MP3 Decoder
The AT8xC51SND2C implement a MPEG I/II audio layer 3 decoder better known as
MP3 decoder.
In MPEG I (ISO 11172-3) three layers of compression have been standardized support-
ing three sampling frequencies: 48, 44.1, and 32 kHz. Among these layers, layer 3
allows highest compression rate of about 12:1 while still maintaining CD audio quality.
For example, 3 minutes of CD audio (16-bit PCM, 44.1 kHz) data, which needs about
32M bytes of storage, can be encoded into only 2.7M bytes of MPEG I audio layer 3
data.
In MPEG II (ISO 13818-3), three additional sampling frequencies: 24, 22.05, and 16 kHz
are supported for low bit rates applications.
The AT8xC51SND2C can decode in real-time the MPEG I audio layer 3 encoded data
into a PCM audio data, and also supports MPEG II audio layer 3 additional frequencies.
Additional features are supported by the AT8xC51SND2C MP3 decoder such as volume
control, bass, medium, and treble controls, bass boost effect and ancillary data
extraction.
Decoder
Description
The C51 core interfaces to the MP3 decoder through nine special function registers:
MP3CON, the MP3 Control register (see Table 74); MP3STA, the MP3 Status register
(see Table 75); MP3DAT, the MP3 Data register (see Table 76); MP3ANC, the Ancillary
Data register (see Table 78); MP3VOL and MP3VOR, the MP3 Volume Left and Right
Control registers (see Table 79 and Table 80); MP3BAS, MP3MED, and MP3TRE, the
MP3 Bass, Medium, and Treble Control registers (see Table 81, Table 82, and
Table 83); and MPCLK, the MP3 Clock Divider register (see Table 84).
Figure 40 shows the MP3 decoder block diagram.
Figure 40. MP3 Decoder Block Diagram
1K Bytes
Frame Buffer
MP3DAT
Audio Data
From C51
Header Checker
Huffman Decoder
8
Dequantizer
Stereo Processor
Side Information
MPxREQ
MP3STA1.n
ERRxxx MPFS1:0 MPVER
MP3STA.5:3 MP3STA.2:1 MP3STA.0
MP3
CLOCK
Ancillary Buffer
MP3ANC
MPEN
MP3CON.7
Sub-band
Synthesis
Decoded Data
To Audio Interface
16
Anti-Aliasing
IMDCT
MPBBST
MP3CON.6
MP3VOL MP3VOR MP3BAS MP3MED MP3TRE
62
AT8xC51SND2C
4341D–MP3–04/05
ATMEL [ ATMEL ]
