US 2001/0043283 A1Published application

Feed forward error correction in video decoder

AssigneeTexas Instruments Incorporated

InventorKarl Renner

Life of this patent

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Abstract

In accordance with an embodiment of the present invention a microprocessor in the horizontal phased lock loop reads the horizontal timing with respect to the sync input and provides an increment inc h to the horizontal discrete time oscillator to make corrections in its timing to maintain lock to the sync input. The horizontal discrete time oscillator output is used to produce a pixel clock which drives the color discrete time oscillator in a color phased locked loop. A microprocessor reads a phase error between the color burst input and the color local oscillator frequency and writes an increment inc sc to the color discrete time oscillator to maintain lock to the color burst. The horizontal phase locked loop adjusts inch that varies about nominal increment (nom_inch) by Δh. The feed forward error correction for the adjustment to the color discrete time oscillator is the nonimal increment (nom_incsc) and a feed forwarded scaled version of Δh.

Claims7

Dependent claims

A video decoder comprising:

a horizontal phased locked loop including a horizontal discrete time oscillator,
a color phased locked loop including a color discrete time oscillator generating a color local oscillator frequency fsc a comparator for comparing the color local oscillator frequency to a color burst to detect any error and a processing means to produce an color PLL nominal increment to the color discrete time oscillator,
means for clocking the horizontal discrete time oscillator by a constant frequency from a ring oscillator fring where fring=m* fcrystal and fcrystal=n* fsc,
means for determining the horizontal phase error Δh from the horizontal sync input and generating an increment inch to the horizontal discrete time oscillator to maintain lock to the horizontal sync input.
means for generating a scaled factor of phase error from the horizontal discrete time oscillator to maintain constant color local oscillator frequency without a division operation,
means for adding said scaled factor of phase error to said color PLL nominal increment and feed forwarding to the color discrete time oscillator to maintain constant color local oscillator frequency.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/849,330Filed 4 May 2001
Priority: 22 May 2000
Published: 22 Nov 2001
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H03L 7/07
Using a reference signal applied to a frequency- or phase-locked loop: using several loops, e.g. for redundant clock signal generation
H03L 7/0805
Details of the phase-locked loop: the loop being adapted to provide an additional control signal for use outside the loop
H03L 7/0994
The oscillator being a digital oscillator, e.g. composed of a fixed oscillator followed by a variable frequency divider: comprising an accumulator
H04N 9/45
Colour synchronisation: generation or recovery of colour sub-carriers

Family

Application60/205,548Us provisional application · filed 22 May 2000
US 6,839,092 B2Related patent
US 2001/0043283 A1This patent

From the US filing history. Foreign family members aren’t listed.

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