doc/ffmpeg: document max_error_rate

doc/ffmpeg.texi

@@ -1739,6 +1739,11 @@ No packets were passed to the muxer, the output is empty.
 No packets were passed to the muxer in some of the output streams.
 @end table
 
+@item -max_error_rate (@emph{global})
+Set fraction of decoding frame failures across all inputs which when crossed
+ffmpeg will return exit code 69. Crossing this threshold does not terminate
+processing. Range is a floating-point number between 0 to 1. Default is 2/3.
+
 @item -xerror (@emph{global})
 Stop and exit on error
 

fftools/ffmpeg_opt.c

@@ -3586,7 +3586,7 @@ const OptionDef options[] = {
     { "debug_ts",       OPT_BOOL | OPT_EXPERT,                       { &debug_ts },
         "print timestamp debugging info" },
     { "max_error_rate",  HAS_ARG | OPT_FLOAT,                        { &max_error_rate },
-        "ratio of errors (0.0: no errors, 1.0: 100% errors) above which ffmpeg returns an error instead of success.", "maximum error rate" },
+        "ratio of decoding errors (0.0: no errors, 1.0: 100% errors) above which ffmpeg returns an error instead of success.", "maximum error rate" },
     { "discard",        OPT_STRING | HAS_ARG | OPT_SPEC |
                         OPT_INPUT,                                   { .off = OFFSET(discard) },
         "discard", "" },