diff options
Diffstat (limited to 'libAACenc/include/aacenc_lib.h')
| -rw-r--r-- | libAACenc/include/aacenc_lib.h | 58 |
1 files changed, 45 insertions, 13 deletions
diff --git a/libAACenc/include/aacenc_lib.h b/libAACenc/include/aacenc_lib.h index 649cfba..6002366 100644 --- a/libAACenc/include/aacenc_lib.h +++ b/libAACenc/include/aacenc_lib.h @@ -316,7 +316,8 @@ if the parameter was not set from extern. The bitrate depends on the number of e channels and sampling rate and is determined as follows. \code AAC-LC (AOT_AAC_LC): 1.5 bits per sample -HE-AAC (AOT_SBR): 0.625 bits per sample +HE-AAC (AOT_SBR): 0.625 bits per sample (dualrate sbr) +HE-AAC (AOT_SBR): 1.125 bits per sample (downsampled sbr) HE-AAC v2 (AOT_PS): 0.5 bits per sample \endcode @@ -416,8 +417,9 @@ determines the maximum allowed bitrate for AAC-LC. For HE-AAC and HE-AAC v2 a li look-up table is used. A good working point in terms of audio quality, sampling rate and bitrate, is at 1 to 1.5 -bits/audio sample for AAC-LC, 0.625 bits/audio sample for HE-AAC and 0.5 bits/audio sample -for HE-AAC v2. For example for one channel with a sampling frequency of 48 kHz, the range from +bits/audio sample for AAC-LC, 0.625 bits/audio sample for dualrate HE-AAC, 1.125 bits/audio sample +for downsampled HE-AAC and 0.5 bits/audio sample for HE-AAC v2. +For example for one channel with a sampling frequency of 48 kHz, the range from 48 kbit/s to 72 kbit/s achieves reasonable audio quality for AAC-LC. For HE-AAC and HE-AAC v2 the lowest possible audio input sampling frequency is 16 kHz because then the @@ -434,7 +436,7 @@ quality at that bitrate than HE-AAC or HE-AAC v2. The following table provides an overview of recommended encoder configuration parameters which we determined by virtue of numerous listening tests. -\subsection reommendedConfigLC AAC-LC, HE-AAC, HE-AACv2. +\subsection reommendedConfigLC AAC-LC, HE-AAC, HE-AACv2 in Dualrate SBR mode. \verbatim ----------------------------------------------------------------------------------- Audio Object Type | Bit Rate Range | Supported | Preferred | No. of @@ -457,8 +459,8 @@ AAC LC + SBR | 64000 - 128000 | 32.00, 44.10, 48.00 | 48.00 | -------------------+------------------+-----------------------+------------+------- AAC LC + SBR | 64000 - 69999 | 32.00, 44.10, 48.00 | 32.00 | 5, 5.1 AAC LC + SBR | 70000 - 159999 | 32.00, 44.10, 48.00 | 44.10 | 5, 5.1 -AAC LC + SBR | 160000 - 319999 | 32.00, 44.10, 48.00 | 48.00 | 5, 5.1 -AAC LC + SBR | 320000 - 640000 | 64.00, 88.20, 96.00 | 96.00 | 5, 5.1 +AAC LC + SBR | 160000 - 245999 | 32.00, 44.10, 48.00 | 48.00 | 5 +AAC LC + SBR | 160000 - 265999 | 32.00, 44.10, 48.00 | 48.00 | 5.1 -------------------+------------------+-----------------------+------------+------- AAC LC | 8000 - 15999 | 11.025, 12.00, 16.00 | 12.00 | 1 AAC LC | 16000 - 23999 | 16.00 | 16.00 | 1 @@ -481,7 +483,7 @@ AAC LC | 280000 - 800000 | 32.00, 44.10, 48.00 | 44.10 | 5, ----------------------------------------------------------------------------------- \endverbatim \n -\subsection reommendedConfigLD AAC-LD, AAC-ELD, AAC-ELD with SBR. +\subsection reommendedConfigLD AAC-LD, AAC-ELD, AAC-ELD with SBR in Dualrate SBR mode. \verbatim ----------------------------------------------------------------------------------- Audio Object Type | Bit Rate Range | Supported | Preferred | No. of @@ -489,18 +491,20 @@ Audio Object Type | Bit Rate Range | Supported | Preferred | No. | | [kHz] | Rate | | | | [kHz] | -------------------+------------------+-----------------------+------------+------- -ELD + SBR | 16000 - 24999 | 32.00 - 44.10 | 32.00 | 1 +ELD + SBR | 18000 - 24999 | 32.00 - 44.10 | 32.00 | 1 ELD + SBR | 25000 - 31999 | 32.00 - 48.00 | 32.00 | 1 ELD + SBR | 32000 - 64000 | 32.00 - 48.00 | 48.00 | 1 -------------------+------------------+-----------------------+------------+------- ELD + SBR | 