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2004 Jan 26 18
Philips Semiconductors Product specification
MPEG-2 video and MPEG-audio/AC-3
audio encoder with multiplexer
SAA6752HS
Table 2 Format conversion
Notes
1. The 8 pixels at the right edge of the scaled picture are
not encoded.
2. Top field only.
7.2.6 VIDEO FILTERING
7.2.6.1 Adaptive mean filter
The SAA6752HS uses an adaptive mean filter. There are
three different filter modes that can be selected: median,
averaging or no filter.
The median algorithm provides better noise performance
and is well suited to suppress single noise spikes without
degrading the signal edges. The averaging algorithm is a
standard low-pass filter so has greater impact on signal
edges.
The default threshold and gain coefficients of this filter can
be overwritten viathe I
2
C-bus to allow user optimization for
different applications.
7.2.6.2 Horizontal pre-filter/decimation filter
There is a horizontal filter for Y and C and this can operate
as a pre-filter or decimation filter. It is a symmetrical FIR
filter with up to 8 coefficients programmable via the
I
2
C-bus.
7.2.6.3 Vertical chrominance filtering
For 4 :2:2to4:2:0 conversion, vertical filtering and
subsampling of the chrominance is performed. The
sequence of coefficients ismirrored in top and bottom field.
This generates the right phases of the chrominance
samples between the luminance samples (a non co-sited
sampling scheme).
7.2.7 VBI DATA EXTRACTION
The SAA6752HS supports the extraction of WSS and CC
data using two independent VBI data extractor modules.
The data is available via the I
2
C-bus.
The following VBI data formats are supported: Closed
Caption (CC525 and CC625) and Wide Screen Signalling
(WSS525 and WSS625). For CC525, CC625 and
WSS625 the sliced data from a video input processor (e.g.
SAA7114, SAA7115 or SAA7118) are extracted from the
digital video input signal and can be read via the I
2
C-bus.
For WSS525 an internal data slicer is available which
slices the oversampled raw data, which are delivered by
the video input processor. The extracted WSS525 signal
can be read via the I
2
C-bus.
Optionally the automatic insertion of extracted Closed
Caption data into the user data area of a video stream is
possible (for details see Section 7.3.8).
7.3 Video compression
7.3.1 GENERAL
Compression of video data is performed by the video
compressor block; see Fig.4. The input to this block is the
uncompressed video information pre-processed by the
video front-end and stored in external SDRAM memory.
The output is a compressed video stream, compliant to
MPEG-2 Video Elementary Stream (VES) up to slice level.
Controlling information (for example, quantizer step size)
as well as the bit stream for higher layers of the VES is
generated by the embedded MIPS
processor of the
SAA6752HS.
The video compressor contains several subblocks. The
MacroBlock Processor (MBP) performs generation of
video ES on macroblock level. Controlling parameters for
this task and MB headers as well as slice headers are
generated by the core control subblock. Bitstream
formatting and concatenation of MBP bitstream and
header information is done by the subblocks pre-packer
and packer.
MODE
PICTURE FORMAT
(PIXEL/LINES)
D1 720
2/3D1 480
1/2D1 352; note 1
SIF 352; notes 1 and 2