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• Two videos playing, how to crop the second video in FFmpeg

  14 janvier 2021, par Rorlingur

  I'm totally new to FFmpeg and I'm still learning.

  


  I've been trying to combine two videos into one. Where there is a "main" video that plays and a secondary video that is much smaller in the corner.

  


  I have managed to figure out almost everything on my own except for how to crop the smaller corner video by half. My goal is to crop/cut the corner video so it will only show the right half of the video but I can't seem to make it work, any help/tips would be much appreciated !

  


  ffmpeg -ss 00:04:10.10 -i corner.m4v -vf "movie=main.mkv [in1]; [in]scale=iw/4:ih/4, pad=0*iw:ih[in0]; [in1][in0] overlay=main_w/1.334:550 [out]" -b:v 3500k out.mkv


  


  The above is what I currently have that works, the only thing that is missing is cropping the corner video.

  


• avutil/half2float : adjust conversion of NaN

  9 août 2022, par Timo Rothenpieler

  avutil/half2float : adjust conversion of NaN
  IEEE-754 differentiates two different kind of NaNs.
  
  Quiet and Signaling ones. They are differentiated by the MSB of the
  
  mantissa.
  For whatever reason, actual hardware conversion of half to single always
  
  sets the signaling bit to 1 if the mantissa is != 0, and to 0 if it's 0.
  
  So our code has to follow suite or fate-testing hardware float16 will be
  
  impossible.
  

  • [DH] libavcodec/exr.c
  • [DH] libavcodec/pnm.h
  • [DH] libavutil/half2float.h
  • [DH] tests/ref/fate/exr-rgb-scanline-zip-half-0x0-0xFFFF

• ffmpeg in:h264 out:yuv to stdout - data format ?

  27 février 2019, par Petr

  I am (like many) trying to get a continuous series of still images out of the camera attached to a raspberry pi. I want to do this in java for all the usual reasons, and am using a Runtime exec command to pipe the output of raspivid to the following ffmpeg command, and then collecting the result via stdout --- note xxx.h264 is a test file generated by the camera that does not play because there is no container, but I am getting images out so half good.

  ffmpeg -i xxx.h264 -vcodec rawvideo -r 2 -pix_fmt yuv420p -f nut -

  I have some code displaying the frames, but they "march" across the display area from left to right, and there appears to be a growing amount of rubbish across the top of the images. I have looked at the bytes it outputs by running the same command and redirecting it into a file, then using vi/xxd and find that there is headder material ("nut/multimedia container ...").

  I am guessing that there is more metadata inserted by my ffmpeg command, that I am failing to remove when processing the raw yuv420p data as described here : https://en.wikipedia.org/wiki/YUV#Y%E2%80%B2UV420sp_%28NV21%29_to_RGB_conversion_%28Android%29

  For the life of me I cannot find the nut documentation anywhere in a readable format and anyway, it seems that is not what I should be looking for. Any pointers as to how I can recognise the frame boundaries in my byte stream ?