mirror of https://github.com/mstorsjo/fdk-aac.git
Enhance encoder audio quality for vbr (FDKenc v4.0.1).
Bug: 149489652 Test: atest android.media.cts.EncoderTest#testAACEncoders Change-Id: I4af82bd104a94710d1977eaa0bd086aa743d3adf
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Fraunhofer IIS FDK
Jean-Michel Trivi
parent
79305e068e
commit
443d38963e
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@ -436,31 +436,32 @@ audio quality.
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\subsection vbrmode Variable Bitrate Mode
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The encoder provides various Variable Bitrate Modes that differ in audio quality
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and average overall bitrate. The given values are averages over time, different
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encoder settings and strongly depend on the type of audio signal. The VBR
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configurations can be adjusted via ::AACENC_BITRATEMODE encoder parameter.
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The variable bitrate (VBR) mode coding adapts the bit consumption to the
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psychoacoustic requirements of the signal. The encoder ignores the user-defined
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bit rate and selects a suitable pre-defined configuration based on the provided
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AOT. The VBR mode 1 is tuned for HE-AACv2, for VBR mode 2, HE-AACv1 should be
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used. VBR modes 3-5 should be used with Low-Complexity AAC. When encoding
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AAC-ELD, the best mode is selected automatically.
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The bitrates given in the table are averages over time and different encoder
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settings. They strongly depend on the type of audio signal. The VBR
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configurations can be adjusted with the ::AACENC_BITRATEMODE encoder parameter.
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\verbatim
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--------------------------------------------
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VBR_MODE | Approx. Bitrate in kbps/channel
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| AAC-LC | AAC-LD/AC_ELD
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----------+---------------+-----------------
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VBR_1 | 32 - 48 | 32 - 56
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VBR_2 | 40 - 56 | 40 - 64
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VBR_3 | 48 - 64 | 48 - 72
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VBR_4 | 64 - 80 | 64 - 88
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VBR_5 | 96 - 120 | 112 - 144
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-----------------------------------------------
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VBR_MODE | Approx. Bitrate in kbps for stereo
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| AAC-LC | AAC-ELD
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----------+---------------+--------------------
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VBR_1 | 32 (HE-AACv2) | 48
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VBR_2 | 72 (HE-AACv1) | 56
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VBR_3 | 112 | 72
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VBR_4 | 148 | 148
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VBR_5 | 228 | 224
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--------------------------------------------
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\endverbatim
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The bitrate ranges apply for individual audio channels. In case of multichannel
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configurations the average bitrate might be estimated by multiplying with the
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number of effective channels. This corresponds to all audio input channels
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exclusively the low frequency channel. At configurations which are making use of
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downmix modules the AAC core channels respectively downmix channels shall be
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considered. For ::AACENC_AOT which are using SBR, the average bitrate can be
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estimated by using the ratio of 0.5 for dualrate SBR and 0.75 for downsampled
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SBR configurations.
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Note that these figures are valid for stereo encoding only. VBR modes 2-5 will
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yield much lower bit rates when encoding single-channel input. For
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configurations which are making use of downmix modules the AAC core channels
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respectively downmix channels shall be considered.
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\subsection encQual Audio Quality Considerations
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The default encoder configuration is suggested to be used. Encoder tools such as
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@ -110,7 +110,7 @@ amm-info@iis.fraunhofer.de
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/* Encoder library info */
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#define AACENCODER_LIB_VL0 4
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#define AACENCODER_LIB_VL1 0
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#define AACENCODER_LIB_VL2 0
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#define AACENCODER_LIB_VL2 1
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#define AACENCODER_LIB_TITLE "AAC Encoder"
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#ifdef __ANDROID__
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#define AACENCODER_LIB_BUILD_DATE ""
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@ -1302,14 +1302,6 @@ static void FDKaacEnc_reduceThresholdsVBR(
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if (sfbThrReducedLdData < FL2FXCONST_DBL(-0.5f))
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sfbThrReducedLdData = FL2FXCONST_DBL(-1.f);
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/* minimum of 29 dB Ratio for Thresholds */
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if ((sfbEnLdData + FL2FXCONST_DBL(1.0f)) >
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FL2FXCONST_DBL(9.6336206 / LD_DATA_SCALING)) {
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sfbThrReducedLdData = fixMax(
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sfbThrReducedLdData,
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sfbEnLdData - FL2FXCONST_DBL(9.6336206 / LD_DATA_SCALING));
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}
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sfbThrReducedLdData = fixMax(MIN_LDTHRESH, sfbThrReducedLdData);
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qcOutChan->sfbThresholdLdData[sfbGrp + sfb] = sfbThrReducedLdData;
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@ -1,7 +1,7 @@
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/* -----------------------------------------------------------------------------
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Software License for The Fraunhofer FDK AAC Codec Library for Android
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© Copyright 1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
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© Copyright 1995 - 2019 Fraunhofer-Gesellschaft zur Förderung der angewandten
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Forschung e.V. All rights reserved.
