avfilter/showcqt: make minimum timeclamp option lower

high basefreq does not require high timeclamp
Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>

doc/filters.texi

@@ -17029,7 +17029,7 @@ Specify the transform timeclamp. At low frequency, there is trade-off between
 accuracy in time domain and frequency domain. If timeclamp is lower,
 event in time domain is represented more accurately (such as fast bass drum),
 otherwise event in frequency domain is represented more accurately
-(such as bass guitar). Acceptable range is @code{[0.1, 1]}. Default value is @code{0.17}.
+(such as bass guitar). Acceptable range is @code{[0.002, 1]}. Default value is @code{0.17}.
 
 @item basefreq
 Specify the transform base frequency. Default value is @code{20.01523126408007475},

libavfilter/avf_showcqt.c

@@ -76,8 +76,8 @@ static const AVOption showcqt_options[] = {
     { "bar_g",    "set bargraph gamma", OFFSET(bar_g),      AV_OPT_TYPE_FLOAT, { .dbl = 1.0 },            1.0, 7.0,      FLAGS },
     { "gamma2",   "set bargraph gamma", OFFSET(bar_g),      AV_OPT_TYPE_FLOAT, { .dbl = 1.0 },            1.0, 7.0,      FLAGS },
     { "bar_t",  "set bar transparency", OFFSET(bar_t),      AV_OPT_TYPE_FLOAT, { .dbl = 1.0 },            0.0, 1.0,      FLAGS },
-    { "timeclamp",     "set timeclamp", OFFSET(timeclamp), AV_OPT_TYPE_DOUBLE, { .dbl = 0.17 },           0.1, 1.0,      FLAGS },
-    { "tc",            "set timeclamp", OFFSET(timeclamp), AV_OPT_TYPE_DOUBLE, { .dbl = 0.17 },           0.1, 1.0,      FLAGS },
+    { "timeclamp",     "set timeclamp", OFFSET(timeclamp), AV_OPT_TYPE_DOUBLE, { .dbl = 0.17 },         0.002, 1.0,      FLAGS },
+    { "tc",            "set timeclamp", OFFSET(timeclamp), AV_OPT_TYPE_DOUBLE, { .dbl = 0.17 },         0.002, 1.0,      FLAGS },
     { "basefreq", "set base frequency", OFFSET(basefreq),  AV_OPT_TYPE_DOUBLE, { .dbl = BASEFREQ },      10.0, 100000.0, FLAGS },
     { "endfreq",   "set end frequency", OFFSET(endfreq),   AV_OPT_TYPE_DOUBLE, { .dbl = ENDFREQ },       10.0, 100000.0, FLAGS },
     { "coeffclamp",   "set coeffclamp", OFFSET(coeffclamp), AV_OPT_TYPE_FLOAT, { .dbl = 1.0 },            0.1, 10.0,     FLAGS },
@@ -1366,7 +1366,7 @@ static int config_output(AVFilterLink *outlink)
     if ((ret = init_volume(s)) < 0)
         return ret;
 
-    s->fft_bits = ceil(log2(inlink->sample_rate * s->timeclamp));
+    s->fft_bits = FFMAX(ceil(log2(inlink->sample_rate * s->timeclamp)), 4);
     s->fft_len = 1 << s->fft_bits;
     av_log(ctx, AV_LOG_INFO, "fft_len = %d, cqt_len = %d.\n", s->fft_len, s->cqt_len);