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• FFMpeg Muxer Internal Buffering

  7 mars 2016, par rkrishnan2012

  I am using libFFmpeg to mux h264 and aac packets into an flv container and streaming that via rtmp.

  I want to be able to detect when frames are being sent to the server or the size of the internal buffer, in order to detect the network lag and apply variable bit-rate. However, when I clock the time it takes for av_write_frame, it is much too fast for it to be syncronous (so we can’t use this to detect network speed).

  I already tried calling av_write_frame with a null parameter (to flush data) every frame, and also directly calling avio_flush but the bitrate is still too high. So, I am wondering if there is another buffer that I am missing (such as a socket-level buffer).

  I also tried to print the AVIOContext->buf_end, buffer_size, and buf_ptr values but none of those are indicative of my network speed getting throttled (when I limit the bandwidth on my router, I would expect the buffer size to increase).

  tl ;dr - I would like to know how to properly detect packets being sent to the server, or the network speed lagging compared to my av_write_frame calls.

  If it makes a difference, this is being run on an arm-v7a Android device.

• ffmpeg get frame time stamp

  19 novembre 2018, par Anshul G.

  I am trying to record a webcam video using ffmpeg. I have a logitech c922 Pro Stream Webcam. This is the command that I use :

  ffmpeg -f v4l2 -framerate 60 -video_size 1280x720 -input_format mjpeg -i /dev/video1 out.mp4

  My application requires me to get the exact timestamp for every frame. While I could use my knowledge of the framerate and frame number to add the required interval to the start time, I am afraid that this might not be completely accurate.

  Firstly, I have noticed that while recording, the console seems to initially display a far higher fps than the one I have set :

  Press [q] to stop, [?] for help
  
  frame=  177 fps= 85 q=-1.0 Lsize=     502kB time=00:00:02.91 bitrate=1410.8kbits/s dup=144 drop=0    

  Also, I think that ffmpeg drops frames in between sometimes.

  However, my videos seem to have the correct number of frames so I think that the fps value displayed could instead be referring to the encoding/ decoding speed. I am not sure about frame dropping.

  I would be happy of you could let me know what you think, or suggest an alternative so that I can timestamp my frames accurately. Thanks !

  Edit :

  I have understood that frame rate is correlated to ambient light which can lead to high duplication in frames. I am currently recording on windows and have set frame rate as the priority in logitech gaming software. However there is still the occasional drop in frame or duplication. Does this affect time stamp of the frames ? Or can I extrapolate from the start time ?

• Create RTP packets with audio or video for a particular codec in FFmpeg

  15 mai 2020, par easy_breezy

  I'm new to FFmpeg and I want to stream audio and video data from my android device to another device (PC, Android, iOS, Mac it doesn't matter) in real time (RTP packets by UDP) by Wi-Fi or LTE. My audio is encoded in G711 or Opus codec and my video is H264, so my question is : is there way to create RTP packets for encoded audio or video using FFmpeg in C++ code ?

  



  I'd like to have something like this :

  



  

  1. I encode my audio and video using FFmpeg or third party library.

  


  2. I pass my encoded data and it's metadata (like a keyframe flag, and
some other codec specific things) to some FFmpeg method and this
method returns to me an RTP packet filled with my encoded data and
codec specific data.

  


  3. I take the RTP packet and send it by UDP using Java/Kotlin socket.

  


  



  It's very important for me to get RTP packets and send it in Java/Kotlin layer not in C++.