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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 ?

• Mpegts packet corrupt with ffmpeg concat protocol

  1er novembre 2022, par Curious Octopus

  I'm trying to use the concat protocol in ffmpeg as described in the ffmpeg docs :
https://trac.ffmpeg.org/wiki/Concatenate

  


  However I'm getting lots of errors about corrupt packets when running the concat, so I'm worried that this isn't the best approach. My actual use case will involve running unsupervised with a ton of different source videos, so I want to be sure that it's solid.

  


  The concat demuxer approach succeeds without errors but takes about 10 times as long.

  


  Steps to reproduce

  


  Download Big Buck Bunny :

  


  wget https://download.blender.org/demo/movies/BBB/bbb_sunflower_1080p_30fps_normal.mp4


  


  Transcode a 30 second chunk :

  


  ffmpeg -i bbb_sunflower_1080p_30fps_normal.mp4 -ss '00:06:30' -t 30 -c:v libx264 -crf 18 bbb30.mp4


  


  Create one second parts :

  


  mkdir -p parts;
for i in $(seq -f "%02g" 0 29); do \
  ffmpeg \
    -i bbb30.mp4 \
    -ss "00:00:$i" -t 1 \
    -c:v libx264 -pix_fmt yuv420p -crf 18 \
    -bsf:v h264_mp4toannexb \
    -f mpegts \
    -y parts/$i.ts;
done


  


  Combine all the parts into a new output mp4 :

  


  ffmpeg -y \
  -i "concat:parts/00.ts|parts/01.ts|parts/02.ts|parts/03.ts|parts/04.ts|parts/05.ts|parts/06.ts|parts/07.ts|parts/08.ts|parts/09.ts|parts/10.ts|parts/11.ts|parts/12.ts|parts/13.ts|parts/14.ts|parts/15.ts|parts/16.ts|parts/17.ts|parts/18.ts|parts/19.ts|parts/20.ts|parts/21.ts|parts/22.ts|parts/23.ts|parts/24.ts|parts/25.ts|parts/26.ts|parts/27.ts|parts/28.ts|parts/29.ts" \
  -c copy \
  output.mp4


  


  Stderr has lots of warnings about corrupt packets (in this case always at dts = 21300) :

  


  [mpegts @ 0x555d172daa00] Packet corrupt (stream = 0, dts = 213000).
concat:parts/00.ts|parts/01.ts|parts/02.ts|parts/03.ts|parts/04.ts|parts/05.ts|parts/06.ts|parts/07.ts|parts/08.ts|parts/09.ts|parts/10.ts|parts/11.ts|parts/12.ts|parts/13.ts|parts/14.ts|parts/15.ts|parts/16.ts|parts/17.ts|parts/18.ts|parts/19.ts|parts/20.ts|parts/21.ts|parts/22.ts|parts/23.ts|parts/24.ts|parts/25.ts|parts/26.ts|parts/27.ts|parts/28.ts|parts/29.ts: corrupt input packet in stream 0


  


  The resulting mp4 looks ok to my eye, but obviously ffmpeg isn't happy about something. Any ideas ?