Fix MP3 metadata average bitrates

RELEASENOTES.md

@@ -102,6 +102,7 @@
     *   MPEG-TS: Ensure the last frame is rendered for streams where the last
         PES packet has a known length
         ([#3206](https://github.com/androidx/media/pull/3206)).
+    *   MP3: Fix bitrate reporting for files with Xing and VBRI header.
 *   Inspector:
 *   Audio:
     *   Add a 100ms grace period in ExoPlayer's audio renderers when

libraries/extractor/src/main/java/androidx/media3/extractor/mp3/IndexSeeker.java

@@ -15,11 +15,11 @@
  */
 package androidx.media3.extractor.mp3;
 
+import static androidx.media3.extractor.mp3.Mp3Util.computeAverageBitrate;
+
 import androidx.annotation.VisibleForTesting;
 import androidx.media3.common.C;
-import androidx.media3.common.util.Util;
 import androidx.media3.extractor.IndexSeekMap;
-import java.math.RoundingMode;
 
 /** MP3 seeker that builds a time-to-byte mapping as the stream is read. */
 /* package */ final class IndexSeeker implements Seeker {
@@ -40,18 +40,7 @@ public IndexSeeker(long durationUs, long dataStartPosition, long dataEndPosition
             durationUs);
     this.dataStartPosition = dataStartPosition;
     this.dataEndPosition = dataEndPosition;
-    if (durationUs != C.TIME_UNSET) {
-      long bitrate =
-          Util.scaleLargeValue(
-              dataEndPosition - dataStartPosition,
-              C.BITS_PER_BYTE * C.MICROS_PER_SECOND,
-              durationUs,
-              RoundingMode.HALF_UP);
-      this.averageBitrate =
-          bitrate > 0 && bitrate <= Integer.MAX_VALUE ? (int) bitrate : C.RATE_UNSET_INT;
-    } else {
-      this.averageBitrate = C.RATE_UNSET_INT;
-    }
+    this.averageBitrate = computeAverageBitrate(dataEndPosition - dataStartPosition, durationUs);
   }
 
   @Override

libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Util.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2026 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
+ *
+ *      https://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 androidx.media3.extractor.mp3;
+
+import androidx.media3.common.C;
+import androidx.media3.common.util.Util;
+import java.math.RoundingMode;
+
+/* package */ class Mp3Util {
+
+  /* package */ static int computeAverageBitrate(long dataSize, long durationUs) {
+    if (dataSize <= 0 || durationUs <= 0) {
+      return C.RATE_UNSET_INT;
+    }
+    long averageBitrate =
+        Util.scaleLargeValue(
+            dataSize, C.BITS_PER_BYTE * C.MICROS_PER_SECOND, durationUs, RoundingMode.HALF_UP);
+    return averageBitrate > 0 && averageBitrate <= Integer.MAX_VALUE
+        ? (int) averageBitrate
+        : C.RATE_UNSET_INT;
+  }
+
+  private Mp3Util() {}
+}

libraries/extractor/src/main/java/androidx/media3/extractor/mp3/VbriSeeker.java

@@ -15,6 +15,7 @@
  */
 package androidx.media3.extractor.mp3;
 
+import static androidx.media3.extractor.mp3.Mp3Util.computeAverageBitrate;
 import static java.lang.Math.max;
 
 import androidx.annotation.Nullable;
@@ -106,30 +107,28 @@ public static VbriSeeker create(
       endOfMp3Data = max(endOfMp3Data, position);
     }
 
-    return new VbriSeeker(
-        timesUs, positions, durationUs, startOfMp3Data, endOfMp3Data, mpegAudioHeader.bitrate);
+    return new VbriSeeker(timesUs, positions, durationUs, startOfMp3Data, endOfMp3Data);
   }
 
   private final long[] timesUs;
   private final long[] positions;
   private final long durationUs;
   private final long dataStartPosition;
   private final long dataEndPosition;
-  private final int bitrate;
+  private final int averageBitrate;
 
   private VbriSeeker(
       long[] timesUs,
       long[] positions,
       long durationUs,
       long dataStartPosition,
-      long dataEndPosition,
-      int bitrate) {
+      long dataEndPosition) {
     this.timesUs = timesUs;
     this.positions = positions;
     this.durationUs = durationUs;
     this.dataStartPosition = dataStartPosition;
     this.dataEndPosition = dataEndPosition;
-    this.bitrate = bitrate;
+    this.averageBitrate = computeAverageBitrate(dataEndPosition - dataStartPosition, durationUs);
   }
 
   @Override
@@ -171,6 +170,6 @@ public long getDataEndPosition() {
 
   @Override
   public int getAverageBitrate() {
-    return bitrate;
+    return averageBitrate;
   }
 }

libraries/extractor/src/main/java/androidx/media3/extractor/mp3/XingSeeker.java

@@ -15,6 +15,7 @@
  */
 package androidx.media3.extractor.mp3;
 
+import static androidx.media3.extractor.mp3.Mp3Util.computeAverageBitrate;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import androidx.annotation.Nullable;
@@ -65,15 +66,14 @@ public static XingSeeker create(XingFrame xingFrame, long position, long streamL
         position,
         xingFrame.header.frameSize,
         durationUs,
-        xingFrame.header.bitrate,
         dataSize,
         xingFrame.tableOfContents);
   }
 
   private final long dataStartPosition;
   private final int xingFrameSize;
   private final long durationUs;
-  private final int bitrate;
+  private final int averageBitrate;
 
