Enhance encoder audio quality for vbr (FDKenc v4.0.1).

Bug: 149489652
Test: atest android.media.cts.EncoderTest#testAACEncoders
Change-Id: I4af82bd104a94710d1977eaa0bd086aa743d3adf

5 files changed, 36 insertions, 48 deletions

diff --git a/libAACenc/include/aacenc_lib.h b/libAACenc/include/aacenc_lib.h
index 01a9d36..71f7556 100644
--- a/libAACenc/include/aacenc_lib.h
+++ b/libAACenc/include/aacenc_lib.h
@@ -436,31 +436,32 @@ audio quality.
 
 
 \subsection vbrmode Variable Bitrate Mode
-The encoder provides various Variable Bitrate Modes that differ in audio quality
-and average overall bitrate. The given values are averages over time, different
-encoder settings and strongly depend on the type of audio signal. The VBR
-configurations can be adjusted via ::AACENC_BITRATEMODE encoder parameter.
+The variable bitrate (VBR) mode coding adapts the bit consumption to the
+psychoacoustic requirements of the signal. The encoder ignores the user-defined
+bit rate and selects a suitable pre-defined configuration based on the provided
+AOT. The VBR mode 1 is tuned for HE-AACv2, for VBR mode 2, HE-AACv1 should be
+used. VBR modes 3-5 should be used with Low-Complexity AAC. When encoding
+AAC-ELD, the best mode is selected automatically.
+
+The bitrates given in the table are averages over time and different encoder
+settings. They strongly depend on the type of audio signal. The VBR
+configurations can be adjusted with the ::AACENC_BITRATEMODE encoder parameter.
 \verbatim
---------------------------------------------
- VBR_MODE | Approx. Bitrate in kbps/channel
-          |     AAC-LC    |  AAC-LD/AC_ELD
-----------+---------------+-----------------
-    VBR_1 |    32 -  48   |      32 -  56
-    VBR_2 |    40 -  56   |      40 -  64
-    VBR_3 |    48 -  64   |      48 -  72
-    VBR_4 |    64 -  80   |      64 -  88
-    VBR_5 |    96 - 120   |     112 - 144
+-----------------------------------------------
+ VBR_MODE | Approx. Bitrate in kbps for stereo
+          |     AAC-LC    |      AAC-ELD
+----------+---------------+--------------------
+    VBR_1 | 32 (HE-AACv2) |         48
+    VBR_2 | 72 (HE-AACv1) |         56
+    VBR_3 |      112      |         72
+    VBR_4 |      148      |        148
+    VBR_5 |      228      |        224
 --------------------------------------------
 \endverbatim
-The bitrate ranges apply for individual audio channels. In case of multichannel
-configurations the average bitrate might be estimated by multiplying with the
-number of effective channels. This corresponds to all audio input channels
-exclusively the low frequency channel. At configurations which are making use of
-downmix modules the AAC core channels respectively downmix channels shall be
-considered. For ::AACENC_AOT which are using SBR, the average bitrate can be
-estimated by using the ratio of 0.5 for dualrate SBR and 0.75 for downsampled
-SBR configurations.
-
+Note that these figures are valid for stereo encoding only. VBR modes 2-5 will
+yield much lower bit rates when encoding single-channel input. For
+configurations which are making use of downmix modules the AAC core channels
+respectively downmix channels shall be considered.
 
 \subsection encQual Audio Quality Considerations
 The default encoder configuration is suggested to be used. Encoder tools such as
diff --git a/libAACenc/src/aacenc_lib.cpp b/libAACenc/src/aacenc_lib.cpp
index 15b06bd..2c2010f 100644
--- a/libAACenc/src/aacenc_lib.cpp
+++ b/libAACenc/src/aacenc_lib.cpp
@@ -110,7 +110,7 @@ amm-info@iis.fraunhofer.de
 /* Encoder library info */
 #define AACENCODER_LIB_VL0 4
 #define AACENCODER_LIB_VL1 0
-#define AACENCODER_LIB_VL2 0
+#define AACENCODER_LIB_VL2 1
 #define AACENCODER_LIB_TITLE "AAC Encoder"
 #ifdef __ANDROID__
 #define AACENCODER_LIB_BUILD_DATE ""
diff --git a/libAACenc/src/adj_thr.cpp b/libAACenc/src/adj_thr.cpp
index 226d003..239abd0 100644
--- a/libAACenc/src/adj_thr.cpp
+++ b/libAACenc/src/adj_thr.cpp
@@ -1302,14 +1302,6 @@ static void FDKaacEnc_reduceThresholdsVBR(
           if (sfbThrReducedLdData < FL2FXCONST_DBL(-0.5f))
             sfbThrReducedLdData = FL2FXCONST_DBL(-1.f);
 
