Add maxNumRefFrames to NalUnitUtil

Needed for AVI support.

PiperOrigin-RevId: 436991922

libraries/extractor/src/main/java/androidx/media3/extractor/NalUnitUtil.java

@@ -53,6 +53,7 @@ public final class NalUnitUtil {
     public final int constraintsFlagsAndReservedZero2Bits;
     public final int levelIdc;
     public final int seqParameterSetId;
+    public final int maxNumRefFrames;
     public final int width;
     public final int height;
     public final float pixelWidthHeightRatio;
@@ -68,6 +69,7 @@ public final class NalUnitUtil {
         int constraintsFlagsAndReservedZero2Bits,
         int levelIdc,
         int seqParameterSetId,
+        int maxNumRefFrames,
         int width,
         int height,
         float pixelWidthHeightRatio,
@@ -81,6 +83,7 @@ public final class NalUnitUtil {
       this.constraintsFlagsAndReservedZero2Bits = constraintsFlagsAndReservedZero2Bits;
       this.levelIdc = levelIdc;
       this.seqParameterSetId = seqParameterSetId;
+      this.maxNumRefFrames = maxNumRefFrames;
       this.width = width;
       this.height = height;
       this.pixelWidthHeightRatio = pixelWidthHeightRatio;
@@ -387,7 +390,7 @@ public final class NalUnitUtil {
         data.readUnsignedExpGolombCodedInt(); // offset_for_ref_frame[i]
       }
     }
-    data.readUnsignedExpGolombCodedInt(); // max_num_ref_frames
+    int maxNumRefFrames = data.readUnsignedExpGolombCodedInt(); // max_num_ref_frames
     data.skipBit(); // gaps_in_frame_num_value_allowed_flag
 
     int picWidthInMbs = data.readUnsignedExpGolombCodedInt() + 1;
@@ -447,6 +450,7 @@ public final class NalUnitUtil {
         constraintsFlagsAndReservedZero2Bits,
         levelIdc,
         seqParameterSetId,
+        maxNumRefFrames,
         frameWidth,
         frameHeight,
         pixelWidthHeightRatio,

libraries/extractor/src/test/java/androidx/media3/extractor/NalUnitUtilTest.java

@@ -126,6 +126,7 @@ public final class NalUnitUtilTest {
   public void parseSpsNalUnit() {
     NalUnitUtil.SpsData data =
         NalUnitUtil.parseSpsNalUnit(SPS_TEST_DATA, SPS_TEST_DATA_OFFSET, SPS_TEST_DATA.length);
+    assertThat(data.maxNumRefFrames).isEqualTo(4);
     assertThat(data.width).isEqualTo(640);
     assertThat(data.height).isEqualTo(360);
     assertThat(data.deltaPicOrderAlwaysZeroFlag).isFalse();