media/java/android/media/MediaCodec.java

/*
 * Copyright (C) 2012 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 android.media;

import android.media.MediaCodecInfo;
import android.media.MediaCodecList;
import android.media.MediaCrypto;
import android.media.MediaFormat;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.view.Surface;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Map;

/**
 * MediaCodec class can be used to access low-level media codec, i.e.
 * encoder/decoder components.
 *
 * <p>MediaCodec is generally used like this:
 * <pre>
 * MediaCodec codec = MediaCodec.createDecoderByType(type);
 * codec.configure(format, ...);
 * codec.start();
 * ByteBuffer[] inputBuffers = codec.getInputBuffers();
 * ByteBuffer[] outputBuffers = codec.getOutputBuffers();
 * for (;;) {
 *   int inputBufferIndex = codec.dequeueInputBuffer(timeoutUs);
 *   if (inputBufferIndex &gt;= 0) {
 *     // fill inputBuffers[inputBufferIndex] with valid data
 *     ...
 *     codec.queueInputBuffer(inputBufferIndex, ...);
 *   }
 *
 *   int outputBufferIndex = codec.dequeueOutputBuffer(timeoutUs);
 *   if (outputBufferIndex &gt;= 0) {
 *     // outputBuffer is ready to be processed or rendered.
 *     ...
 *     codec.releaseOutputBuffer(outputBufferIndex, ...);
 *   } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
 *     outputBuffers = codec.getOutputBuffers();
 *   } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
 *     // Subsequent data will conform to new format.
 *     MediaFormat format = codec.getOutputFormat();
 *     ...
 *   }
 * }
 * codec.stop();
 * codec.release();
 * codec = null;
 * </pre>
 *
 * Each codec maintains a number of input and output buffers that are
 * referred to by index in API calls.
 * The contents of these buffers are represented by the ByteBuffer[] arrays
 * accessible through {@link #getInputBuffers} and {@link #getOutputBuffers}.
 *
 * After a successful call to {@link #start} the client "owns" neither
 * input nor output buffers, subsequent calls to {@link #dequeueInputBuffer}
 * and {@link #dequeueOutputBuffer} then transfer ownership from the codec
 * to the client.<p>
 * The client is not required to resubmit/release buffers immediately
 * to the codec, the sample code above simply does this for simplicity's sake.<p>
 * Once the client has an input buffer available it can fill it with data
 * and submit it it to the codec via a call to {@link #queueInputBuffer}.<p>
 * The codec in turn will return an output buffer to the client in response
 * to {@link #dequeueOutputBuffer}. After the output buffer has been processed
 * a call to {@link #releaseOutputBuffer} will return it to the codec.
 * If a video surface has been provided in the call to {@link #configure},
 * {@link #releaseOutputBuffer} optionally allows rendering of the buffer
 * to the surface.<p>
 *
 * Input buffers (for decoders) and Output buffers (for encoders) contain
 * encoded data according to the format's type. For video types this data
 * is all the encoded data representing a single moment in time, for audio
 * data this is slightly relaxed in that a buffer may contain multiple
 * encoded frames of audio. In either case, buffers do not start and end on
 * arbitrary byte boundaries, this is not a stream of bytes, it's a stream
 * of access units.<p>
 *
 * Most formats also require the actual data to be prefixed by a number
 * of buffers containing setup data, or codec specific data, i.e. the
 * first few buffers submitted to the codec object after starting it must
 * be codec specific data marked as such using the flag {@link #BUFFER_FLAG_CODEC_CONFIG}
 * in a call to {@link #queueInputBuffer}.
 *
 * Codec specific data included in the format passed to {@link #configure}
 * (in ByteBuffer entries with keys "csd-0", "csd-1", ...) is automatically
 * submitted to the codec, this data MUST NOT be submitted explicitly by the
 * client.
 *
 * Once the client reaches the end of the input data it signals the end of
 * the input stream by specifying a flag of {@link #BUFFER_FLAG_END_OF_STREAM} in the call to
 * {@link #queueInputBuffer}. The codec will continue to return output buffers
 * until it eventually signals the end of the output stream by specifying
 * the same flag ({@link #BUFFER_FLAG_END_OF_STREAM}) on the BufferInfo returned in
 * {@link #dequeueOutputBuffer}.
 *
 * In order to start decoding data that's not adjacent to previously submitted
 * data (i.e. after a seek) it is necessary to {@link #flush} the decoder.
 * Any input or output buffers the client may own at the point of the flush are
 * immediately revoked, i.e. after a call to {@link #flush} the client does not
 * own any buffers anymore.
 * Note that the format of the data submitted after a flush must not change,
 * flush does not support format discontinuities,
 * for this a full {@link #stop}, {@link #configure}, {@link #start}
 * cycle is necessary.
 *
 * <p> The factory methods
 * {@link #createByCodecName},
 * {@link #createDecoderByType},
 * and {@link #createEncoderByType}
 * throw {@link java.io.IOException} on failure which
 * the caller must catch or declare to pass up.
 * Other methods will throw {@link java.lang.IllegalStateException}
 * if the codec is in an Uninitialized, Invalid, or Error state (e.g. not
 * initialized properly).  Exceptions are thrown elsewhere as noted. </p>
 *
 */
final public class MediaCodec {
    /**
     * Per buffer metadata includes an offset and size specifying
     * the range of valid data in the associated codec buffer.
     */
    public final static class BufferInfo {
        public void set(
                int newOffset, int newSize, long newTimeUs, int newFlags) {
            offset = newOffset;
            size = newSize;
            presentationTimeUs = newTimeUs;
            flags = newFlags;
        }

