how to create only one thumbnail from flash video

问题:

I"m trying to create only one thumbnail from random location from *flv video. the code example that I found around the net wasn't really helpful. If anyone knows how to do it or has a code or method that would do, please share/explain. Thank you.

回答1:

I have gone through the sample code that is available over here (http://www.javacodegeeks.com/2011/02/xuggler-tutorial-frames-capture-video.html) that creates thumbnails out of a given input video file. In order to create only one, you can introduce a class level member variable (in the sample code the variable name is imageGrabbed). This variable just keeps track of thumbnail generation, once the very first thumbnail is created then in the calling function (in the sample code the calling function is main()) the while loop exits.

Hope this helps.

Regards, Ismail.

/**
 * VideoThumbnailsExample.java Oct 29, 2012
 */
package com.test;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import com.xuggle.mediatool.IMediaReader;
import com.xuggle.mediatool.MediaListenerAdapter;
import com.xuggle.mediatool.ToolFactory;
import com.xuggle.mediatool.event.IVideoPictureEvent;
import com.xuggle.xuggler.Global;

/**
 * <pre>
 * Java File.
 * Title        : VideoThumbnailsExample.java
 * Description  : <Description>
 * </pre>
 */
public class VideoThumbnailsExample
{
    public static final double SECONDS_BETWEEN_FRAMES = 1;

    private static final String inputFilename = "/Users/ismail/practice/vlc/sample.3gp";
    private static final String outputFilePrefix = "/Users/ismail/practice/vlc/";

    // The video stream index, used to ensure we display frames from one and
    // only one video stream from the media container.
    private static int mVideoStreamIndex = -1;

    // Time of last frame write
    private static long mLastPtsWrite = Global.NO_PTS;

    public static final long MICRO_SECONDS_BETWEEN_FRAMES = (long) (Global.DEFAULT_PTS_PER_SECOND * SECONDS_BETWEEN_FRAMES);

    public static void main(String[] args)
    {
        long startTime = System.currentTimeMillis();
        long stopTime = 0L;

        IMediaReader mediaReader = ToolFactory.makeReader(inputFilename);

        // stipulate that we want BufferedImages created in BGR 24bit color
        // space

        try
        {
            mediaReader
            .setBufferedImageTypeToGenerate(BufferedImage.TYPE_3BYTE_BGR);

            ImageSnapListener isListener = new ImageSnapListener();

            mediaReader.addListener(isListener);

            // read out the contents of the media file and
            // dispatch events to the attached listener

            while (!isListener.isImageGrabbed())
            {
                mediaReader.readPacket();
            }
            /*
            while (mediaReader.readPacket() == null)
                ;
            */
            //mediaReader.readPacket();
            stopTime = System.currentTimeMillis();

        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }



        System.out.println("Total Time: " + (stopTime-startTime));


    }

    private static class ImageSnapListener extends MediaListenerAdapter
    {
        public boolean imageGrabbed = false;


        public void onVideoPicture(IVideoPictureEvent event)
        {

            if (event.getStreamIndex() != mVideoStreamIndex)
            {

                // if the selected video stream id is not yet set, go ahead an
                // select this lucky video stream

                if (mVideoStreamIndex == -1)
                    mVideoStreamIndex = event.getStreamIndex();

                // no need to show frames from this video stream
                else
                    return;

            }

            // if uninitialized, back date mLastPtsWrite to get the very first
            // frame

            if (mLastPtsWrite == Global.NO_PTS)

                mLastPtsWrite = event.getTimeStamp()
                        - MICRO_SECONDS_BETWEEN_FRAMES;

            // if it's time to write the next frame

            if (event.getTimeStamp() - mLastPtsWrite >= MICRO_SECONDS_BETWEEN_FRAMES)
            {

                String outputFilename = dumpImageToFile(event.getImage());

                this.imageGrabbed = true; //set this var to true once an image is grabbed out of the movie.

                // indicate file written
                double seconds = ((double) event.getTimeStamp())
                        / Global.DEFAULT_PTS_PER_SECOND;

                System.out.printf("at elapsed time of %6.3f seconds wrote: %s\n",seconds, outputFilename);
                //System.out.printf("at elapsed time of %6.3f seconds wrote: SOMEFILE\n",seconds);

                // update last write time
                mLastPtsWrite += MICRO_SECONDS_BETWEEN_FRAMES;

            }

        }

        private String dumpImageToFile(BufferedImage image)
        {

            try
            {

                String outputFilename = outputFilePrefix
                        + System.currentTimeMillis() + ".jpg";

                System.out.println("Thumbnail image name is going to be : =====>" + outputFilename);

                ImageIO.write(image, "jpg", new File(outputFilename));

                return outputFilename;

            }

            catch (IOException e)
            {
                e.printStackTrace();
                return null;

            }

        }

        public boolean isImageGrabbed() {
            return imageGrabbed;
        }

    }

}