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• ffmpeg : 1 frame manipulation on demand

  7 juillet 2013, par Chris Russo

  Hello folks & friends of SO !

  We need to create a small application to take a random frame from a video, and apply some modifications to it, in real time.

  This has to be done in real time, and in order to do that, we wouldn't mind to create some initial delay, before the video starts streaming. So let's assume we have a total of 6 seconds of preloading time, in order to :

  1) extract a keyframe.
  
  2) create an image with it.
  
  3) manipulate the image.
  
  4) replace the original keyframe with the new one.

  The point (3) of the previous algorithm is already solved using GD as a PHP module. However we would need to find a solution for the rest of the procedure in order to accomplish this.

  Please if anyone is available to help us with this, feel free to contact me.

  Thanks in advance ;
  Chris C. Russo

• How to expose new API methods in the HTTP Reporting API – Introducing the Piwik Platform

  26 février 2015, par Thomas Steur — Development

  This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to write UI tests for your plugin). This time you’ll learn how to extend our Reporting API. For this tutorial you will need to have basic knowledge of PHP.

  What is Piwik’s Reporting API ?

  It allows third party applications to access analytics data and manipulate miscellaneous data (such as users or websites) through HTTP requests.

  What is it good for ?

  The Reporting API is used by the Piwik UI to render reports, to manage users, and more. If you want to add a feature to the Piwik UI, you might have to expose a method in the API to access this data. As the API is called via HTTP it allows you to fetch or manipulate any Piwik related data from anywhere. In these exposed API methods you can do pretty much anything you want, for example :

  • Enhance existing reports with additional data
  • Filter existing reports based on custom rules
  • Access the database and generate custom reports
  • Persist and read any data
  • Request server information

  Getting started

  In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

  To summarize the things you have to do to get setup :

  • Install Piwik (for instance via git).
  • Activate the developer mode : ./console development:enable.
  • Generate a plugin : ./console generate:plugin --name="MyApiPlugin". There should now be a folder plugins/MyApiPlugin.
  • And activate the created plugin : ./console plugin:activate "MyApiPlugin"

  Let’s start creating an API

  We start by using the Piwik Console to create a new API :

  ./console generate:api

  The command will ask you to enter the name of the plugin the created API should belong to. I will simply use the above chosen plugin name “MyApiPlugin”. There should now be a file plugins/MyApiPlugin/API.php which contains already an example to get you started easily :

  class API extends \Piwik\Plugin\API
  {
      public function getAnswerToLife($truth = true)
      {
          if ($truth) {
              return 42;
          }
   
          return 24;
      }
   
      public function getExampleReport($idSite, $period, $date, $wonderful = false)
      {
          $table = DataTable::makeFromSimpleArray(array(
              array('label' => 'My Label 1', 'nb_visits' => '1'),
              array('label' => 'My Label 2', 'nb_visits' => '5'),
          ));
   
          return $table;
      }
  }
  Télécharger

  Any public method in that file will be available via the Reporting API. For example the method getAnswerToLife can be called via this URL : index.php?module=API&method=MyApiPlugin.getAnswerToLife. The URL parameter method is a combination of your plugin name and the method name within this class.

  Passing parameters to your method

  Both example methods define some parameters. To pass any value to a parameter of your method simply specify them by name in the URL. For example ...&method=MyApiPlugin.getExampleReport&idSite=1&period=week&date=today&wonderful=1 to pass values to the parameters of the method getExampleReport.

  Returning a value

  In an API method you can return any boolean, number, string or array value. A resource or an object cannot be returned unless it implements the DataTableInterface such as DataTable (the primary data structure used to store analytics data in Piwik), DataTable\Map (stores a set of DataTables) and DataTable\Simple (a DataTable where every row has two columns : label and value).

  Did you know ? You can choose the response format of your API request by appending a parameter &format=JSON|XML|CSV|... to the URL. Check out the Reporting API Reference for more information.

  Best practices

  Check user permissions

  Do not forget to check whether a user actually has permissions to access data or to perform an action. If you’re not familiar with Piwik’s permissions and how to check them read our User Permission guide.

  Keep API methods small

  At Piwik we aim to write clean code. Therefore, we recommend to keep API methods small (separation of concerns). An API pretty much acts like a Controller :

  public function createLdapUser($idSite, $login, $password)
  {
      Piwik::checkUserHasAdminAccess($idSite);
      $this->checkLogin($login);
      $this->checkPassword($password);
      
      $myModel = new LdapModel();
      $success = $myModel->createUser($idSite, $login, $password);
      
      return $success;
  }
  Télécharger

  This is not only easy to read, it will also allow you to create simple tests for LdapModel (without having to bootstrap the whole Piwik layer) and you will be able to reuse it in other places if needed.

