ffmpeg: add option stats_period

At present, progress stats are updated at a hardcoded interval of
half a second. For long processes, this can lead to bloated
logs and progress reports.

Users can now set a custom period using option -stats_period
Default is kept at 0.5 seconds.

doc/ffmpeg.texi

@@ -675,14 +675,19 @@ Specify the preset for matching stream(s).
 Print encoding progress/statistics. It is on by default, to explicitly
 disable it you need to specify @code{-nostats}.
 
+@item -stats_period @var{time} (@emph{global})
+Set period at which encoding progress/statistics are updated. Default is 0.5 seconds.
+
 @item -progress @var{url} (@emph{global})
 Send program-friendly progress information to @var{url}.
 
-Progress information is written approximately every second and at the end of
+Progress information is written periodically and at the end of
 the encoding process. It is made of "@var{key}=@var{value}" lines. @var{key}
 consists of only alphanumeric characters. The last key of a sequence of
 progress information is always "progress".
 
+The update period is set using @code{-stats_period}.
+
 @anchor{stdin option}
 @item -stdin
 Enable interaction on standard input. On by default unless standard input is

fftools/ffmpeg.c

@@ -1699,7 +1699,7 @@ static void print_report(int is_last_report, int64_t timer_start, int64_t cur_ti
             last_time = cur_time;
             return;
         }
-        if ((cur_time - last_time) < 500000)
+        if ((cur_time - last_time) < stats_period)
             return;
         last_time = cur_time;
     }

fftools/ffmpeg.h

@@ -614,6 +614,7 @@ extern int debug_ts;
 extern int exit_on_error;
 extern int abort_on_flags;
 extern int print_stats;
+extern int64_t stats_period;
 extern int qp_hist;
 extern int stdin_interaction;
 extern int frame_bits_per_raw_sample;

fftools/ffmpeg_opt.c

@@ -174,6 +174,7 @@ int filter_nbthreads = 0;
 int filter_complex_nbthreads = 0;
 int vstats_version = 2;
 int auto_conversion_filters = 1;
+int64_t stats_period = 500000;
 
 
 static int intra_only         = 0;
@@ -282,6 +283,21 @@ static int opt_abort_on(void *optctx, const char *opt, const char *arg)
     return av_opt_eval_flags(&pclass, &opts[0], arg, &abort_on_flags);
 }
 
+static int opt_stats_period(void *optctx, const char *opt, const char *arg)
+{
+    int64_t user_stats_period = parse_time_or_die(opt, arg, 1);
+
+    if (user_stats_period <= 0) {
+        av_log(NULL, AV_LOG_ERROR, "stats_period %s must be positive.\n", arg);
+        return AVERROR(EINVAL);
+    }
+
+    stats_period = user_stats_period;
+    av_log(NULL, AV_LOG_INFO, "ffmpeg stats and -progress period set to %s.\n", arg);
+
+    return 0;
+}
+
 static int opt_sameq(void *optctx, const char *opt, const char *arg)
 {
     av_log(NULL, AV_LOG_ERROR, "Option '%s' was removed. "
@@ -3557,6 +3573,8 @@ const OptionDef options[] = {
         "enable automatic conversion filters globally" },
     { "stats",          OPT_BOOL,                                    { &print_stats },
         "print progress report during encoding", },
+    { "stats_period",    HAS_ARG | OPT_EXPERT,                       { .func_arg = opt_stats_period },
+        "set the period at which ffmpeg updates stats and -progress output", "time" },
     { "attach",         HAS_ARG | OPT_PERFILE | OPT_EXPERT |
                         OPT_OUTPUT,                                  { .func_arg = opt_attach },
         "add an attachment to the output file", "filename" },