Digital Processing of Analog Television

 

Lior ZimetEE392J Final Project

Winter 2002

Project Goals

• Digitize an analog NTSC signal and decode it in software

• Use digital processing to perform– Luminance and Chrominance separation– Color demodulation– Interlace to progressive conversion

CompositeVideo

DCRestoration

and AGCADC

10 bitSync

Detectionand Active

VideoExtraction

Resampler4XFsc

Y+C Y+CY/C

Separation+Motion

Detection

Y

C

ColorDe-

modulation

De-Interlacer

Motion

YUVto

RGBDisplay

RGB Y, U, VFields

Hardware Software

Y, U, VFrames

System Block Diagram

Display

ONE LINE OF NTSC SIGNAL

HSYNC

COLOR BURST

ACTIVE VIDEO

SYNC LEVEL

BLANK LEVEL

PEAK WHITE

SIGNAL PEAK

NTSC – 1D Analog Signal

0.0 1.0 2.0 3.0 4.03.58

Amplitude

Frequency(MHz)

ChrominanceSub-carrier

YUV

UV

F

Y U,V Y YU,V

15.734 KHz

29.97 HzSpacing

Composite Video Spectrum

Y+U

Y-U

Y+U

Y-V

Y+V

Y-V

Y-U

Y+U

Y-U

Y+V

Y-V

Y+V

Y/C Separation – 1D Comb Filter

• Resampling at 4xFsc will take advantage of the alternate phase in the color modulation

• Y/C separation can be done within the field

Y =( (Ycenter+Ccenter) + (YupperCupper)) / 2

C = ((Ycenter+Ccenter) (YupperCupper)) / 2

Y/C Separation – 2D Adaptive Comb Filter

• 1D comb filter works perfectly only for vertically orientated structures in a picture

• 2D adaptive comb filter:– Weighs the upper line and lower line combing

according to horizontal edge detection

– Uses notch filter in cases where 1D fails

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Field n-2 Field n-1 Field n Field n+1 Field n+2

Y/C Separation – 3D Comb Filter

• In still image, pixels are identical from frame to frame

• The Chrominance phase is alternating

• Must be disabled when motion is present

"CHEER LEADER" WITH 3D COMB AND NO MOTION DETECTION

MOTION ARTIFACTS

Motion Artifacts Example

Notch Filter

3D CombFilter

Vertical 1DSeperator

Y

C

Vertical andHorizontal

Edge Detectorfor 2D

AdaptiveComb Filter

Y

C

MotionDetector

for 3DAdaptive

Comb filter

Y

C

Y

C

Y

C

Y+C

Y/C Separation – 3D Adaptive Comb Filter

NOTCH FILTER Y/C SEPERATION

CROSS-LUMINANCE

CROSS-CHROMINANCE

2D ADAPTIVE COMB FILTER Y/C SEPERATION

HANGING DOTS ARTIFACT

3D adaptive Y/C separation

Y/C Separation

Example

COLOR BURST INFORMATION

HORIZONTAL SYNC

PHASE

BACK PORCH

tVtUChroma cossin

Color Information

ChrominanceFrom Y/CSeparator

2cos(2 F sc t)

2sin(2 F sc t)

LPF

LPF

V

U

tVtUUttVtU 2sin2cossin2cossin

tUtVVttVtU 2sin2coscos2cossin

Color Demodulation

tcos2

tsin2

Motion?

InterpolateWithin theSame Field

Merge WithNeighbor

Field

No

Yes

ProgressiveYUV

InterlaceYUV

De-interlacing

• Merge fields or interpolate in the pixel domain• Use motion detector to decide

SNELL & WILCOX WITH ADAPTIVE 3D COMB FILTER

SNELL & WILCOX WITH NOTCH FILTER SNELL & WILCOX 2D ADAPTIVE COMB FILTER

Snell & Wilcox Pattern

Sequence from “Cheer Leader”

"CHEER LEADER" WITH 3D ADAPTIVE COMB FILTER

Decoded Frame from “Cheer Leader”

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Field n-2 Field n-1 Field n Field n+1 Field n+2

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Y-C

Y+C

Field n-2 Field n-1 Field n Field n+1 Field n+2

Motion Detection• Apply small motion and large motion detection

using adjacent fields

Small Motion Large Motion