feat: Add feature flag to calculate timestampOffset for each segment …

…to handle streams with corrupted pts or dts timestamps (#1426)

* Use audio/video start time info from Transmuxer instead of probeTs because Transmuxer aligns time between audio and video in the timestampRollover stream.

* Add a feature flag to calculate timestampOffset for each segment, regardless of its timeline, so timestampOffset should always be valid.

---------

Co-authored-by: Dzianis Dashkevich <ddashkevich@brightcove.com>

README.md

@@ -463,6 +463,12 @@ This option defaults to `false`.
 * Default: `false`
 * Use [Decode Timestamp](https://www.w3.org/TR/media-source/#decode-timestamp) instead of [Presentation Timestamp](https://www.w3.org/TR/media-source/#presentation-timestamp) for [timestampOffset](https://www.w3.org/TR/media-source/#dom-sourcebuffer-timestampoffset) calculation. This option was introduced to align with DTS-based browsers. This option affects only transmuxed data (eg: transport stream). For more info please check the following [issue](https://github.com/videojs/http-streaming/issues/1247).  
 
+##### calculateTimestampOffsetForEachSegment
+* Type: `boolean`,
+* Default: `false`
+* Calculate timestampOffset for each segment, regardless of its timeline. Sometimes it is helpful when you have corrupted DTS/PTS timestamps during discontinuities.
+
+
 ##### useForcedSubtitles
 * Type: `boolean`
 * Default: `false`

index.html

@@ -144,6 +144,11 @@
           <label class="form-check-label" for="dts-offset">Use DTS instead of PTS for Timestamp Offset calculation (reloads player)</label>
         </div>
 
+        <div class="form-check">
+          <input id=offset-each-segment type="checkbox" class="form-check-input">
+          <label class="form-check-label" for="offset-each-segment">Calculate timestampOffset for each segment, regardless of its timeline (reloads player)</label>
+        </div>
+
         <div class="form-check">
           <input id=llhls type="checkbox" class="form-check-input">
           <label class="form-check-label" for="llhls">[EXPERIMENTAL] Enables support for ll-hls (reloads player)</label>

scripts/index.js

@@ -470,6 +470,7 @@
     'pixel-diff-selector',
     'network-info',
     'dts-offset',
+    'offset-each-segment',
     'override-native',
     'preload',
     'mirror-source',
@@ -525,6 +526,7 @@
       'pixel-diff-selector',
       'network-info',
       'dts-offset',
+      'offset-each-segment',
       'exact-manifest-timings',
       'forced-subtitles'
     ].forEach(function(name) {
@@ -609,6 +611,7 @@
               leastPixelDiffSelector: getInputValue(stateEls['pixel-diff-selector']),
               useNetworkInformationApi: getInputValue(stateEls['network-info']),
               useDtsForTimestampOffset: getInputValue(stateEls['dts-offset']),
+              calculateTimestampOffsetForEachSegment: getInputValue(stateEls['offset-each-segment']),
               useForcedSubtitles: getInputValue(stateEls['forced-subtitles'])
             }
           }

src/media-segment-request.js

@@ -389,15 +389,6 @@ const transmuxAndNotify = ({
           isMuxed
         });
         trackInfoFn = null;
-
-        if (probeResult.hasAudio && !isMuxed) {
-          audioStartFn(probeResult.audioStart);
-        }
-        if (probeResult.hasVideo) {
-          videoStartFn(probeResult.videoStart);
-        }
-        audioStartFn = null;
-        videoStartFn = null;
       }
 
       finish();

src/playlist-controller.js

@@ -239,6 +239,7 @@ export class PlaylistController extends videojs.EventTarget {
       vhs: this.vhs_,
       parse708captions: options.parse708captions,
       useDtsForTimestampOffset: options.useDtsForTimestampOffset,
+      calculateTimestampOffsetForEachSegment: options.calculateTimestampOffsetForEachSegment,
       captionServices,
       mediaSource: this.mediaSource,
       currentTime: this.tech_.currentTime.bind(this.tech_),

src/segment-loader.js

@@ -179,6 +179,10 @@ export const segmentInfoString = (segmentInfo) => {
 
 const timingInfoPropertyForMedia = (mediaType) => `${mediaType}TimingInfo`;
 
