Allow empty information attributes in RTSP Session Description

Issue: androidx/media#1087
PiperOrigin-RevId: 608534659

RELEASENOTES.md

@@ -42,6 +42,8 @@
 *   DASH Extension:
 *   Smooth Streaming Extension:
 *   RTSP Extension:
+    *   Skip empty session information values (i-tags) in SDP parsing
+        ([#1087](https://github.com/androidx/media/issues/1087)).
 *   Decoder Extensions (FFmpeg, VP9, AV1, MIDI, etc.):
 *   Leanback extension:
 *   Cast Extension:

libraries/exoplayer_rtsp/src/main/java/androidx/media3/exoplayer/rtsp/SessionDescriptionParser.java

@@ -26,6 +26,7 @@ import androidx.annotation.Nullable;
 import androidx.media3.common.ParserException;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.common.util.Util;
+import java.util.Objects;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -35,6 +36,8 @@ import java.util.regex.Pattern;
   // SDP line always starts with an one letter tag, followed by an equal sign. The information
   // under the given tag follows an optional space.
   private static final Pattern SDP_LINE_PATTERN = Pattern.compile("([a-z])=\\s?(.+)");
+  // SDP line with a one letter tag, an equal sign, and an empty value.
+  private static final Pattern SDP_LINE_WITH_EMPTY_VALUE_PATTERN = Pattern.compile("^([a-z])=$");
   // Matches an attribute line (with a= sdp tag removed. Example: range:npt=0-50.0).
   // Attribute can also be a flag, i.e. without a value, like recvonly. Reference RFC4566 Section 9
   // Page 43, under "token-char".
@@ -81,6 +84,11 @@ import java.util.regex.Pattern;
 
       Matcher matcher = SDP_LINE_PATTERN.matcher(line);
       if (!matcher.matches()) {
+        Matcher sdpTagMatcher = SDP_LINE_WITH_EMPTY_VALUE_PATTERN.matcher(line);
+        if (sdpTagMatcher.matches() && Objects.equals(sdpTagMatcher.group(1), INFORMATION_TYPE)) {
+          // Allow and skip empty Session Information (tag 'i') attributes
+          continue;
+        }
         throw ParserException.createForMalformedManifest(
             "Malformed SDP line: " + line, /* cause= */ null);
       }

libraries/exoplayer_rtsp/src/test/java/androidx/media3/exoplayer/rtsp/SessionDescriptionTest.java

@@ -29,6 +29,7 @@ import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertThrows;
 
 import android.net.Uri;
+import androidx.media3.common.ParserException;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -270,6 +271,38 @@ public class SessionDescriptionTest {
     assertThat(rtpMapAttribute.clockRate).isEqualTo(44100);
   }
 
+  @Test
+  public void parse_sdpStringWithEmptyInformationAttribute_succeeds() throws Exception {
+    String testMediaSdpInfo =
+        "v=0\r\n"
+            + "o=MNobody 2890844526 2890842807 IN IP4 192.0.2.46\r\n"
+            + "s=SDP Seminar\r\n"
+            + "i=\r\n"
+            + "t=0 0\r\n"
+            + "a=control:*\r\n"
+            + "m=audio 3456 RTP/AVP 0\r\n"
+            + "i=\r\n"
+            + "a=rtpmap:97 AC3/44100  \r\n";
+
+    SessionDescription sessionDescription = SessionDescriptionParser.parse(testMediaSdpInfo);
+
+    assertThat(sessionDescription.sessionInfo).isNull();
+    assertThat(sessionDescription.mediaDescriptionList.get(0).mediaTitle).isNull();
+  }
+
+  @Test
+  public void parse_sdpStringWithEmptySessionAttribute_throwsParserException() {
+    String testMediaSdpInfo =
+        "v=0\r\n"
+            + "o=MNobody 2890844526 2890842807 IN IP4 192.0.2.46\r\n"
+            + "s=\r\n"
+            + "a=control:*\r\n"
+            + "m=audio 3456 RTP/AVP 0\r\n"
+            + "a=rtpmap:97 AC3/44100  \r\n";
+
+    assertThrows(ParserException.class, () -> SessionDescriptionParser.parse(testMediaSdpInfo));
+  }
+
   @Test
   public void buildMediaDescription_withInvalidRtpmapAttribute_throwsIllegalStateException() {
     assertThrows(