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• How to paint in Qt using hardware acceleration ?

  19 octobre 2020, par FennecFix

  I need to do some quite intensive drawing processes in my appliation - I'm recording a camera and a desktop. I'm using ffmpeg to capture and encode/decode my videos. Those processes are quite fast and they working in a separate thread, but when it comes to render - perfomance drops drastically. I'm using QLabel to display captured frames via setPixmap() method and I see that Qt not using any GPU power even if a matrix operation, such as scaling an image to fit the window is clearly implied. Is there any way to paint images in Qt using hardware acceleration ? Or is there another ways to speed up painting process ?

  


• How do I configure ffmpeg & openh264 so that the video file can be opened in Windows Media Player 12

  10 mars 2017, par Sacha Guyer

  I have successfully created h264/mp4 movie files with ffmpeg and the x264 library.

  Now I would like to change the h264 library from x264 to openH264. I could replace the x264 library with openH264, recompile ffmpeg and produce movie files, without changing my sources that produce the movie. The resulting movie opens fine in Quicktime on Mac, but on Windows, Windows Media Player 12 cannot play it.

  The documentation about Windows Media Player support for h264 is unclear. File types supported by Windows Media Player states in the table that Windows Media Player 12 supports mp4, but the text below says :

  Windows Media Player does not support the playback of the .mp4 file format.

  From what I have observed, Windows Media Player 12 IS capable of playing h264/mp4 files, but only when created with x264.

  Does anyone know how I need to adjust the configuration of the codec/context so that the movie plays in Windows Media Player ? Does Windows Media Player only support certain h264 profiles ?

  I noticed the warning :

  [libopenh264 @ 0x...] [OpenH264] this = 0x..., Warning:bEnableFrameSkip = 0,bitrate can’t be controlled for RC_QUALITY_MODE,RC_BITRATE_MODE and RC_TIMESTAMP_MODE without enabling skip frame

  With the configuration :

  av_dict_set(&options, "allow_skip_frames", "1", 0);

  I could get rid of this warning, but the movie still does not play. Are there other options that need to be set so that the movie plays in Windows Media Player ?

  Thank you for your help

  ffprobe output of the file that does play fine in Windows Media Player :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_x264.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      title           : retina
  
      encoder         : Lavf57.56.100
  
      comment         : Creation Date: 2017-03-10 07:47:39.601
  
    Duration: 00:00:04.17, start: 0.000000, bitrate: 17497 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661),
  
        yuv420p, 852x754, 17495 kb/s, 24 fps, 24 tbr, 24k tbn, 48 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler

  ffprobe output of the file that does not play in Windows Media Player :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_openh264.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      title           : retina
  
      encoder         : Lavf57.56.100
  
      comment         : Creation Date: 2017-03-10 07:49:27.024
  
    Duration: 00:00:04.17, start: 0.000000, bitrate: 17781 kb/s
  
      Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661),
  
        yuv420p, 852x754, 17779 kb/s, 24 fps, 24 tbr, 24k tbn, 48k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler

• FFMPEG Runs OK locally but fails when run on Heroku server

  9 mars 2017, par Berni

  I’m working on a project which takes a video and converts it to a sprite sheet image.

  When I run the app locally using npm start the video uploads and the sprite sheet is generated.

  However when I deploy the app to Heroku and perform the same actions I get the following errors from the Heroku log :

  2017-03-09T16:03:43.069886+00:00 app[web.1]: error: ffmpeg exited with code 1: Error while opening encoder for output stream #23:0 - maybe incorrect parameters such as bit_rate, rate, width or height
  
  
  
  2017-03-09T16:03:43.069897+00:00 app[web.1]: 
  
  2017-03-09T16:03:43.069922+00:00 app[web.1]: stdout: 
  
  
  
  2017-03-09T16:03:43.069989+00:00 app[web.1]: stderr:   split:output4 (graph 0) -> Stream #5:0 (png)
  
  
  
  2017-03-09T16:03:43.070083+00:00 app[web.1]: Error while opening encoder for output stream #23:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I’ve checked that the bit_rate, rate, width and height are all correctly set.

  Any advice on how to get this resolved would be appreciated :)