content: /*
   * Copyright (C) 2016 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
   *
   *      http://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 com.google.android.exoplayer2.util;
  
  import static java.lang.Math.min;
  
  import androidx.annotation.Nullable;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.video.ColorInfo;
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  
  /** Utility methods for handling H.264/AVC and H.265/HEVC NAL units. */
  public final class NalUnitUtil {
  
    private static final String TAG = "NalUnitUtil";
  
    /** Coded slice of a non-IDR picture. */
    public static final int NAL_UNIT_TYPE_NON_IDR = 1;
    /** Coded slice data partition A. */
    public static final int NAL_UNIT_TYPE_PARTITION_A = 2;
    /** Coded slice of an IDR picture. */
    public static final int NAL_UNIT_TYPE_IDR = 5;
    /** Supplemental enhancement information. */
    public static final int NAL_UNIT_TYPE_SEI = 6;
    /** Sequence parameter set. */
    public static final int NAL_UNIT_TYPE_SPS = 7;
    /** Picture parameter set. */
    public static final int NAL_UNIT_TYPE_PPS = 8;
    /** Access unit delimiter. */
    public static final int NAL_UNIT_TYPE_AUD = 9;
  
    /** Holds data parsed from a H.264 sequence parameter set NAL unit. */
    public static final class SpsData {
  
      public final int profileIdc;
      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;
      public final boolean separateColorPlaneFlag;
      public final boolean frameMbsOnlyFlag;
      public final int frameNumLength;
      public final int picOrderCountType;
      public final int picOrderCntLsbLength;
      public final boolean deltaPicOrderAlwaysZeroFlag;
  
      public SpsData(
          int profileIdc,
          int constraintsFlagsAndReservedZero2Bits,
          int levelIdc,
          int seqParameterSetId,
          int maxNumRefFrames,
          int width,
          int height,
          float pixelWidthHeightRatio,
          boolean separateColorPlaneFlag,
          boolean frameMbsOnlyFlag,
          int frameNumLength,
          int picOrderCountType,
          int picOrderCntLsbLength,
          boolean deltaPicOrderAlwaysZeroFlag) {
        this.profileIdc = profileIdc;
        this.constraintsFlagsAndReservedZero2Bits = constraintsFlagsAndReservedZero2Bits;
        this.levelIdc = levelIdc;
        this.seqParameterSetId = seqParameterSetId;
        this.maxNumRefFrames = maxNumRefFrames;
        this.width = width;
        this.height = height;
        this.pixelWidthHeightRatio = pixelWidthHeightRatio;
        this.separateColorPlaneFlag = separateColorPlaneFlag;
        this.frameMbsOnlyFlag = frameMbsOnlyFlag;
        this.frameNumLength = frameNumLength;
        this.picOrderCountType = picOrderCountType;
        this.picOrderCntLsbLength = picOrderCntLsbLength;
        this.deltaPicOrderAlwaysZeroFlag = deltaPicOrderAlwaysZeroFlag;
      }
    }
  
    /** Holds data parsed from a H.265 sequence parameter set NAL unit. */
    public static final class H265SpsData {
  
      public final int generalProfileSpace;
      public final boolean generalTierFlag;
      public final int generalProfileIdc;
      public final int generalProfileCompatibilityFlags;
      public final int[] constraintBytes;
      public final int generalLevelIdc;
      public final int seqParameterSetId;
      public final int width;
      public final int height;
      public final float pixelWidthHeightRatio;
      public final @C.ColorSpace int colorSpace;
      public final @C.ColorRange int colorRange;
      public final @C.ColorTransfer int colorTransfer;
  
      public H265SpsData(
          int generalProfileSpace,
          boolean generalTierFlag,
          int generalProfileIdc,
          int generalProfileCompatibilityFlags,
          int[] constraintBytes,
          int generalLevelIdc,
          int seqParameterSetId,
          int width,
          int height,
          float pixelWidthHeightRatio,
          @C.ColorSpace int colorSpace,
          @C.ColorRange int colorRange,
          @C.ColorTransfer int colorTransfer) {
        this.generalProfileSpace = generalProfileSpace;
        this.generalTierFlag = generalTierFlag;
        this.generalProfileIdc = generalProfileIdc;
        this.generalProfileCompatibilityFlags = generalProfileCompatibilityFlags;
        this.constraintBytes = constraintBytes;
        this.generalLevelIdc = generalLevelIdc;
        this.seqParameterSetId = seqParameterSetId;
        this.width = width;
        this.height = height;
        this.pixelWidthHeightRatio = pixelWidthHeightRatio;
        this.colorSpace = colorSpace;
        this.colorRange = colorRange;
        this.colorTransfer = colorTransfer;
      }
    }
  
    /** Holds data parsed from a picture parameter set NAL unit. */
    public static final class PpsData {
  
      public final int picParameterSetId;
      public final int seqParameterSetId;
      public final boolean bottomFieldPicOrderInFramePresentFlag;
  
      public PpsData(
          int picParameterSetId,
          int seqParameterSetId,
          boolean bottomFieldPicOrderInFramePresentFlag) {
        this.picParameterSetId = picParameterSetId;
        this.seqParameterSetId = seqParameterSetId;
        this.bottomFieldPicOrderInFramePresentFlag = bottomFieldPicOrderInFramePresentFlag;
      }
    }
  
