Recherche avancée

Sur d’autres sites (9895)

• Passing commands with double quotes to subprocess.call in python

  7 juin 2018, par Georgе Stoyanov

  I want to pass a command to a Linux machine running ffmpeg using python containing a double quotes. That’s my script :

  drawtext = "drawtext=\"fontfile=DejaVuSans: text='Random Name': fontcolor=white: fontsize=24: box=1: boxcolor=black@0.5: boxborderw=5: x=20: y=20\""
  
  subprocess.call(["ffmpeg", "-v", "error", "-i", input.mp4, "-vf", drawtext, output.mp4])

  If I print the drawtext variable this is the output :

  drawtext="fontfile=DejaVuSans: text='Reference Image': fontcolor=white: fontsize=24: box=1: boxcolor=black@0.5: boxborderw=5: x=20: y=20"

  And this is my error in ffmpeg :

  [Parsed_drawtext_0 @ 0x564ad79f99c0] [Eval @ 0x7ffd41131810] Invalid chars '"' at the end of expression '20"'
  
  [Parsed_drawtext_0 @ 0x564ad79f99c0] Failed to configure input pad on Parsed_drawtext_0
  
  Error reinitializing filters!
  
  Failed to inject frame into filter network: Invalid argument
  
  Error while processing the decoded data for stream #0:0

  If I execute the following command in Linux shell it works just fine :

  $ ffmpeg -ss 10 -i input.mp4 -vf drawtext="fontfile=DejaVuSans: text='Random Name': fontcolor=white: fontsize=24: box=1: boxcolor=black@0.5: boxborderw=5: x=20: y=20" output.mp4

• ffmpeg taking so much time to extract frames from mpeg-ts file

  19 septembre 2016, par Syed Azaruddin

  I got a problem from one mpeg-ts video. Actually it was created by some one else and even I don’t know how they are created. The problem is that, ffmpeg is taking so much time to decode all frames from the mpeg-ts video. The command I used for this operation is...

  ffmpeg -i shame-run.mov -r 24/1 test/output%d.jpg

  Actually my application is integrated with ffmpeg v2.1.1. and I had a code for detecting black frames in a mpeg-ts video. Here, my code is not able to detect all black frames from ffmpeg for this mpeg-ts video. So, I taken standalone ffmpeg of same version as mentioned above and decoded standalone. But, it is taking so much time i.e., it is taken half an hour for decoding 1 min duration video.

  So, is there any reason is that ffmpeg not able to extract as fast as required, and is there any reason that video got some errors.

• How come the quality of HEVC with alpha from my ffmpeg with videotoolbox is not ok

  27 juin 2023, par Jos

  I'm encoding ProRes 4444 with alpha channel video's to transparent video for web in both VP9 (webm) and HEVC (mp4). I'm using a great free tool by Rotato to encode to both formats at once.

  


  However, because I would like to have more control over e.g. the dimensions and the bitrate, I'm looking into ffmpeg. I can encode to both formats with the following params.

  


  # vp9
ffmpeg -i in.mov -vf scale=-1:720 -c:v libvpx-vp9 -auto-alt-ref 0 -pix_fmt yuva420p -acodec libvorbis -cpu-used 3 -deadline good -crf 40 out.webm 

# hevc
ffmpeg -i in.mov -vf scale=-1:720 -c:v hevc_videotoolbox -allow_sw 1 -alpha_quality 0.9 -tag:v hvc1 -q:v 65 out.mp4


  


  The problem : the videotoolbox encoder generates a weird white garbage around the black pencil animations and fade-in's from transparent to black pencil become fade-in's from white pencil to black pencil !?

  


  Here are screenshots of the two compared (top one is my ffmpeg output) :

  


  

  


  

  


  Anyone have good settings for ffmpeg I cano use to encode good quality HEVC with alpha ?
Hardware : MacBook Air M1 and Win11 + GTX 1060 (I should be able to use NVEnc, but don't know how)