[FFmpeg-devel] [PATCH 46/61] avcodec/aacdec_common: Avoid superfluous VLC structures

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

For all VLCs here, the number of bits of the VLC is
write-only, because it is hardcoded at the call site.
Therefore one can replace these VLC structures with
the only thing that is actually used: The pointer
to the VLCElem table. And in some cases one can even
avoid this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/aacdec_common.c   | 43 +++++++++++++++++-------------------
 libavcodec/aacdec_template.c | 12 +++++-----
 libavcodec/aacdectab.h       |  4 ++--
 3 files changed, 28 insertions(+), 31 deletions(-)

diff --git a/libavcodec/aacdec_common.c b/libavcodec/aacdec_common.c
index 45f1986258..61d81343fe 100644
--- a/libavcodec/aacdec_common.c
+++ b/libavcodec/aacdec_common.c
@@ -123,36 +123,33 @@ const AVChannelLayout ff_aac_ch_layout[] = {
     { 0 },
 };
 
-VLC ff_vlc_scalefactors;
-VLC ff_vlc_spectral[11];
+VLCElem ff_vlc_scalefactors[352];
+const VLCElem *ff_vlc_spectral[11];
 
 static av_cold void aacdec_common_init(void)
 {
     static VLCElem vlc_buf[304 + 270 + 550 + 300 + 328 +
                            294 + 306 + 268 + 510 + 366 + 462];
-    for (unsigned i = 0, offset = 0; i < 11; i++) {
-        ff_vlc_spectral[i].table           = &vlc_buf[offset];
-        ff_vlc_spectral[i].table_allocated = FF_ARRAY_ELEMS(vlc_buf) - offset;
-        ff_vlc_init_sparse(&ff_vlc_spectral[i], 8, ff_aac_spectral_sizes[i],
-                           ff_aac_spectral_bits[i],       sizeof(ff_aac_spectral_bits[i][0]),
-                                                          sizeof(ff_aac_spectral_bits[i][0]),
-                           ff_aac_spectral_codes[i],      sizeof(ff_aac_spectral_codes[i][0]),
-                                                          sizeof(ff_aac_spectral_codes[i][0]),
-                           ff_aac_codebook_vector_idx[i], sizeof(ff_aac_codebook_vector_idx[i][0]),
-                                                          sizeof(ff_aac_codebook_vector_idx[i][0]),
-                 VLC_INIT_STATIC_OVERLONG);
-        offset += ff_vlc_spectral[i].table_size;
+    VLCInitState state = VLC_INIT_STATE(vlc_buf);
+
+    for (unsigned i = 0; i < 11; i++) {
+#define TAB_WRAP_SIZE(name) name[i], sizeof(name[i][0]), sizeof(name[i][0])
+        ff_vlc_spectral[i] =
+            ff_vlc_init_tables_sparse(&state, 8, ff_aac_spectral_sizes[i],
+                                      TAB_WRAP_SIZE(ff_aac_spectral_bits),
+                                      TAB_WRAP_SIZE(ff_aac_spectral_codes),
+                                      TAB_WRAP_SIZE(ff_aac_codebook_vector_idx),
+                                      0);
     }
 
-    VLC_INIT_STATIC(&ff_vlc_scalefactors, 7,
-                    FF_ARRAY_ELEMS(ff_aac_scalefactor_code),
-                    ff_aac_scalefactor_bits,
-                    sizeof(ff_aac_scalefactor_bits[0]),
-                    sizeof(ff_aac_scalefactor_bits[0]),
-                    ff_aac_scalefactor_code,
-                    sizeof(ff_aac_scalefactor_code[0]),
-                    sizeof(ff_aac_scalefactor_code[0]),
-                    352);
+    VLC_INIT_STATIC_TABLE(ff_vlc_scalefactors, 7,
+                          FF_ARRAY_ELEMS(ff_aac_scalefactor_code),
+                          ff_aac_scalefactor_bits,
+                          sizeof(ff_aac_scalefactor_bits[0]),
+                          sizeof(ff_aac_scalefactor_bits[0]),
+                          ff_aac_scalefactor_code,
+                          sizeof(ff_aac_scalefactor_code[0]),
+                          sizeof(ff_aac_scalefactor_code[0]), 0);
 }
 
