[FFmpeg-cvslog] avcodec/aacsbr_template: Remove pointless runtime initialization

Andreas Rheinhardt git at videolan.org
Fri Jan 1 01:07:25 EET 2021

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Sun Dec 27 20:46:06 2020 +0100| [3526f3856abc7586c98ea98cad04abf7696e89e7] | committer: Andreas Rheinhardt

avcodec/aacsbr_template: Remove pointless runtime initialization

The sbr_qmf_window_us array is basically symmetric around its middle
element and therefore the latter half is currently initialized from the
first half at runtime. Yet because the first half is initialized, the
array can't be placed in .bss at all, so that one gains nothing from not
already initializing the whole array statically. Therefore this commit
does exactly this.

(There are two exceptions to the symmetry: Elements 384 and 512 are the
negations of their mirror element; for the fixed-point decoder, Q31(-x)
does not equal -Q31(x). In order to keep the array exactly the same, the
latter form has been used for these two elements.)

Reviewed-by: Lynne <dev at lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3526f3856abc7586c98ea98cad04abf7696e89e7

 libavcodec/aacsbr_template.c |  4 ---
 libavcodec/aacsbrdata.h      | 85 ++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 83 insertions(+), 6 deletions(-)

diff --git a/libavcodec/aacsbr_template.c b/libavcodec/aacsbr_template.c
index 821615f2ab..48d91650f7 100644
--- a/libavcodec/aacsbr_template.c
+++ b/libavcodec/aacsbr_template.c
@@ -37,10 +37,6 @@
 static av_cold void aacsbr_tableinit(void)
     int n;
-    for (n = 1; n < 320; n++)
-        sbr_qmf_window_us[320 + n] = sbr_qmf_window_us[320 - n];
-    sbr_qmf_window_us[384] = -sbr_qmf_window_us[384];
-    sbr_qmf_window_us[512] = -sbr_qmf_window_us[512];
     for (n = 0; n < 320; n++)
         sbr_qmf_window_ds[n] = sbr_qmf_window_us[2*n];
diff --git a/libavcodec/aacsbrdata.h b/libavcodec/aacsbrdata.h
index 8f67f85311..bba50db9bd 100644
--- a/libavcodec/aacsbrdata.h
+++ b/libavcodec/aacsbrdata.h
@@ -534,7 +534,9 @@ const DECLARE_ALIGNED(16, INTFLOAT, AAC_RENAME(ff_sbr_noise_table))[][2] = {
 ///< window coefficients for analysis/synthesis QMF banks
 static DECLARE_ALIGNED(32, INTFLOAT, sbr_qmf_window_ds)[320];
-static DECLARE_ALIGNED(32, INTFLOAT, sbr_qmf_window_us)[640] = {
+/* This table contains redundancy: It is symmetric about the entry #320
+ * with the exception of entries 384 and 512 which are negated. */
+static const DECLARE_ALIGNED(32, INTFLOAT, sbr_qmf_window_us)[640] = {
      Q31( 0.0000000000f), Q31(-0.0005525286f), Q31(-0.0005617692f), Q31(-0.0004947518f),
      Q31(-0.0004875227f), Q31(-0.0004893791f), Q31(-0.0005040714f), Q31(-0.0005226564f),
      Q31(-0.0005466565f), Q31(-0.0005677802f), Q31(-0.0005870930f), Q31(-0.0006132747f),
@@ -615,7 +617,86 @@ static DECLARE_ALIGNED(32, INTFLOAT, sbr_qmf_window_us)[640] = {
      Q31( 0.8311038457f), Q31( 0.8346937361f), Q31( 0.8379717337f), Q31( 0.8409541392f),
      Q31( 0.8436238281f), Q31( 0.8459818469f), Q31( 0.8480315777f), Q31( 0.8497805198f),
      Q31( 0.8511971524f), Q31( 0.8523047035f), Q31( 0.8531020949f), Q31( 0.8535720573f),
-     Q31( 0.8537385600f),
+     Q31( 0.8537385600f), Q31( 0.8535720573f), Q31( 0.8531020949f), Q31( 0.8523047035f),
+     Q31( 0.8511971524f), Q31( 0.8497805198f), Q31( 0.8480315777f), Q31( 0.8459818469f),
+     Q31( 0.8436238281f), Q31( 0.8409541392f), Q31( 0.8379717337f), Q31( 0.8346937361f),
