Add NTP client to get time offset for live streams without UTCTiming.

Dash live streams require that the client has an accurate wall clock
time and in absence of a UTCTiming element, this is assumed to be the
NTP time.

This change adds NTP time offset resolution for DASH live streams
without such timing elements.

PiperOrigin-RevId: 289098796

library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -54,6 +54,7 @@ import com.google.android.exoplayer2.upstream.ParsingLoadable;
 import com.google.android.exoplayer2.upstream.TransferListener;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Log;
+import com.google.android.exoplayer2.util.SntpClient;
 import com.google.android.exoplayer2.util.Util;
 import java.io.BufferedReader;
 import java.io.IOException;
@@ -821,8 +822,12 @@ public final class DashMediaSource extends BaseMediaSource {
     }
 
     if (oldPeriodCount == 0) {
-      if (manifest.dynamic && manifest.utcTiming != null) {
-        resolveUtcTimingElement(manifest.utcTiming);
+      if (manifest.dynamic) {
+        if (manifest.utcTiming != null) {
+          resolveUtcTimingElement(manifest.utcTiming);
+        } else {
+          loadNtpTimeOffset();
+        }
       } else {
         processManifest(true);
       }
@@ -915,6 +920,9 @@ public final class DashMediaSource extends BaseMediaSource {
     } else if (Util.areEqual(scheme, "urn:mpeg:dash:utc:http-xsdate:2014")
         || Util.areEqual(scheme, "urn:mpeg:dash:utc:http-xsdate:2012")) {
       resolveUtcTimingElementHttp(timingElement, new XsDateTimeParser());
+    } else if (Util.areEqual(scheme, "urn:mpeg:dash:utc:ntp:2014")
+        || Util.areEqual(scheme, "urn:mpeg:dash:utc:ntp:2012")) {
+      loadNtpTimeOffset();
     } else {
       // Unsupported scheme.
       onUtcTimestampResolutionError(new IOException("Unsupported UTC timing scheme"));
@@ -936,13 +944,29 @@ public final class DashMediaSource extends BaseMediaSource {
         C.DATA_TYPE_TIME_SYNCHRONIZATION, parser), new UtcTimestampCallback(), 1);
   }
 
+  private void loadNtpTimeOffset() {
+    SntpClient.initialize(
+        loader,
+        new SntpClient.InitializationCallback() {
+          @Override
+          public void onInitialized() {
+            onUtcTimestampResolved(SntpClient.getElapsedRealtimeOffsetMs());
+          }
+
+          @Override
+          public void onInitializationFailed(IOException error) {
+            onUtcTimestampResolutionError(error);
+          }
+        });
+  }
+
   private void onUtcTimestampResolved(long elapsedRealtimeOffsetMs) {
     this.elapsedRealtimeOffsetMs = elapsedRealtimeOffsetMs;
     processManifest(true);
   }
 
   private void onUtcTimestampResolutionError(IOException error) {
-    Log.e(TAG, "Failed to resolve UtcTiming element.", error);
+    Log.e(TAG, "Failed to resolve time offset.", error);
     // Be optimistic and continue in the hope that the device clock is correct.
     processManifest(true);
   }