+const getBufferedEndOrFallback = (buffered, fallback) => buffered.length ?
+  buffered.end(buffered.length - 1) :
+  fallback;
+
 /**
  * Returns the timestamp offset to use for the segment.
  *
@@ -190,6 +194,8 @@ const timingInfoPropertyForMedia = (mediaType) => `${mediaType}TimingInfo`;
  *        The estimated segment start
  * @param {TimeRange[]} buffered
  *        The loader's buffer
+ * @param {boolean} calculateTimestampOffsetForEachSegment
+ *        Feature flag to always calculate timestampOffset
  * @param {boolean} overrideCheck
  *        If true, no checks are made to see if the timestamp offset value should be set,
  *        but sets it directly to a value.
@@ -203,8 +209,13 @@ export const timestampOffsetForSegment = ({
   currentTimeline,
   startOfSegment,
   buffered,
+  calculateTimestampOffsetForEachSegment,
   overrideCheck
 }) => {
+  if (calculateTimestampOffsetForEachSegment) {
+    return getBufferedEndOrFallback(buffered, startOfSegment);
+  }
+
   // Check to see if we are crossing a discontinuity to see if we need to set the
   // timestamp offset on the transmuxer and source buffer.
   //
@@ -248,7 +259,7 @@ export const timestampOffsetForSegment = ({
   // should often be correct, it's better to rely on the buffered end, as the new
   // content post discontinuity should line up with the buffered end as if it were
   // time 0 for the new content.
-  return buffered.length ? buffered.end(buffered.length - 1) : startOfSegment;
+  return getBufferedEndOrFallback(buffered, startOfSegment);
 };
 
 /**
@@ -559,6 +570,7 @@ export default class SegmentLoader extends videojs.EventTarget {
     this.shouldSaveSegmentTimingInfo_ = true;
     this.parse708captions_ = settings.parse708captions;
     this.useDtsForTimestampOffset_ = settings.useDtsForTimestampOffset;
+    this.calculateTimestampOffsetForEachSegment_ = settings.calculateTimestampOffsetForEachSegment;
     this.captionServices_ = settings.captionServices;
     this.exactManifestTimings = settings.exactManifestTimings;
     this.addMetadataToTextTrack = settings.addMetadataToTextTrack;
@@ -1586,6 +1598,7 @@ export default class SegmentLoader extends videojs.EventTarget {
       currentTimeline: this.currentTimeline_,
       startOfSegment,
       buffered: this.buffered_(),
+      calculateTimestampOffsetForEachSegment: this.calculateTimestampOffsetForEachSegment_,
       overrideCheck
     });
 

src/source-updater.js

@@ -9,7 +9,7 @@ import {getMimeForCodec} from '@videojs/vhs-utils/es/codecs.js';
 import window from 'global/window';
 import toTitleCase from './util/to-title-case.js';
 import { QUOTA_EXCEEDED_ERR } from './error-codes';
-import {createTimeRanges} from './util/vjs-compat';
+import {createTimeRanges, prettyBuffered} from './util/vjs-compat';
 
 const bufferTypes = [
   'video',
@@ -297,6 +297,11 @@ const pushQueue = ({type, sourceUpdater, action, doneFn, name}) => {
 };
 
 const onUpdateend = (type, sourceUpdater) => (e) => {
+  const buffered = sourceUpdater[`${type}Buffered`]();
+  const bufferedAsString = prettyBuffered(buffered);
+
+  sourceUpdater.logger_(`${type} source buffer update end. Buffered: \n`, bufferedAsString);
+
   // Although there should, in theory, be a pending action for any updateend receieved,
   // there are some actions that may trigger updateend events without set definitions in
   // the w3c spec. For instance, setting the duration on the media source may trigger

src/util/vjs-compat.js

@@ -24,3 +24,28 @@ export function createTimeRanges(...args) {
 
   return fn.apply(context, args);
 }
+
+/**
+ * Converts any buffered time range to a descriptive string
+ *
+ * @param {TimeRanges} buffered - time ranges
+ * @return {string} - descriptive string
+ */
+export function prettyBuffered(buffered) {
+  let result = '';
+
+  for (let i = 0; i < buffered.length; i++) {
+    const start = buffered.start(i);
+    const end = buffered.end(i);
+
+    const duration = end - start;
+
+    if (result.length) {
+      result += '\n';
+    }
+
+    result += `[${duration}](${start} -> ${end})`;
+  }
+
+  return result || 'empty';
+}

