[FFmpeg-user] Fix of the program ffmpeg to improve performance when working with QSV.

[Сергей Граматчиков]

FFmpeg can simultaneously decode + encode 6 full hd chanell qsv using a
single processor. But tvheadend https://github.com/TheTroll/tvheadend can
decode + encode 12 full hd chanell using qsv on a single processor, in
general, twice the performance. This suggests that the program itself is
not enough ffmpeg code to achieve this performance. It is necessary to
build upon. Tell someone can help solve this problem?