    /** Four initial bytes that must prefix NAL units for decoding. */
    public static final byte[] NAL_START_CODE = new byte[] {0, 0, 0, 1};
  
    /** Value for aspect_ratio_idc indicating an extended aspect ratio, in H.264 and H.265 SPSs. */
    public static final int EXTENDED_SAR = 0xFF;
    /** Aspect ratios indexed by aspect_ratio_idc, in H.264 and H.265 SPSs. */
    public static final float[] ASPECT_RATIO_IDC_VALUES =
        new float[] {
          1f /* Unspecified. Assume square */,
          1f,
          12f / 11f,
          10f / 11f,
          16f / 11f,
          40f / 33f,
          24f / 11f,
          20f / 11f,
          32f / 11f,
          80f / 33f,
          18f / 11f,
          15f / 11f,
          64f / 33f,
          160f / 99f,
          4f / 3f,
          3f / 2f,
          2f
        };
  
    private static final int H264_NAL_UNIT_TYPE_SEI = 6; // Supplemental enhancement information
    private static final int H264_NAL_UNIT_TYPE_SPS = 7; // Sequence parameter set
    private static final int H265_NAL_UNIT_TYPE_PREFIX_SEI = 39;
  
    private static final Object scratchEscapePositionsLock = new Object();
  
    /**
     * Temporary store for positions of escape codes in {@link #unescapeStream(byte[], int)}. Guarded
     * by {@link #scratchEscapePositionsLock}.
     */
    private static int[] scratchEscapePositions = new int[10];
  
    /**
     * Unescapes {@code data} up to the specified limit, replacing occurrences of [0, 0, 3] with [0,
     * 0]. The unescaped data is returned in-place, with the return value indicating its length.
     *
     * <p>Executions of this method are mutually exclusive, so it should not be called with very large
     * buffers.
     *
     * @param data The data to unescape.
     * @param limit The limit (exclusive) of the data to unescape.
     * @return The length of the unescaped data.
     */
    public static int unescapeStream(byte[] data, int limit) {
      synchronized (scratchEscapePositionsLock) {
        int position = 0;
        int scratchEscapeCount = 0;
        while (position < limit) {
          position = findNextUnescapeIndex(data, position, limit);
          if (position < limit) {
            if (scratchEscapePositions.length <= scratchEscapeCount) {
              // Grow scratchEscapePositions to hold a larger number of positions.
              scratchEscapePositions =
                  Arrays.copyOf(scratchEscapePositions, scratchEscapePositions.length * 2);
            }
            scratchEscapePositions[scratchEscapeCount++] = position;
            position += 3;
          }
        }
  
        int unescapedLength = limit - scratchEscapeCount;
        int escapedPosition = 0; // The position being read from.
        int unescapedPosition = 0; // The position being written to.
        for (int i = 0; i < scratchEscapeCount; i++) {
          int nextEscapePosition = scratchEscapePositions[i];
          int copyLength = nextEscapePosition - escapedPosition;
          System.arraycopy(data, escapedPosition, data, unescapedPosition, copyLength);
          unescapedPosition += copyLength;
          data[unescapedPosition++] = 0;
          data[unescapedPosition++] = 0;
          escapedPosition += copyLength + 3;
        }
  
        int remainingLength = unescapedLength - unescapedPosition;
        System.arraycopy(data, escapedPosition, data, unescapedPosition, remainingLength);
        return unescapedLength;
      }
    }
  
    /**
     * Discards data from the buffer up to the first SPS, where {@code data.position()} is interpreted
     * as the length of the buffer.
     *
     * <p>When the method returns, {@code data.position()} will contain the new length of the buffer.
     * If the buffer is not empty it is guaranteed to start with an SPS.
     *
     * @param data Buffer containing start code delimited NAL units.
     */
    public static void discardToSps(ByteBuffer data) {
      int length = data.position();
      int consecutiveZeros = 0;
      int offset = 0;
      while (offset + 1 < length) {
        int value = data.get(offset) & 0xFF;
        if (consecutiveZeros == 3) {
          if (value == 1 && (data.get(offset + 1) & 0x1F) == H264_NAL_UNIT_TYPE_SPS) {
            // Copy from this NAL unit onwards to the start of the buffer.
            ByteBuffer offsetData = data.duplicate();
            offsetData.position(offset - 3);
            offsetData.limit(length);
            data.position(0);
            data.put(offsetData);
            return;
          }
        } else if (value == 0) {
          consecutiveZeros++;
        }
        if (value != 0) {
          consecutiveZeros = 0;
        }
        offset++;
      }
      // Empty the buffer if the SPS NAL unit was not found.
      data.clear();
    }
  
