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• FFmpeg zoom not smooth-centered (but zigzag)

  10 juin 2016, par SebSob

  I try to perform a basic zoompan with FFmpeg. I have an input image (.png 1280x720) and i create an 8 seconds video (.mp4 320x180) from it, with a zoom. This is my command :

  ffmpeg -loop 1 -i in_img.png -c:v libx264 -pix_fmt yuv420p -strict experimental -framerate 25 -vf zoompan=z=’min(zoom+0.011835363,2.1835363)’:d=375:x=400:y=247 -s 320x180 -t 00:00:08.882 out_vid.mp4

  Everything works...but the zoom is not looking okay. It is going zig-zag.

  Does anyone know how to make it zoom smooth, like centered ? (And not first left then right)

  Thanks

  EDIT

  ---

  I’ve come a small step closer to a solution by slightly modifying the ’x’ and ’y’ in the -vf filter (rest of the command is the same as above) :

  -vf
  zoompan=z=’min(zoom+0.022,3.25)’:d=375:x=’if(gte(zoom,3.25),x,x+8.24)’:y=’if(gte(zoom,3.25),y,y+4.72)’:s=1280x720

  I incement x and y every frame (for x +8.24, for y +4.72, i know those values because i know how many frames it takes get to the end-zoom state) so that it will move to its end zoom state coordinate (1011,582), see image :

  
  This is the video of the result, as you can see it does not do the zig-zag effect, but now it looks like its going first to the center and then to the zoomed result. Or is that only an illusion ??
  Any idea’s ?

• Compile FFMPEG for iOS development

  7 avril 2016, par Alec Gamble

  So I’ve been googling around and there seem to be a lot of answers to this questions... for people who know what they’re doing. Unfortunately I am not one of these people. I had a version of FFMPEG I was using in a project and now I want to port that project to iOS. So I have a version of FFMPEG with LAME installed on my desktop and in my C++ application I was just accessing this through the command line via the system() method. I also just downloaded the FFMPEG iOS build from here :

  https://github.com/kewlbear/FFmpeg-iOS-build-script

  and the gas-preprocessor from the link on that page but I’m unsure as to what to do with it now and how to get it to a state where I would be able to compile a basic FFMPEG test to my iPhone.

  ---

  I tried adding the libraries as mentioned in :
  How to Build FFMpeg as iOS Framework so my project hierarchy looks like :

  

  but when I do :

  #import <libavcodec></libavcodec>avcodec.h> as suggested

  or any other import I can think to do it always errors me out saying it can’t find it. I’m not sure if this is because I’m not using search paths correctly or my import line is wrong or what...

• What are all the command `options` to execute with ?

  25 janvier 2023, par Phil Lucks

  I'd like to be able to compress the video in a way to help improve upload times.

  


  In reading the docs for FFMpeg Kit, using React Native, there is a basic execute command string of '-i file1.mp4 -c:v mpeg4 file2.mp4'... I can guess at what some of this means, in terms of input & output file names based on the ffMPEG docs, however, some of these options I am not sure of.

  


  Like why is there a -i flag prefix ? Is this "input" ?
Why is there -c:v ? Is this "convert video" ?
What if I want to reduce frame rate, or change size of video ?

  


  The TS def is just a string...

  


  Is there a good place to understand what the official docs options map to the strings ? I think