Specifications
VLSI
Solution
y
VS1053b
VS1053B
9. OPERATION
9.11.3 AAC
Parameter Address Usage
config1 0x1e03(7:4) SBR and PS select
sceFoundMask 0x1e2a Single channel elements found
cpeFoundMask 0x1e2b Channel pair elements found
lfeFoundMask 0x1e2c Low frequency elements found
playSelect 0x1e2d Play element selection
dynCompress 0x1e2e Compress coefficient for DRC, -8192=1.0
dynBoost 0x1e2f Boost coefficient for DRC, 8192=1.0
sbrAndPsStatus 0x1e30 SBR and PS available flags
playSelect determines which element to decode if a stream has multiple elements. The value is
set to 0 each time AAC decoding starts, which causes the first element that appears in the stream to be
selected for decoding. Other values are: 0x01 - select first single channel element (SCE), 0x02 - select
first channel pair element (CPE), 0x03 - select first low frequency element (LFE), S ∗ 16 + 5 - select
SCE number S, P ∗ 16 + 6 - select CPE number P, L ∗ 16 + 7 - select LFE number L. When automatic
selection has been performed, playSelect reflects the selected element.
sceFoundMask, cpeFoundMask, and lfeFoundMask indicate which elements have been found
in an AAC stream since the variables have last been cleared. The values can be used to present an element
selection menu with only the available elements.
dynCompress and dynBoost change the behavior of the dynamic range control (DRC) that is present
in some AAC streams. These are also initialized when AAC decoding starts.
sbrAndPsStatus indicates spectral band replication (SBR) and parametric stereo (PS) status.
Bit Usage
0 SBR present
1 upsampling active
2 PS present
3 PS active
Bits 7 to 4 in config1 can be used to control the SBR and PS decoding. Bits 5 and 4 select SBR mode
and bits 7 and 6 select PS mode. These configuration bits are useful if your AAC license does not cover
SBR and/or PS.
config1(5:4) Usage
’00’ normal mode, upsample <24 kHz AAC files
’01’ do not automatically upsample <24 kHz AAC files, but
enable upsampling if SBR is encountered
’10’ never upsample
’11’ disable SBR (also disables PS)
Version 1.01, 2008-05-22 61