    /**
     * Returns whether the NAL unit with the specified header contains supplemental enhancement
     * information.
     *
     * @param mimeType The sample MIME type, or {@code null} if unknown.
     * @param nalUnitHeaderFirstByte The first byte of nal_unit().
     * @return Whether the NAL unit with the specified header is an SEI NAL unit. False is returned if
     *     the {@code MimeType} is {@code null}.
     */
    public static boolean isNalUnitSei(@Nullable String mimeType, byte nalUnitHeaderFirstByte) {
      return (MimeTypes.VIDEO_H264.equals(mimeType)
              && (nalUnitHeaderFirstByte & 0x1F) == H264_NAL_UNIT_TYPE_SEI)
          || (MimeTypes.VIDEO_H265.equals(mimeType)
              && ((nalUnitHeaderFirstByte & 0x7E) >> 1) == H265_NAL_UNIT_TYPE_PREFIX_SEI);
    }
  
    /**
     * Returns the type of the NAL unit in {@code data} that starts at {@code offset}.
     *
     * @param data The data to search.
     * @param offset The start offset of a NAL unit. Must lie between {@code -3} (inclusive) and
     *     {@code data.length - 3} (exclusive).
     * @return The type of the unit.
     */
    public static int getNalUnitType(byte[] data, int offset) {
      return data[offset + 3] & 0x1F;
    }
  
    /**
     * Returns the type of the H.265 NAL unit in {@code data} that starts at {@code offset}.
     *
     * @param data The data to search.
     * @param offset The start offset of a NAL unit. Must lie between {@code -3} (inclusive) and
     *     {@code data.length - 3} (exclusive).
     * @return The type of the unit.
     */
    public static int getH265NalUnitType(byte[] data, int offset) {
      return (data[offset + 3] & 0x7E) >> 1;
    }
  
    /**
     * Parses a SPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection
     * 7.3.2.1.1.
     *
     * @param nalData A buffer containing escaped SPS data.
     * @param nalOffset The offset of the NAL unit header in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the SPS data.
     */
    public static SpsData parseSpsNalUnit(byte[] nalData, int nalOffset, int nalLimit) {
      return parseSpsNalUnitPayload(nalData, nalOffset + 1, nalLimit);
    }
  
    /**
     * Parses a SPS NAL unit payload (excluding the NAL unit header) using the syntax defined in ITU-T
     * Recommendation H.264 (2013) subsection 7.3.2.1.1.
     *
     * @param nalData A buffer containing escaped SPS data.
     * @param nalOffset The offset of the NAL unit payload in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the SPS data.
     */
    public static SpsData parseSpsNalUnitPayload(byte[] nalData, int nalOffset, int nalLimit) {
      ParsableNalUnitBitArray data = new ParsableNalUnitBitArray(nalData, nalOffset, nalLimit);
      int profileIdc = data.readBits(8);
      int constraintsFlagsAndReservedZero2Bits = data.readBits(8);
      int levelIdc = data.readBits(8);
      int seqParameterSetId = data.readUnsignedExpGolombCodedInt();
  
      int chromaFormatIdc = 1; // Default is 4:2:0
      boolean separateColorPlaneFlag = false;
      if (profileIdc == 100
          || profileIdc == 110
          || profileIdc == 122
          || profileIdc == 244
          || profileIdc == 44
          || profileIdc == 83
          || profileIdc == 86
          || profileIdc == 118
          || profileIdc == 128
          || profileIdc == 138) {
        chromaFormatIdc = data.readUnsignedExpGolombCodedInt();
        if (chromaFormatIdc == 3) {
          separateColorPlaneFlag = data.readBit();
        }
        data.readUnsignedExpGolombCodedInt(); // bit_depth_luma_minus8
        data.readUnsignedExpGolombCodedInt(); // bit_depth_chroma_minus8
        data.skipBit(); // qpprime_y_zero_transform_bypass_flag
        boolean seqScalingMatrixPresentFlag = data.readBit();
        if (seqScalingMatrixPresentFlag) {
          int limit = (chromaFormatIdc != 3) ? 8 : 12;
          for (int i = 0; i < limit; i++) {
            boolean seqScalingListPresentFlag = data.readBit();
            if (seqScalingListPresentFlag) {
              skipScalingList(data, i < 6 ? 16 : 64);
            }
          }
        }
      }
  
      int frameNumLength = data.readUnsignedExpGolombCodedInt() + 4; // log2_max_frame_num_minus4 + 4
      int picOrderCntType = data.readUnsignedExpGolombCodedInt();
      int picOrderCntLsbLength = 0;
      boolean deltaPicOrderAlwaysZeroFlag = false;
      if (picOrderCntType == 0) {
        // log2_max_pic_order_cnt_lsb_minus4 + 4
        picOrderCntLsbLength = data.readUnsignedExpGolombCodedInt() + 4;
      } else if (picOrderCntType == 1) {
        deltaPicOrderAlwaysZeroFlag = data.readBit(); // delta_pic_order_always_zero_flag
        data.readSignedExpGolombCodedInt(); // offset_for_non_ref_pic
        data.readSignedExpGolombCodedInt(); // offset_for_top_to_bottom_field
        long numRefFramesInPicOrderCntCycle = data.readUnsignedExpGolombCodedInt();
        for (int i = 0; i < numRefFramesInPicOrderCntCycle; i++) {
          data.readUnsignedExpGolombCodedInt(); // offset_for_ref_frame[i]
        }
      }
      int maxNumRefFrames = data.readUnsignedExpGolombCodedInt(); // max_num_ref_frames
      data.skipBit(); // gaps_in_frame_num_value_allowed_flag
  
