GB2320840A

GB2320840A - Television system identification

Info

Publication number: GB2320840A
Application number: GB9726374A
Authority: GB
Inventors: Hyun-Jeong Park
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1996-12-19
Filing date: 1997-12-12
Publication date: 1998-07-01
Anticipated expiration: 2017-12-12
Also published as: GB2320840B; KR100232958B1; KR19980049380A; GB9726374D0; DE19756572B4; DE19756572A1

Abstract

In order to determine the type of a composite video signals (CVS), the chrominance subcarrier frequency is detected by timing the duration of a predetermined number of chrominance burst cycles. A first counter (61) counts four colour burst cycles and a second counter (63) counts clock pulses (EX_CLK) while the four colour burst cycles are being counted. The value counted to by the second counter (63) indicates the frequency of the chrominance subcarrier.

Description

Television System Identification

Description

The present invention relates to an apparatus and a method for use in identifying the type of a television signal.

Terrestrial television broadcasters use variously NTSC, PAL, PAL-M, PAL-N, SECAM. NTSC is used in the United States, Japan, and the Republic of Korea. China and most of Western Europe use PAL systems. SECAM is used in France and in Eastern Europe.

The different systems have different technical characteristics. For instance, NTSC has its chrominance subcarrier at 3.579545MHz whereas PAL has its chrominance subcarrier at 4.433618MHz.

A conventional television system identifying apparatus is manufactured using analogue integrated circuits and identifies a television system from the chrominance subcarrier frequency. In order to detect the chrominance subcarrier component of 3.58MHz/4.43MHz, the conventional apparatus separates a chrominance signal from 2o a received composite video signal, and looks for the chrominance subcarrier at 3.58MHz and 4. 43MHz from the separated chrominance signal.

However, this conventional analogue apparatus has the drawback that it is adversely affected by temperature, noise, etc.

The development of digital processing techniques, using custom integrated circuits, has ameliorated these problems.

In addition to the aforementioned drawback, the conventional apparatus suffers from the disadvantage of needing filters suitable for the chrominance signals of each of the different systems to be identified and attendant manufacturing costs.

30730SPC.DOC According to the present invention, there is provided a method for use in identifying the type of a television signal, the method comprising timing a predetermined number of cycles of a colour burst of a composite television signal to produce a value indicative of the chrominance subcarrier frequency of said composite television signal.

Preferably, a method according to the present invention comprises counting the predetermined number of cycles to define a count period and counting clock signal io pulses during the count period so as to time the count period, wherein the count of clock pulses achieved during the count period is indicative of the chrominance subcarrier frequency of said composite television signal.

Preferably, a method according to the present invention includes outputting a signal at a first level is the time required for the predetermined number of cycles exceeds a threshold and otherwise outputting the signal at a second level.

Preferably, the predetermined number is four. Preferably, the timing of the burst cycles does not start with the first and, more preferably, starts with the third.

According to the present invention, there is also provided an apparatus for use in identifying the type of a television signal, the apparatus comprising timing means for timing a predetermined number of cycles of a colour burst of a composite television signal to produce a value indicative of the chrominance subcarrier frequency of said 25 composite television signal.

Preferably, an apparatus according to the present invention comprises input means for receiving a composite video signal, a source of clock pulses, colour burst extraction means for extracting a colour burst from a composite video signal received by the input means, a first counter for counting a predetermined number of cycles of a colour burst extracted by the colour burst extraction means, a second counter responsive to the first counter to count clock pulses from the source of clock pulses during counting by the first counter, and means responsive to the count achieved by the second counter to output a signal having a value indicative of the chrominance subcarrier frequency of said composite television signal.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:Figure 1 is a schematic circuit diagram of an apparatus for use in identifying a television system according to the present invention; io Figures 2A to 2J are waveform diagrams illustrating waveforms appearing at various points in Figure 1; and Figure 3 is a flow chart illustrating a method according to the present invention.

Referring to Figures 1, 2A to 2j, an apparatus according to the present invention comprises a sync separating section 10, a pulse generating section 20, a burst amplifying section 40, a detecting section 60, and an output section 80.

The sync separating section 10 separates the horizontal sync signal HSYNC from an input composite video signal CVS.

