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• Improve ffmpeg scene detection in particular scenario

  17 septembre 2021, par Nobody-Knows-I-am-a-Dog

  I have 50 hours of video where a speaker is in the lower right corner of the video and the by far larger part of the video consists of slides in the center. The speaker moves a bit, the slides transition into the video. I need to detect the time codes of the slide transitions. +- 1 second precision is fine. I am playing around with select filters in ffmpeg such as ffmpeg -i lecture.mp4  -filter:v "select='gt(scene,0.1)',showinfo"   -f null - but I have remaining problems where some help or hint would be highly appreciated.

  


  Problem 1 : Speaker movement occasionally triggers false positives. If there is some possibility to restrict frame comparison to a certain (spatial, cropped) area of the scene then I could focus on the slide area and this would greatly help.

  


  Problem 2 : Speed of slide transition is slow so I occasionally miss a transition since the change from frame(n) to frame(n+1) is too small. It would be great if I could compare, for example, frame(n) to frame(n+10) for threshold detection. ffmpeg scene detection : check only every nth frame ? does not help here, because it only checks every n-th frame but still compares a frame with its immediate neighbor.

  


  Of course, both problems can be solved by producing a cropped version with reduced framerate. However, I am looking for a solution where I can do this in a single pass with some complex filter expression ... and this is exactly the place where my own experience with ffmpeg fails me and where I would appreciate some help.

  


  Problem 3 : Occasionally a single slide transition triggers several times in a row throughout the transition. I have no idea how to solve this in ffmpeg.

  


• FFMPEG encoding 16bit video data results in 10bit

  12 mars 2023, par Jl arto

  I want to compress a depth map that has 16 bits of information per pixel. In general, such depth maps can be stored in different ways, e.g. p016le, gray16le, yuv420p16le, yuv444p16le, ... but for simplicity, let's assume the depth map is a yuv420p16le (where the y-channel contains the depth).

  


  For some reason when encoding with hevc_nvenc (I use an NVIDIA GTX 1660 Ti GPU), ffmpeg (the command line tool) changes the pixel format to a 10 or 12 bit variant (p010le, gray12le, yuv420p10le, yuv444p12le, ...), but I would like to keep the full 16 bits, since this affects the quality of the depth stored.

  


  For example :

  


  ffmpeg.exe -s:v 1920x1080 -r 30 -pix_fmt yuv420p16le -i depth_yuv420p16le.yuv -c:v hevc_nvenc -pix_fmt yuv444p16le output.mp4


  


  If I use ffprobe on the output.mp4, it tells me that the underlying pixel format is actually yuv444p10le. (Decoding and looking at the raw pixel data, I can confirm that the precision has decreased from 16 bits to 10 bits).

  


  I hope 16 bit compression is possible, since according to

  


  ffmpeg -h encoder=hevc_nvenc


  


  the supported pixel formats are :

  


  hevc_nvenc: yuv420p nv12 p010le yuv444p p016le yuv444p16le bgr0 rgb0 cuda d3d11


  


  But p016le results in a p010le output, and yuv444p16le in yuv444p10le.

  


  Does anyone know where the problem could lie ? Should I re-install ffmpeg (version 4.3.2-2021-02-27-essentials_build-www.gyan.dev) ? Is it because of Windows 10 having limited encoding/decoding capabilities ? Will buying the HEVC Video Extensions help solve this problem ?

  


  Additional info : using libx256 does not look like it will work for this purpose, since the supported pixel formats are :

  


  libx256 : yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p gbrp yuv420p10le yuv422p10le yuv444p10le gbrp10le yuv420p12le yuv422p12le yuv444p12le gbrp12le gray gray10le gray12le


  


  Any help would be greatly appreciated.

  


• libavcodec/libx265 : add user data unregistered SEI encoding

  12 juillet 2021, par Brad Hards

  libavcodec/libx265 : add user data unregistered SEI encoding
  MISB ST 0604 and ST 2101 require user data unregistered SEI messages
  
  (precision timestamps and sensor identifiers) to be included. That
  
  currently isn't supported for libx265. This patch adds support
  
  for user data unregistered SEI messages in accordance with
  
  ISO/IEC 23008-2:2020 Section D.2.7
  The design is based on nvenc, with support finished up at
  
  57de80673cb
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavcodec/libx265.c