      int picWidthInMbs = data.readUnsignedExpGolombCodedInt() + 1;
      int picHeightInMapUnits = data.readUnsignedExpGolombCodedInt() + 1;
      boolean frameMbsOnlyFlag = data.readBit();
      int frameHeightInMbs = (2 - (frameMbsOnlyFlag ? 1 : 0)) * picHeightInMapUnits;
      if (!frameMbsOnlyFlag) {
        data.skipBit(); // mb_adaptive_frame_field_flag
      }
  
      data.skipBit(); // direct_8x8_inference_flag
      int frameWidth = picWidthInMbs * 16;
      int frameHeight = frameHeightInMbs * 16;
      boolean frameCroppingFlag = data.readBit();
      if (frameCroppingFlag) {
        int frameCropLeftOffset = data.readUnsignedExpGolombCodedInt();
        int frameCropRightOffset = data.readUnsignedExpGolombCodedInt();
        int frameCropTopOffset = data.readUnsignedExpGolombCodedInt();
        int frameCropBottomOffset = data.readUnsignedExpGolombCodedInt();
        int cropUnitX;
        int cropUnitY;
        if (chromaFormatIdc == 0) {
          cropUnitX = 1;
          cropUnitY = 2 - (frameMbsOnlyFlag ? 1 : 0);
        } else {
          int subWidthC = (chromaFormatIdc == 3) ? 1 : 2;
          int subHeightC = (chromaFormatIdc == 1) ? 2 : 1;
          cropUnitX = subWidthC;
          cropUnitY = subHeightC * (2 - (frameMbsOnlyFlag ? 1 : 0));
        }
        frameWidth -= (frameCropLeftOffset + frameCropRightOffset) * cropUnitX;
        frameHeight -= (frameCropTopOffset + frameCropBottomOffset) * cropUnitY;
      }
  
      float pixelWidthHeightRatio = 1;
      boolean vuiParametersPresentFlag = data.readBit();
      if (vuiParametersPresentFlag) {
        boolean aspectRatioInfoPresentFlag = data.readBit();
        if (aspectRatioInfoPresentFlag) {
          int aspectRatioIdc = data.readBits(8);
          if (aspectRatioIdc == NalUnitUtil.EXTENDED_SAR) {
            int sarWidth = data.readBits(16);
            int sarHeight = data.readBits(16);
            if (sarWidth != 0 && sarHeight != 0) {
              pixelWidthHeightRatio = (float) sarWidth / sarHeight;
            }
          } else if (aspectRatioIdc < NalUnitUtil.ASPECT_RATIO_IDC_VALUES.length) {
            pixelWidthHeightRatio = NalUnitUtil.ASPECT_RATIO_IDC_VALUES[aspectRatioIdc];
          } else {
            Log.w(TAG, "Unexpected aspect_ratio_idc value: " + aspectRatioIdc);
          }
        }
      }
  
      return new SpsData(
          profileIdc,
          constraintsFlagsAndReservedZero2Bits,
          levelIdc,
          seqParameterSetId,
          maxNumRefFrames,
          frameWidth,
          frameHeight,
          pixelWidthHeightRatio,
          separateColorPlaneFlag,
          frameMbsOnlyFlag,
          frameNumLength,
          picOrderCntType,
          picOrderCntLsbLength,
          deltaPicOrderAlwaysZeroFlag);
    }
  
    /**
     * Parses a H.265 SPS NAL unit using the syntax defined in ITU-T Recommendation H.265 (2019)
     * subsection 7.3.2.2.1.
     *
     * @param nalData A buffer containing escaped SPS data.
     * @param nalOffset The offset of the NAL unit header in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the SPS data.
     */
    public static H265SpsData parseH265SpsNalUnit(byte[] nalData, int nalOffset, int nalLimit) {
      return parseH265SpsNalUnitPayload(nalData, nalOffset + 2, nalLimit);
    }
  