The pulse generating section 20 counts the pulses of an externally generated master clock signal EX_CLK to generate a burst gate pulse signal BW. The pulse generating section 20 is reset by the sync signal H- SYNC.

A burst amplifying section 40 is synchronised with the rising edge of the burst gate pulse signal BGP and amplifies the colour bursts of the composite video signal CVS.

The detecting section 60 identifies the chrominance subcarrier frequency of the composite video signal CVS by counting cycles of the colour bursts.

The output section 80 responds to the falling edge of the burst gate pulse signal by outpurting a signal indicating the chrominance subcarrier frequency on the basis of the output of the detecting section 60.

The pulse generating section 20 includes a first counter 21 and a first flip-flop 22. The first counter 21 is reset by the sync signal H-SYNC and counts the master clock signal EX_CLK for a predetermined period. The first flip-flop 22 is also reset by the sync signal H_SYNC and responds to the first counter 21 by outputting the burst gate pulse signal BGP which is thereby synchronised with the master clock signal lo EX-CLK.

The detecting section 60 includes a second counter 61, a second flip-flop 62, and a third counter 63. The second counter 61 is reset by the sync signal H-SYNC and counts the cycles of the colour burst signal CBS output by the burst amplifying section 40. The second flip-flop 62 is reset by the sync signal H-SYNC and generates a pulse signal during a portion of the duration of the colour burst applied to the second counter 61. The third counter 63 is reset by the sync signal H_SYNC and counts the master clock signal while a pulse signal is being output by the second flipflop 62.

The output section 80 includes a third flip-flop 8 1, a fourth flip-flop 82, an inverter 83, and a fifth flip-flop 84. The third flip-flop 81 delays the output signal of the detecting section 60 for a predetermined time in synchrony with the master clock signal EX_CLK. The fourth flipflop 82 is reset by the sync signal H-SYNC, receives the supply voltage Vcc as its first and second inputs, and generates an output signal synchronised with the rising edge of the output signal of the third flipflop 81. The inverter 83 inverts the burst gate pulse signal BGR The fifth flip-flop 84 delays the output signal of the fourth flip-flop 82 in response to the output signal of the inverter 83.

The first, second, and fourth flip-flops may comprise JK-type flip-flops, and the third and fifth flip-flops may comprise D-type flip-flops.

The operation of the above-described apparatus will be explained with reference to Figures 1 to 3.

First, If a composite video signal CVS, consisting of a sync signal, a colour burst signal and a video signal, as shown in Figure 2A, is input, the sync separating section 10 separates the sync signal H-SYNC, as shown in Figure 2B, from the composite io video signal CVS (step S1 of Figure 3).

The first counter 21 in the pulse generating section 20 is reset at the falling edge of the sync signal H_SYNC, and counts the master clock signal EX_CLK as shown in Figure 2C, starting from the rising edge of the sync signal H-SYNC. The counting operation is performed during the period of the second pulse to the hundredth pulse of the master clock signal. The first flip-flop 22 is reset at the falling edge of the sync signal H-SYNC and receives the count signal of the first counter 21. The first flipflop 22 generates the burst gate pulse signal BW, as shown in Figure 2D, which goes to a 'high' state at the rising edge of the second pulse of the master clock signal, stays in the 'high' state until the 100th pulse of the master clock signal, and then goes to a 'low' state at the 100th pulse of the master clock signal (step S2 of Figure 3). The master clock signal EX-CLK has a frequency of 26MHz.

The burst amplifying section 40 extracts the colour burst signal as shown in Figure 2E from the composite video signal CVS in synchrony with the burst gate pulse signal BGP of Figure 2D which acts as a window pulse signal (step S3 of Figure 3).

Thereafter, the second counter 61 is reset at the falling edge of the sync signal H-SYNC and counts the cycles of the colour burst signal CBS, amplified by the burst amplifying section 40. The count values are provided to the second flip- flop 62 as its first and second input signals. The second flip-flop 62 produces a window signal in such a manner that its output signal goes to the 'high' state when a count value of 3 is input as its first input signal, maintains its 'high' state until the count value of 7, and then is returned to the 'low' state when a count value of 7 is Input as its second input signal (step S4 of Figure3). Figure 2F shows the resultant output waveform of the 5 second flip-flop 62.

