ilbmtoppm, pcxtoppm, ppmtoilbm, ppmtoleaf, ppmtomitsu, ppmtompeg, ppmtoneo, ppmtopcx: add pages (#11432)

pages/common/ppmtompeg.md

@@ -0,0 +1,20 @@
+# ppmtompeg
+
+> Encode an MPEG-1 stream.
+> More information: <https://netpbm.sourceforge.net/doc/ppmtompeg.html>.
+
+- Produce an MPEG-1 stream using the parameter file to specify inputs and outputs:
+
+`ppmtompeg {{path/to/parameter_file}}`
+
+- Encode the GOP with the specified number only:
+
+`ppmtompeg -gop {{gop_num}} {{path/to/parameter_file}}`
+
+- Specify the first and last frame to encode:
+
+`ppmtompeg -frames {{first_frame}} {{last_frame}} {{path/to/parameter_file}}`
+
+- Combine multiple MPEG frames into a single MPEG-1 stream:
+
+`ppmtompeg -combine_frames {{path/to/parameter_file}}`