Crash on same input and output sampling rate.

[Chin Kuan Chu]

SoXR crashes on the calling soxr_create if the input sampling rate is the same or very close to the output sampling rate.

soxr_io_spec_t      const soxIOs = soxr_io_spec(SOXR_INT16_I, SOXR_FLOAT32_I);
soxr_quality_spec_t const soxQs  = soxr_quality_spec(SOXR_MQ, 0);
soxr_runtime_spec_t const soxRTs = soxr_runtime_spec(1);

soxr = soxr_create(
        static_cast<double>  (sample->getSampleRate()),     // 48000
        static_cast<double>  (output_sample_rate),          // 48000
        static_cast<unsigned>(sample->getChannelCount()),   // 2
        &soxr_error, &soxIOs, &soxQs, &soxRTs
        );

It was compiled with GCC 4.9.0. (distro: Arch Linux x64)

GDB backtrace; note the NaN on frame 2:

#0  0x00007ffff76e8f1b in _soxr_bessel_I_0 (x=-nan(0x8000000000000)) at .../soxr-0.1.1/src/dbesi0.c:143
#1  0x00007ffff76ea6aa in _soxr_make_lpf (num_taps=-1, Fc=0, beta=-nan(0x8000000000000), rho=0.5, scale=1) at .../soxr-0.1.1/src/filter.c:97
#2  0x00007ffff76eacb8 in _soxr_design_lpf (Fp=0, Fs=0, Fn=inf, att=102.35019852575361, num_taps=0x7fffffffd298, k=0, beta=-nan(0x8000000000000))
    at .../soxr-0.1.1/src/filter.c:142
#3  0x00007ffff7720b88 in rate_init (p=0x6929c0, shared=0x692960, factor=1, bits=16, phase=50, passband_end=0.91505264245819784, stopband_begin=1, rolloff=rolloff_medium, maintain_3dB_pt=0, 
    multiplier=3.0517578125e-05, use_hi_prec_clock=0, interpolator=-1, max_coefs_size=400, noSmallIntOpt=0, log2_min_dft_size=10, log2_large_dft_size=17)
    at .../soxr-0.1.1/src/rate.h:534
#4  0x00007ffff7721a5c in rate_create (channel=0x6929c0, shared=0x692960, io_ratio=1, q_spec=0x692838, r_spec=0x692888, scale=3.0517578125e-05)
    at .../soxr-0.1.1/src/rate.h:689
#5  0x00007ffff76e38ca in initialise (p=0x692820) at .../soxr-0.1.1/src/soxr.c:336
#6  0x00007ffff76e3a2b in soxr_set_io_ratio (p=0x692820, io_ratio=1, slew_len=0) at .../soxr-0.1.1/src/soxr.c:373
#7  0x00007ffff76e3522 in soxr_create (input_rate=48000, output_rate=48000, num_channels=2, error0=0x6947b8, io_spec=0x7fffffffd5e0, q_spec=0x7fffffffd620, runtime_spec=0x7fffffffd600)
    at .../soxr-0.1.1/src/soxr.c:265
...

[robs]

Thanks very much for this report — I think you've found a (the first?) bug in soxr.

As a temporary workaround, you could try something like:

bool workaround(fabs(sample->getSampleRate()/output_sample_rate - 1) < 1e-6);

and then:

soxr_quality_spec(workaround? SOXR_QQ : SOXR_MQ, 0);

Here is the probable fix for the library itself:

diff --git a/src/rate.h b/src/rate.h
index 81cabff..06dcc3f 100644
--- a/src/rate.h
+++ b/src/rate.h
@@ -447,7 +447,7 @@ static char const * rate_init(

   p->num_stages = shift + have_pre_stage + have_arb_stage + have_post_stage;
   if (!p->num_stages && multiplier != 1) {
-    arbL = 0;
+    bits = arbL = 0;
     ++p->num_stages;
   }
   p->stages = calloc((size_t)p->num_stages + 1, sizeof(*p->stages));