avcodec/opustab: Avoid indirection to access ff_celt_window

Currently, it is accessed via a pointer (ff_celt_window)
exported from opustab.h which points inside a static array
(ff_celt_window_padded) in opustab.h. Instead export
ff_celt_window_padded directly and make opustab.h
a static const pointer pointing inside ff_celt_window_padded.
Also mark all the declarations in opustab.h as hidden,
so that the compiler knows that ff_celt_window has a fixed
offset from the code even when compiling position-independent
code.

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

libavcodec/opusenc.c

@@ -205,7 +205,7 @@ static void celt_frame_mdct(OpusEncContext *s, CeltFrame *f)
                 float *src2 = &b->samples[CELT_OVERLAP*t];
                 s->dsp->vector_fmul(win, src1, ff_celt_window, 128);
                 s->dsp->vector_fmul_reverse(&win[CELT_OVERLAP], src2,
-                                            ff_celt_window - 8, 128);
+                                            ff_celt_window_padded, 128);
                 src1 = src2;
                 s->tx_fn[0](s->tx[0], b->coeffs + t, win, sizeof(float)*f->blocks);
             }
@@ -226,7 +226,7 @@ static void celt_frame_mdct(OpusEncContext *s, CeltFrame *f)
 
             /* Samples, windowed */
             s->dsp->vector_fmul_reverse(temp, b->samples + rwin,
-                                        ff_celt_window - 8, 128);
+                                        ff_celt_window_padded, 128);
             memcpy(win + lap_dst + blk_len, temp, CELT_OVERLAP*sizeof(float));
 
             s->tx_fn[f->size](s->tx[f->size], b->coeffs, win, sizeof(float));

libavcodec/opustab.c

@@ -1101,7 +1101,7 @@ const float ff_celt_postfilter_taps[3][3] = {
     { 0.7998046875f, 0.1000976562f, 0.0           }
 };
 
-DECLARE_ALIGNED(32, static const float, ff_celt_window_padded)[136] = {
+DECLARE_ALIGNED(32, const float, ff_celt_window_padded)[136] = {
     0.00000000f, 0.00000000f, 0.00000000f, 0.00000000f,
     0.00000000f, 0.00000000f, 0.00000000f, 0.00000000f,
     6.7286966e-05f, 0.00060551348f, 0.0016815970f, 0.0032947962f, 0.0054439943f,
@@ -1132,8 +1132,6 @@ DECLARE_ALIGNED(32, static const float, ff_celt_window_padded)[136] = {
     1.00000000f, 1.00000000f, 1.00000000f,
 };
 
-const float *const ff_celt_window = &ff_celt_window_padded[8];
-
 /* square of the window, used for the postfilter */
 const float ff_celt_window2[120] = {
     4.5275357e-09f, 3.66647e-07f, 2.82777e-06f, 1.08557e-05f, 2.96371e-05f, 6.60594e-05f,

libavcodec/opustab.h

@@ -25,6 +25,9 @@
 
 #include <stdint.h>
 
+#include "libavutil/attributes_internal.h"
+
+FF_VISIBILITY_PUSH_HIDDEN
 extern const uint8_t  ff_celt_band_end[];
 
 extern const uint8_t  ff_opus_default_coupled_streams[];
@@ -154,8 +157,11 @@ extern const uint16_t ff_celt_qn_exp2[];
 extern const float    ff_celt_postfilter_taps[3][3];
 
 extern const float    ff_celt_window2[120];
-extern const float *const ff_celt_window;
+
+extern const float    ff_celt_window_padded[];
+static const float *const ff_celt_window = &ff_celt_window_padded[8];
 
 extern const uint32_t * const ff_celt_pvq_u_row[15];
+FF_VISIBILITY_POP_HIDDEN
 
 #endif /* AVCODEC_OPUSTAB_H */