feat(ABR): Add abr.removeLatencyFromFirstPacketTime config (#8446)

Co-authored-by: Wojciech Tyczyński <[email protected]>

Author: avelad

demo/config.js

@@ -343,7 +343,9 @@ shakaDemo.Config = class {
             /* canBeDecimal= */ true,
             /* canBeZero= */ true)
         .addBoolInput_('Prefer Network Information bandwidth',
-            'abr.preferNetworkInformationBandwidth');
+            'abr.preferNetworkInformationBandwidth')
+        .addBoolInput_('Remove latency from first packet time',
+            'abr.removeLatencyFromFirstPacketTime');
     this.addRestrictionsSection_('abr', 'Adaptation Restrictions');
   }
 

externs/shaka/player.js

@@ -2266,7 +2266,8 @@ shaka.extern.AdsConfiguration;
  *   safeMarginSwitch: number,
  *   cacheLoadThreshold: number,
  *   minTimeToSwitch: number,
- *   preferNetworkInformationBandwidth: boolean
+ *   preferNetworkInformationBandwidth: boolean,
+ *   removeLatencyFromFirstPacketTime: boolean
  * }}
  *
  * @property {boolean} enabled
@@ -2359,6 +2360,11 @@ shaka.extern.AdsConfiguration;
  *   trust the information provided by the browser.
  *   <br>
  *   Defaults to <code>false</code>.
+ * @property {boolean} removeLatencyFromFirstPacketTime
+ *   If true, we remove the latency from first packet time. This time is
+ *   used to calculate the real bandwidth.
+ *   <br>
+ *   Defaults to <code>true</code>.
  * @exportDoc
  */
 shaka.extern.AbrConfiguration;

lib/abr/simple_abr_manager.js

@@ -340,19 +340,24 @@ shaka.abr.SimpleAbrManager = class {
    * @export
    */
   segmentDownloaded(deltaTimeMs, numBytes, allowSwitch, request, context) {
-    if (deltaTimeMs < this.config_.cacheLoadThreshold) {
+    let realTimeMs = deltaTimeMs;
+    if (this.config_.removeLatencyFromFirstPacketTime &&
+        request && request.packetNumber === 1 && request.timeToFirstByte) {
+      realTimeMs = deltaTimeMs - request.timeToFirstByte;
+    }
+    if (realTimeMs < this.config_.cacheLoadThreshold) {
       // The time indicates that it could be a cache response, so we should
       // ignore this value.
       return;
     }
     shaka.log.v2('Segment downloaded:',
         'contentType=' + (request && request.contentType),
-        'deltaTimeMs=' + deltaTimeMs,
+        'deltaTimeMs=' + realTimeMs,
         'numBytes=' + numBytes,
         'lastTimeChosenMs=' + this.lastTimeChosenMs_,
         'enabled=' + this.enabled_);
-    goog.asserts.assert(deltaTimeMs >= 0, 'expected a non-negative duration');
-    this.bandwidthEstimator_.sample(deltaTimeMs, numBytes);
+    goog.asserts.assert(realTimeMs >= 0, 'expected a non-negative duration');
+    this.bandwidthEstimator_.sample(realTimeMs, numBytes);
 
     if (allowSwitch && (this.lastTimeChosenMs_ != null) && this.enabled_) {
       this.suggestStreams_();

lib/util/player_configuration.js

@@ -388,6 +388,7 @@ shaka.util.PlayerConfiguration = class {
       cacheLoadThreshold: 20,
       minTimeToSwitch: shaka.util.Platform.isApple() ? 0.5 : 0,
       preferNetworkInformationBandwidth: false,
+      removeLatencyFromFirstPacketTime: true,
     };
 
     const cmcd = {