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• Why are the actual QP values in block-level in minus 3 from the initial QP with CQP mode in x265 ?

  27 septembre 2022, par Alearner

  I am encoding a video with different initial QP values using the x265 encoder. I am surprised when I checked the bitstream to see the actual QP values for every block across frames are not exactly the same as the given initial QP value. Specifically, the actual QP decreases to minus 3 from the initial value, as shown in the figure below (my initial QP is set to 27). But I don't understand why. Then, I run the encoder from HM-16.20, the actual QP value is the same as the initial QP. Can someone help me to understand the motivation for this ? From my point of view, the x265 encoder wants to retain more visual quality by lowering the actual QP values than those in HM software. I used the following command line to run the x265 encoder :

  


  x265.exe --input BQSquare_416x240_60.yuv --fps 60 --input-res 416x240 --interlace 0 -f 20  --input-depth 8 --input-csp i420 --ctu 64 --no-open-gop --keyint 1 --ref 1 --aq-mode 0 --qp 27 -r BQSquare_416x240_8bit_27.yuv --output-depth 8 --output BQSquare_416x240_8bit_27.bin


  


  

  


• What happens when I use too much RAM from spawning process with Popen in Python ? [closed]

  2 février 2020, par lms702

  I have a Python script that is rendering a video with FFmpeg where I have all the images and audio I need. I am currently invoking FFmpeg via multiprocessing.Popen, which works very quickly on my computer but the Task Manager shows that I am using 12 GB of RAM while doing so (since there end up being 100s of instances of FFmpeg.exe running). I want to deploy this on a linux server one day with much less RAM, but I worry that I’ll run into problems with my approach. Does Python/the OS handle this or should I limit the number of processes I spawn myself ?

• Hls.js record file

  28 février 2023, par Huhngut

  Hello and thanks for reading,

  


  I have a Hls stream with an m3u8 playlist.
The Video is playing just fine on an Html page with a Video element and https://github.com/video-dev/hls.js

  


  But if I download the segments to join them they are only white pixels. VLC and FFmpeg can't handle them. VLC shows a white pixel for 10seconds and FFmpeg says that there's no stream in the file.

  


  So now I want to know what this hls.js is doing to make it running. To me a non-js developer it all looks a bit confusing. I was able to understand stuff like which function is called when a new segment is loaded. Unfortunately, I was unable to understand stuff about the data. The one character variables are confusing to me.

  


  For now, I capture the stream of the video element and download it later but I don't like this solution at all.

  


  How to help me

  


  


  It would be very nice if anyone can tell me how to hook into the
script and tell it to download directly to the disk so I'm independent
of framerate drops.

  


  If anyone can tell how the script is able to convert the data so that
the element can use it and I would be able to implement or do
it with FFmpeg would be really helpful.

  


  I also thought it might be possible to have a listener when the blob
changes to store its contents.

  


  


  Thanks for everyone helping. I'm trying to find a solution for too many hours now.