+     Q31( 0.8311038457f), Q31( 0.8272275347f), Q31( 0.8230419890f), Q31( 0.8185776004f),
+     Q31( 0.8138191270f), Q31( 0.8087695004f), Q31( 0.8034485751f), Q31( 0.7978466413f),
+     Q31( 0.7919735841f), Q31( 0.7858353120f), Q31( 0.7794287519f), Q31( 0.7727780881f),
+     Q31( 0.7658674865f), Q31( 0.7587080760f), Q31( 0.7513137456f), Q31( 0.7436827863f),
+     Q31( 0.7358211758f), Q31( 0.7277448900f), Q31( 0.7194462634f), Q31( 0.7109410426f),
+     Q31( 0.7022388719f), Q31( 0.6933282376f), Q31( 0.6842353293f), Q31( 0.6749663190f),
+     Q31( 0.6655139880f), Q31( 0.6559016302f), Q31( 0.6461269695f), Q31( 0.6361980107f),
+     Q31( 0.6261242695f), Q31( 0.6159109932f), Q31( 0.6055783538f), Q31( 0.5951123086f),
+     Q31( 0.5845403235f), Q31( 0.5738524131f), Q31( 0.5630789140f), Q31( 0.5522051258f),
+     Q31( 0.5412553448f), Q31( 0.5302240895f), Q31( 0.5191234970f), Q31( 0.5079817500f),
+     Q31( 0.4967708254f), Q31( 0.4855253091f), Q31( 0.4742453214f), Q31( 0.4629308085f),
+     Q31( 0.4515996535f), Q31( 0.4402553754f), Q31( 0.4289119920f), Q31( 0.4175696896f),
+     Q31( 0.4062317676f), Q31( 0.3949211761f), Q31( 0.3836350013f), Q31( 0.3723795546f),
+    -Q31( 0.3611589903f), Q31(-0.3499914122f), Q31(-0.3388722693f), Q31(-0.3278113727f),
+     Q31(-0.3168278913f), Q31(-0.3059098575f), Q31(-0.2950716717f), Q31(-0.2843214189f),
+     Q31(-0.2736634040f), Q31(-0.2631053299f), Q31(-0.2526480309f), Q31(-0.2423016884f),
+     Q31(-0.2320690870f), Q31(-0.2219652696f), Q31(-0.2119735853f), Q31(-0.2021250176f),
+     Q31(-0.1923966745f), Q31(-0.1828172548f), Q31(-0.1733808172f), Q31(-0.1640958855f),
+     Q31(-0.1549607071f), Q31(-0.1459766491f), Q31(-0.1371551761f), Q31(-0.1285002850f),
+     Q31(-0.1200077984f), Q31(-0.1116826931f), Q31(-0.1035329531f), Q31(-0.0955533352f),
+     Q31(-0.0877547536f), Q31(-0.0801372934f), Q31(-0.0726943300f), Q31(-0.0654409853f),
+     Q31(-0.0583705326f), Q31(-0.0514804176f), Q31(-0.0447806821f), Q31(-0.0382776572f),
+     Q31(-0.0319531274f), Q31(-0.0258227288f), Q31(-0.0198834129f), Q31(-0.0141288827f),
+     Q31(-0.0085711749f), Q31(-0.0032086896f), Q31( 0.0019765601f), Q31( 0.0069636862f),
+     Q31( 0.0117623832f), Q31( 0.0163701258f), Q31( 0.0207997072f), Q31( 0.0250307561f),
+     Q31( 0.0290824006f), Q31( 0.0329583930f), Q31( 0.0366418116f), Q31( 0.0401458278f),
+     Q31( 0.0434768782f), Q31( 0.0466303305f), Q31( 0.0495978676f), Q31( 0.0524093821f),
+     Q31( 0.0550460034f), Q31( 0.0575152691f), Q31( 0.0598166570f), Q31( 0.0619602779f),
+     Q31( 0.0639444805f), Q31( 0.0657690668f), Q31( 0.0674525021f), Q31( 0.0689664013f),
+     Q31( 0.0703533073f), Q31( 0.0715826364f), Q31( 0.0726774642f), Q31( 0.0736406005f),
+     Q31( 0.0744664394f), Q31( 0.0751576255f), Q31( 0.0757305756f), Q31( 0.0761748321f),
+     Q31( 0.0765050718f), Q31( 0.0767204924f), Q31( 0.0768230011f), Q31( 0.0768173975f),
+     Q31( 0.0767093490f), Q31( 0.0764992170f), Q31( 0.0761992479f), Q31( 0.0758008358f),
+     Q31( 0.0753137336f), Q31( 0.0747452558f), Q31( 0.0741003642f), Q31( 0.0733620255f),
+     Q31( 0.0725682583f), Q31( 0.0717002673f), Q31( 0.0707628710f), Q31( 0.0697630244f),
+     Q31( 0.0687043828f), Q31( 0.0676075985f), Q31( 0.0664367512f), Q31( 0.0652247106f),
+     Q31( 0.0639715898f), Q31( 0.0626857808f), Q31( 0.0613455171f), Q31( 0.0599837480f),
+     Q31( 0.0585915683f), Q31( 0.0571616450f), Q31( 0.0557173648f), Q31( 0.0542452768f),
+     Q31( 0.0527630746f), Q31( 0.0512556155f), Q31( 0.0497385755f), Q31( 0.0482165720f),