        public int offset;
        public int size;
        public long presentationTimeUs;
        public int flags;
    };

    // The follow flag constants MUST stay in sync with their equivalents
    // in MediaCodec.h !

    /**
     * This indicates that the buffer marked as such contains the data
     * for a sync frame.
     */
    public static final int BUFFER_FLAG_SYNC_FRAME   = 1;

    /**
     * This indicated that the buffer marked as such contains codec
     * initialization / codec specific data instead of media data.
     */
    public static final int BUFFER_FLAG_CODEC_CONFIG = 2;

    /**
     * This signals the end of stream, i.e. no buffers will be available
     * after this, unless of course, {@link #flush} follows.
     */
    public static final int BUFFER_FLAG_END_OF_STREAM         = 4;

    private EventHandler mEventHandler;
    private volatile NotificationCallback mNotificationCallback;

    static final int EVENT_NOTIFY = 1;

    private class EventHandler extends Handler {
        private MediaCodec mCodec;

        public EventHandler(MediaCodec codec, Looper looper) {
            super(looper);
            mCodec = codec;
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case EVENT_NOTIFY:
                {
                    NotificationCallback cb = mNotificationCallback;
                    if (cb != null) {
                        cb.onCodecNotify(mCodec);
                    }
                    break;
                }
            }
        }
    }

    /**
     * Instantiate a decoder supporting input data of the given mime type.
     *
     * The following is a partial list of defined mime types and their semantics:
     * <ul>
     * <li>"video/x-vnd.on2.vp8" - VP8 video (i.e. video in .webm)
     * <li>"video/x-vnd.on2.vp9" - VP9 video (i.e. video in .webm)
     * <li>"video/avc" - H.264/AVC video
     * <li>"video/mp4v-es" - MPEG4 video
     * <li>"video/3gpp" - H.263 video
     * <li>"audio/3gpp" - AMR narrowband audio
     * <li>"audio/amr-wb" - AMR wideband audio
     * <li>"audio/mpeg" - MPEG1/2 audio layer III
     * <li>"audio/mp4a-latm" - AAC audio (note, this is raw AAC packets, not packaged in LATM!)
     * <li>"audio/vorbis" - vorbis audio
     * <li>"audio/g711-alaw" - G.711 alaw audio
     * <li>"audio/g711-mlaw" - G.711 ulaw audio
     * </ul>
     *
     * @param type The mime type of the input data.
     * @throws IOException if the codec cannot be created.
     * @throws IllegalArgumentException if type is null.
     */
    public static MediaCodec createDecoderByType(String type)
            throws IOException {
        return new MediaCodec(type, true /* nameIsType */, false /* encoder */);
    }

