On Tue, Dec 15, 2015 at 9:53 PM, Ganesh Ajjanagadde
<gajjanaga...@gmail.com> wrote:
> This uses ff_exp2fi to get a speedup (~ 6x).
>
> sample benchmark (Haswell, GNU/Linux):
> old:
> 19102 decicycles in sbr_dequant, 1023 runs, 1 skips
> 19002 decicycles in sbr_dequant, 2045 runs, 3 skips
> 17638 decicycles in sbr_dequant, 4093 runs, 3 skips
> 15825 decicycles in sbr_dequant, 8189 runs, 3 skips
> 16404 decicycles in sbr_dequant, 16379 runs, 5 skips
>
> new:
> 3063 decicycles in sbr_dequant, 1024 runs, 0 skips
> 3049 decicycles in sbr_dequant, 2048 runs, 0 skips
> 2968 decicycles in sbr_dequant, 4096 runs, 0 skips
> 2818 decicycles in sbr_dequant, 8191 runs, 1 skips
> 2853 decicycles in sbr_dequant, 16383 runs, 1 skips
>
> Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
> ---
> libavcodec/aacsbr.c | 34 ++++++++++++++++++++++------------
> 1 file changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/libavcodec/aacsbr.c b/libavcodec/aacsbr.c
> index d1e3a91..15956e3 100644
> --- a/libavcodec/aacsbr.c
> +++ b/libavcodec/aacsbr.c
> @@ -33,6 +33,7 @@
> #include "aacsbrdata.h"
> #include "aacsbr_tablegen.h"
> #include "fft.h"
> +#include "internal.h"
> #include "aacps.h"
> #include "sbrdsp.h"
> #include "libavutil/internal.h"
> @@ -73,15 +74,22 @@ static void sbr_dequant(SpectralBandReplication *sbr, int
> id_aac)
> {
> int k, e;
> int ch;
> -
> + static const double exp2_tab[2] = {1, M_SQRT2};
> if (id_aac == TYPE_CPE && sbr->bs_coupling) {
> - float alpha = sbr->data[0].bs_amp_res ? 1.0f : 0.5f;
> - float pan_offset = sbr->data[0].bs_amp_res ? 12.0f : 24.0f;
> + int pan_offset = sbr->data[0].bs_amp_res ? 12 : 24;
> for (e = 1; e <= sbr->data[0].bs_num_env; e++) {
> for (k = 0; k < sbr->n[sbr->data[0].bs_freq_res[e]]; k++) {
> - float temp1 = exp2f(sbr->data[0].env_facs_q[e][k] * alpha +
> 7.0f);
> - float temp2 = exp2f((pan_offset -
> sbr->data[1].env_facs_q[e][k]) * alpha);
> - float fac;
> + float temp1, temp2, fac;
> + if (sbr->data[0].bs_amp_res) {
> + temp1 = ff_exp2fi(sbr->data[0].env_facs_q[e][k] + 7);
> + temp2 = ff_exp2fi(pan_offset -
> sbr->data[1].env_facs_q[e][k]);
> + }
> + else {
> + temp1 = ff_exp2fi((sbr->data[0].env_facs_q[e][k]>>1) +
> 7) *
> + exp2_tab[sbr->data[0].env_facs_q[e][k] & 1];
> + temp2 = ff_exp2fi((pan_offset -
> sbr->data[1].env_facs_q[e][k])>>1) *
> + exp2_tab[(pan_offset -
> sbr->data[1].env_facs_q[e][k]) & 1];
> + }
> if (temp1 > 1E20) {
> av_log(NULL, AV_LOG_ERROR, "envelope scalefactor
> overflow in dequant\n");
> temp1 = 1;
> @@ -93,8 +101,8 @@ static void sbr_dequant(SpectralBandReplication *sbr, int
> id_aac)
> }
> for (e = 1; e <= sbr->data[0].bs_num_noise; e++) {
> for (k = 0; k < sbr->n_q; k++) {
> - float temp1 = exp2f(NOISE_FLOOR_OFFSET -
> sbr->data[0].noise_facs_q[e][k] + 1);
> - float temp2 = exp2f(12 - sbr->data[1].noise_facs_q[e][k]);
> + float temp1 = ff_exp2fi(NOISE_FLOOR_OFFSET -
> sbr->data[0].noise_facs_q[e][k] + 1);
> + float temp2 = ff_exp2fi(12 -
> sbr->data[1].noise_facs_q[e][k]);
> float fac;
> av_assert0(temp1 <= 1E20);
> fac = temp1 / (1.0f + temp2);
> @@ -104,11 +112,13 @@ static void sbr_dequant(SpectralBandReplication *sbr,
> int id_aac)
> }
> } else { // SCE or one non-coupled CPE
> for (ch = 0; ch < (id_aac == TYPE_CPE) + 1; ch++) {
> - float alpha = sbr->data[ch].bs_amp_res ? 1.0f : 0.5f;
> for (e = 1; e <= sbr->data[ch].bs_num_env; e++)
> for (k = 0; k < sbr->n[sbr->data[ch].bs_freq_res[e]]; k++){
> - sbr->data[ch].env_facs[e][k] =
> - exp2f(alpha * sbr->data[ch].env_facs_q[e][k] + 6.0f);
> + if (sbr->data[ch].bs_amp_res)
> + sbr->data[ch].env_facs[e][k] =
> ff_exp2fi(sbr->data[ch].env_facs_q[e][k] + 6);
> + else
> + sbr->data[ch].env_facs[e][k] =
> ff_exp2fi((sbr->data[ch].env_facs_q[e][k]>>1) + 6)
> + *
> exp2_tab[sbr->data[ch].env_facs_q[e][k] & 1];
> if (sbr->data[ch].env_facs[e][k] > 1E20) {
> av_log(NULL, AV_LOG_ERROR, "envelope scalefactor
> overflow in dequant\n");
> sbr->data[ch].env_facs[e][k] = 1;
> @@ -118,7 +128,7 @@ static void sbr_dequant(SpectralBandReplication *sbr, int
> id_aac)
> for (e = 1; e <= sbr->data[ch].bs_num_noise; e++)
> for (k = 0; k < sbr->n_q; k++)
> sbr->data[ch].noise_facs[e][k] =
> - exp2f(NOISE_FLOOR_OFFSET -
> sbr->data[ch].noise_facs_q[e][k]);
> + ff_exp2fi(NOISE_FLOOR_OFFSET -
> sbr->data[ch].noise_facs_q[e][k]);
> }
> }
> }
> --
> 2.6.4
>
ping for aac maintainers: Rostislav? thanks.
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