src/videojs-http-streaming.js

@@ -690,6 +690,7 @@ class VhsHandler extends Component {
     this.options_.useForcedSubtitles = this.options_.useForcedSubtitles || false;
     this.options_.useNetworkInformationApi = this.options_.useNetworkInformationApi || false;
     this.options_.useDtsForTimestampOffset = this.options_.useDtsForTimestampOffset || false;
+    this.options_.calculateTimestampOffsetForEachSegment = this.options_.calculateTimestampOffsetForEachSegment || false;
     this.options_.customTagParsers = this.options_.customTagParsers || [];
     this.options_.customTagMappers = this.options_.customTagMappers || [];
     this.options_.cacheEncryptionKeys = this.options_.cacheEncryptionKeys || false;
@@ -743,6 +744,7 @@ class VhsHandler extends Component {
       'useForcedSubtitles',
       'useNetworkInformationApi',
       'useDtsForTimestampOffset',
+      'calculateTimestampOffsetForEachSegment',
       'exactManifestTimings',
       'leastPixelDiffSelector'
     ].forEach((option) => {

test/segment-loader.test.js

@@ -222,6 +222,54 @@ QUnit.test('illegalMediaSwitch detects illegal media switches', function(assert)
 
 QUnit.module('timestampOffsetForSegment');
 
+QUnit.test('returns startOfSegment when calculateTimestampOffsetForEachSegment is enabled and the buffer is empty with the same timeline', function(assert) {
+  const timestampOffset = timestampOffsetForSegment({
+    calculateTimestampOffsetForEachSegment: true,
+    segmentTimeline: 0,
+    currentTimeline: 0,
+    startOfSegment: 3,
+    buffered: createTimeRanges()
+  });
+
+  assert.equal(timestampOffset, 3, 'returned startOfSegment');
+});
+
+QUnit.test('returns startOfSegment when calculateTimestampOffsetForEachSegment is enabled and the buffer is empty with different timeline', function(assert) {
+  const timestampOffset = timestampOffsetForSegment({
+    calculateTimestampOffsetForEachSegment: true,
+    segmentTimeline: 1,
+    currentTimeline: 0,
+    startOfSegment: 3,
+    buffered: createTimeRanges()
+  });
+
+  assert.equal(timestampOffset, 3, 'returned startOfSegment');
+});
+
+QUnit.test('returns buffered.end when calculateTimestampOffsetForEachSegment is enabled and there exists buffered content with the same timeline', function(assert) {
+  const timestampOffset = timestampOffsetForSegment({
+    calculateTimestampOffsetForEachSegment: true,
+    segmentTimeline: 0,
+    currentTimeline: 0,
+    startOfSegment: 3,
+    buffered: createTimeRanges([[1, 5], [7, 8]])
+  });
+
+  assert.equal(timestampOffset, 8, 'returned buffered.end');
+});
+
+QUnit.test('returns buffered.end when calculateTimestampOffsetForEachSegment is enabled and there exists buffered content with different timeline', function(assert) {
+  const timestampOffset = timestampOffsetForSegment({
+    calculateTimestampOffsetForEachSegment: true,
+    segmentTimeline: 1,
+    currentTimeline: 0,
+    startOfSegment: 3,
+    buffered: createTimeRanges([[1, 5], [7, 8]])
+  });
+
+  assert.equal(timestampOffset, 8, 'returned buffered.end');
+});
+
 QUnit.test('returns startOfSegment when timeline changes and the buffer is empty', function(assert) {
   assert.equal(
     timestampOffsetForSegment({

test/source-updater.test.js

@@ -216,14 +216,14 @@ QUnit.test('verifies that sourcebuffer is in source buffers list before attempti
   assert.deepEqual(actionCalls, {
     audioAbort: 1,
     audioAppendBuffer: 1,
-    audioBuffered: 8,
+    audioBuffered: 12,
     audioChangeType: 1,
     audioRemove: 1,
     audioRemoveSourceBuffer: 1,
     audioTimestampOffset: 1,
     videoAbort: 1,
     videoAppendBuffer: 1,
-    videoBuffered: 8,
+    videoBuffered: 12,
     videoChangeType: 1,
     videoRemove: 1,
     videoRemoveSourceBuffer: 1,