The counting periods corresponding to different respective television systems are as follows:- NTSC358 Fsc = 3.579545MHz = 279ns, 279 X 4 = 1116ns PAL Fsc = 4.433619MHz = 226ns, 226 X 4 = 904ns PAL-M Fsc = 3.575611MHz = 280ns, 280 X 4 = 1120ns PAL-N Fsc = 3.582056MHz = 279ns, 279 X 4 = 11 16ns Here, the term "Fsc" means the frequency of the chrominance subcarrier. The reason why the respective counting periods are multiplied by 4 is that the second counter 61 counts during four cycles, i.e., the third to seventh cycles.

The third counter 63 is reset at the falling edge of the sync signal HSYNC, is enabled at the rising edge of the output signal of the second flip-flop 62 as shown in Figure 2F, and counts the input master clock signal EX-CLK of Figure 2C to identify the chrominance subcarrier frequency (step S5 of Figure 3). Specifically, the third counter 63 counts the master clock signal EX_CLK, and it is determined whether or not the counted value is identical with the predetermined value.

Here, the third counter 64 performs its counting operation up to 27. If the counted value is identical with the predetermined value as a result of the determination at step S5, the received composite video signal CVS is identified as having a chrominance subcarrier of 3.58MHz, and the counter 63 outputs the 27th pulse of the master clock signal EX_CLK of a 'high' level to the output section 80 as shown in Figure 2G.

On the other hand, if the counted value is not identical with the predetermined value as a result of discrimination at step S5, it is determined that composite video signal CVS has a chrominance subcarrier of 4.43MHz, and the counter 63 outputs a 'low' level signal to the output section 80 as shown in Figure 2G.

The count values for the respective broadcasting systems are as follows:

NTSC 1116ns/38ns 29.3 = 29(values) PAL 904ns/38ns 23.7 = 23(values) PAL-M 1120ns/38ns = 29.4 = 29(values) PAL-N 1116ns/38ns= 29.3 = 29(values) (The period of the master clock signal EX_ CLK is 38ns.) Thereafter, the third flip-flop 81 delays the 27th pulse of the master clock signal EX-CLK for a predetermined time as shown in Figure 2H, and outputs the delayed pulse to the output section 80. The fourth flip-flop 82 outputs a 'high' level signal as shown in Figure 21 in case that the chrominance subcarrier frequency is 3.58MHz, in synchrony with the rising edge of the output signal of the third flip-flop 81 (step S6 of Figure 3). Accordingly, the NTSC, PAL-M, and PAL-N systems can be decoded as necessary.

On the other hand, in case that the chrominance subearrier frequency is 4. 43MHz, a 'low' level signal is outputted as shown in Figure 2H., and thus the PAL system can be decoded. Thereafter, the fifth flip-flop 84 is synchronised with the inverted burst gate pulse signal outputted through the inverter 83, and delays the output signal of the fourth flip-flop 82. Accordingly, the fifth flip- flop 84 outputs a 'high' level signal as shown in Figure 21 in the case that the chrominance subcarrier is of 3.58MHz, while it outputs a 'low' level signal as shown in Figure 2J in case the that the chrominance subearrier is of 4.43MHz.

As a result, the 3.58MHz/4.4311Hz component is digitally discriminated.

As described above, according to the present invention, the broadcasting system can be automatically identified, at least in part, by detecting the chrominance subcarrier using the colour burst signal, and thus the present invention provides convenience to the users who are not familiar with the various broadcasting systems. Also, since the present invention is digitally implemented, it is less susceptible to noise than analogue apparatus.

While the present invention has been described and illustrated herein with reference lo to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may he made therein.

Claims

1. A method for use in identifying the type of a television signal, the method comprising timing a predetermined number of cycles of a colour burst of a composite television signal to produce a value indicative of the chrominance subcarrier frequency of said composite television signal.

2. A method according to claim 1, comprising counting said predetermined number of cycles to define a count period and counting clock signal pulses during the io count period so as to time the count period, wherein the count of clock pulses achieved during the count period is indicative of the chrominance subcarrier frequency of said composite television signal.

3. A method according to claim 1 or 2, including outputting a signal at a first level is the time required for said predetermined number of cycles exceeds a threshold and otherwise outputting the signal at a second level.

