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• VLC snytax to transcode & stream to stdout ?

  4 octobre 2016, par Will Tower

  Goal : I am trying to use VLC as a local server to expand the video capabilities of an app created with Adobe AIR, Flex and Actionscript. I am using VLC to stream to stdoutand reading that output from within my app.

  VLC Streaming capabilities
  VLC Flash Video

  Status : I am able to launch VLC as a background process and control it through its remote control interface (more detail). I can load, transcode and stream a local video file. The example app below is a barebones testbed demonstrating this.

  Issue : I am getting data in to my app but it is not rendering as video. I don’t know if it is a problem with my VLC commands or with writing to/reading from stdout. This technique of reading from stdout in AIR works (with ffmpeg for example).

  One of the various transcoding commands I have tried :

  -I rc  // remote control interface  
  
  -vvv   // verbose debuging  
  
  --sout  // transcode, stream to stdout 
  
  "#transcode{vcodec=FLV1}:std{access=file,mux=ffmpeg{mux=flv},dst=-}"

  This results in data coming into to my app but for some reason it is not rendering as video when using appendBytes with the NetStream instance.

  If instead I write the data to an .flv file, a valid file is created – so the broken part seems to be writing it to stdout. One thing I have noticed : I am not getting metadata through the stdout`method. If I play the file created with the command below, I do see metadata.

  Hoping someone sees where I am going wrong here.

  ---

  // writing to a file
  
  var output:File = File.desktopDirectory.resolvePath("stream.flv");
  
  var outputPath:String = output.nativePath;
  
  "#transcode{vcodec=FLV1}:std{access=file,mux=ffmpeg{mux=flv},dst=" + outputPath + "}");

  ---

  Note : In order to get this to work in AIR, you need to define the app profile as "extendedDesktop"

  ---

    <?xml version="1.0" encoding="utf-8"?>
  
    
  
  
  
      
  
          
  
      
  
  
  
      

• Unable to Access IP Camera in OpenCV

  3 janvier 2017, par user7258890

  I’m trying to use Javafx and OpenCV to access a webcam (Axis M1013) over wireless to run vision processing for my FRC team. When I run my code, I can access the GUI that I made using Scenebuilder, but when I try to start the camera, the program crashes. It seems to me like it’s having trouble utilizing the VideoCapture class. I know for a fact that my problem is not with the camera, because i can access the feed through a browser feed, and my laptop’s webcam will work fine. I’m using OpevCV version 2.4.13, jdk 8u101x64, and ffmpeg 3.2

  I have looked at other posts at :

  stackoverflow.com/questions/18625948/opencv-java-unsatisfiedlinkerror

  answers.opencv.org/question/21720/java-webcam-capture

  answers.opencv.org/question/20071/unsatisfiedlinkerror-given-by-highghuiimread-on-java

  I have tried the solutions mentioned in all of these. So far, none have resolved my problem.

  My code is based mostly off the tutorials at :

  opencv-java-tutorials.readthedocs.io/en/latest/03-first-javafx-application-with-opencv.html

  Here is my main java code :

      @Override 
  
  public void start(Stage primaryStage) {
  
      System.load("C:\\opencv\\build\\x64\\vc12\\bin\\opencv_ffmpeg_64.dll");
  
      try {
  
          FXMLLoader loader = new FXMLLoader(getClass().getResource("Sample.fxml"));
  
          BorderPane root = (BorderPane) loader.load();
  
          Scene scene = new Scene(root, 400, 400);
  
          scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
  
          primaryStage.setScene(scene);
  
          primaryStage.show();
  
      } catch(Exception e) {
  
          System.out.println("error opening camera gui");
  
      }
  
  }
  
  
  
  public static void main(String[] args) {
  
      launch(args);
  
  }

  And here is my camera controller :

  public class SampleController {
  
  @FXML
  
  private Button Start_btn;
  
  
  
  @FXML
  
  private ImageView currentFrame;
  
  private ScheduledExecutorService timer;
  
  private VideoCapture capture;
  
  private boolean cameraActive = false;
  
  
  
  @FXML
  
  public void startCamera()
  
  {
  
      System.loadLibrary("opencv_ffmpeg_64");
  
      if (!this.cameraActive)
  
      {
  
          try
  
          {
  
           capture = new VideoCapture("http://FRC:FRC@axis-camera-223-catapult.lan:554/mjpg/1/video.mjpg");
  
          }
  
          catch (Exception e)
  
          {
  
              System.out.println("an error occured when attempting to access camera.");
  
          }
  
          // is the video stream available?
  
          if (this.capture.isOpened())
  
          {
  
              this.cameraActive = true;
  
