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• Fire events at specific timestamps during video playback

  27 octobre 2017, par Simon

  I’m using a Raspberry Pi 3 running Raspbian. I need to play a video file via HDMI, and I need events to be fired at specific timecodes during the playback of the video. The events are simple write operations to the GPIO. My problem is : what approach should I use to do this ?

  My first approach was to use OpenCv (python) and VideoCapture(), but the raspberry pi is too slow, and my FPS is very low (I need at least 25 FPS @ 1080p).

  So now I’m looking into other solutions : Gstreamer, FFMPEG, omxplayer, I read the documentations but I can’t figure out which tool to use for this job.

• AV playback synchronization using ffmpeg on WPF

  10 août 2017, par learner

  I have Video( H264-1080p-30fps) and Audio (Mu-law-8k) in separate files both are generated from same camera source. My work is to play them both synchronously using ffmpeg. I can able to decode video and audio without any issue but I don’t know how to play AV synchronously on WPF.

  1. What is the best way to render the video and play audio on Wpf after decoding ?
  2. How to play them synchronously ?

  Thanks in advance..

• Resize camera preview frame using Ffmpeg

  20 avril 2015, par Vipul Purohit

  Scenario :
  I’m working on a live video stream application, in that I need to stream video at resolution around 380x240. I’m sending the camera preview byte[] to streamer from onPreviewFrame event of Camera.PreviewCallback.
  But I need to show camera preview in 720p/1080p but its not possible due to low resolution video streaming.

  Problem
  The solution I’m working is to reduce the video frame size from HD to a low resolution and then send it to streamer and for that I’m using FFMPEG’s sws_scale.

  I’ve successfully compiled the FFMPEG and can access and execute the JNI methods. But I’m completely new to android NDK development and not very familiar with the C/C++ language so I need help in writing JNI method to scale down the video frame.

  Here is what I’m having in my JNI method :

  JNIEXPORT jbyteArray JNICALL Java_com_example_ffmpegtest_MainActivity_resizeFrame(
  
      JNIEnv * env, jobject pObj, jbyteArray *input, jbyteArray * output,
  
      int width, int height) {
  
  struct SwsContext *resize;
  
  
  
  resize = sws_getContext(width, height, PIX_FMT_YUV420P, width, height,
  
          AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
  
  LOGI("---RESIZE");
  
  AVFrame* picture = avcodec_alloc_frame(); // this is your original frame
  
  AVFrame* outpic = avcodec_alloc_frame();
  
  
  
  int num_bytes = avpicture_get_size(PIX_FMT_YUV420P, width, height);
  
  jbyteArray data = (*env)->NewByteArray(env, num_bytes);
  
  uint8_t* frame2_buffer = (uint8_t *) av_malloc(num_bytes * sizeof(uint8_t));
  
  LOGI("---NUMBYTES ED");
  
  
  
  avpicture_fill((AVPicture*) picture, input, PIX_FMT_YUV420P, width, width);
  
  
  
  avpicture_fill((AVPicture*) outpic, frame2_buffer, PIX_FMT_YUV420P, 600,
  
          600);
  
  
  
  sws_scale(resize, picture->data, picture->linesize, 600, 600, outpic->data,
  
          outpic->linesize);
  
  
  
  sws_freeContext(resize);
  
  
  
  (*env)->SetByteArrayRegion(env, data, 0, num_bytes, outpic);
  
  LOGI("---SCALE %d", picture->data);
  
  LOGI("---SCALE_OUT %d", outpic->data);
  
  return output;

  }

  Here is the fuction for JNI method :

  private static native byte[] resizeFrame(byte[] input, byte[] output, int width, int height);

  and the Camera.PreviewCallback

  @Override
  
  public void onPreviewFrame(byte[] data, Camera camera) {
  
      byte[] data2 = null;
  
  
  
      data2 = resizeFrame(data, data2, mPreview.mPreviewSize.width,
  
              mPreview.mPreviewSize.height);
  
  
  
      // Code to send camera frame to streamer
  
  }

  I’m always getting data2 null.
  I know its a bad coding practices but I’m just keep changing the code to make it work but failed.