Splits an array of NAL units. - Android java.lang

Android examples for java.lang:array

  1. HOME
  2. Android
  3. java.lang
  4. array

Description

Splits an array of NAL units.

Demo Code

/*//from   ww  w . j  a v a 2 s .co  m
 * Copyright (C) 2014 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.java2s;

import java.util.ArrayList;
import java.util.List;

public class Main {
    private static final byte[] NAL_START_CODE = new byte[] { 0, 0, 0, 1 };

    /**
     * Splits an array of NAL units.
     * <p>
     * If the input consists of NAL start code delimited units, then the returned array consists of
     * the split NAL units, each of which is still prefixed with the NAL start code. For any other
     * input, null is returned.
     *
     * @param data An array of data.
     * @return The individual NAL units, or null if the input did not consist of NAL start code
     *     delimited units.
     */
    public static byte[][] splitNalUnits(byte[] data) {
        if (!isNalStartCode(data, 0)) {
            // data does not consist of NAL start code delimited units.
            return null;
        }
        List<Integer> starts = new ArrayList<>();
        int nalUnitIndex = 0;
        do {
            starts.add(nalUnitIndex);
            nalUnitIndex = findNalStartCode(data, nalUnitIndex
                    + NAL_START_CODE.length);
        } while (nalUnitIndex != -1);
        byte[][] split = new byte[starts.size()][];
        for (int i = 0; i < starts.size(); i++) {
            int startIndex = starts.get(i);
            int endIndex = i < starts.size() - 1 ? starts.get(i + 1)
                    : data.length;
            byte[] nal = new byte[endIndex - startIndex];
            System.arraycopy(data, startIndex, nal, 0, nal.length);
            split[i] = nal;
        }
        return split;
    }

    /**
     * Tests whether there exists a NAL start code at a given index.
     *
     * @param data The data.
     * @param index The index to test.
     * @return Whether there exists a start code that begins at {@code index}.
     */
    private static boolean isNalStartCode(byte[] data, int index) {
        if (data.length - index <= NAL_START_CODE.length) {
            return false;
        }
        for (int j = 0; j < NAL_START_CODE.length; j++) {
            if (data[index + j] != NAL_START_CODE[j]) {
                return false;
            }
        }
        return true;
    }

    /**
     * Finds the next occurrence of the NAL start code from a given index.
     *
     * @param data The data in which to search.
     * @param index The first index to test.
     * @return The index of the first byte of the found start code, or -1.
     */
    private static int findNalStartCode(byte[] data, int index) {
        int endIndex = data.length - NAL_START_CODE.length;
        for (int i = index; i <= endIndex; i++) {
            if (isNalStartCode(data, i)) {
                return i;
            }
        }
        return -1;
    }
}

Related Tutorials