    /**
     * Parses a H.265 SPS NAL unit payload (excluding the NAL unit header) using the syntax defined in
     * ITU-T Recommendation H.265 (2019) subsection 7.3.2.2.1.
     *
     * @param nalData A buffer containing escaped SPS data.
     * @param nalOffset The offset of the NAL unit payload in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the SPS data.
     */
    public static H265SpsData parseH265SpsNalUnitPayload(
        byte[] nalData, int nalOffset, int nalLimit) {
      ParsableNalUnitBitArray data = new ParsableNalUnitBitArray(nalData, nalOffset, nalLimit);
      // HDR related metadata.
      @C.ColorSpace int colorSpace = Format.NO_VALUE;
      @C.ColorRange int colorRange = Format.NO_VALUE;
      @C.ColorTransfer int colorTransfer = Format.NO_VALUE;
      data.skipBits(4); // sps_video_parameter_set_id
      int maxSubLayersMinus1 = data.readBits(3);
      data.skipBit(); // sps_temporal_id_nesting_flag
      int generalProfileSpace = data.readBits(2);
      boolean generalTierFlag = data.readBit();
      int generalProfileIdc = data.readBits(5);
      int generalProfileCompatibilityFlags = 0;
      for (int i = 0; i < 32; i++) {
        if (data.readBit()) {
          generalProfileCompatibilityFlags |= (1 << i);
        }
      }
      int[] constraintBytes = new int[6];
      for (int i = 0; i < constraintBytes.length; ++i) {
        constraintBytes[i] = data.readBits(8);
      }
      int generalLevelIdc = data.readBits(8);
      int toSkip = 0;
      for (int i = 0; i < maxSubLayersMinus1; i++) {
        if (data.readBit()) { // sub_layer_profile_present_flag[i]
          toSkip += 89;
        }
        if (data.readBit()) { // sub_layer_level_present_flag[i]
          toSkip += 8;
        }
      }
      data.skipBits(toSkip);
      if (maxSubLayersMinus1 > 0) {
        data.skipBits(2 * (8 - maxSubLayersMinus1));
      }
      int seqParameterSetId = data.readUnsignedExpGolombCodedInt();
      int chromaFormatIdc = data.readUnsignedExpGolombCodedInt();
      if (chromaFormatIdc == 3) {
        data.skipBit(); // separate_colour_plane_flag
      }
      int frameWidth = data.readUnsignedExpGolombCodedInt();
      int frameHeight = data.readUnsignedExpGolombCodedInt();
      if (data.readBit()) { // conformance_window_flag
        int confWinLeftOffset = data.readUnsignedExpGolombCodedInt();
        int confWinRightOffset = data.readUnsignedExpGolombCodedInt();
        int confWinTopOffset = data.readUnsignedExpGolombCodedInt();
        int confWinBottomOffset = data.readUnsignedExpGolombCodedInt();
        // H.265/HEVC (2014) Table 6-1
        int subWidthC = chromaFormatIdc == 1 || chromaFormatIdc == 2 ? 2 : 1;
        int subHeightC = chromaFormatIdc == 1 ? 2 : 1;
        frameWidth -= subWidthC * (confWinLeftOffset + confWinRightOffset);
        frameHeight -= subHeightC * (confWinTopOffset + confWinBottomOffset);
      }
      data.readUnsignedExpGolombCodedInt(); // bit_depth_luma_minus8
      data.readUnsignedExpGolombCodedInt(); // bit_depth_chroma_minus8
      int log2MaxPicOrderCntLsbMinus4 = data.readUnsignedExpGolombCodedInt();
      // for (i = sps_sub_layer_ordering_info_present_flag ? 0 : sps_max_sub_layers_minus1; ...)
      for (int i = data.readBit() ? 0 : maxSubLayersMinus1; i <= maxSubLayersMinus1; i++) {
        data.readUnsignedExpGolombCodedInt(); // sps_max_dec_pic_buffering_minus1[i]
        data.readUnsignedExpGolombCodedInt(); // sps_max_num_reorder_pics[i]
        data.readUnsignedExpGolombCodedInt(); // sps_max_latency_increase_plus1[i]
      }
      data.readUnsignedExpGolombCodedInt(); // log2_min_luma_coding_block_size_minus3
      data.readUnsignedExpGolombCodedInt(); // log2_diff_max_min_luma_coding_block_size
      data.readUnsignedExpGolombCodedInt(); // log2_min_luma_transform_block_size_minus2
      data.readUnsignedExpGolombCodedInt(); // log2_diff_max_min_luma_transform_block_size
      data.readUnsignedExpGolombCodedInt(); // max_transform_hierarchy_depth_inter
      data.readUnsignedExpGolombCodedInt(); // max_transform_hierarchy_depth_intra
      // if (scaling_list_enabled_flag) { if (sps_scaling_list_data_present_flag) {...}}
      boolean scalingListEnabled = data.readBit();
      if (scalingListEnabled && data.readBit()) {
        skipH265ScalingList(data);
      }
      data.skipBits(2); // amp_enabled_flag (1), sample_adaptive_offset_enabled_flag (1)
      if (data.readBit()) { // pcm_enabled_flag
        // pcm_sample_bit_depth_luma_minus1 (4), pcm_sample_bit_depth_chroma_minus1 (4)
        data.skipBits(8);
        data.readUnsignedExpGolombCodedInt(); // log2_min_pcm_luma_coding_block_size_minus3
        data.readUnsignedExpGolombCodedInt(); // log2_diff_max_min_pcm_luma_coding_block_size
        data.skipBit(); // pcm_loop_filter_disabled_flag
      }
      skipShortTermReferencePictureSets(data);
      if (data.readBit()) { // long_term_ref_pics_present_flag
        // num_long_term_ref_pics_sps
        for (int i = 0; i < data.readUnsignedExpGolombCodedInt(); i++) {
          int ltRefPicPocLsbSpsLength = log2MaxPicOrderCntLsbMinus4 + 4;
          // lt_ref_pic_poc_lsb_sps[i], used_by_curr_pic_lt_sps_flag[i]
          data.skipBits(ltRefPicPocLsbSpsLength + 1);
        }
      }
      data.skipBits(2); // sps_temporal_mvp_enabled_flag, strong_intra_smoothing_enabled_flag
      float pixelWidthHeightRatio = 1;
      if (data.readBit()) { // vui_parameters_present_flag
        if (data.readBit()) { // aspect_ratio_info_present_flag
          int aspectRatioIdc = data.readBits(8);
          if (aspectRatioIdc == NalUnitUtil.EXTENDED_SAR) {
            int sarWidth = data.readBits(16);
            int sarHeight = data.readBits(16);
            if (sarWidth != 0 && sarHeight != 0) {
              pixelWidthHeightRatio = (float) sarWidth / sarHeight;
            }
          } else if (aspectRatioIdc < NalUnitUtil.ASPECT_RATIO_IDC_VALUES.length) {
            pixelWidthHeightRatio = NalUnitUtil.ASPECT_RATIO_IDC_VALUES[aspectRatioIdc];
          } else {
            Log.w(TAG, "Unexpected aspect_ratio_idc value: " + aspectRatioIdc);
          }
        }
        if (data.readBit()) { // overscan_info_present_flag
          data.skipBit(); // overscan_appropriate_flag
        }
        if (data.readBit()) { // video_signal_type_present_flag
          data.skipBits(3); // video_format
          boolean fullRangeFlag = data.readBit(); // video_full_range_flag
          if (data.readBit()) { // colour_description_present_flag
            int colorPrimaries = data.readBits(8); // colour_primaries
            int transferCharacteristics = data.readBits(8); // transfer_characteristics
            data.skipBits(8); // matrix_coeffs
  
