SPECTRAL_HT20_SAMPLE_LEN
sample_len = SPECTRAL_HT20_SAMPLE_LEN;
if (bytes_read < SPECTRAL_HT20_SAMPLE_LEN - 1)
sample = sample_end - SPECTRAL_HT20_SAMPLE_LEN + 1;
if (bytes_read < SPECTRAL_HT20_SAMPLE_LEN && max_index < 1)