Fusion 878A
2.0 Functional Description
PCI Video Decoder
2.4 Video Scaling, Cropping, and Temporal Decimation
100600B
Conexant
2-9
Vertical Scaling
For vertical scaling, the Fusion 878A uses a line store to implement four different
filtering options. The filter characteristics are illustrated in
Fusion 878A provides up to 5-tap filtering to ensure removal of aliasing artifacts.
The Video Timing Control (VTC) register sets the number of taps in the
vertical filter. The user may select 2, 3, 4 or 5 taps. The number of taps must be
chosen in conjunction with the horizontal scale factor in order to ensure the
needed data fits in the internal FIFO (see the VFILT bits in the VTC register for
limitations). As the scaling ratio is increased, the number of taps available for
vertical scaling increases. In addition to low-pass filtering, vertical interpolation
is also employed to minimize artifacts when scaling to non-integer scaling ratios.
Figure 2-7. Combined Luma Notch, 2x Oversampling and Optional Low-Pass Filter Response (PAL/SECAM)
ICON
QCIF
CIF
ICON
QCIF
CIF
Pass Band
Full Spectrum
Amplitude in dB [20*log10(ampl)]
Amplitude in dB [20*log10(ampl)]
Frequency in MHz
Frequency in MHz
879A_011
Figure 2-8. Combined Luma Notch and 2x Oversampling Filter Response
NTSC
PAL/SECAM
Amplitude in dB [20*log10(ampl)]
Frequency in MHz
879A_012