            colorSpace = ColorInfo.isoColorPrimariesToColorSpace(colorPrimaries);
            colorRange = fullRangeFlag ? C.COLOR_RANGE_FULL : C.COLOR_RANGE_LIMITED;
            colorTransfer =
                ColorInfo.isoTransferCharacteristicsToColorTransfer(transferCharacteristics);
          }
        }
        if (data.readBit()) { // chroma_loc_info_present_flag
          data.readUnsignedExpGolombCodedInt(); // chroma_sample_loc_type_top_field
          data.readUnsignedExpGolombCodedInt(); // chroma_sample_loc_type_bottom_field
        }
        data.skipBit(); // neutral_chroma_indication_flag
        if (data.readBit()) { // field_seq_flag
          // field_seq_flag equal to 1 indicates that the coded video sequence conveys pictures that
          // represent fields, which means that frame height is double the picture height.
          frameHeight *= 2;
        }
      }
  
      return new H265SpsData(
          generalProfileSpace,
          generalTierFlag,
          generalProfileIdc,
          generalProfileCompatibilityFlags,
          constraintBytes,
          generalLevelIdc,
          seqParameterSetId,
          frameWidth,
          frameHeight,
          pixelWidthHeightRatio,
          colorSpace,
          colorRange,
          colorTransfer);
    }
  
    /**
     * Parses a PPS NAL unit using the syntax defined in ITU-T Recommendation H.264 (2013) subsection
     * 7.3.2.2.
     *
     * @param nalData A buffer containing escaped PPS data.
     * @param nalOffset The offset of the NAL unit header in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the PPS data.
     */
    public static PpsData parsePpsNalUnit(byte[] nalData, int nalOffset, int nalLimit) {
      return parsePpsNalUnitPayload(nalData, nalOffset + 1, nalLimit);
    }
  
    /**
     * Parses a PPS NAL unit payload (excluding the NAL unit header) using the syntax defined in ITU-T
     * Recommendation H.264 (2013) subsection 7.3.2.2.
     *
     * @param nalData A buffer containing escaped PPS data.
     * @param nalOffset The offset of the NAL unit payload in {@code nalData}.
     * @param nalLimit The limit of the NAL unit in {@code nalData}.
     * @return A parsed representation of the PPS data.
     */
    public static PpsData parsePpsNalUnitPayload(byte[] nalData, int nalOffset, int nalLimit) {
      ParsableNalUnitBitArray data = new ParsableNalUnitBitArray(nalData, nalOffset, nalLimit);
      int picParameterSetId = data.readUnsignedExpGolombCodedInt();
      int seqParameterSetId = data.readUnsignedExpGolombCodedInt();
      data.skipBit(); // entropy_coding_mode_flag
      boolean bottomFieldPicOrderInFramePresentFlag = data.readBit();
      return new PpsData(picParameterSetId, seqParameterSetId, bottomFieldPicOrderInFramePresentFlag);
    }
  