   /** Data size, including the XING frame. */
   private final long dataSize;
@@ -90,13 +90,12 @@ private XingSeeker(
       long dataStartPosition,
       int xingFrameSize,
       long durationUs,
-      int bitrate,
       long dataSize,
       @Nullable long[] tableOfContents) {
     this.dataStartPosition = dataStartPosition;
     this.xingFrameSize = xingFrameSize;
     this.durationUs = durationUs;
-    this.bitrate = bitrate;
+    this.averageBitrate = computeAverageBitrate(dataSize - xingFrameSize, durationUs);
     this.dataSize = dataSize;
     this.tableOfContents = tableOfContents;
     dataEndPosition = dataSize == C.LENGTH_UNSET ? C.INDEX_UNSET : dataStartPosition + dataSize;
@@ -173,7 +172,7 @@ public long getDataEndPosition() {
 
   @Override
   public int getAverageBitrate() {
-    return bitrate;
+    return averageBitrate;
   }
 
   /**

libraries/extractor/src/test/java/androidx/media3/extractor/mp3/VbriSeekerTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2026 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
+ *
+ *      https://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 androidx.media3.extractor.mp3;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.media3.common.C;
+import androidx.media3.common.util.ParsableByteArray;
+import androidx.media3.common.util.Util;
+import androidx.media3.extractor.MpegAudioUtil;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import java.math.RoundingMode;
+import java.nio.ByteBuffer;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Tests for {@link VbriSeeker}. */
+@RunWith(AndroidJUnit4.class)
+public final class VbriSeekerTest {
+
+  private static final int VBRI_FRAME_HEADER_DATA = 0xFFFB3000;
+  private static final int VBRI_FRAME_POSITION = 157;
+
+  @Test
+  public void getAverageBitrate_returnsAverageFromDataSizeAndDuration() {
+    MpegAudioUtil.Header header = new MpegAudioUtil.Header();
+    header.setForHeaderData(VBRI_FRAME_HEADER_DATA);
+    int dataSize = 1_000;
+    int frameCount = 40;
+    VbriSeeker seeker =
+        checkNotNull(
+            VbriSeeker.create(
+                /* inputLength= */ C.LENGTH_UNSET,
+                VBRI_FRAME_POSITION,
+                header,
+                createVbriFrame(dataSize, frameCount, /* segmentSizes...= */ 400, 600)));
+    long durationUs =
+        Util.sampleCountToDurationUs(
+            ((long) frameCount * header.samplesPerFrame) - 1, header.sampleRate);
+    int expectedAverageBitrate =
+        (int)
+            Util.scaleLargeValue(
+                dataSize, C.BITS_PER_BYTE * C.MICROS_PER_SECOND, durationUs, RoundingMode.HALF_UP);
+
+    assertThat(seeker.getAverageBitrate()).isEqualTo(expectedAverageBitrate);
+    assertThat(seeker.getAverageBitrate()).isNotEqualTo(header.bitrate);
+  }
+
+  private static ParsableByteArray createVbriFrame(
+      int dataSize, int frameCount, int... segmentSizes) {
+    ByteBuffer payload = ByteBuffer.allocate(6 + 4 + 4 + 2 + 2 + 2 + 2 + 2 * segmentSizes.length);
+    payload.position(6);
+    payload.putInt(dataSize);
+    payload.putInt(frameCount);
+    payload.putShort((short) segmentSizes.length);
+    payload.putShort((short) 1); // scale
+    payload.putShort((short) 2); // entry size
+    payload.putShort((short) 0);
+    for (int segmentSize : segmentSizes) {
+      payload.putShort((short) segmentSize);
+    }
+    return new ParsableByteArray(payload.array());
+  }
+}

libraries/extractor/src/test/java/androidx/media3/extractor/mp3/XingSeekerTest.java

@@ -24,6 +24,7 @@
 import androidx.media3.extractor.SeekMap.SeekPoints;
 import androidx.media3.extractor.SeekPoint;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
+import java.math.RoundingMode;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -86,6 +87,20 @@ public void getTimeUsAtEndOfStream() {
     assertThat(seeker.getTimeUs(XING_AUDIO_END_POSITION)).isEqualTo(XING_STREAM_DURATION_US);
   }
 
+  @Test
+  public void getAverageBitrate_returnsAverageFromDataSizeAndDuration() {
+    int expectedAverageBitrate =
+        (int)
+            Util.scaleLargeValue(
+                XING_FRAME.dataSize - XING_FRAME.header.frameSize,
+                C.BITS_PER_BYTE * C.MICROS_PER_SECOND,
+                XING_STREAM_DURATION_US,
+                RoundingMode.HALF_UP);
+
+    assertThat(seeker.getAverageBitrate()).isEqualTo(expectedAverageBitrate);
+    assertThat(seeker.getAverageBitrate()).isNotEqualTo(XING_FRAME.header.bitrate);
+  }
+
   // https://github.com/androidx/media/issues/3117#issuecomment-4046538506
   @Test
   public void getTimeUsAtEndOfStream_xingLengthLongerThanStream() {

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header-truncated-toc.mp3.0.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header-truncated-toc.mp3.1.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header-truncated-toc.mp3.2.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 88
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header-truncated-toc.mp3.3.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 88
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header-truncated-toc.mp3.unknown_length.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header.mp3.0.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header.mp3.1.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 88
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header.mp3.2.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 59
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header.mp3.3.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 30
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-vbri-header.mp3.unknown_length.dump

@@ -11,7 +11,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 32000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-xing-header-no-toc.mp3.0.dump

@@ -8,7 +8,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 64000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-xing-header-no-toc.mp3.unknown_length.dump

@@ -8,7 +8,7 @@ track 0:
   sample count = 117
   track duration = 2807979
   format 0:
-    averageBitrate = 64000
+    averageBitrate = 108719
     containerMimeType = audio/mpeg
     sampleMimeType = audio/mpeg
     maxInputSize = 4096