Adjust LAME MP3 trim metadata to decoded PCM timeline

RELEASENOTES.md

@@ -77,6 +77,8 @@
         ([#3088](https://github.com/androidx/media/issues/3088)).
     *   MP3: Ignore Xing data length if it's longer than the known stream length
         ([#3117](https://github.com/androidx/media/issues/3117)).
+    *   MP3: Adjust LAME/Xing encoder delay and padding metadata to match
+        decoded PCM trimming.
     *   Ignore `av1C` data with unsupported version.
     *   MP4: Add support for big-endian floating point PCM in `fpcm` boxes.
     *   Matroska: Parse chapter info to `Chapter` entries in a track's

libraries/exoplayer/src/test/java/androidx/media3/exoplayer/e2etest/EndToEndGaplessTest.java

@@ -90,8 +90,8 @@ public void testPlayback_twoIdenticalMp3Files() throws Exception {
     int bytesPerFrame = audioTrackListener.getAudioTrackOutputFormat().getFrameSizeInBytes();
     int paddingBytes = max(0, playerAudioFormat.encoderPadding) * bytesPerFrame;
     int delayBytes = max(0, playerAudioFormat.encoderDelay) * bytesPerFrame;
-    assertThat(paddingBytes).isEqualTo(2808);
-    assertThat(delayBytes).isEqualTo(1152);
+    assertThat(paddingBytes).isEqualTo(1750);
+    assertThat(delayBytes).isEqualTo(2210);
 
     byte[] decoderOutputBytes = Bytes.concat(mp3Decoder.getAllOutputBytes().toArray(new byte[0][]));
     int bytesPerAudioFile = decoderOutputBytes.length / 2;

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

@@ -25,6 +25,13 @@
 /** Representation of a LAME Xing or Info frame. */
 /* package */ final class XingFrame {
 
+  /**
+   * Offset between LAME/Xing delay/padding fields and decoded PCM trim samples. FFmpeg's MP3 muxer
+   * subtracts this offset when writing LAME metadata, and its demuxer adds it back when exposing
+   * decoded PCM skip/discard samples.
+   */
+  private static final int LAME_TO_DECODED_PCM_TRIM_OFFSET_SAMPLES = 528 + 1;
+
   /** The header of the Xing or Info frame. */
   public final MpegAudioUtil.Header header;
 
@@ -113,7 +120,8 @@ public static XingFrame parse(MpegAudioUtil.Header mpegAudioHeader, ParsableByte
     int bytesToSkipAfterReplayGain = 1 + 1;
     // And account for values we parse, ReplayGain (8) and encoder delay & padding (3).
     if (frame.bytesLeft() >= bytesToSkipBeforeReplayGain + 8 + bytesToSkipAfterReplayGain + 3) {
-      frame.skipBytes(bytesToSkipBeforeReplayGain);
+      String encoderIdentifier = frame.readString(9);
+      frame.skipBytes(bytesToSkipBeforeReplayGain - 9);
       float peak = frame.readFloat();
       int field1 = frame.readUnsignedShort();
       int field2 = frame.readUnsignedShort();
@@ -123,6 +131,10 @@ public static XingFrame parse(MpegAudioUtil.Header mpegAudioHeader, ParsableByte
       int encoderDelayAndPadding = frame.readUnsignedInt24();
       encoderDelay = (encoderDelayAndPadding & 0xFFF000) >> 12;
       encoderPadding = (encoderDelayAndPadding & 0xFFF);
+      if (usesLameGaplessEncoding(encoderIdentifier)) {
+        encoderDelay += LAME_TO_DECODED_PCM_TRIM_OFFSET_SAMPLES;
+        encoderPadding = Math.max(0, encoderPadding - LAME_TO_DECODED_PCM_TRIM_OFFSET_SAMPLES);
+      }
     } else {
       replayGain = null;
       encoderDelay = C.LENGTH_UNSET;
@@ -155,6 +167,12 @@ public long computeDurationUs() {
         (frameCount * header.samplesPerFrame) - 1, header.sampleRate);
   }
 
+  private static boolean usesLameGaplessEncoding(String encoderIdentifier) {
+    return encoderIdentifier.startsWith("LAME")
+        || encoderIdentifier.startsWith("Lavf")
+        || encoderIdentifier.startsWith("Lavc");
+  }
+
   /** Provide the metadata derived from this Xing frame, such as ReplayGain data. */
   @Nullable
   public Metadata getMetadata() {

