usbtuner/src/com/android/usbtuner/exoplayer/SampleExtractor.java

/*
 * Copyright (C) 2015 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.android.usbtuner.exoplayer;

import com.google.android.exoplayer.MediaFormat;
import com.google.android.exoplayer.MediaFormatHolder;
import com.google.android.exoplayer.SampleHolder;
import com.google.android.exoplayer.SampleSource;
import com.google.android.exoplayer.TrackRenderer;

import java.io.IOException;

/**
 * Extractor for reading track metadata and samples stored in tracks.
 *
 * <p>Call {@link #prepare} until it returns {@code true}, then access track metadata via
 * {@link #getTrackFormats} and {@link #getTrackMediaFormat}.
 *
 * <p>Pass indices of tracks to read from to {@link #selectTrack}. A track can later be deselected
 * by calling {@link #deselectTrack}. It is safe to select/deselect tracks after reading sample
 * data or seeking. Initially, all tracks are deselected.
 *
 * <p>Call {@link #release()} when the extractor is no longer needed to free resources.
 */
public interface SampleExtractor {

    /**
    * Prepares the extractor for reading track metadata and samples.
    *
    * @return whether the source is ready; if {@code false}, {@link #prepare()} must be called
     *        again
    * @throws {@link IOException} thrown if the source can't be read
    */
    boolean prepare() throws IOException;

    /** Returns track information about all tracks that can be selected. */
    MediaFormat[] getTrackFormats();

    /** Selects the track at {@code index} for reading sample data. */
    void selectTrack(int index);

    /** Deselects the track at {@code index}, so no more samples will be read from that track. */
    void deselectTrack(int index);

    /**
    * Returns an estimate of the position up to which data is buffered.
    *
    * <p>This method should not be called until after the extractor has been successfully prepared.
    *
    * @return an estimate of the absolute position in microseconds up to which data is buffered,
    *     or {@link TrackRenderer#END_OF_TRACK_US} if data is buffered to the end of the stream, or
    *     {@link TrackRenderer#UNKNOWN_TIME_US} if no estimate is available.
    */
    long getBufferedPositionUs();

    /**
    * Seeks to the specified time in microseconds.
    *
    * <p>This method should not be called until after the extractor has been successfully prepared.
    *
    * @param positionUs the seek position in microseconds
    */
    void seekTo(long positionUs);

    /** Stores the {@link MediaFormat} of {@code track}. */
    void getTrackMediaFormat(int track, MediaFormatHolder outMediaFormatHolder);

    /**
    * Reads the next sample in the track at index {@code track} into {@code sampleHolder}, returning
    * {@link SampleSource#SAMPLE_READ} if it is available.
    *
    * <p>Advances to the next sample if a sample was read.
    *
    * @param track the index of the track from which to read a sample
    * @param sampleHolder the holder for read sample data, if {@link SampleSource#SAMPLE_READ} is
    *     returned
    * @return {@link SampleSource#SAMPLE_READ} if a sample was read into {@code sampleHolder}, or
    *     {@link SampleSource#END_OF_STREAM} if the last samples in all tracks have been read, or
    *     {@link SampleSource#NOTHING_READ} if the sample cannot be read immediately as it is not
    *     loaded.
    */
    int readSample(int track, SampleHolder sampleHolder);

    /** Releases resources associated with this extractor. */
    void release();

    /** Indicates to the source that it should still be buffering data. */
    boolean continueBuffering(long positionUs);
}