 av_cold void ff_aacdec_common_init_once(void)
diff --git a/libavcodec/aacdec_template.c b/libavcodec/aacdec_template.c
index 4591eac6b9..1ea551b533 100644
--- a/libavcodec/aacdec_template.c
+++ b/libavcodec/aacdec_template.c
@@ -1497,7 +1497,7 @@ static int decode_scalefactors(AACContext *ac, INTFLOAT sf[120], GetBitContext *
             } else if ((band_type[idx] == INTENSITY_BT) ||
                        (band_type[idx] == INTENSITY_BT2)) {
                 for (; i < run_end; i++, idx++) {
-                    offset[2] += get_vlc2(gb, ff_vlc_scalefactors.table, 7, 3) - SCALE_DIFF_ZERO;
+                    offset[2] += get_vlc2(gb, ff_vlc_scalefactors, 7, 3) - SCALE_DIFF_ZERO;
                     clipped_offset = av_clip(offset[2], -155, 100);
                     if (offset[2] != clipped_offset) {
                         avpriv_request_sample(ac->avctx,
@@ -1516,7 +1516,7 @@ static int decode_scalefactors(AACContext *ac, INTFLOAT sf[120], GetBitContext *
                     if (noise_flag-- > 0)
                         offset[1] += get_bits(gb, NOISE_PRE_BITS) - NOISE_PRE;
                     else
-                        offset[1] += get_vlc2(gb, ff_vlc_scalefactors.table, 7, 3) - SCALE_DIFF_ZERO;
+                        offset[1] += get_vlc2(gb, ff_vlc_scalefactors, 7, 3) - SCALE_DIFF_ZERO;
                     clipped_offset = av_clip(offset[1], -100, 155);
                     if (offset[1] != clipped_offset) {
                         avpriv_request_sample(ac->avctx,
@@ -1532,7 +1532,7 @@ static int decode_scalefactors(AACContext *ac, INTFLOAT sf[120], GetBitContext *
                 }
             } else {
                 for (; i < run_end; i++, idx++) {
-                    offset[0] += get_vlc2(gb, ff_vlc_scalefactors.table, 7, 3) - SCALE_DIFF_ZERO;
+                    offset[0] += get_vlc2(gb, ff_vlc_scalefactors, 7, 3) - SCALE_DIFF_ZERO;
                     if (offset[0] > 255U) {
                         av_log(ac->avctx, AV_LOG_ERROR,
                                "Scalefactor (%d) out of range.\n", offset[0]);
@@ -1705,7 +1705,7 @@ static int decode_spectrum_and_dequant(AACContext *ac, INTFLOAT coef[1024],
 #if !USE_FIXED
                 const float *vq = ff_aac_codebook_vector_vals[cbt_m1];
 #endif /* !USE_FIXED */
-                const VLCElem *vlc_tab = ff_vlc_spectral[cbt_m1].table;
+                const VLCElem *vlc_tab = ff_vlc_spectral[cbt_m1];
                 OPEN_READER(re, gb);
 
                 switch (cbt_m1 >> 1) {
@@ -2279,7 +2279,7 @@ static int decode_cce(AACContext *ac, GetBitContext *gb, ChannelElement *che)
         INTFLOAT gain_cache = FIXR10(1.);
         if (c) {
             cge = coup->coupling_point == AFTER_IMDCT ? 1 : get_bits1(gb);
-            gain = cge ? get_vlc2(gb, ff_vlc_scalefactors.table, 7, 3) - 60: 0;
+            gain = cge ? get_vlc2(gb, ff_vlc_scalefactors, 7, 3) - 60: 0;
             gain_cache = GET_GAIN(scale, gain);
 #if USE_FIXED
             if ((abs(gain_cache)-1024) >> 3 > 30)
@@ -2293,7 +2293,7 @@ static int decode_cce(AACContext *ac, GetBitContext *gb, ChannelElement *che)
                 for (sfb = 0; sfb < sce->ics.max_sfb; sfb++, idx++) {
                     if (sce->band_type[idx] != ZERO_BT) {
                         if (!cge) {
-                            int t = get_vlc2(gb, ff_vlc_scalefactors.table, 7, 3) - 60;
+                            int t = get_vlc2(gb, ff_vlc_scalefactors, 7, 3) - 60;
                             if (t) {
                                 int s = 1;
                                 t = gain += t;
diff --git a/libavcodec/aacdectab.h b/libavcodec/aacdectab.h
index a009e9f46e..d62f170136 100644
--- a/libavcodec/aacdectab.h
+++ b/libavcodec/aacdectab.h
@@ -38,8 +38,8 @@
 FF_VISIBILITY_PUSH_HIDDEN
 void ff_aacdec_common_init_once(void);
 
-extern VLC ff_vlc_scalefactors;
-extern VLC ff_vlc_spectral[11];
+extern VLCElem ff_vlc_scalefactors[];
+extern const VLCElem *ff_vlc_spectral[11];
 
 extern const int8_t ff_tags_per_config[16];
 
-- 
2.34.1

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