android 项目中视频的特定帧集速度慢

Question

我需要实现一个应用程序，在视频视图中显示视频。用户 select 特定范围的视频帧和帧速度减慢。基本上我已经完成了显示视频帧，用户也可以 select 帧集。接下来不知道如何降低 selected 帧集的音频和视频速度。

Answer 1

使用Vitamio Api video slowing(playing video with change playback speed) can be performed. For test purpose user can use vitamio sample available on GitHub Vitamio android sample。或者可以将 vitamio 示例中可用的 class MediaPlayerDemo_Video 添加到慢速视频。

这是 MediaPlayerDemo_Video

的代码

    public class MediaPlayerDemo_Video extends Activity implements OnBufferingUpdateListener, OnCompletionListener, OnPreparedListener, OnVideoSizeChangedListener, SurfaceHolder.Callback {

    private static final String TAG = "MediaPlayerDemo";
    private int mVideoWidth;
    private int mVideoHeight;
    private MediaPlayer mMediaPlayer;
    private SurfaceView mPreview;
    private SurfaceHolder holder;
    private String path;
    private Bundle extras;
    private static final String MEDIA = "media";
    private static final int LOCAL_AUDIO = 1;
    private static final int STREAM_AUDIO = 2;
    private static final int RESOURCES_AUDIO = 3;
    private static final int LOCAL_VIDEO = 4;
    private static final int STREAM_VIDEO = 5;
    private boolean mIsVideoSizeKnown = false;
    private boolean mIsVideoReadyToBePlayed = false;

    /**
     * 
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        if (!LibsChecker.checkVitamioLibs(this))
            return;
        setContentView(R.layout.mediaplayer_2);
        mPreview = (SurfaceView) findViewById(R.id.surface);
        holder = mPreview.getHolder();
        holder.addCallback(this);
        holder.setFormat(PixelFormat.RGBA_8888); 
        extras = getIntent().getExtras();

    }

    private void playVideo(Integer Media) {
        doCleanUp();
        try {

            switch (Media) {
            case LOCAL_VIDEO:
                /*
                 * TODO: Set the path variable to a local media file path.
                 */
                path = "";
                if (path == "") {
                    // Tell the user to provide a media file URL.
                    Toast.makeText(MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity, " + "and set the path variable to your media file path." + " Your media file must be stored on sdcard.", Toast.LENGTH_LONG).show();
                    return;
                }
                break;
            case STREAM_VIDEO:
                /*
                 * TODO: Set path variable to progressive streamable mp4 or
                 * 3gpp format URL. Http protocol should be used.
                 * Mediaplayer can only play "progressive streamable
                 * contents" which basically means: 1. the movie atom has to
                 * precede all the media data atoms. 2. The clip has to be
                 * reasonably interleaved.
                 * 
                 */
                path = "";
                if (path == "") {
                    // Tell the user to provide a media file URL.
                    Toast.makeText(MediaPlayerDemo_Video.this, "Please edit MediaPlayerDemo_Video Activity," + " and set the path variable to your media file URL.", Toast.LENGTH_LONG).show();
                    return;
                }

                break;

            }

            // Create a new media player and set the listeners
            mMediaPlayer = new MediaPlayer(this);
            mMediaPlayer.setDataSource(path);
            mMediaPlayer.setDisplay(holder);
            mMediaPlayer.prepareAsync();
            mMediaPlayer.setOnBufferingUpdateListener(this);
            mMediaPlayer.setOnCompletionListener(this);
            mMediaPlayer.setOnPreparedListener(this);
            mMediaPlayer.setOnVideoSizeChangedListener(this);
            setVolumeControlStream(AudioManager.STREAM_MUSIC);

        } catch (Exception e) {
            Log.e(TAG, "error: " + e.getMessage(), e);
        }
    }

    public void onBufferingUpdate(MediaPlayer arg0, int percent) {
        // Log.d(TAG, "onBufferingUpdate percent:" + percent);

    }

    public void onCompletion(MediaPlayer arg0) {
        Log.d(TAG, "onCompletion called");
    }

    public void onVideoSizeChanged(MediaPlayer mp, int width, int height) {
        Log.v(TAG, "onVideoSizeChanged called");
        if (width == 0 || height == 0) {
            Log.e(TAG, "invalid video width(" + width + ") or height(" + height + ")");
            return;
        }
        mIsVideoSizeKnown = true;
        mVideoWidth = width;
        mVideoHeight = height;
        if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) {
            startVideoPlayback();
        }
    }

    public void onPrepared(MediaPlayer mediaplayer) {
        Log.d(TAG, "onPrepared called");
        mIsVideoReadyToBePlayed = true;
        if (mIsVideoReadyToBePlayed && mIsVideoSizeKnown) {
            startVideoPlayback();
        }
    }

    public void surfaceChanged(SurfaceHolder surfaceholder, int i, int j, int k) {
        Log.d(TAG, "surfaceChanged called");

    }

    public void surfaceDestroyed(SurfaceHolder surfaceholder) {
        Log.d(TAG, "surfaceDestroyed called");
    }

    public void surfaceCreated(SurfaceHolder holder) {
        Log.d(TAG, "surfaceCreated called");
        playVideo(extras.getInt(MEDIA));

    }

    @Override
    protected void onPause() {
        super.onPause();
        releaseMediaPlayer();
        doCleanUp();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        releaseMediaPlayer();
        doCleanUp();
    }

    private void releaseMediaPlayer() {
        if (mMediaPlayer != null) {
            mMediaPlayer.release();
            mMediaPlayer = null;
        }
    }

    private void doCleanUp() {
        mVideoWidth = 0;
        mVideoHeight = 0;
        mIsVideoReadyToBePlayed = false;
        mIsVideoSizeKnown = false;
    }

    private void startVideoPlayback() {
        Log.v(TAG, "startVideoPlayback");
        holder.setFixedSize(mVideoWidth, mVideoHeight);
        mMediaPlayer.start();
    }
}

布局代码

 <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <io.vov.vitamio.widget.CenterLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >

        <SurfaceView
            android:id="@+id/surface"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center" >
        </SurfaceView>
    </io.vov.vitamio.widget.CenterLayout>

</LinearLayout>