M_SOS             320 jcmarker.c       emit_marker(cinfo, M_SOS);
M_SOS             352 jcmarker.c       emit_marker(cinfo, M_SOS);
M_SOS            1057 jdmarker.c         case M_SOS:
M_SOS             374 rdjpgcom.c         case M_SOS:			/* stop before hitting compressed data */
M_SOS             320 wrjpgcom.c         case M_SOS:			/* should not see compressed data before SOF */