Mp3Extractor: Avoid outputting non-zero position seek frame as a sample

Checking inputPosition == 0 isn't sufficient because the synchronization
at the top of read() may advance the input (i.e. in the case where there's
some garbage prior to the seek frame).

PiperOrigin-RevId: 261086901

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/Mp3Extractor.java

@@ -117,7 +117,7 @@ public final class Mp3Extractor implements Extractor {
   private Seeker seeker;
   private long basisTimeUs;
   private long samplesRead;
-  private int firstSamplePosition;
+  private long firstSamplePosition;
   private int sampleBytesRemaining;
 
   public Mp3Extractor() {
@@ -215,10 +215,13 @@ public final class Mp3Extractor implements Extractor {
               /* selectionFlags= */ 0,
               /* language= */ null,
               (flags & FLAG_DISABLE_ID3_METADATA) != 0 ? null : metadata));
-      firstSamplePosition = (int) input.getPosition();
-    } else if (input.getPosition() == 0 && firstSamplePosition != 0) {
-      // Skip past the seek frame.
-      input.skipFully(firstSamplePosition);
+      firstSamplePosition = input.getPosition();
+    } else if (firstSamplePosition != 0) {
+      long inputPosition = input.getPosition();
+      if (inputPosition < firstSamplePosition) {
+        // Skip past the seek frame.
+        input.skipFully((int) (firstSamplePosition - inputPosition));
+      }
     }
     return readSample(input);
   }