ffmpeg: add max_error_rate to allow tuning the point decoding errors are considered a failure of the whole transcoding.

Suggested-by: Daemon404
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -3420,7 +3420,7 @@ int main(int argc, char **argv)
     }
     av_log(NULL, AV_LOG_DEBUG, "%"PRIu64" frames successfully decoded, %"PRIu64" decoding errors\n",
            decode_error_stat[0], decode_error_stat[1]);
-    if (2*decode_error_stat[0] < decode_error_stat[1])
+    if ((decode_error_stat[0] + decode_error_stat[1]) * max_error_rate < decode_error_stat[1])
         exit_program(69);
 
     exit_program(received_nb_signals ? 255 : 0);

ffmpeg.h

@@ -420,6 +420,7 @@ extern int qp_hist;
 extern int stdin_interaction;
 extern int frame_bits_per_raw_sample;
 extern AVIOContext *progress_avio;
+extern float max_error_rate;
 
 extern const AVIOInterruptCB int_cb;
 

ffmpeg_opt.c

@@ -84,6 +84,7 @@ int print_stats       = -1;
 int qp_hist           = 0;
 int stdin_interaction = 1;
 int frame_bits_per_raw_sample = 0;
+float max_error_rate  = 2.0/3;
 
 
 static int intra_only         = 0;
@@ -2717,6 +2718,8 @@ const OptionDef options[] = {
         "extract an attachment into a file", "filename" },
     { "debug_ts",       OPT_BOOL | OPT_EXPERT,                       { &debug_ts },
         "print timestamp debugging info" },
+    { "max_error_rate",  HAS_ARG | OPT_FLOAT,                        { &max_error_rate },
+        "maximum error rate", "ratio of errors (0.0: no errors, 1.0: 100% errors) above which ffmpeg returns an error instead of success." },
 
     /* video options */
     { "vframes",      OPT_VIDEO | HAS_ARG  | OPT_PERFILE | OPT_OUTPUT,           { .func_arg = opt_video_frames },