    /**
     * Finds the first NAL unit in {@code data}.
     *
     * <p>If {@code prefixFlags} is null then the first three bytes of a NAL unit must be entirely
     * contained within the part of the array being searched in order for it to be found.
     *
     * <p>When {@code prefixFlags} is non-null, this method supports finding NAL units whose first
     * four bytes span {@code data} arrays passed to successive calls. To use this feature, pass the
     * same {@code prefixFlags} parameter to successive calls. State maintained in this parameter
     * enables the detection of such NAL units. Note that when using this feature, the return value
     * may be 3, 2 or 1 less than {@code startOffset}, to indicate a NAL unit starting 3, 2 or 1 bytes
     * before the first byte in the current array.
     *
     * @param data The data to search.
     * @param startOffset The offset (inclusive) in the data to start the search.
     * @param endOffset The offset (exclusive) in the data to end the search.
     * @param prefixFlags A boolean array whose first three elements are used to store the state
     *     required to detect NAL units where the NAL unit prefix spans array boundaries. The array
     *     must be at least 3 elements long.
     * @return The offset of the NAL unit, or {@code endOffset} if a NAL unit was not found.
     */
    public static int findNalUnit(
        byte[] data, int startOffset, int endOffset, boolean[] prefixFlags) {
      int length = endOffset - startOffset;
  
      Assertions.checkState(length >= 0);
      if (length == 0) {
        return endOffset;
      }
  
      if (prefixFlags[0]) {
        clearPrefixFlags(prefixFlags);
        return startOffset - 3;
      } else if (length > 1 && prefixFlags[1] && data[startOffset] == 1) {
        clearPrefixFlags(prefixFlags);
        return startOffset - 2;
      } else if (length > 2
          && prefixFlags[2]
          && data[startOffset] == 0
          && data[startOffset + 1] == 1) {
        clearPrefixFlags(prefixFlags);
        return startOffset - 1;
      }
  
      int limit = endOffset - 1;
      // We're looking for the NAL unit start code prefix 0x000001. The value of i tracks the index of
      // the third byte.
      for (int i = startOffset + 2; i < limit; i += 3) {
        if ((data[i] & 0xFE) != 0) {
          // There isn't a NAL prefix here, or at the next two positions. Do nothing and let the
          // loop advance the index by three.
        } else if (data[i - 2] == 0 && data[i - 1] == 0 && data[i] == 1) {
          clearPrefixFlags(prefixFlags);
          return i - 2;
        } else {
          // There isn't a NAL prefix here, but there might be at the next position. We should
          // only skip forward by one. The loop will skip forward by three, so subtract two here.
          i -= 2;
        }
      }
  
      // True if the last three bytes in the data seen so far are {0,0,1}.
      prefixFlags[0] =
          length > 2
              ? (data[endOffset - 3] == 0 && data[endOffset - 2] == 0 && data[endOffset - 1] == 1)
              : length == 2
                  ? (prefixFlags[2] && data[endOffset - 2] == 0 && data[endOffset - 1] == 1)
                  : (prefixFlags[1] && data[endOffset - 1] == 1);
      // True if the last two bytes in the data seen so far are {0,0}.
      prefixFlags[1] =
          length > 1
              ? data[endOffset - 2] == 0 && data[endOffset - 1] == 0
              : prefixFlags[2] && data[endOffset - 1] == 0;
      // True if the last byte in the data seen so far is {0}.
      prefixFlags[2] = data[endOffset - 1] == 0;
  
      return endOffset;
    }
  
    /**
     * Clears prefix flags, as used by {@link #findNalUnit(byte[], int, int, boolean[])}.
     *
     * @param prefixFlags The flags to clear.
     */
    public static void clearPrefixFlags(boolean[] prefixFlags) {
      prefixFlags[0] = false;
      prefixFlags[1] = false;
      prefixFlags[2] = false;
    }
  
    private static int findNextUnescapeIndex(byte[] bytes, int offset, int limit) {
      for (int i = offset; i < limit - 2; i++) {
        if (bytes[i] == 0x00 && bytes[i + 1] == 0x00 && bytes[i + 2] == 0x03) {
          return i;
        }
      }
      return limit;
    }
  
    private static void skipScalingList(ParsableNalUnitBitArray bitArray, int size) {
      int lastScale = 8;
      int nextScale = 8;
      for (int i = 0; i < size; i++) {
        if (nextScale != 0) {
          int deltaScale = bitArray.readSignedExpGolombCodedInt();
          nextScale = (lastScale + deltaScale + 256) % 256;
        }
        lastScale = (nextScale == 0) ? lastScale : nextScale;
      }
    }
  
    private static void skipH265ScalingList(ParsableNalUnitBitArray bitArray) {
      for (int sizeId = 0; sizeId < 4; sizeId++) {
        for (int matrixId = 0; matrixId < 6; matrixId += sizeId == 3 ? 3 : 1) {
          if (!bitArray.readBit()) { // scaling_list_pred_mode_flag[sizeId][matrixId]
            // scaling_list_pred_matrix_id_delta[sizeId][matrixId]
            bitArray.readUnsignedExpGolombCodedInt();
          } else {
            int coefNum = min(64, 1 << (4 + (sizeId << 1)));
            if (sizeId > 1) {
              // scaling_list_dc_coef_minus8[sizeId - 2][matrixId]
              bitArray.readSignedExpGolombCodedInt();
            }
            for (int i = 0; i < coefNum; i++) {
              bitArray.readSignedExpGolombCodedInt(); // scaling_list_delta_coef
            }
          }
        }
      }
    }
  
