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• A random pixel on a keyframe. (ffmpeg)

  5 juin 2013, par Chris Russo

  Hello folks of SO !

  We're trying to do some very small and simple code in PHP to generate a variation of a video, using always the same file.

  The script would have to make a small pixel mark, on random or specific frame of the video file, and this would have to be streamed in real time.

  Here's some pseudo code to explain my idea :

  $frame = $_GET[frame];
  
  $videofile = 'video.avi';
  
  
  
  make_random_red_pixel_mark($videofile, $frame);

  Does anyone know if this is possible using ffmpeg ? As well, it is of extreamly importance for us, to execute this procedure as fast as possible.

  A solution that would imply reprocessing the whole video, won't be useful for our purposes. It should be something like a closed caption, or a quick image / overlay filter that could be applied without an entire video reprocessing. As well, we can't put the overlay using Javascript nor any HTML approach, since the actual manipulation has to be on the video file itself.

  The quality, and framerate of the original video, should be kept intact. Perhaps some other PHP module or software that could be execute from PHP using an exec() ?

  Any recommendation ?

  Thanks in advance !!
  Chris C. Russo

  More information :

  1) It's possible for us to apply this procedure on any frame we want to, so we could use a "keyframe" in order to avoid the decoding and reencoding of an entire GOP.

  2) As previously stated, the video stream would have to flow in real time.

• Inputting Audio Stream to FFMPEG

  5 avril 2018, par Wijaya

  I’m building a real time chat application with C# and ffmpeg.exe. My requirement is to get a memory stream from Microsoft Speech API and feed it to ffmpeg process in real time. I can take a memory stream from Microsoft Speech API. I’m using following code to create the memory stream.

          using (MemoryStream stream = new MemoryStream())
  
          {
  
              MemoryStream streamAudio = new MemoryStream();
  
              System.Media.SoundPlayer m_SoundPlayer = new System.Media.SoundPlayer();
  
              _speechSynthesizerVisemesSender.SetOutputToWaveStream(streamAudio);
  
              _speechSynthesizerVisemesSender.SetOutputToNull();
  
              stream.WriteTo(proc.StandardInput.BaseStream);
  
          }   

  I’m already using another datapipe with another command to feed video content to ffmpeg. But I couldn’t find a stable solution to feed audio through a datapipe. This article briefly explains about audio datapipe. I’m using following command to stream audio.

  "ffmpeg -re -f s16le -i pipe:wav -f mpegts udp://127.0.0.1:1234"

  But it is not working with the datapipe. If I try the command with mp3 or wav file, it works.

• How to remove hoax subtitles from mp4 files by ffmpeg ?

  22 février 2020, par hamidi

  Sometimes I get some mp4 files which include a stream of type data. When I play such files by vlc I see an additional subtitle which is not really a subtitle stream. For example it just includes "Chapter 03" ! Indeed the original mp4 file should include a video and an audio stream, while ffmpeg shows an additional data stream. This is the same stream vlc shows as an additional subtitle stream. Sometimes the file includes four streams, a video, an audio and a real subtitle stream. I don’t want to use -sn to remove this real subtitle. I just want to remove what to claim to be a subtitle stream and it’s not. They’re usually introduced to be a data stream, but vlc shows them as subtitle stream. I also don’t want to use -dn or -map_metadata -1 to remove data from mp4, because sometimes the mp4 includes chapters data which I don’t want to be removed. I just want to remove these hoax subtitles which are introduced as data.

  How it’s possible to be done by ffmpeg ?