-          /* minimum of 29 dB Ratio for Thresholds */
-          if ((sfbEnLdData + FL2FXCONST_DBL(1.0f)) >
-              FL2FXCONST_DBL(9.6336206 / LD_DATA_SCALING)) {
-            sfbThrReducedLdData = fixMax(
-                sfbThrReducedLdData,
-                sfbEnLdData - FL2FXCONST_DBL(9.6336206 / LD_DATA_SCALING));
-          }
-
           sfbThrReducedLdData = fixMax(MIN_LDTHRESH, sfbThrReducedLdData);
 
           qcOutChan->sfbThresholdLdData[sfbGrp + sfb] = sfbThrReducedLdData;
diff --git a/libAACenc/src/bandwidth.cpp b/libAACenc/src/bandwidth.cpp
index 36cd64d..e814f05 100644
--- a/libAACenc/src/bandwidth.cpp
+++ b/libAACenc/src/bandwidth.cpp
@@ -1,7 +1,7 @@
 /* -----------------------------------------------------------------------------
 Software License for The Fraunhofer FDK AAC Codec Library for Android
 
-© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
+© Copyright  1995 - 2019 Fraunhofer-Gesellschaft zur Förderung der angewandten
 Forschung e.V. All rights reserved.
 
  1.    INTRODUCTION
@@ -151,11 +151,11 @@ typedef struct {
 
 static const BANDWIDTH_TAB_VBR bandWidthTableVBR[] = {
     {AACENC_BR_MODE_CBR, 0, 0},
-    {AACENC_BR_MODE_VBR_1, 13050, 13050},
-    {AACENC_BR_MODE_VBR_2, 13050, 13050},
-    {AACENC_BR_MODE_VBR_3, 14260, 14260},
-    {AACENC_BR_MODE_VBR_4, 15500, 15500},
-    {AACENC_BR_MODE_VBR_5, 48000, 48000},
+    {AACENC_BR_MODE_VBR_1, 13000, 13000},
+    {AACENC_BR_MODE_VBR_2, 13000, 13000},
+    {AACENC_BR_MODE_VBR_3, 15750, 15750},
+    {AACENC_BR_MODE_VBR_4, 16500, 16500},
+    {AACENC_BR_MODE_VBR_5, 19293, 19293},
     {AACENC_BR_MODE_SFR, 0, 0},
     {AACENC_BR_MODE_FF, 0, 0}
 
diff --git a/libAACenc/src/qc_main.cpp b/libAACenc/src/qc_main.cpp
index ba3bc7e..bcfaa23 100644
--- a/libAACenc/src/qc_main.cpp
+++ b/libAACenc/src/qc_main.cpp
@@ -1,7 +1,7 @@
 /* -----------------------------------------------------------------------------
 Software License for The Fraunhofer FDK AAC Codec Library for Android
 
-© Copyright  1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
+© Copyright  1995 - 2019 Fraunhofer-Gesellschaft zur Förderung der angewandten
 Forschung e.V. All rights reserved.
 
  1.    INTRODUCTION
@@ -121,20 +121,15 @@ typedef struct {
 
 static const TAB_VBR_QUAL_FACTOR tableVbrQualFactor[] = {
     {QCDATA_BR_MODE_VBR_1,
-     FL2FXCONST_DBL(0.160f)}, /* Approx. 32 -  48 (AC-LC),  32 -  56
-                                 (AAC-LD/ELD) kbps/channel */
+     FL2FXCONST_DBL(0.150f)}, /* Approx.  32 kbps mono   AAC-LC + SBR + PS */
     {QCDATA_BR_MODE_VBR_2,
-     FL2FXCONST_DBL(0.148f)}, /* Approx. 40 -  56 (AC-LC),  40 -  64
-                                 (AAC-LD/ELD) kbps/channel */
+     FL2FXCONST_DBL(0.162f)}, /* Approx.  64 kbps stereo AAC-LC + SBR      */
     {QCDATA_BR_MODE_VBR_3,
-     FL2FXCONST_DBL(0.135f)}, /* Approx. 48 -  64 (AC-LC),  48 -  72
-                                 (AAC-LD/ELD) kbps/channel */
+     FL2FXCONST_DBL(0.176f)}, /* Approx.  96 kbps stereo AAC-LC            */
     {QCDATA_BR_MODE_VBR_4,
-     FL2FXCONST_DBL(0.111f)}, /* Approx. 64 -  80 (AC-LC),  64 -  88
-                                 (AAC-LD/ELD) kbps/channel */
+     FL2FXCONST_DBL(0.120f)}, /* Approx. 128 kbps stereo AAC-LC            */
     {QCDATA_BR_MODE_VBR_5,
-     FL2FXCONST_DBL(0.070f)} /* Approx. 96 - 120 (AC-LC), 112 - 144
-                                (AAC-LD/ELD) kbps/channel */
+     FL2FXCONST_DBL(0.070f)} /* Approx. 192 kbps stereo AAC-LC            */
 };
 
 static INT isConstantBitrateMode(const QCDATA_BR_MODE bitrateMode) {