    /**
     * Instantiate an encoder supporting output data of the given mime type.
     * @param type The desired mime type of the output data.
     * @throws IOException if the codec cannot be created.
     * @throws IllegalArgumentException if type is null.
     */
    public static MediaCodec createEncoderByType(String type)
            throws IOException {
        return new MediaCodec(type, true /* nameIsType */, true /* encoder */);
    }

    /**
     * If you know the exact name of the component you want to instantiate
     * use this method to instantiate it. Use with caution.
     * Likely to be used with information obtained from {@link android.media.MediaCodecList}
     * @param name The name of the codec to be instantiated.
     * @throws IOException if the codec cannot be created.
     * @throws IllegalArgumentException if name is null.
     */
    public static MediaCodec createByCodecName(String name)
            throws IOException {
        return new MediaCodec(
                name, false /* nameIsType */, false /* unused */);
    }

    private MediaCodec(
            String name, boolean nameIsType, boolean encoder) {
        Looper looper;
        if ((looper = Looper.myLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else if ((looper = Looper.getMainLooper()) != null) {
            mEventHandler = new EventHandler(this, looper);
        } else {
            mEventHandler = null;
        }

        native_setup(name, nameIsType, encoder);
    }

    @Override
    protected void finalize() {
        native_finalize();
    }

    /**
     * Make sure you call this when you're done to free up any opened
     * component instance instead of relying on the garbage collector
     * to do this for you at some point in the future.
     */
    public native final void release();

    /**
     * If this codec is to be used as an encoder, pass this flag.
     */
    public static final int CONFIGURE_FLAG_ENCODE = 1;

    /**
     * Configures a component.
     *
     * @param format The format of the input data (decoder) or the desired
     *               format of the output data (encoder).
     * @param surface Specify a surface on which to render the output of this
     *                decoder.
     * @param crypto  Specify a crypto object to facilitate secure decryption
     *                of the media data.
     * @param flags   Specify {@link #CONFIGURE_FLAG_ENCODE} to configure the
     *                component as an encoder.
     */
    public void configure(
            MediaFormat format,
            Surface surface, MediaCrypto crypto, int flags) {
        Map<String, Object> formatMap = format.getMap();

        String[] keys = null;
        Object[] values = null;

        if (format != null) {
            keys = new String[formatMap.size()];
            values = new Object[formatMap.size()];

            int i = 0;
            for (Map.Entry<String, Object> entry: formatMap.entrySet()) {
                keys[i] = entry.getKey();
                values[i] = entry.getValue();
                ++i;
            }
        }

        native_configure(keys, values, surface, crypto, flags);
    }

    private native final void native_configure(
            String[] keys, Object[] values,
            Surface surface, MediaCrypto crypto, int flags);

    /**
     * Requests a Surface to use as the input to an encoder, in place of input buffers.  This
     * may only be called after {@link #configure} and before {@link #start}.
     * <p>
     * The application is responsible for calling release() on the Surface when
     * done.
     */
    public native final Surface createInputSurface();

    /**
     * After successfully configuring the component, call start. On return
     * you can query the component for its input/output buffers.
     */
    public native final void start();

    /**
     * Finish the decode/encode session, note that the codec instance
     * remains active and ready to be {@link #start}ed again.
     * To ensure that it is available to other client call {@link #release}
     * and don't just rely on garbage collection to eventually do this for you.
     */
    public final void stop() {
        native_stop();

        if (mEventHandler != null) {
            mEventHandler.removeMessages(EVENT_NOTIFY);
        }
    }

    private native final void native_stop();

    /**
     * Flush both input and output ports of the component, all indices
     * previously returned in calls to {@link #dequeueInputBuffer} and
     * {@link #dequeueOutputBuffer} become invalid.
     */
    public native final void flush();

    /**
     * Thrown when a crypto error occurs while queueing a secure input buffer.
     */
    public final static class CryptoException extends RuntimeException {
        public CryptoException(int errorCode, String detailMessage) {
            super(detailMessage);
            mErrorCode = errorCode;
        }

