Relax session timing requirement.

Some RTSP servers do not include the RANGE attribute for live contents.

#minor-release

PiperOrigin-RevId: 370662587

library/rtsp/src/main/java/com/google/android/exoplayer2/source/rtsp/RtspClient.java

@@ -443,12 +443,15 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     }
     }
 
 
     public void onDescribeResponseReceived(RtspDescribeResponse response) {
     public void onDescribeResponseReceived(RtspDescribeResponse response) {
+      @Nullable
       String sessionRangeAttributeString =
       String sessionRangeAttributeString =
-          checkNotNull(response.sessionDescription.attributes.get(SessionDescription.ATTR_RANGE));
+          response.sessionDescription.attributes.get(SessionDescription.ATTR_RANGE);
 
 
       try {
       try {
         sessionInfoListener.onSessionTimelineUpdated(
         sessionInfoListener.onSessionTimelineUpdated(
-            RtspSessionTiming.parseTiming(sessionRangeAttributeString),
+            sessionRangeAttributeString != null
+                ? RtspSessionTiming.parseTiming(sessionRangeAttributeString)
+                : RtspSessionTiming.DEFAULT,
             buildTrackList(response.sessionDescription, uri));
             buildTrackList(response.sessionDescription, uri));
         hasUpdatedTimelineAndTracks = true;
         hasUpdatedTimelineAndTracks = true;
       } catch (ParserException e) {
       } catch (ParserException e) {

library/rtsp/src/main/java/com/google/android/exoplayer2/source/rtsp/RtspSessionTiming.java

@@ -31,7 +31,7 @@ import java.util.regex.Pattern;
  * <p>Currently only NPT is supported. See RFC2326 Section 3.6 for detail of NPT.
  * <p>Currently only NPT is supported. See RFC2326 Section 3.6 for detail of NPT.
  */
  */
 public final class RtspSessionTiming {
 public final class RtspSessionTiming {
-  /** The default session timing starting from 0.000 and indefinite length. */
+  /** The default session timing starting from 0.000 and indefinite length, effectively live. */
   public static final RtspSessionTiming DEFAULT =
   public static final RtspSessionTiming DEFAULT =
       new RtspSessionTiming(/* startTimeMs= */ 0, /* stopTimeMs= */ C.TIME_UNSET);
       new RtspSessionTiming(/* startTimeMs= */ 0, /* stopTimeMs= */ C.TIME_UNSET);