+     Q31( 0.0466843027f), Q31( 0.0451488405f), Q31( 0.0436097542f), Q31( 0.0420649094f),
+     Q31( 0.0405349170f), Q31( 0.0390053679f), Q31( 0.0374812850f), Q31( 0.0359697560f),
+     Q31( 0.0344620948f), Q31( 0.0329754081f), Q31( 0.0315017608f), Q31( 0.0300502657f),
+     Q31( 0.0286072173f), Q31( 0.0271859429f), Q31( 0.0257875847f), Q31( 0.0244160992f),
+     Q31( 0.0230680169f), Q31( 0.0217467550f), Q31( 0.0204531793f), Q31( 0.0191872431f),
+     Q31( 0.0179433381f), Q31( 0.0167324712f), Q31( 0.0155405553f), Q31( 0.0143904666f),
+    -Q31( 0.0132718220f), Q31(-0.0121849995f), Q31(-0.0111315548f), Q31(-0.0101150215f),
+     Q31(-0.0091325329f), Q31(-0.0081798233f), Q31(-0.0072615816f), Q31(-0.0063792293f),
+     Q31(-0.0055337211f), Q31(-0.0047222596f), Q31(-0.0039401124f), Q31(-0.0031933778f),
+     Q31(-0.0024826723f), Q31(-0.0018039472f), Q31(-0.0011568135f), Q31(-0.0005464280f),
+     Q31( 0.0000276045f), Q31( 0.0005832264f), Q31( 0.0010902329f), Q31( 0.0015784682f),
+     Q31( 0.0020274176f), Q31( 0.0024508540f), Q31( 0.0028446757f), Q31( 0.0032091885f),
+     Q31( 0.0035401246f), Q31( 0.0038456408f), Q31( 0.0041251642f), Q31( 0.0043801861f),
+     Q31( 0.0046039530f), Q31( 0.0048109469f), Q31( 0.0049839687f), Q31( 0.0051382275f),
+     Q31( 0.0052715758f), Q31( 0.0053838975f), Q31( 0.0054753783f), Q31( 0.0055404363f),
+     Q31( 0.0055917128f), Q31( 0.0056266114f), Q31( 0.0056389199f), Q31( 0.0056455196f),
+     Q31( 0.0056220643f), Q31( 0.0055938023f), Q31( 0.0055475714f), Q31( 0.0054876040f),
+     Q31( 0.0054196775f), Q31( 0.0053471681f), Q31( 0.0052461166f), Q31( 0.0051407353f),
+     Q31( 0.0050393022f), Q31( 0.0049137603f), Q31( 0.0047932560f), Q31( 0.0046606460f),
+     Q31( 0.0045209852f), Q31( 0.0043730719f), Q31( 0.0042264269f), Q31( 0.0040819753f),
+     Q31( 0.0039207432f), Q31( 0.0037603922f), Q31( 0.0036008268f), Q31( 0.0034418874f),
+     Q31( 0.0032739613f), Q31( 0.0031125420f), Q31( 0.0029469447f), Q31( 0.0027870464f),
+     Q31( 0.0026201758f), Q31( 0.0024625616f), Q31( 0.0023017254f), Q31( 0.0021461583f),
+     Q31( 0.0019841140f), Q31( 0.0018348265f), Q31( 0.0016868083f), Q31( 0.0015443219f),
+     Q31( 0.0013902494f), Q31( 0.0012577884f), Q31( 0.0011250155f), Q31( 0.0009885988f),
+     Q31( 0.0008608443f), Q31( 0.0007458025f), Q31( 0.0006239376f), Q31( 0.0005107388f),
+     Q31( 0.0004026540f), Q31( 0.0002949531f), Q31( 0.0002043017f), Q31( 0.0001094383f),
+     Q31( 0.0000134949f), Q31(-0.0000617334f), Q31(-0.0001446380f), Q31(-0.0002098337f),
+     Q31(-0.0002896981f), Q31(-0.0003501175f), Q31(-0.0004095121f), Q31(-0.0004606325f),
+     Q31(-0.0005145572f), Q31(-0.0005564576f), Q31(-0.0005946118f), Q31(-0.0006341594f),
+     Q31(-0.0006650415f), Q31(-0.0006917937f), Q31(-0.0007215391f), Q31(-0.0007319357f),
+     Q31(-0.0007530001f), Q31(-0.0007630793f), Q31(-0.0007757977f), Q31(-0.0007801449f),
+     Q31(-0.0007803664f), Q31(-0.0007779869f), Q31(-0.0007834332f), Q31(-0.0007724848f),
+     Q31(-0.0007681371f), Q31(-0.0007490598f), Q31(-0.0007440941f), Q31(-0.0007255043f),
+     Q31(-0.0007157736f), Q31(-0.0006941614f), Q31(-0.0006777690f), Q31(-0.0006540333f),
+     Q31(-0.0006312493f), Q31(-0.0006132747f), Q31(-0.0005870930f), Q31(-0.0005677802f),
+     Q31(-0.0005466565f), Q31(-0.0005226564f), Q31(-0.0005040714f), Q31(-0.0004893791f),
+     Q31(-0.0004875227f), Q31(-0.0004947518f), Q31(-0.0005617692f), Q31(-0.0005525286f),

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