<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def skip(self, video_name, out, start, duration):
 """ Skips a section of the clip @param video_name : name of video input file @param out : name of output file @param start : start time of the skip (seconds) @param duration : duration of the skip (seconds) """

        cfilter = (r"[0:v]trim=duration={start}[av];"
                   r"[0:a]atrim=duration={start}[aa];"
                   r"[0:v]trim=start={offset},setpts=PTS-STARTPTS[bv];"
                   r"[0:a]atrim=start={offset},asetpts=PTS-STARTPTS[ba];"
                   r"[av][bv]concat[outv];[aa][ba]concat=v=0:a=1[outa]")\
            .format(start=start, offset=start + duration)\
            .replace(' ', '')

        command = ['ffmpeg', '-i', video_name,
            '-filter_complex', cfilter, '-y',
            '-map', '[outv]',
            '-map', '[outa]', '-c:v', 'huffyuv', '-preset', 'veryslow',
            out]

        if self.verbose:
            print 'Skipping {0} into {1}'.format(video_name, out)
            print ' '.join(command)

        call(command)