4. A method according to claim 1, 2 or 3, wherein said predetermined number is four.

5. An apparatus for use in identifying the type of a television signal, the apparatus comprising tinuing means for timing a predetermined number of cycles of a colour burst of a composite television signal to produce a value indicative of the chrominance subcarrier frequency of said composite television signal.

6. An apparatus according to claim 5, comprising input means for receiving a composite video signal, a source of clock pulses, colour burst extraction means for extracting a colour burst from a composite video signal received by the input means, a first counter for counting a predetermined number of cycles of a colour burst extracted by the colour burst extraction means, a second counter responsive to the first counter to count clock pulses from the source of clock pulses during counting by the first counter, and means responsive to the count achieved by the second counter to output a signal having a value indicative of the chrominance subcarrier frequency of said composite television signal.

7. A broadcasting system discriminating apparatus comprising:sync separating means for separating a sync signal from a composite video signal; pulse generating means for generating a burst gate pulse signal by counting a master clock signal inputted externally, said pulse generating means being reset by io said sync signal; burst amplifying means for amplifying a colour burst signal of said composite video signal, being synchronised with a rising edge of said burst gate pulse signal; detecting means for detecting a first broadcasting system by counting said amplified colour burst signal for each horizontal scanning period; and output means for outputting a detected signal provided from said detecting means as a broadcasting system discrimination signal in response to a failing edge of said burst gate pulse signal.

8. A broadcasting system discriminating apparatus as claimed in claim 7, wherein 20 said first broadcasting system adopts a chrominance subcarrier of 3.58MHz.

9. A broadcasting system discriminating apparatus as claimed in claim 7, wherein said master clock signal is a clock signal of 26MHz to detect said first broadcasting system.

10. A broadcasting system discriminating apparatus as claimed in claim 7, wherein said pulse generating means comprises: a first counter which is reset by said sync signal separated from said composite video signal by said sync separating means and counts said master clock signal for a I predetermined period; and a first flip-flop which is reset by said sync signal and outputs said burst gate pulse signal, being synchronised with said master clock signal.

11. A broadcasting system discriminating apparatus as claimed in claim 10, wherein said first counter counts second to 100th clocks of said master clock signal.

12. A broadcasting system discriminating apparatus as claimed in claim 7, wherein said detecting means comprises: a second counter which is reset by said sync signal and counts said colour io burst signal amplified by said burst amplifying means; a second flip- flop which is reset by said sync signal and generates a pulse signal continuing during a portion of said counting period, being synchronised with said colour burst signal amplified by said burst amplifying section; and a third counter which is reset by said sync signal and counts said master clock signal at a rising edge of said pulse signal outputted from said second flip-flop.

13. A broadcasting system discriminating apparatus as claimed in claim 12, wherein said second counter counts third to seventh clocks of said amplified colour burst signal.

14. A broadcasting system discriminating apparatus as claimed in claim 12, wherein said third counter is enabled by said output pulse signal of said second flipflop, and counts first to 27th clocks of said master clock signal.

15. a broadcasting system discriminating apparatus as claimed in claim 7, wherein said output means comprises:

a third flip-flop for outpurting said output signal of said detecting means after delaying it for a predetermined time, being synchronised with said master clock signal; a fourth flip-flop which is reset by said sync signal, receives a supply voltage as its first and second inputs, and generates a corresponding output signal, being synchronised with a rising edge of said output signal of said third flip-flop; an inverter for inverting said burst gate pulse signal from said pulse generating means; and a fifth flip-flop for outputting said output signal of said fourth flip-flop after delaying it in response to an output signal of said inverter.

16. A broadcasting system discriminating method comprising the steps of: 10 separating a sync signal from a received composite video signal; generating a burst gate pulse signal by counting a master clock signal inputted externally for each horizontal scanning period; extracting a colour burst signal from said composite video signal, and amplifying said extracted colour burst signal; counting said amplified colour burst signal for a predetermined period; counting said master clock signal for a predetermined period, and determining whether or not a counted value is identical with a predetermined value; and generating a first broadcasting system discrimination signal if it is determined that said counted value is identical with said predetermined value, while generating a second broadcasting system discrimination signal if it is determined that said counted value is not identical with said predetermined value.

17. A method for use in identifying the type of a television signal, the method being substantially as hereinbefore described.

18. An apparatus for use in identifying the type of a television signal, the apparatus being substantially as hereinbefore described with reference to the accompanying drawings.