    /**
     * Skips any short term reference picture sets contained in a SPS.
     *
     * <p>Note: The st_ref_pic_set parsing in this method is simplified for the case where they're
     * contained in a SPS, and would need generalizing for use elsewhere.
     */
    private static void skipShortTermReferencePictureSets(ParsableNalUnitBitArray bitArray) {
      int numShortTermRefPicSets = bitArray.readUnsignedExpGolombCodedInt();
      // As this method applies in a SPS, each short term reference picture set only accesses data
      // from the previous one. This is because RefRpsIdx = stRpsIdx - (delta_idx_minus1 + 1), and
      // delta_idx_minus1 is always zero in a SPS. Hence we just keep track of variables from the
      // previous one as we iterate.
      int previousNumNegativePics = C.INDEX_UNSET;
      int previousNumPositivePics = C.INDEX_UNSET;
      int[] previousDeltaPocS0 = new int[0];
      int[] previousDeltaPocS1 = new int[0];
      for (int stRpsIdx = 0; stRpsIdx < numShortTermRefPicSets; stRpsIdx++) {
        int numNegativePics;
        int numPositivePics;
        int[] deltaPocS0;
        int[] deltaPocS1;
  
        boolean interRefPicSetPredictionFlag = stRpsIdx != 0 && bitArray.readBit();
        if (interRefPicSetPredictionFlag) {
          int previousNumDeltaPocs = previousNumNegativePics + previousNumPositivePics;
  
          int deltaRpsSign = bitArray.readBit() ? 1 : 0;
          int absDeltaRps = bitArray.readUnsignedExpGolombCodedInt() + 1;
          int deltaRps = (1 - 2 * deltaRpsSign) * absDeltaRps;
  
          boolean[] useDeltaFlags = new boolean[previousNumDeltaPocs + 1];
          for (int j = 0; j <= previousNumDeltaPocs; j++) {
            if (!bitArray.readBit()) { // used_by_curr_pic_flag[j]
              useDeltaFlags[j] = bitArray.readBit();
            } else {
              // When use_delta_flag[j] is not present, its value is 1.
              useDeltaFlags[j] = true;
            }
          }
  
          // Derive numNegativePics, numPositivePics, deltaPocS0 and deltaPocS1 as per Rec. ITU-T
          // H.265 v6 (06/2019) Section 7.4.8
          int i = 0;
          deltaPocS0 = new int[previousNumDeltaPocs + 1];
          deltaPocS1 = new int[previousNumDeltaPocs + 1];
          for (int j = previousNumPositivePics - 1; j >= 0; j--) {
            int dPoc = previousDeltaPocS1[j] + deltaRps;
            if (dPoc < 0 && useDeltaFlags[previousNumNegativePics + j]) {
              deltaPocS0[i++] = dPoc;
            }
          }
          if (deltaRps < 0 && useDeltaFlags[previousNumDeltaPocs]) {
            deltaPocS0[i++] = deltaRps;
          }
          for (int j = 0; j < previousNumNegativePics; j++) {
            int dPoc = previousDeltaPocS0[j] + deltaRps;
            if (dPoc < 0 && useDeltaFlags[j]) {
              deltaPocS0[i++] = dPoc;
            }
          }
          numNegativePics = i;
          deltaPocS0 = Arrays.copyOf(deltaPocS0, numNegativePics);
  
          i = 0;
          for (int j = previousNumNegativePics - 1; j >= 0; j--) {
            int dPoc = previousDeltaPocS0[j] + deltaRps;
            if (dPoc > 0 && useDeltaFlags[j]) {
              deltaPocS1[i++] = dPoc;
            }
          }
          if (deltaRps > 0 && useDeltaFlags[previousNumDeltaPocs]) {
            deltaPocS1[i++] = deltaRps;
          }
          for (int j = 0; j < previousNumPositivePics; j++) {
            int dPoc = previousDeltaPocS1[j] + deltaRps;
            if (dPoc > 0 && useDeltaFlags[previousNumNegativePics + j]) {
              deltaPocS1[i++] = dPoc;
            }
          }
          numPositivePics = i;
          deltaPocS1 = Arrays.copyOf(deltaPocS1, numPositivePics);
        } else {
          numNegativePics = bitArray.readUnsignedExpGolombCodedInt();
          numPositivePics = bitArray.readUnsignedExpGolombCodedInt();
          deltaPocS0 = new int[numNegativePics];
          for (int i = 0; i < numNegativePics; i++) {
            deltaPocS0[i] = bitArray.readUnsignedExpGolombCodedInt() + 1;
            bitArray.skipBit(); // used_by_curr_pic_s0_flag[i]
          }
          deltaPocS1 = new int[numPositivePics];
          for (int i = 0; i < numPositivePics; i++) {
            deltaPocS1[i] = bitArray.readUnsignedExpGolombCodedInt() + 1;
            bitArray.skipBit(); // used_by_curr_pic_s1_flag[i]
          }
        }
        previousNumNegativePics = numNegativePics;
        previousNumPositivePics = numPositivePics;
        previousDeltaPocS0 = deltaPocS0;
        previousDeltaPocS1 = deltaPocS1;
      }
    }
  
    private NalUnitUtil() {
      // Prevent instantiation.
    }
  }
  