  
  
              // grab a frame every 33 ms (30 frames/sec)
  
              Runnable frameGrabber = new Runnable() {
  
  
  
                  @Override
  
                  public void run()
  
                  {
  
                      // effectively grab and process a single frame
  
                      Mat frame = grabFrame();
  
                      // convert and show the frame
  
                      Image imageToShow = Utils.mat2Image(frame);
  
                      updateImageView(currentFrame, imageToShow);
  
                  }
  
              };
  
  
  
              this.timer = Executors.newSingleThreadScheduledExecutor();
  
              this.timer.scheduleAtFixedRate(frameGrabber, 0, 33, TimeUnit.MILLISECONDS);
  
  
  
              // update the button content
  
              this.Start_btn.setText("Stop Camera");
  
          }
  
          else
  
          {
  
              // log the error
  
              System.err.println("Impossible to open the camera connection...");
  
          }
  
      }
  
      else
  
      {
  
          // the camera is not active at this point
  
          this.cameraActive = false;
  
          // update again the button content
  
          this.Start_btn.setText("Start Camera");
  
  
  
          // stop the timer
  
          this.stopAquisition();
  
      }
  
  
  
      System.out.println("Camera is now on.");
  
  }
  
  
  
  /**
  
   * Get frame from open video
  
   * @return
  
   */
  
      private Mat grabFrame()
  
  
  
      {
  
          Mat frame = new Mat();
  
          if (this.capture.isOpened())
  
          {
  
              try
  
              {
  
                  this.capture.read(frame);
  
  
  
                  }
  
          catch (Exception e)
  
          {
  
              System.err.println("Exception during the image elaboration: " + e);
  
          }
  
      }
  
      return frame;
  
  }
  
      private void stopAquisition()
  
      {
  
          if (this.timer!=null && !this.timer.isShutdown())
  
          {
  
              try
  
              {
  
                  this.timer.shutdown();
  
                  this.timer.awaitTermination(33, TimeUnit.MILLISECONDS);
  
              }
  
              catch (InterruptedException e)
  
              {
  
                  System.err.println("Exception in stopping the frame capture, trying to release camera now..." + e);
  
  
  
              }
  
          }
  
          if (this.capture.isOpened())
  
          {
  
              this.capture.release();
  
          }
  
      }
  
      private void updateImageView(ImageView view, Image image)
  
      {
  
          Utils.onFXThread(view.imageProperty(), image);
  
      }
  
      protected void setClosed()
  
      { 
  
          this.stopAquisition();
  
      }
  
  }

  When I try and run this as i have said before, the GUI will launch, but when i try and open the camera, i get an error message :

  Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
  
  at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
  
  at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
  
  at javafx.event.Event.fireEvent(Event.java:198)
  
  at javafx.scene.Node.fireEvent(Node.java:8411)
  
  at javafx.scene.control.Button.fire(Button.java:185)
  
  at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
  
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
  
  at javafx.event.Event.fireEvent(Event.java:198)
  
  at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
  
  at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
  
  at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
  
  at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
  
  at java.security.AccessController.doPrivileged(Native Method)
  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
  
  at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
  
  at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
  
  at com.sun.glass.ui.View.notifyMouse(View.java:937)
  
  at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
  
  at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
  
  at java.lang.Thread.run(Unknown Source)
  
  Caused by: java.lang.reflect.InvocationTargetException
  
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  
  at java.lang.reflect.Method.invoke(Unknown Source)
  
  at sun.reflect.misc.Trampoline.invoke(Unknown Source)
  
  at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  
  at java.lang.reflect.Method.invoke(Unknown Source)
  
  at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
  
  at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
  
  ... 48 more
  
  Caused by: java.lang.UnsatisfiedLinkError:     org.opencv.highgui.VideoCapture.VideoCapture_1(Ljava/lang/String;)J
  
  at org.opencv.highgui.VideoCapture.VideoCapture_1(Native Method)
  
  at org.opencv.highgui.VideoCapture.<init>(VideoCapture.java:128)
  
  at jfxtest1.SampleController.startCamera(SampleController.java:36)
  
  ... 58 more
  
  </init>

  If anyone can help me, that would be much appreciated.

  Thanks in advance.

• Subtitling Sierra VMD Files

  1er juin 2016, par Multimedia Mike — Game Hacking

  I was contacted by a game translation hobbyist from Spain (henceforth known as The Translator). He had set his sights on Sierra’s 7-CD Phantasmagoria. This mammoth game was driven by a lot of FMV files and animations that have speech. These require language translation in the form of video subtitling. He’s lucky that he found possibly the one person on the whole internet who has just the right combination of skill, time, and interest to pull this off. And why would I care about helping ? I guess I share a certain camaraderie with game hackers. Don’t act so surprised. You know what kind of stuff I like to work on.

