avcodec/aacdec: Split SBR context from ChannelElement

The AAC fixed-point and floating-point decoders have
a lot of duplicated code; the main obstacle to
deduplicating it is that several structures with the
same name are actually different types, because
they contain INTFLOATs (int or float) and AAC_FLOATs
(SoftFloat or float). SoftFloat and float typically
have different sizes, so dealing with it is the more
complicated of the two.

AAC_FLOAT is mainly used in the sbr code and structures,
so one can still deduplicate the code by only exposing
the common part of ChannelElement (without SBR context)
to the common decoder part. One prerequisite of this
is to move allocating the whole ChannelElement to
code that will stay unduplicated. It is most natural
to move said allocation to ff_aac_sbr_ctx_init().

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/aacdec.h

@@ -41,7 +41,6 @@
 #include "aac.h"
 #include "aac_defines.h"
 #include "mpeg4audio.h"
-#include "sbr.h"
 
 /**
  * Output configuration status
@@ -153,7 +152,6 @@ typedef struct ChannelElement {
     SingleChannelElement ch[2];
     // CCE specific
     ChannelCoupling coup;
-    SpectralBandReplication sbr;
 } ChannelElement;
 
 typedef struct OutputConfiguration {

libavcodec/aacdec_template.c

@@ -134,10 +134,7 @@ static av_cold int che_configure(AACDecContext *ac,
         return AVERROR_INVALIDDATA;
     if (che_pos) {
         if (!ac->che[type][id]) {
-            int ret;
-            if (!(ac->che[type][id] = av_mallocz(sizeof(ChannelElement))))
-                return AVERROR(ENOMEM);
-            ret = AAC_RENAME(ff_aac_sbr_ctx_init)(ac, ac->che[type][id], type);
+            int ret = AAC_RENAME(ff_aac_sbr_ctx_alloc_init)(ac, &ac->che[type][id], type);
             if (ret < 0)
                 return ret;
         }

libavcodec/aacsbr.h

@@ -68,8 +68,11 @@ enum {
 
 /** Initialize SBR. */
 void AAC_RENAME(ff_aac_sbr_init)(void);
-/** Initialize one SBR context. */
-int AAC_RENAME(ff_aac_sbr_ctx_init)(AACDecContext *ac, ChannelElement *che, int id_aac);
+/**
+ * Allocate an ExtChannelElement (if necessary) and
+ * initialize the SBR context contained in it.
+ */
+int AAC_RENAME(ff_aac_sbr_ctx_alloc_init)(AACDecContext *ac, ChannelElement **che, int id_aac);
 /** Close one SBR context. */
 void AAC_RENAME(ff_aac_sbr_ctx_close)(ChannelElement *che);
 /** Decode one SBR element. */

libavcodec/aacsbr_template.c

@@ -38,6 +38,16 @@
 #include "libavutil/qsort.h"
 #include "libavutil/mem.h"
 
+typedef struct ExtChannelElement {
+    ChannelElement ch;
+    SpectralBandReplication sbr;
+} ExtChannelElement;
+
+static inline SpectralBandReplication *get_sbr(ChannelElement *ch)
+{
+    return &((ExtChannelElement*)ch)->sbr;
+}
+
 static av_cold void aacsbr_tableinit(void)
 {
     int n;
@@ -65,14 +75,18 @@ static void sbr_turnoff(SpectralBandReplication *sbr) {
     memset(&sbr->spectrum_params, -1, sizeof(SpectrumParameters));
 }
 
-av_cold int AAC_RENAME(ff_aac_sbr_ctx_init)(AACDecContext *ac, ChannelElement *che, int id_aac)
+av_cold int AAC_RENAME(ff_aac_sbr_ctx_alloc_init)(AACDecContext *ac,
+                                                  ChannelElement **che, int id_aac)
 {
-    SpectralBandReplication *sbr = &che->sbr;
+    SpectralBandReplication *sbr;
+    ExtChannelElement *ext = av_mallocz(sizeof(*ext));
     int ret;
     float scale;
 
-    if (sbr->mdct)
-        return 0;
+    if (!ext)
+        return AVERROR(ENOMEM);
+    *che = &ext->ch;
+    sbr  = &ext->sbr;
 
     sbr->kx[0] = sbr->kx[1];
     sbr->id_aac = id_aac;
@@ -106,7 +120,7 @@ av_cold int AAC_RENAME(ff_aac_sbr_ctx_init)(AACDecContext *ac, ChannelElement *c
 
 av_cold void AAC_RENAME(ff_aac_sbr_ctx_close)(ChannelElement *che)
 {
-    SpectralBandReplication *sbr = &che->sbr;
+    SpectralBandReplication *sbr = get_sbr(che);
     av_tx_uninit(&sbr->mdct);
     av_tx_uninit(&sbr->mdct_ana);
 }
@@ -1097,7 +1111,7 @@ int AAC_RENAME(ff_aac_sbr_decode_extension)(AACDecContext *ac, ChannelElement *c
                                             GetBitContext *gb_host, int crc,
                                             int cnt, int id_aac)
 {
-    SpectralBandReplication *sbr = &che->sbr;
+    SpectralBandReplication *sbr = get_sbr(che);
     unsigned int num_sbr_bits = 0, num_align_bits;
     unsigned bytes_read;
     GetBitContext gbc = *gb_host, *gb = &gbc;
@@ -1464,7 +1478,7 @@ static void sbr_env_estimate(AAC_FLOAT (*e_curr)[48], INTFLOAT X_high[64][40][2]
 void AAC_RENAME(ff_aac_sbr_apply)(AACDecContext *ac, ChannelElement *che,
                                   int id_aac, INTFLOAT* L, INTFLOAT* R)
 {
-    SpectralBandReplication *sbr = &che->sbr;
+    SpectralBandReplication *sbr = get_sbr(che);
     int downsampled = ac->oc[1].m4ac.ext_sample_rate < sbr->sample_rate;
     int ch;
     int nch = (id_aac == TYPE_CPE) ? 2 : 1;