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• How to convert MP4 to MP3 in VLC using Command-Prompt ?

  9 juillet 2016, par user6472523

  I have close to 0 programming experience but would like to figure out how to do this and have been trying to figure out how to do this for awhile. I’m getting very frustrated - wish I could understand it. I’m trying to convert a bunch of MP4 files to MP3 files. I would like to keep the original file and just spit out a bunch of MP3 files with same name as the original file.

  From here : https://wiki.videolan.org/How_to_Batch_Encode/

  Apparently, all you need to do is use this code in the Command-Prompt. I have never really used the Command-Prompt before so no idea what to do.

  FOR /R %%G IN (*.m4a) DO (CALL :SUB_VLC "%%G")
  
  FOR /R %%G IN (*.m4a.mp*) DO (CALL :SUB_RENAME "%%G")
  
  GOTO :eof
  
  
  
  :SUB_VLC
  
   SET _firstbit=%1
  
   SET _qt="
  
   CALL SET _newnm=%%_firstbit:%_qt%=%%
  
   SET _commanm=%_newnm:,=_COMMA_%
  
   REM echo %_commanm%
  
   CALL "C:\Program Files\VideoLAN\VLC\vlc" -I dummy -vvv %1 --sout=#transcode{acodec="mpga",ab="512","channels=2",samplerate="44100"}:standard{access="file",mux="mpeg1",dst="%_commanm%.mp3"} vlc://quit
  
  GOTO :eof
  
  
  
  :SUB_RENAME
  
   SET _origfnm=%1
  
   SET _endbit=%_origfnm:*.m4a=%
  
   CALL SET _newfilenm=%%_origfnm:.m4a%_endbit%=.mp3%%
  
   SET _newfilenm=%_newfilenm:_COMMA_=,%
  
   COPY %1 %_newfilenm%
  
   DEL %1
  
  GOTO :eof
  
  
  
  :eof

  1. So far I changed the directory in the Command-Prompt to the
     folder where the MP4 files are located.
  2. In the code, I’ve changed all mention of .m4a to .mp4.
  3. I’ve change mpga to mp3.
  4. I’ve changed "C :\Program Files\VideoLAN\VLC\vlc" to where my vlc program
     is located.

  What else do I need to do ? And what do all the %% mean in the code ?

  Thank you so much !

• c FFmpeg undefined refference error [duplicate]

  14 août 2017, par galagala

  This question already has an answer here :

  • What is an undefined reference/unresolved external symbol error and how do I fix it ?
    
    28 answers
    

  I want to write my own video player, so I am trying to use FFmpeg with C.
  I am using Ubuntu 16.04.3 LTS and compile FFmpeg following this tutorial https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu

  after that I did add libavcodec.a to linker setting list and the source code path to search directory (using codeblocks)

  but my code still get error : undefined refference to "avcodec_register_all()"

  #include 
  
  #include "libavcodec/avcodec.h"
  
  int main()
  
  {
  
      avcodec_register_all();
  
      return 0;
  
  }

  after that, I search the libavcodec folder
  I did find avcodec.h and void avcodec_register_all(void) defined in it
  but I couldn’t find avcodec.c in the folder

  Is that normal ? and is that the reason why I got undefined reference error ?
  how to fix it ?

• AVI to MP4 - ffmpeg conversion

  4 juin 2014, par Emmanuel Brunet

  I’m running a debian 7.5 machine with ffmpeg-2.2 installed following these instructions

  Issue

  I’m trying to display a mp4 video inside my browser. The original file has an AVI container format. I can successfully convert it to mp4 and the targetfile is readable (video + sound) with the totem movie player. So I thought everything would be OK displaying the bellow page

  HTML5 web page

      
  
  
  
  
  
  <video width="640" height="480" controls="controls">
  
    <source src="/path/to/output.mp4" type="video/mp4">
  
  <h3>Your browser does not support the video tag</h3>
  
  </source></video>

  Input probe

  $ ffprobe -show_streams input.avi
  
  
  
    Duration: 00:08:22.90, start: 0.000000, bitrate: 1943 kb/s
  
      Stream #0:0: Audio: mp3 (U[0][0][0] / 0x0055), 48000 Hz, stereo, s16p, 64 kb/s
  
      Stream #0:1: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 720x540 [SAR 1:1 DAR 4:3], 1870 kb/s, 29.97 fps, 25 tbr, 29.97 tbn, 25 tbc

  Convert

  $ ffmpeg -y -fflags +genpts -i input.avi -acodec copy -vcodec copy ouput.mp4

  Html browser

  Opening the above html file plays sound but no video is displayed.

  When I use other .mp4 files, videos succesfully displayed so I’m sure I face a conversion issue.

  Not : I’ve tryed a lot of other ffmpeg options but without success.

  Any idea ?

  Thanks in advance.