All files / src/controller gap-controller.js

78.46% Statements 51/65
75.76% Branches 25/33
83.33% Functions 5/6
78.46% Lines 51/65
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168          11x 11x       12x 12x 12x 12x 12x                   5x 5x 5x   5x   1x 1x 1x   1x 1x 1x     4x       4x           4x 4x 4x 1x 1x 3x   1x     3x                   7x 7x   7x 7x     1x     7x       1x 1x                   3x 3x   2x 2x 2x                                                                                     3x 3x 3x 3x   3x 2x 2x   2x 2x           1x 1x                
import { BufferHelper } from '../utils/buffer-helper';
import { ErrorTypes, ErrorDetails } from '../errors';
import Event from '../events';
import { logger } from '../utils/logger';
 
const stallDebounceInterval = 1000;
const jumpThreshold = 0.5; // tolerance needed as some browsers stalls playback before reaching buffered range end
 
export default class GapController {
  constructor (config, media, fragmentTracker, hls) {
    this.config = config;
    this.media = media;
    this.fragmentTracker = fragmentTracker;
    this.hls = hls;
    this.stallReported = false;
  }
 
  /**
   * Checks if the playhead is stuck within a gap, and if so, attempts to free it.
   * A gap is an unbuffered range between two buffered ranges (or the start and the first buffered range).
   * @param lastCurrentTime
   * @param buffered
   */
  poll (lastCurrentTime, buffered) {
    const { config, media } = this;
    const currentTime = media.currentTime;
    const tnow = window.performance.now();
 
    if (currentTime !== lastCurrentTime) {
      // The playhead is now moving, but was previously stalled
      Eif (this.stallReported) {
        logger.warn(`playback not stuck anymore @${currentTime}, after ${Math.round(tnow - this.stalled)}ms`);
        this.stallReported = false;
      }
      this.stalled = null;
      this.nudgeRetry = 0;
      return;
    }
 
    Iif (media.ended || !media.buffered.length || media.readyState > 2) {
      return;
    }
 
    Iif (media.seeking && BufferHelper.isBuffered(media, currentTime)) {
      return;
    }
 
    // The playhead isn't moving but it should be
    // Allow some slack time to for small stalls to resolve themselves
    const stalledDuration = tnow - this.stalled;
    const bufferInfo = BufferHelper.bufferInfo(media, currentTime, config.maxBufferHole);
    if (!this.stalled) {
      this.stalled = tnow;
      return;
    } else if (stalledDuration >= stallDebounceInterval) {
      // Report stalling after trying to fix
      this._reportStall(bufferInfo.len);
    }
 
    this._tryFixBufferStall(bufferInfo, stalledDuration);
  }
 
  /**
   * Detects and attempts to fix known buffer stalling issues.
   * @param bufferInfo - The properties of the current buffer.
   * @param stalledDuration - The amount of time Hls.js has been stalling for.
   * @private
   */
  _tryFixBufferStall (bufferInfo, stalledDuration) {
    const { config, fragmentTracker, media } = this;
    const currentTime = media.currentTime;
 
    const partial = fragmentTracker.getPartialFragment(currentTime);
    if (partial) {
      // Try to skip over the buffer hole caused by a partial fragment
      // This method isn't limited by the size of the gap between buffered ranges
      this._trySkipBufferHole(partial);
    }
 
    if (bufferInfo.len > jumpThreshold && stalledDuration > config.highBufferWatchdogPeriod * 1000) {
      // Try to nudge currentTime over a buffer hole if we've been stalling for the configured amount of seconds
      // We only try to jump the hole if it's under the configured size
      // Reset stalled so to rearm watchdog timer
      this.stalled = null;
      this._tryNudgeBuffer();
    }
  }
 
  /**
   * Triggers a BUFFER_STALLED_ERROR event, but only once per stall period.
   * @param bufferLen - The playhead distance from the end of the current buffer segment.
   * @private
   */
  _reportStall (bufferLen) {
    const { hls, media, stallReported } = this;
    if (!stallReported) {
      // Report stalled error once
      this.stallReported = true;
      logger.warn(`Playback stalling at @${media.currentTime} due to low buffer`);
      hls.trigger(Event.ERROR, {
        type: ErrorTypes.MEDIA_ERROR,
        details: ErrorDetails.BUFFER_STALLED_ERROR,
        fatal: false,
        buffer: bufferLen
      });
    }
  }
 
  /**
   * Attempts to fix buffer stalls by jumping over known gaps caused by partial fragments
   * @param partial - The partial fragment found at the current time (where playback is stalling).
   * @private
   */
  _trySkipBufferHole (partial) {
    const { hls, media } = this;
    const currentTime = media.currentTime;
    let lastEndTime = 0;
    // Check if currentTime is between unbuffered regions of partial fragments
    for (let i = 0; i < media.buffered.length; i++) {
      let startTime = media.buffered.start(i);
      if (currentTime >= lastEndTime && currentTime < startTime) {
        media.currentTime = Math.max(startTime, media.currentTime + 0.1);
        logger.warn(`skipping hole, adjusting currentTime from ${currentTime} to ${media.currentTime}`);
        this.stalled = null;
        hls.trigger(Event.ERROR, {
          type: ErrorTypes.MEDIA_ERROR,
          details: ErrorDetails.BUFFER_SEEK_OVER_HOLE,
          fatal: false,
          reason: `fragment loaded with buffer holes, seeking from ${currentTime} to ${media.currentTime}`,
          frag: partial
        });
        return;
      }
      lastEndTime = media.buffered.end(i);
    }
  }
 
  /**
   * Attempts to fix buffer stalls by advancing the mediaElement's current time by a small amount.
   * @private
   */
  _tryNudgeBuffer () {
    const { config, hls, media } = this;
    const currentTime = media.currentTime;
    const nudgeRetry = (this.nudgeRetry || 0) + 1;
    this.nudgeRetry = nudgeRetry;
 
    if (nudgeRetry < config.nudgeMaxRetry) {
      const targetTime = currentTime + nudgeRetry * config.nudgeOffset;
      logger.log(`adjust currentTime from ${currentTime} to ${targetTime}`);
      // playback stalled in buffered area ... let's nudge currentTime to try to overcome this
      media.currentTime = targetTime;
      hls.trigger(Event.ERROR, {
        type: ErrorTypes.MEDIA_ERROR,
        details: ErrorDetails.BUFFER_NUDGE_ON_STALL,
        fatal: false
      });
    } else {
      logger.error(`still stuck in high buffer @${currentTime} after ${config.nudgeMaxRetry}, raise fatal error`);
      hls.trigger(Event.ERROR, {
        type: ErrorTypes.MEDIA_ERROR,
        details: ErrorDetails.BUFFER_STALLED_ERROR,
        fatal: true
      });
    }
  }
}