Two functions in the IVAS encoder rely on sinf()/cosf() for computations that feed directly into discrete or threshold-sensitive decisions. On platforms where sinf/cosf are evaluated with <=2 ULP error, the resulting bitstream diverges from the reference, causing high MLD scores on the SBA 24.4 kbps / 32 kHz input test case. ``` IVAS_cod -q -sba 3 24400 32 testvec/testv/stv3OA32c_cut_16.0.wav stv3OA32c_cut_16.0.wav_SBA_at_24_4_kbps_32kHz_in_32kHz_out_BINAURAL_out_HR_OT.192 IVAS_dec -q -fr 20 -t testvec/testv/headrot.csv -otr avg BINAURAL 32 stv3OA32c_cut_16.0.wav_SBA_at_24_4_kbps_32kHz_in_32kHz_out_BINAURAL_out_HR_OT.192 stv3OA32c_cut_16.0.wav_SBA_at_24_4_kbps_32kHz_in_32kHz_out_BINAURAL_out_HR_OT.dec.wav scripts/tools/Linux/wav-diff stv3OA32c_cut_16.0.wav_SBA_at_24_4_kbps_32kHz_in_32kHz_out_BINAURAL_out_HR_OT.dec.wav.48k.ref.wav stv3OA32c_cut_16.0.wav_SBA_at_24_4_kbps_32kHz_in_32kHz_out_BINAURAL_out_HR_OT.dec.wav.48k.wav ``` Affected Files/Functions : | File| Function| Call type| | ------ | ------ | ------ | | lib_com/ivas_fb_mixer.c | ivas_get_hanning_win() | Init-time | | lib_com/ivas_fb_mixer.c | ivas_get_ld_fb_resp() | Init-time | | lib_com/ivas_agc_com.c | ivas_agc_initWindowFunc() | Init-time | ISSUE 1 — lib_com/ivas_fb_mixer.c : The 12-band filterbank uses hardcoded ROM tables (ivas_fb_fr_12band_1ms_re[], ivas_fb_fr_12band_1ms_im[]) for 48 kHz input — always bit-exact. For 32 kHz, the coefficients are calculated on the fly in ivas_get_ld_fb_resp(), which calls ivas_get_hanning_win(). This results in platform-dependent behavior. ISSUE 2 — lib_com/ivas_agc_com.c : The AGC is active for nchan_transport == 1 (SBA FOA paths). At encoder open, ivas_agc_initWindowFunc() fills winFunc[] — a gain attenuation base function. Per frame, the encoder computes a discrete gain exponent using ceilf(). ``` a = 0.5f * (1.f - powf(10.f, -6.f/20.f)); // a ≈ 0.2481 (no sinf/cosf here) for (i = 0; i < length; i++) { winFunc[i] = 1.f + a * (cosf(EVS_PI*i/N) - 1.f); // range: 1.0 → ~0.504 } /* per-frame — called EVERY frame */ gainExpVal = ceilf( -logf(maxAbs * NORM) / logf(winFunc[idx])); // ← integer! gain = powf(winFunc[idx], gainExpVal); pcm_out[idx] *= gain; // applied to PCM ``` Observed Impact on MLD: 10.1 (before fix) -> 0.0 (after fix)