static int cng_decode_frame(AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt) { AVFrame *frame = data; CNGContext *p = avctx->priv_data; int buf_size = avpkt->size; int ret, i; int16_t *buf_out; float e = 1.0; float scaling; if (avpkt->size) { int dbov = -avpkt->data[0]; p->target_energy = 1081109975 * ff_exp10(dbov / 10.0) * 0.75; memset(p->target_refl_coef, 0, p->order * sizeof(*p->target_refl_coef)); for (i = 0; i < FFMIN(avpkt->size - 1, p->order); i++) { p->target_refl_coef[i] = (avpkt->data[1 + i] - 127) / 128.0; if (p->inited) { p->energy = p->energy / 2 + p->target_energy / 2; for (i = 0; i < p->order; i++) p->refl_coef[i] = 0.6 *p->refl_coef[i] + 0.4 * p->target_refl_coef[i]; } else { p->energy = p->target_energy; memcpy(p->refl_coef, p->target_refl_coef, p->order * sizeof(*p->refl_coef)); p->inited = 1; make_lpc_coefs(p->lpc_coef, p->refl_coef, p->order); for (i = 0; i < p->order; i++) e *= 1.0 - p->refl_coef[i]*p->refl_coef[i]; scaling = sqrt(e * p->energy / 1081109975); for (i = 0; i < avctx->frame_size; i++) { int r = (av_lfg_get(&p->lfg) & 0xffff) - 0x8000; p->excitation[i] = scaling * r; ff_celp_lp_synthesis_filterf(p->filter_out + p->order, p->lpc_coef, p->excitation, avctx->frame_size, p->order); frame->nb_samples = avctx->frame_size; if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) return ret; buf_out = (int16_t *)frame->data[0]; for (i = 0; i < avctx->frame_size; i++) buf_out[i] = p->filter_out[i + p->order]; memcpy(p->filter_out, p->filter_out + avctx->frame_size, p->order * sizeof(*p->filter_out)); *got_frame_ptr = 1; return buf_size;