  Calling APIs of other plugins

  For example if you want to fetch an existing report from another plugin, say a list of all Page URLs, do not request this report by calling that method directly :

  \Piwik\Plugins\Actions\API::getInstance()->getPageUrls($idSite, $period, $date);

  . Instead, issue a new API request :

  $report = \Piwik\API\Request::processRequest('Actions.getPageUrls', array(
  
      'idSite' => $idSite,
  
      'period' => $period,
  
      'date'   => $date,
  
  ));

  This has several advantages :

  • It avoids a fatal error if the requested plugin is not available on a Piwik installation
  • Other plugins can extend the called API method via events (adding additional report data to a report, doing additional permission checks) but those events will be only triggered when requesting the report as suggested
  • If the method parameters change, your request will most likely still work

  Publishing your Plugin on the Marketplace

  In case you want to share your API with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin and best practices when publishing a plugin.

  Isn’t it easy to create a API ? We never even created a file ! If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

• Muxing Android MediaCodec encoded H264 packets into RTMP

  31 décembre 2015, par Vadym

  I am coming from a thread Encoding H.264 from camera with Android MediaCodec. My setup is very similar. However, I attempt to write mux the encoded frames and with javacv and broadcast them via rtmp.

  RtmpClient.java

  ...
  
  private volatile BlockingQueue mFrameQueue = new LinkedBlockingQueue(MAXIMUM_VIDEO_FRAME_BACKLOG);
  
  ...
  
  private void startStream() throws FrameRecorder.Exception, IOException {
  
      if (TextUtils.isEmpty(mDestination)) {
  
          throw new IllegalStateException("Cannot start RtmpClient without destination");
  
      }
  
  
  
      if (mCamera == null) {
  
          throw new IllegalStateException("Cannot start RtmpClient without camera.");
  
      }
  
  
  
      Camera.Parameters cameraParams = mCamera.getParameters();
  
  
  
      mRecorder = new FFmpegFrameRecorder(
  
              mDestination,
  
              mVideoQuality.resX,
  
              mVideoQuality.resY,
  
              (mAudioQuality.channelType.equals(AudioQuality.CHANNEL_TYPE_STEREO) ? 2 : 1));
  
  
  
      mRecorder.setFormat("flv");
  
  
  
      mRecorder.setFrameRate(mVideoQuality.frameRate);
  
      mRecorder.setVideoBitrate(mVideoQuality.bitRate);
  
      mRecorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);
  
  
  
      mRecorder.setSampleRate(mAudioQuality.samplingRate);
  
      mRecorder.setAudioBitrate(mAudioQuality.bitRate);
  
      mRecorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
  
  
  
      mVideoStream = new VideoStream(mRecorder, mVideoQuality, mFrameQueue, mCamera);
  
      mAudioStream = new AudioStream(mRecorder, mAudioQuality);
  
  
  
      mRecorder.start();
  
  
  
      // Setup a bufferred preview callback
  
      setupCameraCallback(mCamera, mRtmpClient, DEFAULT_PREVIEW_CALLBACK_BUFFERS,
  
              mVideoQuality.resX * mVideoQuality.resY * ImageFormat.getBitsPerPixel(
  
                      cameraParams.getPreviewFormat())/8);
  
  
  
      try {
  
          mVideoStream.start();
  
          mAudioStream.start();
  
      }
  
      catch(Exception e) {
  
          e.printStackTrace();
  
          stopStream();
  
      }
  
  }
  
  ...
  
  @Override
  
  public void onPreviewFrame(byte[] data, Camera camera) {
  
      boolean frameQueued = false;
  
  
  
      if (mRecorder == null || data == null) {
  
          return;
  
      }
  
  
  
      frameQueued = mFrameQueue.offer(data);
  
  
  
      // return the buffer to be reused - done in videostream
  
      //camera.addCallbackBuffer(data);
  
  }
  
  ...

  VideoStream.java

  ...
  