        /**
         * This indicates that no key has been set to perform the requested
         * decrypt operation.
         */
        public static final int ERROR_NO_KEY = 1;

        /**
         * This indicates that the key used for decryption is no longer
         * valid due to license term expiration.
         */
        public static final int ERROR_KEY_EXPIRED = 2;

        /**
         * This indicates that a required crypto resource was not able to be
         * allocated while attempting the requested operation.
         */
        public static final int ERROR_RESOURCE_BUSY = 3;

        /**
         * Retrieve the error code associated with a CryptoException
         */
        public int getErrorCode() {
            return mErrorCode;
        }

        private int mErrorCode;
    }

    /**
     * After filling a range of the input buffer at the specified index
     * submit it to the component.
     *
     * Many decoders require the actual compressed data stream to be
     * preceded by "codec specific data", i.e. setup data used to initialize
     * the codec such as PPS/SPS in the case of AVC video or code tables
     * in the case of vorbis audio.
     * The class {@link android.media.MediaExtractor} provides codec
     * specific data as part of
     * the returned track format in entries named "csd-0", "csd-1" ...
     *
     * These buffers should be submitted using the flag {@link #BUFFER_FLAG_CODEC_CONFIG}.
     *
     * To indicate that this is the final piece of input data (or rather that
     * no more input data follows unless the decoder is subsequently flushed)
     * specify the flag {@link #BUFFER_FLAG_END_OF_STREAM}.
     *
     * @param index The index of a client-owned input buffer previously returned
     *              in a call to {@link #dequeueInputBuffer}.
     * @param offset The byte offset into the input buffer at which the data starts.
     * @param size The number of bytes of valid input data.
     * @param presentationTimeUs The time at which this buffer should be rendered.
     * @param flags A bitmask of flags {@link #BUFFER_FLAG_SYNC_FRAME},
     *              {@link #BUFFER_FLAG_CODEC_CONFIG} or {@link #BUFFER_FLAG_END_OF_STREAM}.
     * @throws CryptoException if a crypto object has been specified in
     *         {@link #configure}
     */
    public native final void queueInputBuffer(
            int index,
            int offset, int size, long presentationTimeUs, int flags)
        throws CryptoException;

    // The following mode constants MUST stay in sync with their equivalents
    // in media/hardware/CryptoAPI.h !
    public static final int CRYPTO_MODE_UNENCRYPTED = 0;
    public static final int CRYPTO_MODE_AES_CTR     = 1;

    /**
     * Metadata describing the structure of a (at least partially) encrypted
     * input sample.
     * A buffer's data is considered to be partitioned into "subSamples",
     * each subSample starts with a (potentially empty) run of plain,
     * unencrypted bytes followed by a (also potentially empty) run of
     * encrypted bytes.
     * numBytesOfClearData can be null to indicate that all data is encrypted.
     * This information encapsulates per-sample metadata as outlined in
     * ISO/IEC FDIS 23001-7:2011 "Common encryption in ISO base media file format files".
     */
    public final static class CryptoInfo {
        public void set(
                int newNumSubSamples,
                int[] newNumBytesOfClearData,
                int[] newNumBytesOfEncryptedData,
                byte[] newKey,
                byte[] newIV,
                int newMode) {
            numSubSamples = newNumSubSamples;
            numBytesOfClearData = newNumBytesOfClearData;
            numBytesOfEncryptedData = newNumBytesOfEncryptedData;
            key = newKey;
            iv = newIV;
            mode = newMode;
        }

        /**
         * The number of subSamples that make up the buffer's contents.
         */
        public int numSubSamples;
        /**
         * The number of leading unencrypted bytes in each subSample.
         */
        public int[] numBytesOfClearData;
        /**
         * The number of trailing encrypted bytes in each subSample.
         */
        public int[] numBytesOfEncryptedData;
        /**
         * A 16-byte opaque key
         */
        public byte[] key;
        /**
         * A 16-byte initialization vector
         */
        public byte[] iv;
        /**
         * The type of encryption that has been applied,
         * see {@link #CRYPTO_MODE_UNENCRYPTED} and {@link #CRYPTO_MODE_AES_CTR}.
         */
        public int mode;

