CS6652 Amphion, CS6652 Datasheet - Page 6

• Manufacturer Part Number: CS6652
• Description: 2-stream Video Decoder
• Manufacturer: Amphion

Figure 3 represents a block diagram of the main functional blocks in the CS6652. This is followed by a high-level description of
these blocks, which is equally applicable to the CS6654.
Figure 3: CS6652 Multi-stream MPEG-2 Video Decoder Block Diagram Showing Memory Blocks
This controls switching between input elementary streams
and the selection of the correct parameters for a particular
stream, when the decoding of that stream is in progress. In
multi-stream mode switching from decoding one elementary
stream to another is done at the slice layer, specifically at the
end of a macroblock row. In MPEG-2 video the start and end
of a row of macroblocks always corresponds with the start
and end of a slice, although a macroblock row may contain
more than one slice. Within a slice various macroblock data is
coded differentially between the macroblocks (e.g. DC DCT
coefficient, motion vectors). This means that the slice provides
a carefully encapsulated group of data, at the end of which
6
STREAM SWITCHING AND SELECTION
CS6652/54
ES Select
processor
Video ES
micro-
ASD mem
CS mem
QM mem
TRN mem
PB mem
IDCT mem
PWB mem
DB mem
Input
Host
STREAMSELECT: ELEMENTARY
Interface
- Additional Stream Data memories
- Convert Scan memory
- Quantization matrix memories
- IDCT matrix memories
- Prediction Buffer memory
- IDCT coefficient memory
- Pixel Write-back memory
- Display Line-Buffer memory
mem
Host
ASD
mem
ASD
ES Parser
CS6652/CS6654 FUNCTIONAL DESCRIPTION
Regs
0
Multi-stream MPEG-2 Video Decoders
Stream Control 0
Regs
1
Stream Control 1
VLC Decoder
mem
mem
TRN
CS
Inverse DCT
Control & Stream Select
RLD &
Iquant
mem
QM
switching from one stream to another can be done with a
minimal requirement to store state, base and incremental
values of macroblock parameters.
Switching from decoding one stream to another is only done
when the last slice of the macroblock row has been decoded.
Therefore, each elementary stream is decoded one macroblock
row at a time, rather than simply slice by slice. This prevents
streams with a longer slice structure from monopolizing the
decoder. Switching at the slice layer necessitates the storage of
state variables in both the Video Stream Parser and VLC
Decoder, as well as the replication of various input buffers
and FIFOs for each elementary stream.
mem
QM
mem
IDCT
mem
PB
Motion
Comp
Recon
Pixel
PWB
mem
mem
mem
DB
DB
Display
Display
DMA1
Interface
DMA0
Frame
Store
Picture Data
Picture Data
SDRAMs
(stream 1)
(stream 0)
Frame
Store
Output
Output