title: ffmpeg speed encoding problem
body: <p>I am currently developing an application that makes capturing video from a webcam on Linux using the Qt Designer tool and V4L2 and ffmpeg libraries under C + +, to capture the image there is no problem using lib V4L2, and since That a picture is ready I send it to the encoder which is based on ffmpeg libs, initially the encoder creates a video file, and it receives images to encode it in this file, my problem is as follows: the encoding is normally done, but  after if I start playing the recorded video file, speed appears to be accelerated compared to the regular speed! So what is clear, the problem is in video encoding,
  my question is, is there a method or function that manages ffmpeg encoding speed pictures ?????
  thank you for your help.</p>