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• FMP4 moof box sequence number ordering

  15 avril 2024, par Daniel

  I wanted to do a basic fragmented mp4 broadcast program with avformat libs and HTML5 video and MSE.

  



  This is a live stream and I use avformat to copy h264 data to mp4 fragments.

  



  Here is my basic drawing of clients attaching to the stream :

  



  

  



  So, with words :

  



  

  1. C1J : First Client joins :


     

     • avformat process starts

     


     • ftyp, moov, moof, mdat boxes will be served to Client1

     


     • ftyp and moov atoms are both saved for later reuse

     


  


  2. C2J : Second Client joins (later in time) :


     

     • avformat process is ongoing (because it is still serving moof and mdat boxes for Client1)

     


     • previously saved ftyp and moov boxes will be served first to Client2

     


     • after ftyp and moov boxes were served, Client2 will join to the stream at the next moof box.

     


  


  



  I have saved an mp4 file to disk from both clients.

  



  Atoms' order within both files looks good : ftype, moov, moof, mdat, moof, mdat...

  



  Both files can be played by media players (like VLC) and also in browsers directly (Opera).

  



  Client1 can be played also via MSE in the browser (Opera), but Client2's stream is not displaying with MSE (Opera).

  



  No errors on the JS console, and media-internals looks also good (at least equivalent with Client1's one).

  



  Now I realized that every moof box contains an mfhd box (header) with a sequenceNumber field.

  



  Of course in Client1's first moof box this sequenceNumber is 1.
However in the later joined Client2's first moof box this sequenceNumber is always >= 1 (in my case it is 16).

  



  What do I need to modify in the moof boxes in Client2 to have a valid fmp4 from the beginning ?

  



  I think Opera's HTML5 video does not like if sequenceNumber does not start from 1, but there shall be other requirements for being it valid.

  


• How to create side by side horizontally stacked video with delay in video and audio using ffmpeg-python ?

  29 juillet 2021, par kup

  I am trying to create a video from two videos that will be stacked horizontally but the resulting video is not what i expected. The same video is appearing on both side (left & right). So wondering how that can be achieved ?

  


  The ffmpeg command i tried, which kinda worked :

  


  ffmpeg -i left.mp4 -i right.mp4 -filter_complex "
[0:v]setpts=PTS-STARTPTS[l]; 
[1:v]setpts=PTS-STARTPTS,tpad=start_duration=14:start_mode=add:color=black[r]; 
[l][r]hstack=inputs=2[stacked]; [0:a][1:a]amix=inputs=2[a]
" -map "[stacked]" -map "[a]" -c:a aac -preset superfast result.mp4


  


  ffmpeg-python script that's not working :

  


  in0 = ffmpeg.input('0.mp4')
in1 = ffmpeg.input('right.mkv')
aout = ffmpeg.filter([in0.audio, in1.audio.filter('adelay', "5000|5000")],'amix')
vout = ffmpeg.filter([inv0.video, inv1.video.filter('tpad', start_duration=5, start_mode='add', color='black')], 'hstack')

(
    ffmpeg
    .concat(vout, aout, v=1, a=1)
    .output("out.mkv")
    .run()
)


  


  This script not resulting in the expected output which two videos side-by-side horizontally stacked.

  


• Compilation of ffmpeg results in error in stdlib.h

  5 octobre 2015, par goldenmean

  I am cross-compiling ffmpeg source to a mips-openwrt target using a toolchain I have built for this platform(MIPS openwrt).

  Then ffmpeg make is giving below errors in uclibc header file stdlib.h as below :

  In file included from ./libavutil/avassert.h:30:0,
  
                   from libavfilter/avfilter.c:23:
  
  /home/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/../../../../mips-openwrt-linux-uclibc/sys-include/stdlib.h:546:14: error: expected identifier or '(' before 'void'
  
  /home/staging_dir/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2/lib/gcc/mips-openwrt-linux-uclibc/4.6.3/../../../../mips-openwrt-linux-uclibc/sys-include/stdlib.h:546:14: error: expected ')' before numeric constant

  The code from the uclibc stdlib.h around that line number is

      #ifdef __USE_ISOC99
  
      __BEGIN_NAMESPACE_C99
  
      /* Terminate the program with STATUS without calling any of the
  
         functions registered with `atexit' or `on_exit'.  */
  
      extern void _Exit (int __status) __THROW __attribute__ ((__noreturn__));
  
      __END_NAMESPACE_C99
  
      #endif
  
  
  
     __BEGIN_NAMESPACE_STD
  
     /* Return the value of envariable NAME, or NULL if it doesn't exist.  */
  
     extern char *getenv (__const char *__name) __THROW __nonnull ((1)) __wur; << This is the line where the compilation error is
  
     __END_NAMESPACE_STD

  Any pointers to resovle this would be helpful.