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• kmsgrab : Use GetFB2 if available

  5 juillet 2020, par Mark Thompson

  kmsgrab : Use GetFB2 if available
  The most useful feature here is the ability to automatically extract the
  
  framebuffer format and modifiers.  It also makes support for multi-plane
  
  framebuffers possible, though none are added to the format table in this
  
  patch.
  This requires libdrm 2.4.101 (from April 2020) to build, so it includes a
  
  configure check to allow compatibility with existing distributions.  Even
  
  with libdrm support, it still won't do anything at runtime if you are
  
  running Linux < 5.7 (before June 2020).
  

  • [DH] configure
  • [DH] libavdevice/kmsgrab.c

• Audio Slowly Desynchronizing When Segmenting

  14 avril 2018, par Nimble

  I use ffmpeg’s ability to segment video while I record so I can record constantly without my hard drive filling up.

  It works really well, expect the audio desynchronizes from the video when the file segments. The video seems to be uninterrupted but I can actually hear a tiny jump in the audio when I join segments later on. One would think that ffmpeg would store packets in a queue during segmentation so nothing is lost but that doesn’t seem to be the case... Any way I could force it to do something like that ?

  Here is my current block :

  ffmpeg -y -thread_queue_size 5096 -f dshow -video_size 3440x1440 -rtbufsize 2147.48M -framerate 100 -pixel_format nv12 ^
  
  -itsoffset 00:00:00.012 -i video="Video (00 Pro Capture HDMI 4K+)" -thread_queue_size 5096 -guess_layout_max 0 -f dshow ^
  
  -rtbufsize 2147.48M -i audio="SPDIF/ADAT (1+2) (RME Fireface UC)" -map 0:0,1:0 -map 1:0 -c:v h264_nvenc -preset: llhp ^
  
  -pix_fmt nv12 -b:v 250M -minrate 250M -maxrate 250M -bufsize 250M -b:a 384k -ac 2 -r 100 -vsync 1 ^
  
  -max_muxing_queue_size 5096 -segment_time 600 -segment_wrap 9 -f segment C:\Users\djcim\Videos\PC\PC\PC%02d.mp4 

  I am delaying the video stream because right out the gate it’s a little bit ahead of the audio.

  PS : aresample or async seem to have no effect or at least not a desirable one.

• How to pack the pyav.packet and distribute to another computer

  31 juillet 2024, par lambertk

  I'm currently working on projects which needs to read frames from RTSP server on single entry of computer, do some preprocessing and distribute these frames with preprocessed metadata to different backend for different purpose.

  


  And after googling, I found that PyAV could be the solution which can retrieve the video from RTSP source and make it packets, which could possibly be sent to another computer.

  


  Considering the network bandwidth, transmit the packets instead of the decoded frames could be better choice.

  


  But now comes the problem, socket/MQ, usually only allows to send bytes or string.
  
Encode the PyAV.packet.Packet object into byte is easy by bytes(packet), but I couldn't find out the way to decode it back to PyAV.packet.Packet object.

  


  I've tried to use pickle to serialize the packet, but this method is not implemented in PyAV, and was rejected by the official team.

  


  I've also tried to use another package called msgpack, which also failed to serialize the packet.

  


  I've tried the following code after reading the source code of PyAV

  


  packet_bytes = bytes(packet)
pt = av.packet.Packet(len(packet_bytes))
pt.update(packet_bytes)


  


  the update function seems did not update anything

  


  Is there anyway to decode the bytes back to packet object ?

  


  Or, can someone give out a way to encode the frame packet and the preprocessed metadata (which is differ frame by frame) together (like H264 SEI Message, which I tried, but could not be inserted when using Python) then send to backend ?