[FFmpeg-devel] [PATCH 1/4] aacdec_usac: respect tns_on_lr flag

[FFmpeg-devel] [PATCH 1/4] aacdec_usac: respect tns_on_lr flag

[Lynne via ffmpeg-devel]

This was left out, and due to av_unused, forgotten about.
---
 libavcodec/aac/aacdec.h      |  1 +
 libavcodec/aac/aacdec_usac.c | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/libavcodec/aac/aacdec.h b/libavcodec/aac/aacdec.h
index ee21a94007..f0a33e7ac3 100644
--- a/libavcodec/aac/aacdec.h
+++ b/libavcodec/aac/aacdec.h
@@ -230,6 +230,7 @@ typedef struct SingleChannelElement {
 typedef struct AACUsacStereo {
     uint8_t common_window;
     uint8_t common_tw;
+    uint8_t tns_on_lr; ///< Apply TNS before M/S and stereo prediction
 
     uint8_t ms_mask_mode;
     uint8_t config_idx;
diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 561734f930..3b4e980df4 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -876,14 +876,14 @@ static int decode_usac_stereo_info(AACDecContext *ac, AACUSACConfig *usac,
         return AVERROR_PATCHWELCOME;
     }
 
+    us->tns_on_lr = 0;
     sce1->tns.present = sce2->tns.present = 0;
     if (tns_active) {
-        av_unused int tns_on_lr;
         int common_tns = 0;
         if (us->common_window)
             common_tns = get_bits1(gb);
 
-        tns_on_lr = get_bits1(gb);
+        us->tns_on_lr = get_bits1(gb);
         if (common_tns) {
             ret = ff_aac_decode_tns(ac, &sce1->tns, gb, ics1);
             if (ret < 0)
@@ -1214,6 +1214,14 @@ static void spectrum_decode(AACDecContext *ac, AACUSACConfig *usac,
     }
 
     if (nb_channels > 1 && us->common_window) {
+        for (int ch = 0; ch < nb_channels; ch++) {
+            SingleChannelElement *sce = &cpe->ch[ch];
+
+            /* Apply TNS, if the tns_on_lr bit is not set. */
+            if (sce->tns.present && !us->tns_on_lr)
+                ac->dsp.apply_tns(sce->coeffs, &sce->tns, &sce->ics, 1);
+        }
+
         if (us->ms_mask_mode == 3) {
             const float *filt;
             complex_stereo_downmix_cur(ac, cpe, us->dmix_re);
@@ -1248,8 +1256,8 @@ static void spectrum_decode(AACDecContext *ac, AACUSACConfig *usac,
     for (int ch = 0; ch < nb_channels; ch++) {
         SingleChannelElement *sce = &cpe->ch[ch];
 
-        /* Apply TNS */
-        if (sce->tns.present)
+        /* Apply TNS, if it hasn't been applied yet. */
+        if (sce->tns.present && ((nb_channels == 1) || (us->tns_on_lr)))
             ac->dsp.apply_tns(sce->coeffs, &sce->tns, &sce->ics, 1);
 
         ac->oc[1].m4ac.frame_length_short ? ac->dsp.imdct_and_windowing_768(ac, sce) :
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 2/4] aacdec_usac: do not continue parsing bitstream on core_mode == 1

[Lynne via ffmpeg-devel]

Although LPD is not functional yet, the bitstream ends at that point.
---
 libavcodec/aac/aacdec_usac.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 3b4e980df4..9b28a9e90b 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -1301,6 +1301,7 @@ static int decode_usac_core_coder(AACDecContext *ac, AACUSACConfig *usac,
             ret = ff_aac_ldp_parse_channel_stream(ac, usac, ue, gb);
             if (ret < 0)
                 return ret;
+            continue;
         }
 
         if ((nb_channels == 1) ||
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 3/4] aacdec_usac: decouple TNS active from TNS data present flag

[Lynne via ffmpeg-devel]

The issue was that in case of common TNS parameters, TNS was
entirely skipped, as tns.present was set to 0.
---
 libavcodec/aac/aacdec.h      |  1 +
 libavcodec/aac/aacdec_usac.c | 25 +++++++++++++++----------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/libavcodec/aac/aacdec.h b/libavcodec/aac/aacdec.h
index f0a33e7ac3..a2ef4a82e8 100644
--- a/libavcodec/aac/aacdec.h
+++ b/libavcodec/aac/aacdec.h
@@ -125,6 +125,7 @@ typedef struct LongTermPrediction {
 typedef struct AACUsacElemData {
     uint8_t core_mode;
     uint8_t scale_factor_grouping;
+    uint8_t tns_data_present;
 
