64_t pos = c->first_timestamp == AV_NOPTS_VALUE ? 0 :
                        av_rescale_rnd(c->first_timestamp, 1, stream_index >= 0 ?
                                 s->streams[stream_index]->time_base.den :
                                 AV_TIME_BASE, flags & AVSEEK_FLAG_BACKWARD ?
                                 AV_ROUND_DOWN : AV_ROUND_UP);
           if (var->input) {
              ffurl_close(var->input);
              var->input = NULL;
          }
          av_free_packet(&var->pkt);
          reset_packet(&var->pkt);
          var->pb.eof_reached = 0;
          /* Clear any buffered data */
          var->pb.buf_end = var->pb.buf_ptr = var->pb.buffer;
          /* Reset the pos, to let the mpegts demuxer know we've seeked. */
          var->pb.pos = 0;
  
          /* Locate the segment that contains the target timestamp */
          for (j = 0; j < var->n_segments; j++) {
              if (timestamp >= pos &&
                  timestamp < pos + var->segments[j]->duration) {
                  var->cur_seq_no = var->start_seq_no + j;
                  ret = 0;
                  break;
              }
              pos += var->segments[j]->duration;
          }
          if (ret)
              c->seek_timestamp = AV_NOPTS_VALUE;
      }
      return ret;
  }
  
  static int hls_probe(AVProbeData *p)
  {
      /* Require #EXTM3U at the start, and either one of the ones below
       * somewhere for a proper match. */
      if (strncmp(p->buf, "#EXTM3U", 7))
          return 0;
      if (strstr(p->buf, "#EXT-X-STREAM-INF:")     ||
          strstr(p->buf, "#EXT-X-TARGETDURATION:") ||
          strstr(p->buf, "#EXT-X-MEDIA-SEQUENCE:"))
          return AVPROBE_SCORE_MAX;
      return 0;
  }
  
  AVInputFormat ff_hls_demuxer = {
      .name           = "hls,applehttp",
      .long_name      = NULL_IF_CONFIG_SMALL("Apple HTTP Live Streaming"),
      .priv_data_size = sizeof(HLSContext),
      .read_probe     = hls_probe,
      .read_header    = hls_read_header,
      .read_packet    = hls_read_packet,
      .read_close     = hls_close,
      .read_seek      = hls_read_seek,
  };
  