1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.tv.util;
18
19import java.util.concurrent.TimeUnit;
20
21/**
22 * A class that includes convenience methods for time shift plays.
23 */
24public class TimeShiftUtils {
25    private static final String TAG = "TimeShiftUtils";
26    private static final boolean DEBUG = false;
27
28    private static final long SHORT_PROGRAM_THRESHOLD_MILLIS = TimeUnit.MINUTES.toMillis(46);
29    private static final int[] SHORT_PROGRAM_SPEED_FACTORS = new int[] {2, 4, 12, 48};
30    private static final int[] LONG_PROGRAM_SPEED_FACTORS = new int[] {2, 8, 32, 128};
31
32    /**
33     * The maximum play speed level support by time shift play. In other words, the valid
34     * speed levels are ranged from 0 to MAX_SPEED_LEVEL (included).
35     */
36    public static final int MAX_SPEED_LEVEL = SHORT_PROGRAM_SPEED_FACTORS.length - 1;
37
38    /**
39     * Returns real speeds used in time shift play. This method is only for fast-forwarding and
40     * rewinding. The normal play speed is not addressed here.
41     *
42     * @param speedLevel the valid value is ranged from 0 to {@link #MAX_SPEED_LEVEL}.
43     * @param programDurationMillis the length of program under playing.
44     * @throws IndexOutOfBoundsException if speed level is out of its range.
45     */
46    public static int getPlaybackSpeed(int speedLevel, long programDurationMillis)
47            throws IndexOutOfBoundsException {
48        return (programDurationMillis > SHORT_PROGRAM_THRESHOLD_MILLIS) ?
49                LONG_PROGRAM_SPEED_FACTORS[speedLevel] : SHORT_PROGRAM_SPEED_FACTORS[speedLevel];
50    }
51
52    /**
53     * Returns the maxium possible play speed according to the program's length.
54     * @param programDurationMillis the length of program under playing.
55     */
56    public static int getMaxPlaybackSpeed(long programDurationMillis) {
57        return (programDurationMillis > SHORT_PROGRAM_THRESHOLD_MILLIS) ?
58                LONG_PROGRAM_SPEED_FACTORS[MAX_SPEED_LEVEL]
59                : SHORT_PROGRAM_SPEED_FACTORS[MAX_SPEED_LEVEL];
60    }
61}
62