  @Override
  
  public void run() {
  
      try {
  
          mMediaCodec = MediaCodec.createEncoderByType("video/avc");
  
          MediaFormat mediaFormat = MediaFormat.createVideoFormat("video/avc", mVideoQuality.resX, mVideoQuality.resY);
  
          mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, mVideoQuality.bitRate);
  
          mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, mVideoQuality.frameRate);
  
          mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatYUV420SemiPlanar);
  
          mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1);
  
          mMediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
  
          mMediaCodec.start();
  
      }
  
      catch(IOException e) {
  
          e.printStackTrace();
  
      }
  
  
  
      long startTimestamp = System.currentTimeMillis();
  
      long frameTimestamp = 0;
  
      byte[] rawFrame = null;
  
  
  
      try {
  
          while (!Thread.interrupted()) {
  
              rawFrame = mFrameQueue.take();
  
  
  
              frameTimestamp = 1000 * (System.currentTimeMillis() - startTimestamp);
  
  
  
              encodeFrame(rawFrame, frameTimestamp);
  
  
  
              // return the buffer to be reused
  
              mCamera.addCallbackBuffer(rawFrame);
  
          }
  
      }
  
      catch (InterruptedException ignore) {
  
          // ignore interrup while waiting
  
      }
  
  
  
      // Clean up video stream allocations
  
      try {
  
          mMediaCodec.stop();
  
          mMediaCodec.release();
  
          mOutputStream.flush();
  
          mOutputStream.close();
  
      } catch (Exception e){
  
          e.printStackTrace();
  
      }
  
  }
  
  ...
  
  private void encodeFrame(byte[] input, long timestamp) {
  
      try {
  
          ByteBuffer[] inputBuffers = mMediaCodec.getInputBuffers();
  
          ByteBuffer[] outputBuffers = mMediaCodec.getOutputBuffers();
  
  
  
          int inputBufferIndex = mMediaCodec.dequeueInputBuffer(0);
  
  
  
          if (inputBufferIndex >= 0) {
  
              ByteBuffer inputBuffer = inputBuffers[inputBufferIndex];
  
              inputBuffer.clear();
  
              inputBuffer.put(input);
  
              mMediaCodec.queueInputBuffer(inputBufferIndex, 0, input.length, timestamp, 0);
  
          }
  
  
  
          MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
  
  
  
          int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);
  
  
  
          if (outputBufferIndex >= 0) {
  
              while (outputBufferIndex >= 0) {
  
                  ByteBuffer outputBuffer = outputBuffers[outputBufferIndex];
  
  
  
                  // Should this be a direct byte buffer?
  
                  byte[] outData = new byte[bufferInfo.size - bufferInfo.offset];
  
                  outputBuffer.get(outData);
  
  
  
                  mFrameRecorder.record(outData, bufferInfo.offset, outData.length, timestamp);
  
  
  
                  mMediaCodec.releaseOutputBuffer(outputBufferIndex, false);
  
                  outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);
  
              }
  
          }
  
          else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_BUFFERS_CHANGED) {
  
              outputBuffers = mMediaCodec.getOutputBuffers();
  
          } else if (outputBufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
  
              // ignore for now
  
          }
  
      } catch (Throwable t) {
  
          t.printStackTrace();
  
      }
  
  
  
  }
  
  ...

  FFmpegFrameRecorder.java

  ...
  
  // Hackish codec copy frame recording function
  
  public boolean record(byte[] encodedData, int offset, int length, long frameCount) throws Exception {
  
      int ret;
  
  
  
      if (encodedData == null) {
  
          return false;
  
      }
  
  
  
      av_init_packet(video_pkt);
  
  
  
      // this is why i wondered whether I should get outputbuffer data into direct byte buffer
  
      video_outbuf.put(encodedData, 0, encodedData.length);
  
  
  
      video_pkt.data(video_outbuf);
  
      video_pkt.size(video_outbuf_size);
  
  
  
      video_pkt.pts(frameCount);
  
      video_pkt.dts(frameCount);
  
  
  
      video_pkt.stream_index(video_st.index());
  
  
  
      synchronized (oc) {
  
          /* write the compressed frame in the media file */
  
          if (interleaved && audio_st != null) {
  
              if ((ret = av_interleaved_write_frame(oc, video_pkt)) < 0) {
  
                  throw new Exception("av_interleaved_write_frame() error " + ret + " while writing interleaved video frame.");
  
              }
  
          } else {
  
              if ((ret = av_write_frame(oc, video_pkt)) < 0) {
  
                  throw new Exception("av_write_frame() error " + ret + " while writing video frame.");
  
              }
  
          }
  
      }
  
      return (video_pkt.flags() & AV_PKT_FLAG_KEY) == 1;
  
  }
  
  ...

