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• Convert audio download with youtube-dl to flac ?

  16 mars 2017, par Urasam

  is it possible to download a youtube video as e.g. mp3 and then convert it to flac with ffmpeg ? I can specify the arguments that ffmpeg shall use after the download with —postprocessor-args but I don’t know how to get the file name there.

  —postprocessor-args "-i downloadedfile.xxx -c:a flac downloadedfile.flac"

  This would be the argument i want to use. Is this possible ?

• Playing a custom avi data stream using QtMultimedia

  26 décembre 2015, par sbabbi

  I need to play back a custom AVI file that contains a classic video stream, an audio stream but also a custom data stream.

  The custom stream contains data that is visualized by some custom widgets ; those widgets only need that each custom frame is written in a buffer at the proper time.

  Our application is based on Qt, and already uses QMediaPlayer/QVideoWidget to play traditional videos, but the additional custom stream makes things more complicated, because AFAIK QMediaPlayer only plays the video/audio and ignores everything else.

  I would like to avoid to reinvent the entire qt-multimedia, but I am not sure how to make the best out of the available Qt classes.

  ---

  My ideas so far are :

  1. Write a custom media player class that demuxes and decodes the video using ffmpeg, implements the timing, uses QAudioOutput for playing the audio, produces a stream of QVideoFrames to be played on the video and write the custom data to some buffer for visualization.

     The problem : In order to avoid writing the code to rescale/convert the video frames, I would like to reuse QVideoWidget, but it seems to work only with the "real" QMediaPlayer.

  2. Demux the input file and feed QMediaPlayer with the AV streams.
     Demux the input with ffmpeg (possibly leaving the decoding to the Qt backend), have one QIODevice to retrieve only the video/audio streams from the input file and another one to retrieve the data stream. Play the video/audio with QMediaPlayer.

                   +-------+                          
     
                   | QFile |                          
     
                   +---^---+                          
     
                       |                              
     
                    inherits                          
     
                       |                              
     
             +--------------------+
     
             |    MyAviDemuxer    |
     
             |                    |
     
             |  holds a queue of  |
     
             |  demuxed packets   |
     
             +--------------------+
     
             |                    |
     
       readDataPacket      readVideoPacket
     
             |                    |
     
     +-------v--------+  +--------v-----------+            +-----------+
     
     | MyCustomReader |  | MyVideoAudioStream +--inherits--> QIODevice |
     
     +----------------+  +--------+-----------+            +-----------+
     
                                  |       
     
                               setMedia                  
     
                                  |                  
     
                          +-------v-------+           
     
                          | QMediaPlayer  |           
     
                          +---------------+           

     The problem : synchronize the timing of the data stream with QMediaPlayer, handle headers and metadata correctly.

  ---

  I am slightly inclined to option 1, just because it gives me more control, but I am wondering if I missed an easier solution (even Windows-only).

• add custom date on video with ffmpeg android

  14 avril 2016, par val_cher

  I used this command for current time "drawtext=fontsize=60:fontfile=/storage/emulated/0/Roboto-Regular.ttf:fontcolor=white:text=’%localtime’:x=0:y=h/2-ascent"
  but it shows encoded time start from current
  And i want video duration from custom date time