ppmtoy4m: invalid option -- '-' **ERROR: [ppmtoy4m] For usage hints, use option '-h'. Please take a hint.

usage: ppmtoy4m [options] [ppm-file] Reads RAW PPM image(s), and produces YUV4MPEG2 stream on stdout. Converts computer graphics R'G'B' colorspace to digital video Y'CbCr, and performs chroma subsampling. If 'ppm-file' is not specified, reads from stdin. options: (defaults specified in []) -o n frame offset (skip n input frames) [0] -n n frame count (output n frames; 0 == all of them) [0] -F n:d framerate [30000:1001 = NTSC] -A w:h pixel aspect ratio [1:1] -I x interlacing [p] p = none/progressive t = top-field-first b = bottom-field-first -L treat PPM images as 2-field interleaved -r repeat last input frame -S mode chroma subsampling mode [444] '420jpeg' -> 4:2:0 JPEG/MPEG-1 (interstitial) '420mpeg2' -> 4:2:0 MPEG-2 (horiz. cositing) '444' -> 4:4:4 (no subsampling) -v n verbosity (0,1,2) [1] -B PPM image is packed with BGR pixels [RGB]