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• Record stream from camera to file / live stream

  8 juillet 2015, par sandman

  I’m trying to stream my camera feed to a webpage. For this I’m trying to use FFmpeg to encode the data from the camera preview and output to a file. (I’m new to this, so I’m only trying to write to a file now)

  The camera feed is captured and it starts writing to a flv file but, it freezes my app after a few seconds and the resulting flv is about half a second long.

  bos is a BufferedOutputStream which servers as an input stream for the Ffmpeg ProcessBuilder.

  When a button is clicked, the Ffmpeg process is executed and the writing begins.
  But as I said, it freezes the app after a while. I tried running the Ffmpeg process in an AsyncTask, but it keeps saying FileDescriptor closed, but the app does not freeze when I do it this way, and there is no output as well.

  Here is my onPreviewFrame() :

  public void onPreviewFrame(byte[] b, Camera c) {
  
      if (recording) {
  
          int previewFormat = p.getPreviewFormat();
  
          Log.v(LOGTAG, "Started Writing Frame");
  
  
  
          im = new YuvImage(b, previewFormat, p.getPreviewSize().width, p.getPreviewSize().height, null);
  
          Rect r = new Rect(0, 0, p.getPreviewSize().width, p.getPreviewSize().height);
  
          if (bos != null)
  
              im.compressToJpeg(r, 40, bos);
  
          im = null;
  
  
  
          Log.v(LOGTAG, "Finished Writing Frame");
  
      }
  
  }

  If I can get this fixed, I can probably move on to live streaming.

• FFMPEG bottleneck in relaying data from a dshow camera to stdout PIPE without any processing or conversion

  19 août 2020, par koonyook

  I have a USB camera (FSCAM_CU135) that can encode the video to MJPEG internally and it supports DirectShow. My goal is to retrieve the binary stream of the encoded video as it is (without decoding or preview) and send it to my program for further processing.

  


  I choose to use FFMPEG to read the MJPEG stream and pipe to stdout so that I can read it using Python's subprocess.Popen .

  


  ffmpeg -y -f dshow -vsync 2 -rtbufsize 1000M -video_size 1920x1440 -vcodec mjpeg -i video="FSCAM_CU135" -vcodec copy -f mjpeg pipe:1


  


  At this resolution, the camera is able to capture and transmit at 60 fps.
In this case, I expect FFMPEG to pass the data as fast as possible with no calculation.
With the output of FFMPEG I can tell how fast it moves the data from rtbuffer to the output pipe.

  


  With just one camera, FFMPEG works with no problem and move the data at 60 fps.
However, when I run 2 cameras simultaneously, the cameras still generate data at 60 fps but FFMPEG can only move the data around 55 fps. This means that I am unable to consume the video in realtime and the buffer consumption will be larger over time.

  


  I guess that FFMPEG didn't just simply move the data but did some processing such as searching for the beginning, the end, and the timestamp of each video frame so that it can count frames and report.
Is there a way to force FFMPEG to not doing those things and focus on passing the data only to make it faster ?

  


  If I purely use directshow API without FFMPEG, can it be faster ?

  


• How do I reduce the video size captured by the default camera using FFMPEG in Android ?

  12 octobre 2011, par Krishnendu

  I am trying to reduce the video size captured by the default camera (it's generating high resolution video) in Android. Does FFMPEG have a property to encode a video with given resolution ? I tried to Google, but all examples are using command line mode for FFMPEG.

  My questions are :

  1. Can we use ffmpeg command line in Android ?
  2. If not then how we will achieve it ?
  3. Can we able record a video directly using ffmpeg in Android ?
  4. Is there any other solution for this ?