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• Fix CBR output for IP multicasting video

  19 août 2014, par ddhung

  I’m using ffmpeg for transcoding live ip multicasting video on server linux Centos 5.9 OS. This is my ffmpeg command

  ffmpeg -i "udp:// x.x.x.x:6000?fifo_size=1000000&overrun_nonfatal=1&timeout=1000000" -filter:v yadif=0:-1:1 -vcodec libx264 -vprofile main -level 30 -tune zerolatency -pass 1 -b:v 900k -minrate 900k -maxrate 900k -bufsize 900k -x264opts nal_hrd=cbr:rc_lookahead=40:interlaced=1:scenecut=0:cabac=1:keyint=120:deblock=0,0:aud=1:qpmin=16:qpmax=51:qpstep=10:ref=2:mixed-refs=1:subme=9:me=esa:chroma_me=0:merange=64:8x8dct=0:fast_pskip=0:chroma_qp_offset=0:trellis=2:psy=0:bframes=0:weightp=2:sliced_threads -s:v 720x576 -r:v 25 -force_key_frames 'expr:gte(t,n_forced*3)' -threads 0 -acodec aac -strict -2 -ac 1 -ar 32000 -b:a 32k -filter:a volume=1 -f mpegts -muxrate 1400k udp://x.x.x.x:6000?pkt_size=1316

  My output video is for broadcasting so I have to configure CBR video output by feature –muxrate. But when I watch this stream on VLC the bitrate change very much not constant. The null packet is very high to force cbr mpeg2ts output.

  I also measure IP output video by HST3000 JDSU equipment and I see the measurement result is very bad as images.
  The PCR Jitter, IGMP Latency, Jitter Max which is not good as measurement standard by JDSU

  I try many way to change the ffmpeg command but not successful. The bitrate changes sometime > 1400kbps a lot. I think the problem may be the bitrate not constant. I have heard to change the muxrate output is CBR, it had to be change the code C mpegtsenc.c in libavformat library to new patch.
  So could you help me fix this problem and make the measurment result is better.
  Thank you so much.

  Best Regards

• How to change the colour of pixels in videos with OpenGL in C++ [closed]

  8 juin 2020, par Dennio

  I would like to overlay a specifically coloured pattern or matrix over every frame of a video, so that every pixel changes it's color slightly corresponding to a data-matrix which I generate from a bitstream. It would begin with the upper left pixel and would go on till the end of the "line" and so on. I would like to change the red and blue values which means if the bitstream begins with a "1" the amount of red should be raised by 5 and if it begins with a "0" the amount of blue should be raised by 5. That would be done for every pixel of the frame.

  



  I can already open a video using FFmpeg in a selfmade videoplayer, I can also generate the data-matrix but I just don't know which way is suitable to manipulate the videoframes in c++. I already successfully compiled some OpenGL and OpenGL ES triangles on my RaspberryPi 4. Is it possible to convert the frames and pixels into textures and go from there to display everything ? Or is there maybe a better way to do this ? I would like to use the GPU of the RaspberryPi for the tasks to get a good performance out of this.

  


• checkasm/x86 : Correctly handle variadic functions

  23 septembre 2015, par Henrik Gramner

  checkasm/x86 : Correctly handle variadic functions
  The System V ABI on x86-64 specifies that the al register contains an upper
  
  bound of the number of arguments passed in vector registers when calling
  
  variadic functions, so we aren’t allowed to clobber it.
  checkasm_fail_func() is a variadic function so also zero al before calling it.
  

  • [DH] tests/checkasm/x86/checkasm.asm