Extraction of data from a television signal using an adaptable slicing level
AssigneeTrident Microsystems (Far East) Ltd.
InventorEdwin Schapendonk
Life of this patent
Estimating the term…
Abstract
From a television signal data such as teletext or closed caption data is extracted by slicing. A binary data signal is formed dependent on whether the television signal level is above or below a slicing level (S). The slicing level (S) is selected by defining a reconstructed data signal (D) with signal values equal to plus and minus an amplitude value relative to a middle level and transitions between these signal values at time points where the television signal crosses the slicing level. An auxiliary signal (R) is formed that contains the television signal (Vi) from which the reconstructed data signal (D) has been subtracted. A feedback loop is provided that adapts the amplitude value (A) to regulate a residual data signal amplitude in the auxiliary signal (R) to zero.
Claims11
A television signal receiver apparatus comprising:
- a receiving circuit for receiving a television signal having a level;
- a data signal slicing circuit for forming a binary data signal dependent on whether the television signal level is above or below a slicing level;
- and
- a slicing level selection circuit for selecting the selected slicing level from a difference between television signal and a reconstructed data signal the slicing level selection circuit comprising:
- a data signal reconstruction circuit for defining the reconstructed data signal with signal values equal to plus and minus an amplitude value (A) relative to a middle level and transitions between these signal values at time points where the television signal crosses the slicing level a subtraction circuit for forming an auxiliary signal that contains the television signal from which the reconstructed data signal has been subtracted;
- a feedback loop arranged to adapt the amplitude value to regulate a residual data signal amplitude in the auxiliary signal to zero.
A method of recovering digital data from a television signal, the method comprising:
- receiving the television signal;
- forming a binary data signal dependent on whether the television signal level is above or below a slicing level the slicing level being determined by:
- defining a reconstructed data signal with signal values equal to plus and minus an amplitude value relative to a middle level and transitions between these signal values at time points where the television signal crosses the slicing level;
- forming an auxiliary signal that contains the television signal from which the reconstructed data signal has been subtracted;
- providing a feedback loop that adapts the amplitude value to regulate a residual data signal amplitude in the auxiliary signal to zero;
- determining the slicing level from a difference between television signal and the reconstructed data signal.
Dependencies are inferred from the claim text.