[FFmpeg-devel] [PATCH][RFC] avcodec/aacsbr_template: replace qsort with AV_QSORT

[Ganesh Ajjanagadde]

When sbr->reset is set in encode_frame, a bunch of qsort calls might get made.
Thus, there is the potential of calling qsort whenever the spectral
contents change.

AV_QSORT is substantially faster due to the inlining of the comparison callback.
Thus, the increase in performance should be worth the increase in binary size.

Tested with FATE.

Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>

--------------------------------------------------------------------------------
Please note that I am not not knowledgable about AAC, and above analysis
was based on a quick glance at the code. I could not get benchmarks with
runs > 1 easily (even with stream_loop), hence they are omitted.
Furthermore, it seems like AAC is under active work, so I defer
meaningful benchmarks to the maintainers.
---
 libavcodec/aacsbr_template.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/libavcodec/aacsbr_template.c b/libavcodec/aacsbr_template.c
index d31b71e..9561ba0 100644
--- a/libavcodec/aacsbr_template.c
+++ b/libavcodec/aacsbr_template.c
@@ -32,6 +32,8 @@
  * @author Zoran Basaric ( zoran.basaric at imgtec.com )
  */
 
+#include "libavutil/qsort.h"
+
 av_cold void AAC_RENAME(ff_aac_sbr_init)(void)
 {
     static const struct {
@@ -138,8 +140,8 @@ static void sbr_make_f_tablelim(SpectralBandReplication *sbr)
             memcpy(sbr->f_tablelim + sbr->n[0] + 1, patch_borders + 1,
                    (sbr->num_patches - 1) * sizeof(patch_borders[0]));
 
-        qsort(sbr->f_tablelim, sbr->num_patches + sbr->n[0],
-              sizeof(sbr->f_tablelim[0]),
+        AV_QSORT(sbr->f_tablelim, sbr->num_patches + sbr->n[0],
+              uint16_t,
               qsort_comparison_function_int16);
 
         sbr->n_lim = sbr->n[0] + sbr->num_patches - 1;
@@ -296,7 +298,7 @@ static int sbr_make_f_master(AACContext *ac, SpectralBandReplication *sbr,
     if (spectrum->bs_stop_freq < 14) {
         sbr->k[2] = stop_min;
         make_bands(stop_dk, stop_min, 64, 13);
-        qsort(stop_dk, 13, sizeof(stop_dk[0]), qsort_comparison_function_int16);
+        AV_QSORT(stop_dk, 13, int16_t, qsort_comparison_function_int16);
         for (k = 0; k < spectrum->bs_stop_freq; k++)
             sbr->k[2] += stop_dk[k];
     } else if (spectrum->bs_stop_freq == 14) {
@@ -389,7 +391,7 @@ static int sbr_make_f_master(AACContext *ac, SpectralBandReplication *sbr,
 
         make_bands(vk0+1, sbr->k[0], sbr->k[1], num_bands_0);
 
-        qsort(vk0 + 1, num_bands_0, sizeof(vk0[1]), qsort_comparison_function_int16);
+        AV_QSORT(vk0 + 1, num_bands_0, int16_t, qsort_comparison_function_int16);
         vdk0_max = vk0[num_bands_0];
 
         vk0[0] = sbr->k[0];
@@ -430,13 +432,13 @@ static int sbr_make_f_master(AACContext *ac, SpectralBandReplication *sbr,
 
             if (vdk1_min < vdk0_max) {
                 int change;
-                qsort(vk1 + 1, num_bands_1, sizeof(vk1[1]), qsort_comparison_function_int16);
+                AV_QSORT(vk1 + 1, num_bands_1, int16_t, qsort_comparison_function_int16);
                 change = FFMIN(vdk0_max - vk1[1], (vk1[num_bands_1] - vk1[1]) >> 1);
                 vk1[1]           += change;
                 vk1[num_bands_1] -= change;
             }
 
-            qsort(vk1 + 1, num_bands_1, sizeof(vk1[1]), qsort_comparison_function_int16);
+            AV_QSORT(vk1 + 1, num_bands_1, int16_t, qsort_comparison_function_int16);
 
             vk1[0] = sbr->k[1];
             for (k = 1; k <= num_bands_1; k++) {
-- 
2.6.2