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• How to properly convert RTL subtitles in ffmpeg ?

  25 octobre 2020, par HTMHell

  I'm using the following command to extract subtitles from a video file, and save it as vtt.

  



  ffmpeg -i video.mkv -map 0:s:0 subs.vtt 2>&1


  



  It's working and outputs the subtitles file. The problem is with RTL (right to left) languages (Hebrew, Arabic etc.)
The punctuation are being misplaced.

  



  I will show you an English example of what's happening, for your convenience :

  



  Input text :

  



  Is he alive?
-I don't know.


  



  Output text :

  



  ?Is he alive
.I don't know-


  



  If you want the original text in Hebrew, there it is :

  



  Input Text :

  



  הוא חי?
-אני לא יודע.


  



  Output text :

  



  ?הוא חי
.אני לא יודע-


  



  As you can see, the punctuation marks at the end are going to the start, and vice versa. How can I avoid this behavior ?

  


• ffmpeg and python usage

  23 février 2014, par user2063350

  I have an ffmpeg setup on my pc, which streams mp3 with this code :

  ffmpeg -f dshow -i audio="Input device" -c:a libmp3lame -f mpegts udp://192.168.1.2:7777

  Also i have a server and I want my python script to run 24/7 on server and start/stop writing stream to mp3 file every time pc get's turned on/off. I need new file every time pc turns on (use time and date for filename for example) to bypass overwriting. Using python's subprocess module and ffmpeg I can save file on my server like this :

  subprocess.call('ffmpeg -y -i udp://192.168.1.2:7777 -acodec copy output.mp3')

  But I need condition, when to start recording(listen if 7777 port is reciving data or something like that), is it even possible to implement such thing, using python ?
  P.S. Sorry for my bad English.

• How to Convert NV12 to BGR(AVFrame to cv::Mat)

  1er janvier 2019, par Steven.Yeun

  I decoded videoframe by using FFMPEG Library from IP Camera.
  This videoframe format is AV_PIX_FMT_NV12. AV_PIX_FMT_NV12 is defined on FFMPEG Library.
  I want to convert NV12 to BGR (AVFrame to cv::Mat), so I try to do this
  but I got wrong image :

  

  Please help me. I want to convert properly. Can anyone guess this problem ?
  Please refer to following code :

  void CALLBACK MyCallbackFunc(AVFrame *avFrame )
  
  {
  
      if (avFrame != NULL)
  
      {
  
          cv::Mat imageRGB;
  
          cv::Mat picI420 = cv::Mat(avFrame->height * 3 / 2, avFrame->width, CV_8UC1, avFrame->data[0]);
  
          cv::cvtColor(picI420, imageRGB, CV_YUV2BGR_NV12);
  
          imshow("imageRGB", imageRGB);
  
  
  
          cvWaitKey(1);
  
      }
  
  }

  Sorry for my bad english. If you want more information please comment below.