Scaling, matrix, clipping
The SAA7135 incorporates an adaptive filter and circuitry to
crop, scale, and reduce frame rate. It can peform horizontal or
vertical video down scaling or zooming to support playback win-
dows of any size.Two alternating settings for active video scaling
support independent capture and preview definition. Adaptive
anti-alias filters reduce board space, system costs, and external
components.
Optional YUV-to-RGB and RGB-to-YUV matrices and a color
lookup table can be used to normalize ITU-standard color values
to the full RGB range and apply gamma correction as needed to
optimize screen contrast and color. A clipping unit allows defini-
tion of overlay rectangles (for Video for Windows (VfW) legacy
requirements) or assignment of alpha values to video pixels.
Output
Decoded, scaled video can be output in various YUV or RGB
formats, including packed and planar, gamma-compensated or
black-stretched.The video stream is transmitted through DMA
writes across the PCI bus or through a digital video output port
in standalone configurations.
digital video,digital audio,rawVBI,digitalTS
PCI BUS
S-Video
audio
audio
line-in
CVBS
C
ITU/VIP
antenna
or cable
audio loop back cable
TVTUNER &
INTERFACE
CHANNEL
DECODER
I2C
SAA7135
TS
M
E
I2C
EEPROM
S
NORTH
BRIDGE
MEMORY
CPU
V
MPEG PS
S
I S
2
ATSC/DVB/
BS-Digital
HYBRIDTV CAPTURE/PVR PCI CARD
AGP
PCI BUS
S-Video
audio
CVBS
C
ITU/VIP
audio loop back cable
I C
2
SAA7135
G
C
S
NORTH
BRIDGE
MEMORY
CPU
S
STANDALONE ANALOGTV GRAPHICS CARD
antenna
or cable
TVTUNER
AGP
audio
line-in
Typical SAA7135 configurations: a PCI add-in card for capture of live analog and digitalTV video and audio (left), and a graphics card
for analog TV capture (right).
Stereo decoding and audio processing
Capture and decoding
The SAA7135 handles capture and on-chip decoding of stereo
formats used in analog TV including: BTSC with dbx noise reduc-
tion and SAP (North America), EIAJ (Japan), and NICAM and A2/
Dual-FM (Europe). After capture from the TV tuner through a
Sound Intermediate Frequency (SIF) port, the TV sound signal is
digitized and FM orAM demodulated.The audio standard is auto-
matically detected, the pilot tone is investigated (mono, stereo,
dual), and the signal is decoded.
Two 16-bit audio ADCs support capture of audio signals from
nonstandard sources such as video cameras,VCRs,andAM (mono)
or FM (stereo) radio through two stereo line-in inputs. The
SAA7135’s analog audio pass-through enables an incoming audio
signal to be rerouted without processing through an external
loop-back cable to a sound card. A field-locked audio clock sam-
ples a constant number of audio clocks per video field,
guaranteeing synchronization between audio and video streams.
Advanced audio feature processing
The SAA7135’s advanced, on-chip audio-feature processing
improves user control and perceived audio quality. A Dolby Pro
Logic decoder ‘unfolds’ four-channel Dolby Surround audio when
it is present in VHS movies and TV broadcasts. A Virtual Dolby