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• avcodec/srtdec : attempt to correct SubRip positioning

  8 février 2015, par Clément Bœsch

  avcodec/srtdec : attempt to correct SubRip positioning
  The positioning was completely wrong. First, the coordinates are
  
  expressed in ASS playback resolution (which is by default 384x288).
  
  Secondly, the coordinates define a drawing rectangle, not a moving area.
  
  The previous code was making subtitles move from a random position to
  
  another random position.
  Here we rescale assuming the video resolution is a DVD one (720x480). We
  
  can’t really do anything better so far, but since this positioning
  
  information is often from a DVD rip we can consider them relatively
  
  safe.
  

  • [DH] libavcodec/srtdec.c
  • [DH] tests/ref/fate/sub-srt

• ffmpeg - how can I get a specific channel using channel masks (e.g. : get only surround left channel)

  26 novembre 2013, par awfulcode

  I'm trying to build a mixer that allows users to toggle specific channels on and off. I know that different codecs encode those channels in different orders (it's not as simple as getting channel #3 as the center channel every time), so the challenge is to properly identify the channel position in surround audio tracks.

  ffmpeg does list the in the beginning of libavutil/channel_layout.h :

  #define AV_CH_FRONT_LEFT             0x00000001
  
  #define AV_CH_FRONT_RIGHT            0x00000002
  
  #define AV_CH_FRONT_CENTER           0x00000004
  
  #define AV_CH_LOW_FREQUENCY          0x00000008
  
  #define AV_CH_BACK_LEFT              0x00000010
  
  #define AV_CH_BACK_RIGHT             0x00000020
  
  #define AV_CH_FRONT_LEFT_OF_CENTER   0x00000040
  
  #define AV_CH_FRONT_RIGHT_OF_CENTER  0x00000080
  
  #define AV_CH_BACK_CENTER            0x00000100
  
  #define AV_CH_SIDE_LEFT              0x00000200
  
  #define AV_CH_SIDE_RIGHT             0x00000400
  
  #define AV_CH_TOP_CENTER             0x00000800
  
  #define AV_CH_TOP_FRONT_LEFT         0x00001000
  
  #define AV_CH_TOP_FRONT_CENTER       0x00002000
  
  #define AV_CH_TOP_FRONT_RIGHT        0x00004000
  
  #define AV_CH_TOP_BACK_LEFT          0x00008000
  
  #define AV_CH_TOP_BACK_CENTER        0x00010000
  
  #define AV_CH_TOP_BACK_RIGHT         0x00020000
  
  #define AV_CH_STEREO_LEFT            0x20000000  ///< Stereo downmix.
  
  #define AV_CH_STEREO_RIGHT           0x40000000  ///< See AV_CH_STEREO_LEFT.
  
  #define AV_CH_WIDE_LEFT              0x0000000080000000ULL
  
  #define AV_CH_WIDE_RIGHT             0x0000000100000000ULL
  
  #define AV_CH_SURROUND_DIRECT_LEFT   0x0000000200000000ULL
  
  #define AV_CH_SURROUND_DIRECT_RIGHT  0x0000000400000000ULL
  
  #define AV_CH_LOW_FREQUENCY_2        0x0000000800000000ULL

  But looking over the header files and whatever little documentation about ffmpeg I couldn't find anything that tells me how to assign a specific channel position (or mask, as it's described in the header file) to a specific bus in a mixer audio unit.

  Do you know how to do that ? Please let me know if you want to look at the code I'm using right now.

  And as always, thank you so much.

• How to show watermark in real time with ffmpeg by Node JS & Angular JS

  29 juillet 2016, par Md. Nazmul Hossain Bilash

  I am working with ffmpeg. I have already worked with watermark by ffmpeg. In my process, I have saved that video(which is marked with watermark) & then I am able to show that video. But I want to show watermark in real time. How can I able this ? Need help for this real time show.

  Here is my code :

          try {
  
              var process = new ffmpeg('public/'+req.body.video);
  
              process.then(function (video) {
  
                console.log('The video is ready to be processed');
  
                var watermarkPath = 'public/images/logo.png',
  
                  newFilepath = 'public/videos/watermarked/'+name,
  
                  settings = {
  
                      position        : "SC"      // Position: NE NC NW SE SC SW C CE CW
  
                    , margin_nord     : null      // Margin nord
  
                    , margin_sud      : null      // Margin sud
  
                    , margin_east     : null      // Margin east
  
                    , margin_west     : null      // Margin west
  
                  };
  
                var callback = function (error, files) {
  
                  if(error){
  
                    console.log('ERROR: ', error);
  
                  }
  
                  else{
  
                    console.log('TERMINOU', files);
  
                    res.send('videos/watermarked/'+name)
  
                  }
  
                }
  
                //add watermark
  
                video.fnAddWatermark(watermarkPath, newFilepath, settings, callback)
  
  
  
              }, function (err) {
  
                console.log('Error: ' + err);
  
              });
  
            } catch (e) {
  
              console.log(e.code);
  
              console.log(e.msg);
  
            }