     /* Timewarping ratio */
 #define NUM_TW_NODES 16
diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 9b28a9e90b..97655787ee 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -877,7 +877,7 @@ static int decode_usac_stereo_info(AACDecContext *ac, AACUSACConfig *usac,
     }
 
     us->tns_on_lr = 0;
-    sce1->tns.present = sce2->tns.present = 0;
+    ue1->tns_data_present = ue2->tns_data_present = 0;
     if (tns_active) {
         int common_tns = 0;
         if (us->common_window)
@@ -889,15 +889,17 @@ static int decode_usac_stereo_info(AACDecContext *ac, AACUSACConfig *usac,
             if (ret < 0)
                 return ret;
             memcpy(&sce2->tns, &sce1->tns, sizeof(sce1->tns));
-            sce2->tns.present = 0;
-            sce1->tns.present = 0;
+            sce2->tns.present = 1;
+            sce1->tns.present = 1;
+            ue1->tns_data_present = 0;
+            ue2->tns_data_present = 0;
         } else {
             if (get_bits1(gb)) {
-                sce2->tns.present = 1;
-                sce1->tns.present = 1;
+                ue1->tns_data_present = 1;
+                ue2->tns_data_present = 1;
             } else {
-                sce2->tns.present = get_bits1(gb);
-                sce1->tns.present = !sce2->tns.present;
+                ue2->tns_data_present = get_bits1(gb);
+                ue1->tns_data_present = !ue2->tns_data_present;
             }
         }
     }
@@ -1277,12 +1279,14 @@ static int decode_usac_core_coder(AACDecContext *ac, AACUSACConfig *usac,
     uint8_t global_gain;
 
     us->common_window = 0;
-    che->ch[0].tns.present = che->ch[1].tns.present = 0;
 
     for (int ch = 0; ch < nb_channels; ch++) {
         SingleChannelElement *sce = &che->ch[ch];
         AACUsacElemData *ue = &sce->ue;
 
+        sce->tns.present = 0;
+        ue->tns_data_present = 0;
+
         ue->core_mode = get_bits1(gb);
     }
 
@@ -1306,7 +1310,7 @@ static int decode_usac_core_coder(AACDecContext *ac, AACUSACConfig *usac,
 
         if ((nb_channels == 1) ||
             (che->ch[0].ue.core_mode != che->ch[1].ue.core_mode))
-            sce->tns.present = get_bits1(gb);
+            ue->tns_data_present = get_bits1(gb);
 
         /* fd_channel_stream */
         global_gain = get_bits(gb, 8);
@@ -1351,7 +1355,8 @@ static int decode_usac_core_coder(AACDecContext *ac, AACUSACConfig *usac,
 
         ac->dsp.dequant_scalefactors(sce);
 
-        if (sce->tns.present) {
+        if (ue->tns_data_present) {
+            sce->tns.present = 1;
             ret = ff_aac_decode_tns(ac, &sce->tns, gb, ics);
             if (ret < 0)
                 return ret;
-- 
2.43.0.381.gb435a96ce8
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[FFmpeg-devel] [PATCH 4/4] aacdec_usac: skip coeff decoding if the number to be decoded is 0

[Lynne via ffmpeg-devel]

Yet another thing not mentioned in the spec.
---
 libavcodec/aac/aacdec_usac.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 97655787ee..5dd489a43b 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -572,9 +572,15 @@ static int decode_spectrum_and_dequant_ac(AACDecContext *s, float coef[1024],
     int gb_count;
     GetBitContext gb2;
 
-    ff_aac_ac_init(&ac, gb);
     c = ff_aac_ac_map_process(state, reset, N);
 
+    if (!len) {
+        ff_aac_ac_finish(state, 0, N);
+        return 0;
+    }
+
+    ff_aac_ac_init(&ac, gb);
+
     /* Backup reader for rolling back by 14 bits at the end */
     gb2 = *gb;
     gb_count = get_bits_count(&gb2);
-- 
2.43.0.381.gb435a96ce8
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