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• FFmpeg : How to split video efficiently ?

  4 novembre 2023, par Antony

  I wish to split a large avi video into two smaller consecutive videos. I am using ffmpeg.

  



  One way is to run ffmpeg two times :

  



  ffmpeg -i input.avi -vcodec copy -acodec copy -ss 00:00:00 -t 00:30:00 output1.avi
ffmpeg -i input.avi -vcodec copy -acodec copy -ss 00:30:00 -t 00:30:00 output2.avi


  



  But according to manpage of ffmpeg, I can make more than one ouput file from one input file using just one line :

  



  ffmpeg -i input.avi -vcodec copy -acodec copy -ss 00:00:00 -t 00:30:00 output1.avi \
   -vcodec copy -acodec copy -ss 00:30:00 -t 00:30:00 output2.avi


  



  My question is, does the later approach save computation time and memory ?

  


• Merge multiple videos without using command line-FFMPEG [on hold]

  19 avril 2018, par Valgrind1691

  I am developing an android application which has video processing features involved.
  For video processing I have been working with FFMPEG library. As for now ffmpeg is directly being consumed by android and the processing is being done by
  framing commands and executing it using ffmpeg executable running in the background.
  This approach has two drawbacks :

  1) Video Processing time is huge even after trying ultrafast and other options to reduce processing

  2) APK size is large

  For solving two major problems we seek c/c++ native implementation for video processing by using the ffmpeg code.
  The C/C++ code will be cross compiled for android and iOS platforms and provided to mobile platform as a library (.so file in case of Android)
  The .so file will have

  1. jni for communication between Android(java) and c/c+

  2. c++ code for functionality implementation of video processing. All
     the video processing i.e scaling, transcoding, merging,
     cropping etc will be done by C/C++ code.

  I have a query around the C/C++ side , how can we use ffmpeg not to process using command line rather we can define algorithms for the process. Transcoding, muxing etc I have achieved looking into the examples of ffmpeg but I am still unable to figure out algorithm for merging of multiple(upto 6) videos in a single video file.
  I have looked into every question posted in this context and none helped.
  Can someone help me merge videos using source code of ffmpeg without using command line ? Any help is appreciated.

• Convert mp4 file with subtitles to compressed gif

  12 mars 2018, par CoXier

  There is a mp4 file whose size is 1.1 MB. Now I want to burn in subtitles to it then convert it to gif.

  Here is my step.

  First remove audio

  As I don’t need audio so I remove audio and size changes from 1.1MB to 784KB.

  # remove audio
  
  ffmpeg -i input.mp4 -c copy -an input_nosound.mp4

  Second resize mp4 file

  In order to resize reulst gif, I resize input mp4 file. Now its size changes from 784KB to 298KB.

  # resize
  
  ffmpeg -i input_nosound.mp4 -s 250x150 -c:a copy input_resize.mp4

  Third add subtitles

  This step is normal. After that size changes from 298KB to 290KB.

  ffmpeg -i input_resize.mp4 -vf ass=subtitles.ass output.mp4

  Fourth speed up video.

  Speeding up video lightly can also reduce size from 290KB to 247KB.

  ffmpeg -i output.mp4 -an  -filter:v "setpts=0.8*PTS" output_speed.mp4

  Firth convert mp4 to gif

  I convert mp4 to gif. The size of gif is 3MB.

  ffmpeg -y -i output_speed.mp4 -vf palettegen palette.png
  
  ffmpeg -y -i output_speed.mp4 -i palette.png -filter_complex paletteuse -r 8 animation.gif

  Finally compress gif

  I use https://github.com/kornelski/giflossy/ to compress gif. Finally the output.gif is 1.5MB. However I think it’s also too large. Is there any acceptable way to compress smaller than 1MB.

  In additional, I am not familiar with ffmpeg so if you think my question is not good please tell me.