FOCUS Enhancements FS453 - Manual (Page 11)

FS453/4 AND FS455/6 DATA SHEET: HARDWARE REFERENCE
3.3 Video Encoding
Unlike component video formats (PC and HDTV) that process the color information separately to avoid
interference, broadcast SDTV combines all picture information into a single, composite signal. SDTV
standards have been strictly defined to protect video quality and to allow television manufacturers to
design and build large volumes of systems with confidence that their signal decoders will work—
regardless of variances in final product tolerances.
3.3.1 Encoding Challenges
If a video encoder does not adhere closely to these standards, it may produce video artifacts on many
consumer televisions. Unfortunately, most scan converters use signal encoders that don't strictly follow
NTSC and PAL guidelines. Their encoders can increase artifacts such as chroma crawl and color
bleeding/smearing.
To meet broadcast quality a video encoder must comply with the NTSC (EIA-170A, SMPTE-170M) and
PAL (ITU-R624-3) standards in all modes. Of key importance are the specifications related to accurate
timing and signal amplitudes, video subcarrier frequency good to +/- 5Hz, and horizontal lock with zero
SC-H phase. The encoder must use a low jitter crystal (50 ppm) to drive DAC output directly. The DACs
should have 10 bits of resolution, and exhibit good differential gain and differential phase characteristics.
The video encoder must be able to pre-filter composite video (CVBS) to prevent luma(Y)/chroma(C) cross
talk.
3.3.2 FS453 Solution
The FS453 features a broadcast quality encoder. It uses tunable Y-notch and C-bandpass filters to
prevent the creation of video artifacts and to meet all specifications. The FS453's encoder subcarrier is
programmable in frequency and phase. Because of the encoder's independence of color format, vertical
sync, and number of lines, the FS453 is able to support many SDTV video standards, including all of the
South American variations. The FS453 can output NTSC M, J and PAL B, D, G, H, I, M, N, Combination
N, and PAL-60 formats with 10 bits of resolution. Both Composite and S-Video outputs are available
simultaneously. In addition to encoded PAL or NTSC, the user may select analog SCART RGB outputs.
Each channel of RGB has 10 bits of resolution. Note that the 10-bit DACs exceed the bit depth supported
by the 8-bits available at the FS453 input.
JANUARY, 2005, VERSION 3.0 11 COPYRIGHT ©2003-4 FOCUS ENHANCEMENTS, INC.
FOCUS Enhancements Semiconductor