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1. INTRODUCTION
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@ -151,11 +151,11 @@ typedef struct {
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static const BANDWIDTH_TAB_VBR bandWidthTableVBR[] = {
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{AACENC_BR_MODE_CBR, 0, 0},
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{AACENC_BR_MODE_VBR_1, 13050, 13050},
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{AACENC_BR_MODE_VBR_2, 13050, 13050},
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{AACENC_BR_MODE_VBR_3, 14260, 14260},
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{AACENC_BR_MODE_VBR_4, 15500, 15500},
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{AACENC_BR_MODE_VBR_5, 48000, 48000},
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{AACENC_BR_MODE_VBR_1, 13000, 13000},
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{AACENC_BR_MODE_VBR_2, 13000, 13000},
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{AACENC_BR_MODE_VBR_3, 15750, 15750},
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{AACENC_BR_MODE_VBR_4, 16500, 16500},
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{AACENC_BR_MODE_VBR_5, 19293, 19293},
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{AACENC_BR_MODE_SFR, 0, 0},
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{AACENC_BR_MODE_FF, 0, 0}
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@ -1,7 +1,7 @@
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/* -----------------------------------------------------------------------------
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Software License for The Fraunhofer FDK AAC Codec Library for Android
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© Copyright 1995 - 2018 Fraunhofer-Gesellschaft zur Förderung der angewandten
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© Copyright 1995 - 2019 Fraunhofer-Gesellschaft zur Förderung der angewandten
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Forschung e.V. All rights reserved.
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1. INTRODUCTION
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@ -121,20 +121,15 @@ typedef struct {
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static const TAB_VBR_QUAL_FACTOR tableVbrQualFactor[] = {
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{QCDATA_BR_MODE_VBR_1,
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FL2FXCONST_DBL(0.160f)}, /* Approx. 32 - 48 (AC-LC), 32 - 56
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(AAC-LD/ELD) kbps/channel */
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FL2FXCONST_DBL(0.150f)}, /* Approx. 32 kbps mono AAC-LC + SBR + PS */
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{QCDATA_BR_MODE_VBR_2,
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FL2FXCONST_DBL(0.148f)}, /* Approx. 40 - 56 (AC-LC), 40 - 64
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(AAC-LD/ELD) kbps/channel */
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FL2FXCONST_DBL(0.162f)}, /* Approx. 64 kbps stereo AAC-LC + SBR */
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{QCDATA_BR_MODE_VBR_3,
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FL2FXCONST_DBL(0.135f)}, /* Approx. 48 - 64 (AC-LC), 48 - 72
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(AAC-LD/ELD) kbps/channel */
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FL2FXCONST_DBL(0.176f)}, /* Approx. 96 kbps stereo AAC-LC */
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{QCDATA_BR_MODE_VBR_4,
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FL2FXCONST_DBL(0.111f)}, /* Approx. 64 - 80 (AC-LC), 64 - 88
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(AAC-LD/ELD) kbps/channel */
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FL2FXCONST_DBL(0.120f)}, /* Approx. 128 kbps stereo AAC-LC */
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{QCDATA_BR_MODE_VBR_5,
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FL2FXCONST_DBL(0.070f)} /* Approx. 96 - 120 (AC-LC), 112 - 144
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(AAC-LD/ELD) kbps/channel */
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FL2FXCONST_DBL(0.070f)} /* Approx. 192 kbps stereo AAC-LC */
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};
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static INT isConstantBitrateMode(const QCDATA_BR_MODE bitrateMode) {
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