fftools/ffmpeg: deprecate -adrift_threshold

This option has had no effect since -async was removed in
3d86a13b47

doc/ffmpeg.texi

@@ -1749,12 +1749,6 @@ The default is -1.1. One possible usecase is to avoid framedrops in case
 of noisy timestamps or to increase frame drop precision in case of exact
 timestamps.
 
-@item -adrift_threshold @var{time}
-Set the minimum difference between timestamps and audio data (in seconds) to trigger
-adding/dropping samples to make it match the timestamps. This option effectively is
-a threshold to select between hard (add/drop) and soft (squeeze/stretch) compensation.
-@code{-async} must be set to a positive value.
-
 @item -apad @var{parameters} (@emph{output,per-stream})
 Pad the output audio stream(s). This is the same as applying @code{-af apad}.
 Argument is a string of filter parameters composed the same as with the @code{apad} filter.

fftools/ffmpeg.h

@@ -55,6 +55,7 @@
 #define FFMPEG_OPT_MAP_SYNC 1
 #define FFMPEG_ROTATION_METADATA 1
 #define FFMPEG_OPT_QPHIST 1
+#define FFMPEG_OPT_ADRIFT_THRESHOLD 1
 
 enum VideoSyncMethod {
     VSYNC_AUTO = -1,
@@ -728,7 +729,6 @@ extern int        nb_filtergraphs;
 extern char *vstats_filename;
 extern char *sdp_filename;
 
-extern float audio_drift_threshold;
 extern float dts_delta_threshold;
 extern float dts_error_threshold;
 

fftools/ffmpeg_opt.c

@@ -1347,6 +1347,14 @@ static int opt_qphist(void *optctx, const char *opt, const char *arg)
 }
 #endif
 
+#if FFMPEG_OPT_ADRIFT_THRESHOLD
+static int opt_adrift_threshold(void *optctx, const char *opt, const char *arg)
+{
+    av_log(NULL, AV_LOG_WARNING, "Option -%s is deprecated and has no effect\n", opt);
+    return 0;
+}
+#endif
+
 #define OFFSET(x) offsetof(OptionsContext, x)
 const OptionDef options[] = {
     /* main options */
@@ -1453,8 +1461,10 @@ const OptionDef options[] = {
         "set video sync method globally; deprecated, use -fps_mode", "" },
     { "frame_drop_threshold", HAS_ARG | OPT_FLOAT | OPT_EXPERT,      { &frame_drop_threshold },
         "frame drop threshold", "" },
-    { "adrift_threshold", HAS_ARG | OPT_FLOAT | OPT_EXPERT,          { &audio_drift_threshold },
-        "audio drift threshold", "threshold" },
+#if FFMPEG_OPT_ADRIFT_THRESHOLD
+    { "adrift_threshold", HAS_ARG | OPT_EXPERT,                      { .func_arg = opt_adrift_threshold },
+        "deprecated, does nothing", "threshold" },
+#endif
     { "copyts",         OPT_BOOL | OPT_EXPERT,                       { &copy_ts },
         "copy timestamps" },
     { "start_at_zero",  OPT_BOOL | OPT_EXPERT,                       { &start_at_zero },