  The FMV format used in this game is VMD, which makes an appearance in numerous Sierra titles. FFmpeg already supports decoding this format. FFmpeg also supports subtitling video. So, ideally, all that’s necessary to support this goal is to add a muxer for the VMD format which can encode raw video and audio, which the format supports. Implement video compression as extra credit.

  The pipeline that I envisioned looks like this :

  
  

  

  VMD Subtitling Process

  
  

  “Trivial !” I surmised. I just never learn, do I ?

  The Plan
  So here’s my initial pitch, outlining the work I estimated that I would need to do towards the stated goal :

  1. Create a new file muxer that produces a syntactically valid VMD file with bogus video and audio data. Make sure it works with both FFmpeg’s playback system as well as the proper Phantasmagoria engine.
  2. Create a new video encoder that essentially operates in pass-through mode while correctly building a palette.
  3. Create a new basic encoder for the video frames.

  A big unknown for me was exactly how subtitle handling operates in FFmpeg. Thanks to this project, I now know. I was concerned because I was pretty sure that font rendering entails anti-aliasing which bodes poorly for keeping the palette count under 256 unique colors.

  Computer Science Puzzle
  When pondering how to process the palette, I was excited for the opportunity to exercise actual computer science. FFmpeg converts frames from paletted frames to full RGB frames. Then it needs to convert them back to paletted frames. I had a vague recollection of solving this problem once before when I was experimenting with a new paletted video codec. I seem to recall that I did the palette conversion in a very naive manner. I just used a static 256-element array and processed each RGB pixel of the frame, seeing if the value already occurred in the table (O(n) lookup) and adding it otherwise.
  

  There are more efficient algorithms, however, such as hash tables and trees. Somewhere along the line, FFmpeg helpfully acquired a rarely-used tree data structure, which was perfect for this project.

  So I was pretty pleased with this optimization. Too bad this wouldn’t survive to the end of the effort.

  Another palette-related challenge was the fact that a group of pictures would be accumulating a new palette but that palette needed to be recorded before the group. Thus, the muxer needed to have extra logic to rewind the file when the video encoder transmitted a palette change.

  Video Compression
  VMD has a few methods in its compression toolbox. It can use interframe differencing, it has some RLE, or it can code a frame raw. It can also use a custom LZ-like format on top of these. For early prototypes, I elected to leave each frame coded raw. After the concept was proved, I implemented the frame differencing.

  
  

  

  
  Top frame compared with the middle frame yields the bottom frame : red pixels indicate changes
  

  Encoding only those red dots in between vast runs of unchanged pixels yielded a vast measurable improvement. The next step was to try wiring up FFmpeg’s existing LZ compression facilities to the encoder. This turned out to be implausible since VMD’s LZ variant has nothing to do with anything FFmpeg already provides. Fortunately, the LZ piece is not absolutely required and the frame differencing + RLE provides plenty of compression.

  Subtitling
  I’ve never done anything, multimedia programming-wise, concerning subtitles. I guess all the entertainment I care about has always been in my native tongue. What a good excuse to program outside of my comfort zone !

  First, I needed to know how to access FFmpeg’s subtitling facilities. Fortunately, The Translator did the legwork on this matter so I didn’t have to figure it out.

  However, I intuitively had misgivings about this phase. I had heard that the subtitling process performs anti-aliasing. That means that the image would need to be promoted to a higher colorspace for this phase and that the anti-aliasing process would likely push the color count way past 256. Some quick tests revealed this to be the case, as the running color count would leap by several hundred colors as soon as the palette accounting algorithm encountered a subtitle.

  So I dug into the subtitle subsystem. I discovered that the subtitle library operates by creating a linked list of subtitle bitmaps that the client app must render. The bitmaps are comprised of 8-bit alpha transparency values that must be composited onto the target frame (i.e., 0 = transparent, 255 = 100% opaque). For example, the letter ‘H’ :

                                    (with 00s removed)
  13 F8 41 00 00 00 00 68 E4  |  13 F8 41             68 E4    
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  14 FF DC D0 D0 D0 D0 E4 EC  |  14 FF DC D0 D0 D0 D0 E4 EC
  14 FF 7E 50 50 50 50 9A EC  |  14 FF 7E 50 50 50 50 9A EC
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  14 FF 44 00 00 00 00 6C EC  |  14 FF 44             6C EC
  11 E0 3B 00 00 00 00 5E CE  |  11 E0 3B             5E CE
  

  To get around the color explosion problem, I chose a threshold value and quantized values above and below to 255 and 0, respectively. Further, the process chooses an appropriate color from the existing palette rather than introducing any new colors.

