Method for obtaining line synchronization information items from a video signal, and apparatus for carrying out the method

• US 20040174461A1
• Filed: 01/06/2004
• Published: 09/09/2004
• Est. Priority Date: 07/06/2001
• Status: Active Grant

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Lares, Roland, Rothermel, Albrecht
• Granted Patent: US 7,271,843 B2
• Time in Patent Office: Days
• US Class Current: 348/521
• CPC Class Codes: H04N 5/10 Separation of line synchronising signal from frame synchronising signal or vice versa

Abstract

A method for obtaining line synchronization information items from a video signal is proposed. The inventive method is based on convolving the relevant part of an analogue video line signal with a pattern function. The result of the convolution operation is further processed to determine the time instants of the occurrence of the horizontal sync signals. The time instants are subsequently filtered to generate horizontal pulses. A video line memory allows to utilize subsequent horizontal sync signals for calculating the horizontal sync pulse of a current video line. The invention also relates to an apparatus for carrying out the method.

Claims

1. Method for correcting line synchronization information of an analogue video line signal by

(a) analyzing the entire or a relevant part of the analogue video line signal comprising the line synchronization pulses to determine time instants (t_i) defining the temporal position of the line synchronization pulse included in the analogue video line signal,

characterized by the following steps:

(b) storing a predetermined number (m) of video lines in a line delay, and

(c) calculating a time instant (T_m) for a video line preceding the currently received video line to mark the temporal position of the synchronization information of the video line, wherein the time instant (T_m) is a function of the line synchronization pulse positions (t_i) of video lines including the currently received, at least one preceding and at least one succeeding video line.

2. Method according to claim 1 characterized in that the video line associated with the calculated time instant T_m precedes the currently received video line by the predetermined number (m) of video lines in the line delay.

3. Method according to claim 1, characterized by

(d) convolving the entire or the relevant part of the analogue video line signal with a pattern function to generate a result function (φ

_sv (k)) of the convolution operation, and

(e) analyzing the result function (φ

_sv (k)) of the convolution operation of step (d) to determine time instants (t_i) defining the temporal position of the line synchronization pulse.

4. Method according to claim 3, characterized by using an idealized line synchronization pulse as the pattern function.

5. Method according to claim 1, characterized by calculating the filtered time instant (T_m) for a currently displayed video line by interpolation of the time instants determined for video lines preceding and following the currently displayed video line.

6. Method according to claim 5, characterized by calculating the filtered time instant (T_m) for a currently displayed video line by linear interpolation of the time instants determined for video lines preceding and following the currently displayed video line.

7. Method according to claim 1, characterized by filtering the time instants (t_i) by an FIR filter having a set of predetermined filter constants (c_n,1).

8. Method according to claim 7, characterized by storing the defined time instants (t_i) in associated delay elements,

wherein the time instants represent the time constant of the delay element, and

wherein the delay elements are incorporated in the FIR filter (24).

9. Apparatus for generating a line synchronization pulse from a analogue video line signal, comprising means for analyzing the entire or a relevant part of the analogue video line signal comprising the line synchronization pulses to determine time instants (t_i) defining the temporal position of the line synchronization pulse included in the video line signal,

characterized by

a line delay for storing a predetermined number (m) of video line signals, and by

means for calculating a time instant (T_m) for a video line preceding the currently received video line to mark the temporal position of the synchronization information of the video line wherein the time instant (T_m) is a function of the line synchronization pulse positions (t_i) of video lines including the currently received, at least one preceding and at least one succeeding video line.

10. Apparatus according to claim 9, characterized by means for convolving the entire or the relevant part of the analogue video line signal with a pattern function.

11. Apparatus according to claim 9, characterized by an FIR filter having a set of predetermined filter constants (c_n,1).

12. Apparatus according to claim 9, characterized by a synchronization pulse detector (23) to measure the time difference between two subsequent synchronization pulses.

13. Apparatus according to claim 12, characterized in that the synchronization pulse detector (23) comprises two counters (36a, 36b) which are alternatingly reset.

14. Apparatus according to claim 11 and 12, characterized in that the synchronization pulse detector (23) comprises a comparator (41) a first input of which is selectively connectable with one of the counters, and the second input of which is provided with a predicted timing value generated by the FIR filter (24).

15. Apparatus according to claim 12, characterized in that the synchronization pulse detector (23) supplies the measured time difference of two subsequent clock cycles in form of an integer number (H_I) and a fraction (φ

_I) of cycles of a system clock.