avfilter/af_afir: adjust min partition size

Minimal value allowed by our FFT is 16 thus min partition size is 8.

doc/filters.texi

@@ -1233,12 +1233,12 @@ Set video stream frame rate. This option is used only when @var{response} is ena
 
 @item minp
 Set minimal partition size used for convolution. Default is @var{8192}.
-Allowed range is from @var{16} to @var{32768}.
+Allowed range is from @var{8} to @var{32768}.
 Lower values decreases latency at cost of higher CPU usage.
 
 @item maxp
 Set maximal partition size used for convolution. Default is @var{8192}.
-Allowed range is from @var{16} to @var{32768}.
+Allowed range is from @var{8} to @var{32768}.
 Lower values may increase CPU usage.
 @end table
 

libavfilter/af_afir.c

@@ -842,8 +842,8 @@ static const AVOption afir_options[] = {
     { "channel", "set IR channel to display frequency response", OFFSET(ir_channel), AV_OPT_TYPE_INT, {.i64=0}, 0, 1024, VF },
     { "size",   "set video size",    OFFSET(w),          AV_OPT_TYPE_IMAGE_SIZE, {.str = "hd720"}, 0, 0, VF },
     { "rate",   "set video rate",    OFFSET(frame_rate), AV_OPT_TYPE_VIDEO_RATE, {.str = "25"}, 0, INT32_MAX, VF },
-    { "minp",   "set min partition size", OFFSET(minp),  AV_OPT_TYPE_INT,   {.i64=8192},  16, 32768, AF },
-    { "maxp",   "set max partition size", OFFSET(maxp),  AV_OPT_TYPE_INT,   {.i64=8192},  16, 32768, AF },
+    { "minp",   "set min partition size", OFFSET(minp),  AV_OPT_TYPE_INT,   {.i64=8192}, 8, 32768, AF },
+    { "maxp",   "set max partition size", OFFSET(maxp),  AV_OPT_TYPE_INT,   {.i64=8192}, 8, 32768, AF },
     { NULL }
 };