av_cold struct FFPsyPreprocessContext* ff_psy_preprocess_init(AVCodecContext *avctx) { FFPsyPreprocessContext *ctx; int i; float cutoff_coeff = 0; ctx = av_mallocz(sizeof(FFPsyPreprocessContext)); ctx->avctx = avctx; if (avctx->cutoff > 0) cutoff_coeff = 2.0 * avctx->cutoff / avctx->sample_rate; if (!cutoff_coeff && avctx->codec_id == AV_CODEC_ID_AAC) cutoff_coeff = 2.0 * AAC_CUTOFF(avctx) / avctx->sample_rate; if (cutoff_coeff && cutoff_coeff < 0.98) ctx->fcoeffs = ff_iir_filter_init_coeffs(avctx, FF_FILTER_TYPE_BUTTERWORTH, FF_FILTER_MODE_LOWPASS, FILT_ORDER, cutoff_coeff, 0.0, 0.0); if (ctx->fcoeffs) { ctx->fstate = av_mallocz(sizeof(ctx->fstate[0]) * avctx->channels); for (i = 0; i < avctx->channels; i++) ctx->fstate[i] = ff_iir_filter_init_state(FILT_ORDER); } ff_iir_filter_init(&ctx->fiir); return ctx; }
int main(void) { struct FFIIRFilterCoeffs *fcoeffs = NULL; struct FFIIRFilterState *fstate = NULL; float cutoff_coeff = 0.4; int16_t x[SIZE], y[SIZE]; int i; fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH, FF_FILTER_MODE_LOWPASS, FILT_ORDER, cutoff_coeff, 0.0, 0.0); fstate = ff_iir_filter_init_state(FILT_ORDER); for (i = 0; i < SIZE; i++) x[i] = lrint(0.75 * INT16_MAX * sin(0.5 * M_PI * i * i / SIZE)); ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1); for (i = 0; i < SIZE; i++) printf("%6d %6d\n", x[i], y[i]); ff_iir_filter_free_coeffsp(&fcoeffs); ff_iir_filter_free_statep(&fstate); return 0; }