32000 - 51999 | 32.00 - 48.00 | 44.10 | 2 ELD + SBR | 52000 - 128000 | 32.00 - 48.00 | 48.00 | 2 -------------------+------------------+-----------------------+------------+------- -ELD + SBR | 72000 - 192000 | 44.10 - 48.00 | 48.00 | 3 +ELD + SBR | 72000 - 160000 | 44.10 - 48.00 | 48.00 | 3 -------------------+------------------+-----------------------+------------+------- -ELD + SBR | 96000 - 256000 | 44.10 - 48.00 | 48.00 | 4 +ELD + SBR | 96000 - 212000 | 44.10 - 48.00 | 48.00 | 4 -------------------+------------------+-----------------------+------------+------- -ELD + SBR | 120000 - 320000 | 44.10 - 48.00 | 48.00 | 5 +ELD + SBR | 120000 - 246000 | 44.10 - 48.00 | 48.00 | 5 +-------------------+------------------+-----------------------+------------+------- +ELD + SBR | 120000 - 266000 | 44.10 - 48.00 | 48.00 | 5.1 -------------------+------------------+-----------------------+------------+------- LD, ELD | 16000 - 19999 | 16.00 - 24.00 | 16.00 | 1 LD, ELD | 20000 - 39999 | 16.00 - 32.00 | 24.00 | 1 @@ -531,13 +535,33 @@ LD, ELD | 340000 - 960000 | 44.10 - 48.00 | 48.00 | ----------------------------------------------------------------------------------- \endverbatim \n +\subsection reommendedConfigELD AAC-ELD with SBR in Downsampled SBR mode. +\verbatim +----------------------------------------------------------------------------------- +Audio Object Type | Bit Rate Range | Supported | Preferred | No. of + | [bit/s] | Sampling Rates | Sampl. | Chan. + | | [kHz] | Rate | + | | | [kHz] | +-------------------+------------------+-----------------------+------------+------- +ELD + SBR | 18000 - 24999 | 16.00 - 22.05 | 22.05 | 1 +(downsampled SBR) | 25000 - 35999 | 22.05 - 32.00 | 24.00 | 1 + | 36000 - 64000 | 32.00 - 48.00 | 32.00 | 1 +----------------------------------------------------------------------------------- +\endverbatim \n + + \page ENCODERBEHAVIOUR Encoder Behaviour \section BEHAVIOUR_BANDWIDTH Bandwidth The FDK AAC encoder usually does not use the full frequency range of the input signal, but restricts the bandwidth according to certain library-internal settings. They can be changed in the table "bandWidthTable" in the -file bandwidth.cpp (if available), or via command-line argument "-w" (see chapter \ref CommandLineUsage). +file bandwidth.cpp (if available). + +The encoder API provides the ::AACENC_BANDWIDTH parameter to adjust the bandwidth explicitly. +\code +aacEncoder_SetParam(hAacEncoder, AACENC_BANDWIDTH, value); +\endcode However it is not recommended to change these settings, because they are based on numerious listening tests and careful tweaks to ensure the best overall encoding quality. @@ -638,7 +662,6 @@ an MPEG-2 AOT is choosen since PNS is an MPEG-4 AAC feature. If SBR is activated, the encoder automatically deactivates PNS internally. If TNS is disabled but PNS is allowed, the encoder deactivates PNS calculation internally. - */ #ifndef _AAC_ENC_LIB_H_ @@ -875,6 +898,15 @@ typedef enum - 0: MPEG channel ordering (e. g. 5.1: C, L, R, SL, SR, LFE). (default) - 1: WAVE file format channel ordering (e. g. 5.1: L, R, C, LFE, SL, SR). */ + AACENC_SBR_RATIO = 0x0108, /*!< Controls activation of downsampled SBR. With downsampled SBR, the delay will be + shorter. On the other hand, for achieving the same quality level, downsampled SBR + needs more bits than dual-rate SBR. + With downsampled SBR, the AAC encoder will work at the same sampling rate as the + SBR encoder (single rate). + Downsampled SBR is supported for AAC-ELD and HE-AACv1. + - 1: Downsampled SBR (default for ELD). + - 2: Dual-rate SBR (default for HE-AAC). */ + AACENC_AFTERBURNER = 0x0200, /*!< This parameter controls the use of the afterburner feature. The afterburner is a type of analysis by synthesis algorithm which increases the audio quality but also the required processing power. It is recommended to always |