  Muxing Matters
  In order to force VMD into a general purpose media framework, a lot of special information needs to be passed around. Like many paletted codecs, the palette needs to be transmitted from the file demuxer to the video decoder via some side channel. For re-encoding, this also implies that the palette needs to make the trip from the video encoder to the file muxer. As if this wasn’t enough, individual VMD frames have even more data that needs to be ferried between the muxer and codec levels, including frame change boundaries. FFmpeg provides methods to do these things, but I could not always rely on the systems to relay the data in all cases. I was probably doing something wrong ; I accept that. Instead, I just packed all the information at the front of an encoded frame and split it apart in the muxer.

  I could not quite figure out how to get the audio and video muxed correctly. As a result, neither FFmpeg nor the Phantasmagoria engine could replay the files correctly.

  Plan B
  Since I was having so much trouble creating an entirely new VMD file, likely due to numerous unknown bits of the file format, I thought of another angle : re-use the existing VMD file. For this approach, I kept the video encoder and file muxer that I created in the initial phase, but modified the file muxer to emit a special intermediate file. Then, I created a Python tool to repackage the original VMD file using compressed video data in the intermediate file.

  For this phase, I also implemented a command line switch for FFmpeg to disable subtitle blending, to make the feature feel like less of an unofficial hack, as though this nonsense would ever have a chance of being incorporated upstream.

  At this point, I was seeing some success with the complete, albeit roundabout, subtitling process. I constructed a subtitle file using “Spanish I Learned From Mexican Telenovelas” and the frames turned out fairly readable :

  
  

  

  “she cheated on him”

  
  

  

  “he’s a scumbag” … these random subtitles could fit surprisingly well !

  
  

  The few files that I tested appeared to work fine. But then I handed off my work to The Translator and he immediately found a bunch of problems. According to my notes, the problems mostly took the form of flashing, solid color frames. Further, I found tiny, mostly imperceptible flaws in my RLE compressor, usually only detectable by running strict comparison tools ; but I wasn’t satisfied.

  At this point, I think I attempted to just encode the entire palette at the front of each frame, as allowed by the format, but that did not seem to fix any problems. My notes are not completely clear on this matter (likely because I was still trying to figure out the exact problem), but I think it had to do with FFmpeg inserting extra video frames in order to even out gaps in the video framerate.

  Sigh, Plan C
  At this point, I was getting tired of trying to force FFmpeg to do this. So I decided to minimize its involvement using lessons learned up to this point.

  The next pitch :

  1. Create a new C program that can open an existing VMD file and output an identical VMD file. I know this sounds easy, but the specific method of copying entails interpreting individual parts of the file and writing those individual parts to the new file. This is in preparation for…
  2. Import the VMD video decoder functions directly into the program to decode the individual video frames and re-encode them, replacing the video frames as the file is rewritten.
  3. Wire up the subtitle system. During the adventure to disable subtitle blending, I accidentally learned enough about interfacing to the subtitle library to just invoke it directly.
  4. Rewrite the RLE method so that it is 100% correct.

  Off to work I went. That part about lifting the existing VMD decoder functions out of their libavcodec nest turned out to not be that straightforward. As an alternative, I modified the decoder to dump the raw frames to an intermediate file. In doing so, I think I was able to avoid the issue of the duplicated frames that plagued the previous efforts.

  Also, remember how I was really pleased with the palette conversion technique in which I was able to leverage computer science big-O theory ? By this stage, I had no reason to convert the paletted video to RGB in the first place ; all of the decoding, subtitling and re-encoding operates in the paletted colorspace.

  This approach seemed to work pretty well. The final program is subtitle-vmd.c. The process is still a little weird. The modifications in my own FFmpeg fork are necessary to create an intermediate file that the new C tool can operate with.

  Next Steps
  The Translator has found some assorted bugs and corner cases that still need to be ironed out. Further, for extra credit, I need find the change windows for each frame to improve compression just a little more. I don’t think I will be trying for LZ compression, though.

  However, almost as soon as I had this whole system working, The Translator informed me that there is another, different movie format in play in the Phantasmagoria engine called ROBOT, with an extension of RBT. Fortunately, enough of the algorithms have been reverse engineered and re-implemented in ScummVM that I was able to sort out enough details for another subtitling project. That will be the subject of a future post.

  See Also :

  • Subtitling Sierra RBT Files : The followup in which I discuss how to scribble text on the other animation format

  The post Subtitling Sierra VMD Files first appeared on Breaking Eggs And Making Omelettes.