Add availabilityTimeOffset to last available segment calculation.

This allows the player to load the unfinished segment of a low-latency
DASH stream.

PiperOrigin-RevId: 333077153

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

@@ -411,8 +411,9 @@ public abstract class Representation {
       // The index is itself unbounded. We need to use the current time to calculate the range of
       // available segments.
       long liveEdgeTimeInPeriodUs = nowUnixTimeUs - periodStartUnixTimeUs;
-      // getSegmentNum(liveEdgeTimeInPeriodUs) will not be completed yet.
-      long firstIncompleteSegmentNum = getSegmentNum(liveEdgeTimeInPeriodUs, periodDurationUs);
+      long availabilityEndTimeUs = liveEdgeTimeInPeriodUs + segmentBase.availabilityTimeOffsetUs;
+      // getSegmentNum(availabilityEndTimeUs) will not be completed yet.
+      long firstIncompleteSegmentNum = getSegmentNum(availabilityEndTimeUs, periodDurationUs);
       long firstAvailableSegmentNum = getFirstAvailableSegmentNum(periodDurationUs, nowUnixTimeUs);
       return (int) (firstIncompleteSegmentNum - firstAvailableSegmentNum);
     }

library/dash/src/test/java/com/google/android/exoplayer2/source/dash/manifest/RepresentationTest.java

+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source.dash.manifest;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit test for {@link Representation}. */
+@RunWith(AndroidJUnit4.class)
+public final class RepresentationTest {
+
+  @Test
+  public void getFirstAvailableSegmentNum_multiSegmentRepresentationWithUnboundedTemplate() {
+    long periodStartUnixTimeUs = 123_000_000_000_000L;
+    SegmentBase.SegmentTemplate segmentTemplate =
+        new SegmentBase.SegmentTemplate(
+            /* initialization= */ null,
+            /* timescale= */ 1000,
+            /* presentationTimeOffset= */ 0,
+            /* startNumber= */ 42,
+            /* endNumber= */ C.INDEX_UNSET,
+            /* duration= */ 2000,
+            /* segmentTimeline= */ null,
+            /* availabilityTimeOffsetUs= */ 500_000,
+            /* initializationTemplate= */ null,
+            /* mediaTemplate= */ null);
+    Representation.MultiSegmentRepresentation representation =
+        new Representation.MultiSegmentRepresentation(
+            /* revisionId= */ 0,
+            new Format.Builder().build(),
+            /* baseUrl= */ "https://baseUrl/",
+            segmentTemplate,
+            /* inbandEventStreams= */ null,
+            /* periodStartUnixTimeMs= */ C.usToMs(periodStartUnixTimeUs),
+            /* timeShiftBufferDepthMs= */ 6_000);
+
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs - 10_000_000))
+        .isEqualTo(42);
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET, /* nowUnixTimeUs= */ periodStartUnixTimeUs))
+        .isEqualTo(42);
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 7_999_999))
+        .isEqualTo(42);
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 8_000_000))
+        .isEqualTo(43);
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 9_999_999))
+        .isEqualTo(43);
+    assertThat(
+            representation.getFirstAvailableSegmentNum(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 10_000_000))
+        .isEqualTo(44);
+  }
+
+  @Test
+  public void getAvailableSegmentCount_multiSegmentRepresentationWithUnboundedTemplate() {
+    long periodStartUnixTimeUs = 123_000_000_000_000L;
+    SegmentBase.SegmentTemplate segmentTemplate =
+        new SegmentBase.SegmentTemplate(
+            /* initialization= */ null,
+            /* timescale= */ 1000,
+            /* presentationTimeOffset= */ 0,
+            /* startNumber= */ 42,
+            /* endNumber= */ C.INDEX_UNSET,
+            /* duration= */ 2000,
+            /* segmentTimeline= */ null,
+            /* availabilityTimeOffsetUs= */ 500_000,
+            /* initializationTemplate= */ null,
+            /* mediaTemplate= */ null);
+    Representation.MultiSegmentRepresentation representation =
+        new Representation.MultiSegmentRepresentation(
+            /* revisionId= */ 0,
+            new Format.Builder().build(),
+            /* baseUrl= */ "https://baseUrl/",
+            segmentTemplate,
+            /* inbandEventStreams= */ null,
+            /* periodStartUnixTimeMs= */ C.usToMs(periodStartUnixTimeUs),
+            /* timeShiftBufferDepthMs= */ 6_000);
+
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs - 10_000_000))
+        .isEqualTo(0);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET, /* nowUnixTimeUs= */ periodStartUnixTimeUs))
+        .isEqualTo(0);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 1_499_999))
+        .isEqualTo(0);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 1_500_000))
+        .isEqualTo(1);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 7_499_999))
+        .isEqualTo(3);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 7_500_000))
+        .isEqualTo(4);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 7_999_999))
+        .isEqualTo(4);
+    assertThat(
+            representation.getAvailableSegmentCount(
+                /* periodDurationUs= */ C.TIME_UNSET,
+                /* nowUnixTimeUs= */ periodStartUnixTimeUs + 8_000_000))
+        .isEqualTo(3);
+  }
+}