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• How to Capture the Desktop and System Sounds using FFMPEG and C ?

  3 décembre 2014, par CaptainObvious

  I’m new to multimedia programming, but have lots of experience in programming in C in general. I want to develop my own program to capture( record ) the desktop and save it to a youtube compatible file using the ffmpeg API. Due to my inexperience in the multimedia field, I don’t know where to start looking in the ffmpeg API for such a function or the terminology commonly used to refer to such functionality. I’ve tried googling to see if I could find any examples or tutorials or how to use ffmpeg to do something similar to this, but I have found nothing except the ways it can be done using the pre-compiled programs on the command line. The only tutorial I have found relating to ffmpeg and C was Dranger’s tutorial, but that only covers how to make a simple video player. Can someone provide an example or direct me to the correct line of API calls in order to implement such a program ?

• Pointers returned by xlib don't match any existing window IDs

  1er septembre 2022, par Kroltan

  I'm using some X11 bindings to query some window information and later pass it to FFmpeg. FFmpeg expects a "window ID" given in hexadecimal notation.

  


  This notation seems somewhat standard, as it is returned by programs like xwininfo or wmctrl. I haven't found much information about it, but it seems to just be the hexadecimal representation of the window pointer ? If I take the ID string given by these programs and give it to FFmpeg, it is able to capture the window correctly :

  


  $ xwininfo

xwininfo: Please select the window about which you
          would like information by clicking the
          mouse in that window.

xwininfo: Window id: 0x2800014 "Desktop — Plasma"

$ ffmpeg -f x11grab -window_id 0x2800014 -i :0+0,0 -f apng -vframes 1 out.png
# works fine


  


  However, if I try listing all the windows in code :

  


  var root = Window.None;
var parent = Window.None;
Xlib.XQueryTree(_display, Xlib.XDefaultRootWindow(_display), ref root, ref parent, out var children);

var ids = children
    .Select(ptr => $"0x{(ulong) ptr:x}")
    .ToArray();


  


  I don't see 0x2800014 in the results (even disregardingleading zeroes), and if I try running FFmpeg on one of those results, it fails terribly :

  


  $ ffmpeg -f x11grab -window_id 0x4400003 -i :0+0,0 -f apng -vframes 1

# snipped for brevity

Trailing option(s) found in the command: may be ignored.
[x11grab @ 0x55b811a8da40] Cannot get the image data event_error: response_type:0 error_code:8 sequence:10 resource_id:167772160 minor_code:4 major_code:130.
[x11grab @ 0x55b811a8da40] Continuing without shared memory.
[x11grab @ 0x55b811a8da40] Cannot get the image data event_error: response_type:0 error_code:8 sequence:11 resource_id:71303171 minor_code:0 major_code:73.
Input #0, x11grab, from ':0+0,0':
  Duration: N/A, bitrate: 38361 kb/s
  Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 200x200, 38361 kb/s, 29.97 fps, 1000k tbr, 1000k tbn
At least one output file must be specified


  


  So I must conclude my guess that they are hex pointers is incorrect, or that the Window type is not the pointer itself, but then the question stands, how can I get the actual window IDs so I can pass them to FFmpeg ?

  


• What is ffmpeg, avcodec, x264 ? [closed]

  11 septembre 2020, par onmyway133

  From wiki, I read that

  



  


  FFmpeg is a free software project that produces libraries and programs
 for handling multimedia data. The most notable parts of FFmpeg are
 libavcodec, an audio/video codec library used by several other
 projects, libavformat, an audio/video container mux and demux library,
 and the ffmpeg command line program for transcoding multimedia files.

  


  



  So ffmpeg is a wrapper of avcodec ? And I often hear that people encode video with x264 using ffmpeg. So ffmpeg is also a wrapper of x264 ?

  



  How are they related ?