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• JavaCV Stream-Test code giving Error

  23 juin 2015, par user1507600

  I’m hoping someone might be able to tell me what I’m doing wrong here. I downloaded vanevery’s GitHub project “JavaCV-0.5-Stream-Test" which is a couple of years old so I updated to the latest JavaCV version 0.11. But Android Studio is returning the error...

  Error :

  "record(org.bytedeco.javacpp.Frame) in FFmpegFrameRecorder cannot be
  applied to (org.bytedeco.javacpp.opencv_core.lplimage)" for the line
  of code which reads recorder.record(yuvIplimage), under
  onPreviewFrame.

  Here is my code :

      @Override
  
      public void onPreviewFrame(byte[] data, Camera camera) {
  
  
  
          if (yuvIplimage != null && recording) {
  
  
  
              videoTimestamp = 1000 * (System.currentTimeMillis() - startTime);
  
  
  
              // Put the camera preview frame right into the yuvIplimage object
  
              yuvIplimage.getByteBuffer().put(data);
  
  
  
              try {
  
                  // Get the correct time
  
                  recorder.setTimestamp(videoTimestamp);
  
  
  
                  // Record the image into FFmpegFrameRecorder
  
                  recorder.record(yuvIplimage);
  
  
  
              } catch (FFmpegFrameRecorder.Exception e) {
  
                  Log.v(LOG_TAG,e.getMessage());
  
                  e.printStackTrace();
  
              }
  
          }
  
      }

• Most efficient way for ffmpeg to make thumbnails ? [Windows 10]

  26 janvier 2017, par gregm

  I normally use ThumbnailMe to make contact sheets of thumbnails. My default setting is 15 rows x 5 columns, so 75 images, in videos that are anywhere from 45 minutes to around 90 minutes. ThumbnailMe makes a contact sheet of this size virtually instantaneously. A recent requirement to make a LOT of contact sheets for a LOT of videos has me looking at a command line option so I can do these in batches. I’ve tried a couple different ways to make the thumbnails from the command line :

  ffmpeg -ss 300 -i myvideo.avi -vf fps=1/300 %d.jpg

  or

  ffmpeg -i myvideo.avi -vf fps=1/60 %d.jpg

  No matter which of these methods I use it takes roughly a minute to make just 16 screenshots (from there I would use ImageMagick to make the contact sheet). As I said above, ThumbnailMe can make a 15x5 grid of images at the mere press of a button. ThumbnailMe is built on an older command line program, Movie Thumbnailer, which I think used an old version of ffmpeg, or at least the codec libavcodec.

  If these other programs can create thumbnails so quickly why does it take ffmpeg so long to make them for me ? Even if I output the screenshots in a very small size, say 50x50, it still takes 2 secs for each image to be created.

• openCV VideoCapture doesn't work with gstreamer x264

  18 juin 2014, par nschoe

  I’d like to display a rtp / vp8 video stream that comes from gstreamer, in openCV.

  I have already a working solution which is implemented like this :

  gst-launch-0.10 udpsrc port=6666 ! "application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)VP8-DRAFT-IETF-01,payload=(int)120" ! rtpvp8depay ! vp8dec ! ffmpegcolorspace ! ffenc_mpeg4 ! filesink location=videoStream

  Basically it grabs incoming data from a UDP socket, depacketize rtp, decode vp8, pass to ffmpegcolorspace (I still don’t understand what this is for, I see it everywhere in gstreamer).

  The videoStream is a pipe I created with mkfifo. On the side, I have my openCV code that does :

  VideoCapture cap("videoStream");

  and uses cap.read() to push into a Mat.

  My main concern is that I use ffenc_mpeg4 here and I believe this alters my video quality. I tried using x264enc in place of ffenc_mpeg4 but I have no output : openCV doesn’t react, neither does gstreamer, and after a couple of seconds, gst-launch just stops.

  Any idea what I could use instead of ffenc_mpeg4 ? I looked for "lossless codec" on the net, but it seems I am confusing things such as codec, contains, format, compression and encoding ; so any help would be (greatly) appreciated !

  Thanks in advance !