VS1053B Datasheet, PDF (34/79 Pages) List of Unclassifed Manufacturers – Ogg Vorbis/MP3/AAC/WMA/MIDI AUDIO CODEC

VLSI
Solution ^y
VS1053b preliminary
VS1053B
8. FUNCTIONAL DESCRIPTION
8.3 Data Flow of VS1053b
SDI
Bitstream
FIFO
MP3 MP2 MP1
WAV ADPCM
WMA AAC
MIDI Vorbis
SM_ADPCM=0
AIADDR = 0
User
Application
AIADDR != 0
SB_AMPLITUDE=0 ST_AMPLITUDE=0
Bass
enhancer
SB_AMPLITUDE!=0
Treble
control
ST_AMPLITUDE!=0
Ear
Speaker
Audio
FIFO
2048 stereo
samples
L
S.rate.conv.
and DAC
R
Volume
SCI_VOL _control
Figure 13: Data Flow of VS1053b.
First, depending on the audio data, and provided ADPCM encoding mode is not set, Ogg Vorbis, MP3,
WMA, AAC, PCM WAV, IMA ADPCM WAV, or MIDI data is received and decoded from the SDI bus.
After decoding, if SCI AIADDR is non-zero, application code is executed from the address pointed to
by that register. For more details, see Application Notes for VS10XX.
Then data may be sent to the Bass Enhancer and Treble Control depending on the SCI BASS register.
Next, headphone processing is performed, if the EarSpeaker spatial processing is active.
After that the data to the Audio FIFO, which holds the data until it is read by the Audio interrupt and fed
to the samplerate converter and DACs. The size of the audio FIFO is 2048 stereo (2×16-bit) samples, or
8 KiB.
The samplerate converter upsamples all different samplerates to XTALI/2, or 128 times the highest usable
samplerate with 18-bit precision. Volume control is performed in the upsampled domain. New volume
settings are loaded only when the upsampled signal crosses the zero point (or after a timeout). This zero-
crossing detection almost completely removes all audible noise that occurs when volume is suddenly
changed.
The samplerate conversion to a common samplerate removes the need for complex PLL-based clocking
schemes and allows almost unlimited sample rate accuracy with one fixed input clock frequency. With
a 12.288 MHz clock, the DA converter operates at 128 × 48 kHz, i.e. 6.144 MHz, and creates a stereo
in-phase analog signal. The oversampled output is low-pass filtered by an on-chip analog filter. This
signal is then forwarded to the earphone amplifier.
Version 0.5, 2007-12-03
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