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• Best logical formula to determine perceptual / "experienced" quality of a video, given resolution / fps and bitrate ?

  20 mars 2023, par JamesK

  I am looking for a formula that can provide me with a relatively decent approximation of a Video's playback quality that can be calculated based off of four metrics : width, height, fps, and bitrate (bits/sec). Alternatively, I can also use FFMPEG or similar tools to calculate a Video's playback quality, if any of those tools provide something like what I am looking for here.

  


  An example of what a Video might look like in my problem is as follows :

  


  interface Video {
  /** The width of the Video (in pixels). */
  width: number
  /** The height of the Video (in pixels). */
  height: number
  /** The frame rate of the Video (frames per second). */
  fps: number
  /** The bitrate of the video, in bits per second (e.g. 5_000_000 = 5Mbit/sec) */
  bitrate: number
}


  


  I came up with the following function to compute the average amount of bits available for any given pixel per second :

  


  const computeVideoQualityScalar = (video: Video): number => {
  // The amount of pixels pushed to the display, per frame.
  const pixelsPerFrame = video.width * video.height
  
  // The amount of pixels pushed to the display, per second.
  const pixelsPerSecond = pixelsPerFrame * video.fps
  
  // The average amount of bits used by each pixel, each second,
  // to convey all data relevant to that pixel (e.g. color data, etc)
  const bitsPerPixelPerSecond = video.bitrate / pixelsPerSecond
  
  return bitsPerPixelPerSecond
}


  


  While my formula does do a good job of providing a more-or-less "standardized" assessment of mathematical quality for any given video, it falls short when I try to use it to compare videos of different resolutions to one another. For example, a 1080p60fps video with a bitrate of 10Mbit/sec has a greater visual fidelity (at least, subjectively speaking, to my eyes) than a 720p30fps video with a bitrate of 9Mbit/sec, but my formula would score the 720p30fps video significantly higher than the 1080p60fps video because the 720p video has more bits available per pixel per second than the 1080p video.

  


  I am struggling to come up with ideas as to how to either come up with a different way to calculate the "subjective video quality" for a given video, or extend upon my existing idea here.

  


• Revision 377d2f027a : Refactor choose_partitioning computing scheme This commit refactors the choose_

  11 décembre 2014, par Jingning Han

  Changed Paths :
   Modify /vp9/encoder/vp9_encodeframe.c

  
  
  Refactor choose_partitioning computing scheme

  This commit refactors the choose_partitioning function. It removes
  redundant memset calls and makes the encoder to calculate
  variance value per block only when it is needed. It reduces the
  average runtime cost of choose_partitioning by 60%. Overall it
  reduces speed -6 runtime by 2-5%.

  Change-Id : I951922c50d901d0fff77a3bafc45992179bacef9

• How to calulate PTS and DTS ? FFmpeg C++

  27 janvier 2024, par kodoma

  I have a mkv file where I want to extract the video stream. While extracting, I got the "... non monotonically increasing dts to muxer ..." Warning/Error. I have tried multiple solutions that I found online, but I could never get the timing to be right.

  


  This is the beginning of the video stream :

  


  DTS: 0    PTS: 0    Duration: 41 
DTS: 375  PTS: 375  Duration: 41 
DTS: 209  PTS: 209  Duration: 41 
DTS: 42   PTS: 42   Duration: 41 
DTS: 83   PTS: 83   Duration: 41 
DTS: 125  PTS: 125  Duration: 41 


  


  I also extracted the stream via the FFmpeg executable, and the extracted video file has the same DTS and PTS as the source.

  


  So how do I calculate the DTS and PTS correctly ? If I don't change the timings, the video is the same length, but it is total garbage.