        @Override
        public String toString() {
            StringBuilder builder = new StringBuilder();
            builder.append(numSubSamples + " subsamples, key [");
            String hexdigits = "0123456789abcdef";
            for (int i = 0; i < key.length; i++) {
                builder.append(hexdigits.charAt((key[i] & 0xf0) >> 4));
                builder.append(hexdigits.charAt(key[i] & 0x0f));
            }
            builder.append("], iv [");
            for (int i = 0; i < key.length; i++) {
                builder.append(hexdigits.charAt((iv[i] & 0xf0) >> 4));
                builder.append(hexdigits.charAt(iv[i] & 0x0f));
            }
            builder.append("], clear ");
            builder.append(Arrays.toString(numBytesOfClearData));
            builder.append(", encrypted ");
            builder.append(Arrays.toString(numBytesOfEncryptedData));
            return builder.toString();
        }
    };

    /**
     * Similar to {@link #queueInputBuffer} but submits a buffer that is
     * potentially encrypted.
     * @param index The index of a client-owned input buffer previously returned
     *              in a call to {@link #dequeueInputBuffer}.
     * @param offset The byte offset into the input buffer at which the data starts.
     * @param info Metadata required to facilitate decryption, the object can be
     *             reused immediately after this call returns.
     * @param presentationTimeUs The time at which this buffer should be rendered.
     * @param flags A bitmask of flags {@link #BUFFER_FLAG_SYNC_FRAME},
     *              {@link #BUFFER_FLAG_CODEC_CONFIG} or {@link #BUFFER_FLAG_END_OF_STREAM}.
     * @throws CryptoException if an error occurs while attempting to decrypt the buffer.
     *              An error code associated with the exception helps identify the
     *              reason for the failure.
     */
    public native final void queueSecureInputBuffer(
            int index,
            int offset,
            CryptoInfo info,
            long presentationTimeUs,
            int flags) throws CryptoException;

    /**
     * Returns the index of an input buffer to be filled with valid data
     * or -1 if no such buffer is currently available.
     * This method will return immediately if timeoutUs == 0, wait indefinitely
     * for the availability of an input buffer if timeoutUs &lt; 0 or wait up
     * to "timeoutUs" microseconds if timeoutUs &gt; 0.
     * @param timeoutUs The timeout in microseconds, a negative timeout indicates "infinite".
     */
    public native final int dequeueInputBuffer(long timeoutUs);

    /**
     * If a non-negative timeout had been specified in the call
     * to {@link #dequeueOutputBuffer}, indicates that the call timed out.
     */
    public static final int INFO_TRY_AGAIN_LATER        = -1;

    /**
     * The output format has changed, subsequent data will follow the new
     * format. {@link #getOutputFormat} returns the new format.
     */
    public static final int INFO_OUTPUT_FORMAT_CHANGED  = -2;

    /**
     * The output buffers have changed, the client must refer to the new
     * set of output buffers returned by {@link #getOutputBuffers} from
     * this point on.
     */
    public static final int INFO_OUTPUT_BUFFERS_CHANGED = -3;

    /**
     * Dequeue an output buffer, block at most "timeoutUs" microseconds.
     * Returns the index of an output buffer that has been successfully
     * decoded or one of the INFO_* constants below.
     * @param info Will be filled with buffer meta data.
     * @param timeoutUs The timeout in microseconds, a negative timeout indicates "infinite".
     */
    public native final int dequeueOutputBuffer(
            BufferInfo info, long timeoutUs);

    /**
     * If you are done with a buffer, use this call to return the buffer to
     * the codec. If you previously specified a surface when configuring this
     * video decoder you can optionally render the buffer.
     * @param index The index of a client-owned output buffer previously returned
     *              in a call to {@link #dequeueOutputBuffer}.
     * @param render If a valid surface was specified when configuring the codec,
     *               passing true renders this output buffer to the surface.
     */
    public native final void releaseOutputBuffer(int index, boolean render);

    /**
     * Signals end-of-stream on input.  Equivalent to submitting an empty buffer with
     * {@link #BUFFER_FLAG_END_OF_STREAM} set.  This may only be used with
     * encoders receiving input from a Surface created by {@link #createInputSurface}.
     */
    public native final void signalEndOfInputStream();

