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• How to create videos with small file size but large resolution ?

  13 février 2017, par Gregory Magarshak

  Is there a programmatic way to create videos that capture, essentially, a powerpoint presentation, that would be not much larger than the audio + screenshots of the powerpoint itself ?

  I want to make software that produces videos with the full resolution of a powerpoint on a large screen, and with a person speaking over it and wvwn doodling. Kind of like "bcontext" software. And then I want to export videos for youtube and other places to be hosted. But I want them to be SMALL. So they can be downloaded by people with slow connections eg in India.

  What factors can affect video size and how can i take advantage of the relative "stillness" of most pixels at most times to make the compression preserve the full sharpness and yet take advantage of the lack of visual changes ? What software do you recommend ?

• ffmpeg - adding Dynamic logo & random position watermark to video ?

  9 août 2021, par JackS

  I am making a tutorial for sending through mail to my uses, and to avoid piracy distribution I thought to put watermarks (logo.png) at random places at interval on the videos.

  


  I tried using the command from ffmpeg - Dynamic letters and random position watermark to video ? :

  


  ffmpeg -i input.mp4 \
-vf \
"drawtext=fontfile=font.ttf:fontsize=80:fontcolor=yellow@0.5:text='studentname': \
 x=if(eq(mod(t\,30)\,0)\,rand(0\,(W-tw))\,x): \
 y=if(eq(mod(t\,30)\,0)\,rand(0\,(H-th))\,y)" \
-c:v libx264 -crf 23 -c:a copy output.mp4


  


  But it gave me error :

  


  [NULL @ 0x55c812525600] Unable to find a suitable output format for '\'
\: Invalid argument


  


• libavutil : Add wchartoutf8(), wchartoansi(), utf8toansi(), getenv_utf8(), freeenv_utf...

  20 juin 2022, par Nil Admirari

  libavutil : Add wchartoutf8(), wchartoansi(), utf8toansi(), getenv_utf8(), freeenv_utf8() and getenv_dup()
  wchartoutf8() converts strings returned by WinAPI into UTF-8,
  
  which is FFmpeg's preffered encoding.
  Some external dependencies, such as AviSynth, are still
  
  not Unicode-enabled. utf8toansi() converts UTF-8 strings
  
  into ANSI in two steps : UTF-8 -> wchar_t -> ANSI.
  
  wchartoansi() is responsible for the second step of the conversion.
  
  Conversion in just one step is not supported by WinAPI.
  Since these character converting functions allocate the buffer
  
  of necessary size, they also facilitate the removal of MAX_PATH limit
  
  in places where fixed-size ANSI/WCHAR strings were used
  
  as filename buffers.
  On Windows, getenv_utf8() wraps _wgetenv() converting its input from
  
  and its output to UTF-8. Strings returned by getenv_utf8()
  
  must be freed by freeenv_utf8().
  On all other platforms getenv_utf8() is a wrapper around getenv(),
  
  and freeenv_utf8() is a no-op.
  The value returned by plain getenv() cannot be modified ;
  
  av_strdup() is usually used when modifications are required.
  
  However, on Windows, av_strdup() after getenv_utf8() leads to
  
  unnecessary allocation. getenv_dup() is introduced to avoid
  
  such an allocation. Value returned by getenv_dup() must be freed
  
  by av_free().
  Because of cleanup complexities, in places that only test the existence
  
  of an environment variable or compare its value with a string
  
  consisting entirely of ASCII characters, the use of plain getenv()
  
  is still preferred. (libavutil/log.c check_color_terminal()
  
  is an example of such a place.)
  Plain getenv() is also preffered in UNIX-only code,
  
  such as bktr.c, fbdev_common.c, oss.c in libavdevice
  
  or af_ladspa.c in libavfilter.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] configure
  • [DH] libavutil/getenv_utf8.h
  • [DH] libavutil/wchar_filename.h