AT89SND2CMP3B_14 Datasheet, PDF (63/242 Pages) ATMEL Corporation – Stand-alone MP3 Decoder

AT8xC51SND2C/MP3B
13. 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 supporting three
sampling frequencies: 48, 44.1, and 32 kHz. Among these layers, layer 3 allows highest com-
pression 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.
13.1 Decoder
13.1.1
Description
The C51 core interfaces to the MP3 decoder through nine special function registers: MP3CON,
the MP3 Control register (see Table 13-5); MP3STA, the MP3 Status register (see Table 13-6);
MP3DAT, the MP3 Data register (see Table 13-7); MP3ANC, the Ancillary Data register (see
Table 13-9); MP3VOL and MP3VOR, the MP3 Volume Left and Right Control registers (see
Table 13-10 and Table 13-11); MP3BAS, MP3MED, and MP3TRE, the MP3 Bass, Medium, and
Treble Control registers (see Table 13-12, Table 13-13, and Table 13-14); and MPCLK, the MP3
Clock Divider register (see Table 13-15).
Figure 13-1 shows the MP3 decoder block diagram.
Figure 13-1. MP3 Decoder Block Diagram
Audio Data 8
From C51
1K Bytes
Frame Buffer
MP3DAT
Header Checker
Huffman Decoder
Dequantizer Stereo Processor
MP3
CLOCK
MPxREQ
MP3STA1.n
ERRxxx MPFS1:0 MPVER
MP3STA.5:3 MP3STA.2:1 MP3STA.0
Side Information
Ancillary Buffer
MP3ANC
MPEN
MP3CON.7
Anti-Aliasing
IMDCT
Sub-band
Synthesis
16 Decoded Data
To Audio Interface
MPBBST
MP3CON.6
MP3VOL
MP3VOR
MP3BAS
MP3MED
MP3TRE
63
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