Make DefaultAudioSink.getFramesPerEncodedSample endianness independent

While most ExoPlayer code parsing ByteBuffers is called with buffers in big
endian, in certain situation, buffers in little endian are used too.

MediaCodec produced ByteBuffers are in little endian, while buffers
receive from the sources are in big endian (ByteBuffer's default).

As a result, some code called from AudioSink in passthrough parsed
bytebuffer in little endian. This is not correct because those
format are specified in BigEndian.

Changing the endianness of the ByteBuffer returned from MediaCodec
would impact a lot more code that can currently be tested in the
current COVID lockdown situation.

As a result, this patch instead make the parsing code independent
of the ByteBuffer.order() set. All the code that is called from
DefaultAudioSink now parses the buffer explicitly in Big Endian.

Additionally, the MPEG big endian header data of size 4 bytes was
retrieved with ByteBuffer.get, which only returns one byte.

PiperOrigin-RevId: 308116173

library/common/src/main/java/com/google/android/exoplayer2/audio/Ac3Util.java

@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.drm.DrmInitData;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.android.exoplayer2.util.ParsableByteArray;
+import com.google.android.exoplayer2.util.Util;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -516,7 +517,7 @@ public final class Ac3Util {
     int endIndex = buffer.limit() - TRUEHD_SYNCFRAME_PREFIX_LENGTH;
     for (int i = startIndex; i <= endIndex; i++) {
       // The syncword ends 0xBA for TrueHD or 0xBB for MLP.
-      if ((buffer.getInt(i + 4) & 0xFEFFFFFF) == 0xBA6F72F8) {
+      if ((Util.getBigEndianInt(buffer, i + 4) & 0xFFFFFFFE) == 0xF8726FBA) {
         return i - startIndex;
       }
     }

library/common/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -60,6 +60,8 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Method;
 import java.math.BigDecimal;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -1859,6 +1861,21 @@ public final class Util {
     return initialValue;
   }
 
+  /**
+   * Absolute <i>get</i> method for reading an int value in {@link ByteOrder#BIG_ENDIAN} in a {@link
+   * ByteBuffer}. Same as {@link ByteBuffer#getInt(int)} except the buffer's order as returned by
+   * {@link ByteBuffer#order()} is ignored and {@link ByteOrder#BIG_ENDIAN} is used instead.
+   *
+   * @param buffer The buffer from which to read an int in big endian.
+   * @param index The index from which the bytes will be read.
+   * @return The int value at the given index with the buffer bytes ordered most significant to
+   *     least significant.
+   */
+  public static int getBigEndianInt(ByteBuffer buffer, int index) {
+    int value = buffer.getInt(index);
+    return buffer.order() == ByteOrder.BIG_ENDIAN ? value : Integer.reverseBytes(value);
+  }
+
   /**
    * Returns the {@link C.NetworkType} of the current network connection.
    *

library/common/src/test/java/com/google/android/exoplayer2/util/UtilTest.java

@@ -27,6 +27,8 @@ 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.testutil.TestUtil;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Random;
@@ -789,6 +791,30 @@ public class UtilTest {
     assertThat(result).isEqualTo(0x4);
   }
 
+  @Test
+  public void getBigEndianInt_fromBigEndian() {
+    byte[] bytes = {0x1F, 0x2E, 0x3D, 0x4C};
+    ByteBuffer byteBuffer = ByteBuffer.wrap(bytes).order(ByteOrder.BIG_ENDIAN);
+
+    assertThat(Util.getBigEndianInt(byteBuffer, 0)).isEqualTo(0x1F2E3D4C);
+  }
+
+  @Test
+  public void getBigEndianInt_fromLittleEndian() {
+    byte[] bytes = {(byte) 0xC2, (byte) 0xD3, (byte) 0xE4, (byte) 0xF5};
+    ByteBuffer byteBuffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);
+
+    assertThat(Util.getBigEndianInt(byteBuffer, 0)).isEqualTo(0xC2D3E4F5);
+  }
+
+  @Test
+  public void getBigEndianInt_unaligned() {
+    byte[] bytes = {9, 8, 7, 6, 5};
+    ByteBuffer byteBuffer = ByteBuffer.wrap(bytes).order(ByteOrder.LITTLE_ENDIAN);
+
+    assertThat(Util.getBigEndianInt(byteBuffer, 1)).isEqualTo(0x08070605);
+  }
+
   @Test
   public void inflate_withDeflatedData_success() {
     byte[] testData = TestUtil.buildTestData(/*arbitrary test data size*/ 256 * 1024);

library/core/src/main/java/com/google/android/exoplayer2/audio/DefaultAudioSink.java

@@ -1242,7 +1242,8 @@ public final class DefaultAudioSink implements AudioSink {
   private static int getFramesPerEncodedSample(@C.Encoding int encoding, ByteBuffer buffer) {
     switch (encoding) {
       case C.ENCODING_MP3:
-        return MpegAudioUtil.parseMpegAudioFrameSampleCount(buffer.get(buffer.position()));
+        int headerDataInBigEndian = Util.getBigEndianInt(buffer, buffer.position());
+        return MpegAudioUtil.parseMpegAudioFrameSampleCount(headerDataInBigEndian);
       case C.ENCODING_AAC_LC:
         return AacUtil.AAC_LC_AUDIO_SAMPLE_COUNT;
       case C.ENCODING_AAC_HE_V1: