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• Extracting image frames from mjpeg given 'frame byte offset' and 'frame size' [on hold]

  2 septembre 2015, par Sonia

  I’m looking for code or pointers to funtions or library that I can use to extract image frames from motion jpeg file. In my case, for each image frame, I know the starting byte offset and the size of the frame (size is not always equal for each frame). Given these data, how can I extract each image frames from mjpeg file.

  I have checked the OpenCV library, I can’t find the detail about giving these two inputs to extract frames. Also, I can’t find it in FFmpeg as well. But, I’m not an expert in these two. I hope anyone could give me pointers to this. It can be just a tool or sourcecode (I use C/C++ and MATLAB but I’m open to other language - just to learn how to do it)

  Thank you very much.

• H.264 / H.265 Compression of a single Bitmap-Image

  3 septembre 2015, par kevf

  I hope someone can help me.

  I started researching different compression methods to compress Bitmap-Images lossless and lossy. The first methods i used were JPEG, JPEG-2000 and JPEG-XR. Now i want to compare these "standard" ones with H.264 and H.265, maybe they perform as well as they do for video compression.

  I tried using ffmpeg, but i can’t find out which parameters i need, there are plenty... So maybe someone can help me or link me to an Article/Howto or something else ?!

  Thanks a lot !

  EDIT :

  I used the following command :
  ffmpeg -i 01.bmp -c:v libx264 -preset veryslow -crf 40 test.avi

  but this created an 7kb file from an 76,8 kb input file... not very good compression ratio... is there any possibility to achieve more ?

• How to stream a usb webcam to an android phone with ffmpeg and ffserver ?

  26 juillet 2015, par victor jung

  I am desperately trying to live stream the usb webcam from a linux computer to my android phone.
  I tried with ffmpeg and ffserver, to create the stream and with videoview in android to display it. I tried all the possible format/encoder/protocols possibilities but nothing worked. In most case I am able to open the stream in VLC in another PC, but I was never able to play on my phone. I always get this error :
  "can’t play this video"
  Here is my app code :

  package com.example.victor.videostream;
  
  import android.os.Bundle;
  
  import android.app.Activity;
  
  import android.view.View;
  
  import android.net.Uri;
  
  import android.widget.MediaController;
  
  import android.widget.VideoView;
  
  public class MainActivity extends Activity
  
   {
  
  VideoView videoView;
  
  @Override
  
   protected void onCreate(Bundle savedInstanceState)
  
  {
  
       super.onCreate(savedInstanceState);
  
       videoView = null;
  
       setContentView(R.layout.activity_main);
  
  
  
       videoView =(VideoView)findViewById(R.id.VideoView);
  
       MediaController mediaController= new MediaController(this);
  
       mediaController.setAnchorView(videoView);
  
  
  
   Uri uri = Uri.parse("http://host:port/mystream.3gp");
  
    videoView.setMediaController(mediaController);
  
    videoView.setVideoURI(uri);
  
    videoView.requestFocus();
  
    videoView.start();
  
         }
  
          }

  I read here

  about god encoding practice for android, but even with .3gp format encoded with mpeg4 as suggested it doesn’t work. Have any body once succeeded doing this ?
  I am also up to discover other possibilities to stream this webcam to my android if you have any ideas.
  this is the closest post I found but no solution...
  Hope somebody can help !
  thanks for reading.