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

@@ -0,0 +1,112 @@
+/*
+ * 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.truth.Truth.assertThat;
+
+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.nio.ByteBuffer;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Tests for {@link XingFrame}. */
+@RunWith(AndroidJUnit4.class)
+public final class XingFrameTest {
+
+  private static final int INFO_FRAME_HEADER_DATA = 0xFFFB40C0;
+
+  @Test
+  public void parse_withLameEncoderIdentifier_adjustsDelayAndPaddingForDecodedPcm() {
+    XingFrame frame =
+        createXingFrame(
+            INFO_FRAME_HEADER_DATA,
+            /* frameCount= */ 40,
+            /* dataSize= */ 8_541,
+            /* encoderDelay= */ 576,
+            /* encoderPadding= */ 1_404,
+            /* encoderIdentifier= */ "LAME3.99r");
+
+    assertThat(frame.encoderDelay).isEqualTo(1_105);
+    assertThat(frame.encoderPadding).isEqualTo(875);
+  }
+
+  @Test
+  public void parse_withLameEncoderIdentifierAndSmallPadding_clampsPaddingToZero() {
+    XingFrame frame =
+        createXingFrame(
+            INFO_FRAME_HEADER_DATA,
+            /* frameCount= */ 40,
+            /* dataSize= */ 8_541,
+            /* encoderDelay= */ 576,
+            /* encoderPadding= */ 398,
+            /* encoderIdentifier= */ "LAME3.99r");
+
+    assertThat(frame.encoderDelay).isEqualTo(1_105);
+    assertThat(frame.encoderPadding).isEqualTo(0);
+  }
+
+  private static XingFrame createXingFrame(
+      int headerData, int frameCount, int dataSize, int encoderDelay, int encoderPadding) {
+    return createXingFrame(
+        headerData,
+        frameCount,
+        dataSize,
+        encoderDelay,
+        encoderPadding,
+        /* encoderIdentifier= */ "");
+  }
+
+  private static XingFrame createXingFrame(
+      int headerData,
+      int frameCount,
+      int dataSize,
+      int encoderDelay,
+      int encoderPadding,
+      String encoderIdentifier) {
+    int encoderDelayAndPadding = (encoderDelay << 12) | encoderPadding;
+    ByteBuffer payload = ByteBuffer.allocate(4 + 4 + 4 + 11 + 8 + 2 + 3);
+    payload.putInt(0x03);
+    payload.putInt(frameCount);
+    payload.putInt(dataSize);
+    payload.put(createFixedLengthEncoderIdentifier(encoderIdentifier));
+    payload.position(payload.position() + 2 + 8 + 2);
+    payload.put((byte) (encoderDelayAndPadding >> 16));
+    payload.put((byte) (encoderDelayAndPadding >> 8));
+    payload.put((byte) encoderDelayAndPadding);
+    return createXingFrame(headerData, payload.array());
+  }
+
+  private static byte[] createFixedLengthEncoderIdentifier(String encoderIdentifier) {
+    byte[] fixedLengthIdentifier = new byte[9];
+    byte[] identifierBytes = Util.getUtf8Bytes(encoderIdentifier);
+    System.arraycopy(
+        identifierBytes,
+        /* srcPos= */ 0,
+        fixedLengthIdentifier,
+        /* destPos= */ 0,
+        Math.min(identifierBytes.length, fixedLengthIdentifier.length));
+    return fixedLengthIdentifier;
+  }
+
+  private static XingFrame createXingFrame(int headerData, byte[] payload) {
+    MpegAudioUtil.Header xingFrameHeader = new MpegAudioUtil.Header();
+    xingFrameHeader.setForHeaderData(headerData);
+    return XingFrame.parse(xingFrameHeader, new ParsableByteArray(payload));
+  }
+}

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3-numeric-genre.mp3.0.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[9]]
   sample 0:
     time = 0

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3-numeric-genre.mp3.1.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[9]]
   sample 0:
     time = 943000

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3-numeric-genre.mp3.2.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[9]]
   sample 0:
     time = 1879000

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3-numeric-genre.mp3.3.dump

@@ -16,7 +16,7 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[9]]
 tracksEnded = true

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3-numeric-genre.mp3.unknown_length.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[9]]
   sample 0:
     time = 0

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-disabled.0.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
   sample 0:
     time = 0
     flags = 1

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-disabled.1.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
   sample 0:
     time = 943000
     flags = 1

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-disabled.2.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
   sample 0:
     time = 1879000
     flags = 1

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-disabled.3.dump

@@ -16,6 +16,6 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
 tracksEnded = true

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-disabled.unknown_length.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
   sample 0:
     time = 0
     flags = 1

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-enabled.0.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[Gorpcore]]
   sample 0:
     time = 0

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-enabled.1.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[Gorpcore]]
   sample 0:
     time = 943000

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-enabled.2.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[Gorpcore]]
   sample 0:
     time = 1879000

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-enabled.3.dump

@@ -16,7 +16,7 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[Gorpcore]]
 tracksEnded = true

libraries/test_data/src/test/assets/extractordumps/mp3/bear-id3.mp3.id3-enabled.unknown_length.dump

@@ -16,8 +16,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TIT2: description=null: values=[Test title], TPE1: description=null: values=[Test Artist], TALB: description=null: values=[Test Album], TXXX: description=Test description: values=[Test user info], COMM: language=eng, description=Test description, text=Test comment, WXXX: url=Test URL, TSSE: description=null: values=[Lavf58.29.100], MLLT, PRIV: owner=test@gmail.com, UNKN, GEOB: mimeType=test/mime, filename=Testfilename.txt, description=Test description, CHAP, CHAP, CTOC, APIC: mimeType=image/jpeg, description=Test description, TCON: description=null: values=[Gorpcore]]
   sample 0:
     time = 0

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

@@ -14,8 +14,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TSSE: description=null: values=[Lavf58.29.100]]
   sample 0:
     time = 0

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

@@ -17,8 +17,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TSSE: description=null: values=[Lavf58.29.100]]
   sample 0:
     time = 0

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-xing-header-no-toc.mp3.cbr-seeking-always.1.dump

@@ -17,8 +17,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TSSE: description=null: values=[Lavf58.29.100]]
   sample 0:
     time = 943055

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-xing-header-no-toc.mp3.cbr-seeking-always.2.dump

@@ -17,8 +17,8 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TSSE: description=null: values=[Lavf58.29.100]]
   sample 0:
     time = 1879045

libraries/test_data/src/test/assets/extractordumps/mp3/bear-vbr-xing-header-no-toc.mp3.cbr-seeking-always.3.dump

@@ -17,7 +17,7 @@ track 0:
     maxInputSize = 4096
     channelCount = 2
     sampleRate = 48000
-    encoderDelay = 576
-    encoderPadding = 576
+    encoderDelay = 1105
+    encoderPadding = 47
     metadata = entries=[TSSE: description=null: values=[Lavf58.29.100]]
 tracksEnded = true