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• GStreamer : cannot link elements

  9 septembre 2018, par Han Jingyu

  when rosruning my own project, I got an unexpected error as below
  I was guessing it was caused by some problems encountered in the process of installing OpenCV.So I reinstalled and recompiled the opencv, but this error still exists.
  then I noticed the message, GStreamer : cannot link elements. I was thinking it probably related to GStreamer. Unfortunately, I don’t know how to fix this problem. little clues would be appreciated.

  ** (ros_exploration:14898): CRITICAL **: gst_missing_encoder_message_new: assertion 'gst_caps_is_fixed (encode_caps)' failed         
  
    (ros_exploration:14898): GStreamer-CRITICAL **: gst_element_post_message: assertion 'message != NULL' failed
  
      OpenCV Error: Unspecified error (GStreamer: cannot link elements        
  
          ) in CvVideoWriter_GStreamer::open, file /home/htf/Downloads/opencv-2.4.13.6/modules/highgui/src/cap_gstreamer.cpp, line 1464
  
      Qt has caught an exception thrown from an event handler. Throwing
  
      exceptions from an event handler is not supported in Qt. You must
  
      reimplement QApplication::notify() and catch all exceptions there.
  
      terminate called after throwing an instance of 'cv::Exception'
  
        what():  /home/htf/Downloads/opencv-2.4.13.6/modules/highgui/src/cap_gstreamer.cpp:1464: error: (-2) GStreamer: cannot link elements
  
       in function CvVideoWriter_GStreamer::open
  
  
  
     Aborted (core dumped)

• Batch convert MP3 and static image to AVI with FFMPEG

  8 décembre 2013, par user3027136

  I'm tired of searching for this problem. I have found 2 solutions here, but both work only partially.
  What I want to do is to convert all the MP3 inside a folder (if possible subfolders, too) to avi or anything else accepted by Youtube. I have created 2 .bat that should do this (according to the other threads here). They don't, one of them creates the avi without the image (black) and the other seems to capture the screen.
  Here they are.
  If you know about ffmpeg please point me to the right direction. Thank you.

  This one uses mp3info.exe - to be honest I have no idea what mp3info does, I just guess it finds the lenght of the song to be mathed later with the length of the video.

  @echo off
  
  for %%a in (*.mp3) do (
  
  for /f "delims=" %%b in ('mp3info.exe -p %%S "%%a"') do (
  
  ffmpeg -i "%%a" -loop 1 -r 1 -i "cover.jpg" -acodec copy "%%~na.mp4" -t %%b
  
  )
  
  )

  This seems more simple, runs faster but captures the screenshot and ignores the cover.jpg file.

  @echo off
  
  for %%A IN (*.mp3) DO ffmpeg -i "%%A" -i "cover.jpg" "%%A.mpg"
  
  done

  mp2info.exe, cover.jpeg and the .bat scripts are in the same folder with the .mp3 files.

• Why doesn't the lame mp3 codec (libmp3lame) create XingHeaders ?

  5 novembre 2012, par user784637

  I downloaded a video from youtube whose audio was encoded in aac and transcoded it to an mp3 using the libmp3lame codec.

  $ ffmpeg -i video.mp4 -vn -acodec libmp3lame -- test.mp3

  Now when I try to write id3 tags to it using the taglib example tagwriter I get the following warning :

  $ ./testwriter -t 'stuff' test.mp3
  
  TagLib: MPEG::XingHeader::parse() -- Xing header doesn't contain the total stream size.

  The id3 tags are written and display correctly, but the lack of the XingHeaders causes older players to loop the song several times.

  Why doesn't the lame mp3 codec create XingHeaders ? How do I create XingHeaders ?