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 android.util.Log;
  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";
  
    /**
     * Holds data parsed from a sequence parameter set NAL unit.
     */
    public static final class SpsData {
  
      public final int seqParameterSetId;
      public final int width;
      public final int height;
      public final float pixelWidthAspectRatio;
      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 seqParameterSetId, int width, int height, float pixelWidthAspectRatio,
          boolean separateColorPlaneFlag, boolean frameMbsOnlyFlag, int frameNumLength,
          int picOrderCountType, int picOrderCntLsbLength, boolean deltaPicOrderAlwaysZeroFlag) {
        this.seqParameterSetId = seqParameterSetId;
        this.width = width;
        this.height = height;
        this.pixelWidthAspectRatio = pixelWidthAspectRatio;
        this.separateColorPlaneFlag = separateColorPlaneFlag;
        this.frameMbsOnlyFlag = frameMbsOnlyFlag;
        this.frameNumLength = frameNumLength;
        this.picOrderCountType = picOrderCountType;
        this.picOrderCntLsbLength = picOrderCntLsbLength;
        this.deltaPicOrderAlwaysZeroFlag = deltaPicOrderAlwaysZeroFlag;
      }
  
    }
  
    /**
     * 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.
     * @param nalUnitHeaderFirstByte The first byte of nal_unit().
     * @return Whether the NAL unit with the specified header is an SEI NAL unit.
     */
    public static boolean isNalUnitSei(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 an 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) {
      ParsableNalUnitBitArray data = new ParsableNalUnitBitArray(nalData, nalOffset, nalLimit);
      data.skipBits(8); // nal_unit
      int profileIdc = data.readBits(8);
      data.skipBits(16); // constraint bits (6), reserved (2) and level_idc (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]
        }
      }
      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(seqParameterSetId, frameWidth, frameHeight, pixelWidthHeightRatio,
          separateColorPlaneFlag, frameMbsOnlyFlag, frameNumLength, picOrderCntType,
          picOrderCntLsbLength, deltaPicOrderAlwaysZeroFlag);
    }
  
    /**
     * 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) {
      ParsableNalUnitBitArray data = new ParsableNalUnitBitArray(nalData, nalOffset, nalLimit);
      data.skipBits(8); // nal_unit
      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 != null) {
        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) {
          if (prefixFlags != null) {
            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;
        }
      }
  
      if (prefixFlags != null) {
        // 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 NalUnitUtil() {
      // Prevent instantiation.
    }
  
  }
  