From cb7ea09af1af54ec220f6dedb64cb6eaa1be62be Mon Sep 17 00:00:00 2001
From: sheenachhabra <sheenachhabra@google.com>
Date: Wed, 31 Jan 2024 10:28:57 -0800
Subject: [PATCH] Add regression test of skipping empty track when writing MP4

The implementation of fragmented MP4 caused a regression where muxer
started writing empty tracks even for non fragmented MP4.

PiperOrigin-RevId: 603091348
---
 .../media3/muxer/Mp4MuxerEndToEndTest.java    | 32 ++++++++++++++++++
 .../mp4_without_empty_track.mp4.dump          | 33 +++++++++++++++++++
 2 files changed, 65 insertions(+)
 create mode 100644 libraries/test_data/src/test/assets/muxerdumps/mp4_without_empty_track.mp4.dump

diff --git a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java
index 99a6f65c56..430993e75e 100644
--- a/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java
+++ b/libraries/muxer/src/test/java/androidx/media3/muxer/Mp4MuxerEndToEndTest.java
@@ -24,6 +24,7 @@ import android.util.Pair;
 import androidx.media3.extractor.mp4.Mp4Extractor;
 import androidx.media3.muxer.Mp4Muxer.TrackToken;
 import androidx.media3.test.utils.DumpFileAsserts;
+import androidx.media3.test.utils.DumpableMp4Box;
 import androidx.media3.test.utils.FakeExtractorOutput;
 import androidx.media3.test.utils.TestUtil;
 import androidx.test.core.app.ApplicationProvider;
@@ -156,4 +157,35 @@ public class Mp4MuxerEndToEndTest {
       mp4Muxer.close();
     }
   }
+
+  @Test
+  public void createMp4File_withOneTrackEmpty_doesNotWriteEmptyTrack() throws Exception {
+    String outputFilePath = temporaryFolder.newFile().getPath();
+    Mp4Muxer mp4Muxer = new Mp4Muxer.Builder(new FileOutputStream(outputFilePath)).build();
+    mp4Muxer.setModificationTime(/* timestampMs= */ 500_000_000L);
+    Pair<ByteBuffer, BufferInfo> track1Sample1 =
+        MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 0L);
+    Pair<ByteBuffer, BufferInfo> track1Sample2 =
+        MuxerTestUtil.getFakeSampleAndSampleInfo(/* presentationTimeUs= */ 100L);
+
+    try {
+      TrackToken track1 = mp4Muxer.addTrack(/* sortKey= */ 0, FAKE_VIDEO_FORMAT);
+      mp4Muxer.writeSampleData(track1, track1Sample1.first, track1Sample1.second);
+      mp4Muxer.writeSampleData(track1, track1Sample2.first, track1Sample2.second);
+      // Add same track again but without any samples.
+      mp4Muxer.addTrack(/* sortKey= */ 1, FAKE_VIDEO_FORMAT);
+    } finally {
+      mp4Muxer.close();
+    }
+
+    // The FakeExtractorOutput omits tracks with no samples so the dump file will be the same
+    // with/without the empty track. Hence used DumpableMp4Box instead.
+    DumpableMp4Box dumpableBox =
+        new DumpableMp4Box(ByteBuffer.wrap(TestUtil.getByteArrayFromFilePath(outputFilePath)));
+    // Output contains only one trak box.
+    DumpFileAsserts.assertOutput(
+        ApplicationProvider.getApplicationContext(),
+        dumpableBox,
+        MuxerTestUtil.getExpectedDumpFilePath("mp4_without_empty_track.mp4"));
+  }
 }
diff --git a/libraries/test_data/src/test/assets/muxerdumps/mp4_without_empty_track.mp4.dump b/libraries/test_data/src/test/assets/muxerdumps/mp4_without_empty_track.mp4.dump
new file mode 100644
index 0000000000..40d8ae50c6
--- /dev/null
+++ b/libraries/test_data/src/test/assets/muxerdumps/mp4_without_empty_track.mp4.dump
@@ -0,0 +1,33 @@
+ftyp (28 bytes):
+  Data = length 20, hash EF896440
+mdat (126 bytes):
+  Data = length 110, hash 48173D41
+moov (674 bytes):
+  mvhd (108 bytes):
+    Data = length 100, hash 3D6D026F
+  trak (558 bytes):
+    tkhd (92 bytes):
+      Data = length 84, hash 3EFBEC22
+    mdia (458 bytes):
+      mdhd (32 bytes):
+        Data = length 24, hash 42F40E1C
+      hdlr (44 bytes):
+        Data = length 36, hash A0852FF2
+      minf (374 bytes):
+        vmhd (20 bytes):
+          Data = length 12, hash EE830681
+        dinf (36 bytes):
+          Data = length 28, hash D535436B
+        stbl (310 bytes):
+          stsd (166 bytes):
+            Data = length 158, hash 11532063
+          stts (32 bytes):
+            Data = length 24, hash 4A7D0E0E
+          stsz (28 bytes):
+            Data = length 20, hash 3828E071
+          stsc (28 bytes):
+            Data = length 20, hash 8F7C9A06
+          co64 (24 bytes):
+            Data = length 16, hash E4EE4D2E
+          stss (24 bytes):
+            Data = length 16, hash 7940D386