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• "Automatic" switchable graphics on desktop, is there a way to disable them ?

  14 août 2021, par Hab-Land0

  Recently, I've updated my graphic drivers for a new system I built, a mix between an amd apu and an nvidia quadro. But I stumbled upon a rare problem, every time I tried to use OpenCL acceleration on ffmpeg for libx264 encoding, ffmpeg notifies me with the next line :

  


  [libx264 @ 0000028149222780] OpenCL acceleration disabled, switchable graphics detected


  


  When searching this line on ffmpeg's code, apparently occurs when the "main OpenCL driver" (if you can call it that) is redirected in such a way that tries to use both devices (Code).

  


  My obvious next step was to search everything I could around this "switchable graphics", but almost all the tutorials on websites told me that I should search around the driver's settings, but literally either Radeon Software or Nvidia's control panel don't display any option about it (It is worth to say that almost all of the tutorials refer to laptops with dedicated graphics and were very outdated).

  


  Another way I use OpenCL is for vapoursynth's filters, such as KNLMeansCL. And, when I make use of this filter, task manager detects that both AMD's APU and Nvidia's gpu are being used simultaneously (I guess that's how the switchable graphics actually works, and partially complementing why x264 OpenCL doesn't work).

  


  My main complain with this is that I attempt to use AMD as a display driver and let Nvidia do the hard work, and I actually was able to do that before updating my drivers. And, talking about the "updates" more in-depth, I updated nvidia's from "462.59" to "471.11" and, unfortunately, I can't remember what versions were my AMD drivers.

  


  Edit : the only way I can make full use of NVIDIA's card is by using it as my main display, but that also apparently disables AMD's igpu, I am not sure if its even able to be used on small tasks (like those that were previously mentioned)

  


• How correctly show video with transparency in Qt with OpenCV + FFMpeg

  11 avril 2022, par TheEnigmist

  I'm trying to show a video with transparency in a Qt6 application using OpenCV + FFMPEG.
Actually those are tool versions :

  


  

  • Win 11

  


  • Qt 6.3.0

  


  • OpenCV 4.5.5 (built with CMake)

  


  • FFMPEG 2022-04-03-git-1291568c98-full_build-www.gyan.dev

  


  


  I've used a base .mov video with transparency as test (link provided below).
First of all I've converted .mov video to .webm video (VP9) and I see in output text that alpha channel remains

  


  


  ffmpeg -i '.\Retro Bars.mov' -c:v libvpx-vp9 -crf 30 -b:v 0 output.webm

  


  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2,
    ...
    Stream #0:0[0x1](eng): Video: qtrle (rle  / 0x20656C72), argb(progressive),
    ...

Output #0, webm, 
   ...
   Stream #0:0(eng): Video: vp9, yuva420p(tv, progressive),
   ...


  


  But when I show info of output file with ffmpeg it loses alpha channel :

  


  


  ffmpeg -i .\output.webm

  


  


  Input #0, matroska,webm,
    ...
    Stream #0:0(eng): Video: vp9 (Profile 0), yuv420p(tv, progressive),
    ...


  


  If I open output.webm with OBS it is shown correctly without a background, as shown in picture :


  


  If I try to open it with OpenCV + FFMPEG it shows a black background under bars, as shown in picture :


  


  This is how I load video in Qt :

  


  cv::VideoCapture capture;
capture.open(filename, cv::CAP_FFMPEG);
capture.set(cv::CAP_PROP_CONVERT_RGB, false); // try forcing load alpha channel
... //in a thread
while (capture.read(frame)) {
    qDebug() << "c" << frame.channels() << "t" <<  frame.type() << "d" <<  frame.depth(); // output: c 3 t 16 d 0
    cv::cvtColor(frame, frame, cv::COLOR_BGR2RGBA); //useless since no alpha channel is detected
    img = QImage(frame.data, frame.cols, frame.rows, QImage::Format_RGBA8888);
    emit processedImage(img); // to show image in a QLabel with QPixmap::fromImage(img)
}


  


  I think the problem is when I load the video with OpenCV, it doens't detect alpha channel, since I can load correctly in other player (obs, html5, etc.)

  


  What I'm wrong with all process to show this video in Qt with transparency ?

  


  EDIT : Added dropbox link with test video + ffmpeg outputs :
sample items

  


• Ffmpeg won't copy excerpt of video correctly

  5 mai 2022, par JR Jr.

  I am using a DOS batch to automate and copy excerpts of various high definition videos (mkv's with more than 1GB each).
The script is very convenient and runs fast and fine, but Ffmpeg is not doing its job correctly (it seems Murphy's law is inexorably enthralled into technology, things never come easy, which is why I love and hate it).

  


  Anyway, to cut a long story short, each time the batch job runs, a code like below is executed (pardon me the indiscrete folder name, it's about the 90's TV show, it's not porn !).

  


  call "C:\ffmpeg\bin\ffmpeg.exe" -y -i "D:\100\Sexo\S01\SATC - S01E03 - Bay of Married Pigs.mkv" -ss 00:18:05 -to 00:19:15 -codec copy "002-SATC - S01E03 - Bay of Married Pigs-00_18_05-00_19_15.mp4"


  


  The problem is that the first 6 seconds or so of the resulting video has no video, only audio with a frozen image that only starts to move after about 6 seconds, which is a huge defect, not to mention very annoying (a big let down, after all my meticulous scripting work :(). And this happens for most of the files, except a few ones.

  


  Even though this is copying and changing the format from mkv to mp4, per another thread on this site (https://askubuntu.com/questions/396883/how-to-simply-convert-video-files-i-e-mkv-to-mp4), this is not re-encoding, so this is not the issue. Actually, the same problem occurs even if I don't change the format from mkv to mp4.

  


  Even though I foresee a "there's no way to fix this", let me ask : is there a way to fix this ? Hopefully there is a way.