ffmpeg cpu preso em 99%

Question

Eu recebo isso algumas vezes ao usar o ffmpeg

Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg -> mjpeg)
Press [q] to stop, [?] for help
Input stream #0:0 frame changed from size:559x1425 fmt:yuvj420p to size:429x323 fmt:yuvj420p
Input stream #0:0 frame changed from size:429x323 fmt:yuvj420p to size:800x600 fmt:yuvj420p
Input stream #0:0 frame changed from size:800x600 fmt:yuvj420p to size:260x259 fmt:yuvj420p
Input stream #0:0 frame changed from size:260x259 fmt:yuvj420p to size:240x160 fmt:yuvj444p
Input stream #0:0 frame changed from size:240x160 fmt:yuvj444p to size:648x783 fmt:yuvj420p
Input stream #0:0 frame changed from size:648x783 fmt:yuvj420p to size:340x254 fmt:yuvj420p
Input stream #0:0 frame changed from size:340x254 fmt:yuvj420p to size:260x259 fmt:yuvj420p
Input stream #0:0 frame changed from size:260x259 fmt:yuvj420p to size:500x438 fmt:yuvj444p
Input stream #0:0 frame changed from size:500x438 fmt:yuvj444p to size:391x512 fmt:yuvj444p
Input stream #0:0 frame changed from size:391x512 fmt:yuvj444p to size:300x225 fmt:yuvj422p

congelamento ffmpeg htop diz que o processador está em 99%

Eu olho se é o jpg que é o problema, não é e quando eu faço novamente o comando ffmpeg ffmpeg ffmpeg -y -f image2 -r 1/5 -i out-%02d.jpg out.avi funciona.

Parece que no meu loop, por vezes, o ffmpeg congela e faz o processador em 99%. Alguma idéia

Obrigado

Eu uso a última versão link