    /**
     * Call this after dequeueOutputBuffer signals a format change by returning
     * {@link #INFO_OUTPUT_FORMAT_CHANGED}
     */
    public final MediaFormat getOutputFormat() {
        return new MediaFormat(getOutputFormatNative());
    }

    private native final Map<String, Object> getOutputFormatNative();

    /**
     * Call this after start() returns.
     */
    public ByteBuffer[] getInputBuffers() {
        return getBuffers(true /* input */);
    }

    /**
     * Call this after start() returns and whenever dequeueOutputBuffer
     * signals an output buffer change by returning
     * {@link #INFO_OUTPUT_BUFFERS_CHANGED}
     */
    public ByteBuffer[] getOutputBuffers() {
        return getBuffers(false /* input */);
    }

    /**
     * The content is scaled to the surface dimensions
     */
    public static final int VIDEO_SCALING_MODE_SCALE_TO_FIT               = 1;

    /**
     * The content is scaled, maintaining its aspect ratio, the whole
     * surface area is used, content may be cropped
     */
    public static final int VIDEO_SCALING_MODE_SCALE_TO_FIT_WITH_CROPPING = 2;

    /**
     * If a surface has been specified in a previous call to {@link #configure}
     * specifies the scaling mode to use. The default is "scale to fit".
     */
    public native final void setVideoScalingMode(int mode);

    /**
     * Get the component name. If the codec was created by createDecoderByType
     * or createEncoderByType, what component is chosen is not known beforehand.
     */
    public native final String getName();

    /**
     * Change a video encoder's target bitrate on the fly. The value is an
     * Integer object containing the new bitrate in bps.
     */
    public static final String PARAMETER_KEY_VIDEO_BITRATE = "video-bitrate";

    /**
     * Temporarily suspend/resume encoding of input data. While suspended
     * input data is effectively discarded instead of being fed into the
     * encoder. This parameter really only makes sense to use with an encoder
     * in "surface-input" mode, as the client code has no control over the
     * input-side of the encoder in that case.
     * The value is an Integer object containing the value 1 to suspend
     * or the value 0 to resume.
     */
    public static final String PARAMETER_KEY_SUSPEND = "drop-input-frames";

    /**
     * Request that the encoder produce a sync frame "soon".
     * Provide an Integer with the value 0.
     */
    public static final String PARAMETER_KEY_REQUEST_SYNC_FRAME = "request-sync";

    /**
     * Communicate additional parameter changes to the component instance.
     */
    public final void setParameters(Bundle params) {
        if (params == null) {
            return;
        }

        String[] keys = new String[params.size()];
        Object[] values = new Object[params.size()];

        int i = 0;
        for (final String key: params.keySet()) {
            keys[i] = key;
            values[i] = params.get(key);
            ++i;
        }

        setParameters(keys, values);
    }

    public void setNotificationCallback(NotificationCallback cb) {
        mNotificationCallback = cb;
    }

    public interface NotificationCallback {
        void onCodecNotify(MediaCodec codec);
    }

    private void postEventFromNative(
            int what, int arg1, int arg2, Object obj) {
        if (mEventHandler != null) {
            Message msg = mEventHandler.obtainMessage(what, arg1, arg2, obj);
            mEventHandler.sendMessage(msg);
        }
    }

    private native final void setParameters(String[] keys, Object[] values);

    /**
     * Get the codec info. If the codec was created by createDecoderByType
     * or createEncoderByType, what component is chosen is not known beforehand,
     * and thus the caller does not have the MediaCodecInfo.
     */
    public MediaCodecInfo getCodecInfo() {
        return MediaCodecList.getCodecInfoAt(
                   MediaCodecList.findCodecByName(getName()));
    }

    private native final ByteBuffer[] getBuffers(boolean input);

    private static native final void native_init();

    private native final void native_setup(
            String name, boolean nameIsType, boolean encoder);

    private native final void native_finalize();

    static {
        System.loadLibrary("media_jni");
        native_init();
    }

    private long mNativeContext;
}