  When I try to stream the video and run ffprobe on it, I get the following output :

  ffprobe version 2.5.3 Copyright (c) 2007-2015 the FFmpeg developers
  
    built on Jan 19 2015 12:56:57 with gcc 4.1.2 (GCC) 20080704 (Red Hat 4.1.2-55)
  
    configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' --enable-bzlib --disable-crystalhd --enable-libass --enable-libdc1394 --enable-libfaac --enable-nonfree --disable-indev=jack --enable-libfreetype --enable-libgsm --enable-libmp3lame --enable-openal --enable-libopencv --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab --enable-avfilter --enable-avresample --enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug --disable-stripping --enable-libcaca --shlibdir=/usr/lib64 --enable-runtime-cpudetect
  
    libavutil      54. 15.100 / 54. 15.100
  
    libavcodec     56. 13.100 / 56. 13.100
  
    libavformat    56. 15.102 / 56. 15.102
  
    libavdevice    56.  3.100 / 56.  3.100
  
    libavfilter     5.  2.103 /  5.  2.103
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Metadata:
  
    Server                NGINX RTMP (github.com/arut/nginx-rtmp-module)
  
    width                 320.00
  
    height                240.00
  
    displayWidth          320.00
  
    displayHeight         240.00
  
    duration              0.00
  
    framerate             0.00
  
    fps                   0.00
  
    videodatarate         261.00
  
    videocodecid          7.00
  
    audiodatarate         62.00
  
    audiocodecid          10.00
  
    profile
  
    level
  
  [live_flv @ 0x1edb0820] Could not find codec parameters for stream 0 (Video: none, none, 267 kb/s): unknown codec
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, live_flv, from 'rtmp://<server>/input/<stream>':
  
    Metadata:
  
      Server          : NGINX RTMP (github.com/arut/nginx-rtmp-module)
  
      displayWidth    : 320
  
      displayHeight   : 240
  
      fps             : 0
  
      profile         :
  
      level           :
  
    Duration: 00:00:00.00, start: 16.768000, bitrate: N/A
  
      Stream #0:0: Video: none, none, 267 kb/s, 1k tbr, 1k tbn, 1k tbc
  
      Stream #0:1: Audio: aac (LC), 16000 Hz, mono, fltp, 63 kb/s
  
  Unsupported codec with id 0 for input stream 0
  
  </stream></server>

  I am not, by any means, an expert in H264 or video encoding. I know that the encoded frames that come out from MediaCodec contain SPS NAL, PPS NAL, and frame NAL units. I’ve also written the MediaCodec output into a file and was able to play it back (I did have to specify the format and framerate as otherwise it would play too fast).

  My assumption is that things should work (see how little I know :)). Knowing that SPS and PPS are written out, decoder should know enough. Yet, ffprobe fails to recognize codec, fps, and other video information. Do I need to pass packet flag information to FFmpegFrameRecorder.java:record() function ? Or should I use direct buffer ? Any suggestion will be appreciated ! I should figure things out with a hint.

  PS : I know that some codecs use Planar and other SemiPlanar color formats. That distinction will come later if I get past this. Also, I didn’t go the Surface to MediaCodec way because I need to support API 17 and it requires more changes than this route, which I think helps me understand the more basic flow. Agan, I appreciate any suggestions. Please let me know if something needs to be clarified.

  Update #1

  So having done more testing, I see that my encoder outputs the following frames :

  000000016742800DDA0507E806D0A1350000000168CE06E2
  
  0000000165B840A6F1E7F0EA24000AE73BEB5F51CC7000233A84240...
  
  0000000141E2031364E387FD4F9BB3D67F51CC7000279B9F9CFE811...
  
  0000000141E40304423FFFFF0B7867F89FAFFFFFFFFFFCBE8EF25E6...
  
  0000000141E602899A3512EF8AEAD1379F0650CC3F905131504F839...
  
  ...

  The very first frame contains SPS and PPS. From what I was able to see, these are transmitted only once. The rest are NAL types 1 and 5. So, my assumption is that, for ffprobe to see stream info not only when the stream starts, I should capture SPS and PPS frames and re-transmit them myself periodically, after a certain number of frames, or perhaps before every I-frame. What do you think ?

  Update #2

  Unable to validate that I’m writing frames successfully. After having tried to read back the written packet, I cannot validate written bytes. As strange, on successful write of IPL image and streaming, I also cannot print out bytes of encoded packet after avcodec_encode_video2. Hit the official dead end.