CN1016552B - Method of transmitting writing broadcast signal and apparatus of receiving same - Google Patents

Abstract

The present invention relates to the transmission mode and the receiving device of a PAL system teletext. The transmission mode is that clock pulse signal for letter signal having a simple frequency relation with the PAL system television signal color subcarrier is produced, the clock pulse length of the 1 group signal is set as 272 bit, and the error correcting (272, 190) which is same as the Japan system can be applied. The receiving device is that a color subcarrier signal is taken off from the PLA system television signal, a signal with the same frequency and phase with the clock pulse series signal is produced from the color subcarrier signal through a circuit APC to be a clock pulse signal, to count the scanning line number of a first field of the television signal, and at the same time, a framing code is detected under the multiple letter signals, to protect the equipment of a frame code regenerated.

Description

Method of transmitting writing broadcast signal and apparatus of receiving same

The invention belongs to text broadcast transmission method of signal and receiving system thereof, particularly have the transmission means and the receiving system thereof of very strong error correcting capability about the pal mode text broadcast.

So-called text broadcast is to transmit multiple signals in television radio wave, broadcasts information such as the literal of relevant TV programme and simple graph and is presented on the cathode ray tube screen.

Pal mode text broadcast in the past adopts the Britain's standard that is called as the B of system in CCIR.This standard is less paid attention to error correction, therefore, for the receiving system in the very harsh place of condition of acceptance or to as Chinese use the receiving system of ideograph country, all be unaccommodated.

And Japanese standard during from system development, is just developed error correction as important contents, owing to adopted (272,190) symbol, has finished the system that very strong error correcting capability is arranged.

In this Japanese standard; keep the continuity of clock pulse signal and the continuity of framing code phase place between each word group; therefore, under normal conditions, the reception of framing code is very weak; then thereafter (272; 190) error correcting capability of symbol can not be given full play to, yet owing to forward protect and rearward protect, has detected the markers of framing code; just can give play to the error correcting capability of (272,190) symbol.

Because impulsive noise and random noise also will produce and detect mistake, but, also can guarantee the framing markers as long as discontinuous generation detects error on framing code.

In the system of foreign countries such as Britain, owing to only in a word group, carry out signal processing, thereby do not have simple frequency relation between clock pulse frequency and colored carrier frequency, and in framing code, produce wrong and can not extract under the situation of framing markers, will lose in this word group all signals.And, with regard to error correction symbol, important sign or program are selected symbol, adopted (8,4) that can correct 1 bit mistake in 8 bits to enlarge symbol; And, only used the mistake that detects 1 bit mistake in 8 bits to detect symbol to other symbols.

Therefore, in the very harsh place of condition of acceptance, the problem that exists wrong literal of appearance and important information not to be transmitted.

The shortcoming of above-mentioned pal mode text broadcast is described in detail in detail below.

In the TV signal of pal mode, carry out the multichannel text broadcast, the text broadcast that is called " Ceefax " of Britain's exploitation is arranged.Shown in the 6th figure, this mode is with the bit rate of 6.9375Mbps, the text broadcast signal as 1 word group, 360 bits, carry out multiplexing, top 16 bits are as bit synchronous clock pulse series of signals, 8 subsequent bits are framing signals of the predetermined pattern of identification signal gap, and 336 bits are message parts.Therefore just in time 444 bits between 1 departure date.

In Britain's standard, clock pulse frequency and colored paying between the carrier wave do not have direct frequency relation.Though between clock pulse frequency and the horizontal-drive signal frequency certain frequency relation is arranged, but because 1. the gain of APC circuit does not utilize, 2. the horizontal synchronization markers after the vertical synchronization is easy to generate delicate phase jitter, so just very difficult from horizontal-drive signal regeneration time clock pulse signal.

According to above reason, in Ceefax, do not consider and the frequency relation of TV signal, adopt the receive mode of in a word group, carrying out signal processing.Therefore, as sending signal, there is no need bit phase unanimity that word group signal is started most, carry out multiplexing with various outs of phase at each row, also no problem.

That is: 16 bits that start most at receiving terminal, with word group signal are synchronous as clock pulse, extract framing pattern.When the framing pattern has a bit wrong, the time target to extract still be possible, but when 2 bits wrong arranged, the time target extract just impossiblely, the signal of this word group will all can not use.

Above-mentioned Ceefax compares with the Japanese standard of carrying out the framing code reception according to forward protect and rearward protect, is its very big shortcoming a little less than the reception of framing code.Under the low situation of framing code receiving ability, the error correcting capability of signal thereafter is surely not very strong.

As mentioned above, Ceefax less considers error correction, and the letter symbol later to framing code, only the parity bit of additional 1 bit in 7 bit symbols does not have wrong detection function yet.

As mentioned above, pal mode TV multichannel text broadcast (Ceefax) is very weak to the bit error correcting capability, the ideograph transmission system that 1 literal such as Japanese or Chinese is had a lot of amount of information, to important transmission of Information system, and the transmission system of bulk information (for example transmitting the telesoftware of computer program) etc. all is unfavorable.

The purpose of this invention is to provide a kind of transmission means and receiving system thereof that improves pal mode text broadcast error correcting capability.

In order to reach above purpose, the feature of transmission means of the present invention is: extract the colored carrier signal of paying from the pal television signal, generation becomes the letter signal of simple integer ratio to use with this signal clock pulse signal, then from specific vertical blanking period, following 296 bit signals of sequential delivery: as the 16 synchronous bit clock trains of impulses of clock pulse, target 8 bit framing codes during as framing, the information of 190 bits, the 82 bit parity signal that go out from this information calculations.

This receiving system has: bear the signal that has same frequency with letter signal again from colored burst signal, and the regenerating unit of regeneration and the synchronous signal of the multipath clock train of impulses; Detect framing code, and utilize the protective device that target multichannel framing code carries out the place ahead and rearward protect processing when certain, when receiving the generation error, also can receive framing code really.

As mentioned above, the present invention has adopted with the colour of pal television signa and has paid the clock pulse signal that carrier wave has same frequency relation, and kept the continuity of clock pulse signal, in 1 row of PAL signal, clock pulse frequency is to adopt identical (272 with Japanese text broadcast, 190) symbol so also just has the strong error correcting capability identical with Japanese text broadcast.

Brief description of drawings:

The 1st figure is the circuit block diagram that produces TV signal of the present invention.

The 2nd figure represents the multichannel word group of 362 bit intervals.

The 3rd figure represents the multichannel word group of 361 bit intervals.

The 4th figure represents the vertical blanking of pal television signa.

The 5th figure represents the relative position of each word group signal.

The 6th figure is the text broadcast signal that is called " Ceefax ".

The 7th figure is the embodiment block diagram of letter signal receiving system of the present invention.

The 8th figure is a framing code generation circuit block diagram.

Describe the present invention in detail with embodiment below.

The principle of transmission means at first, is described.

In pal television signa, the colored frequency f sc that pays carrier signal is decided to be:

fsc＝4433618.75Hz

Represent the clock pulse frequency of text broadcast signal with fcl, wish

fcl＝ (m)/(n) ·fsc

M and n are simple integer.In pal mode, the period T of 1 frame is:

T=1/25=40 * 10 ^-3(second)

Keep the successional condition of clock pulse signal to be:

Tcl×N＝M×40×10 ^-3

N is illustrated in the clock pulses number in the above-mentioned cycle, the frame number when M represents to be unit with 1 frame.Therefore,

$\mathrm{N\; =}\frac{M}{\mathrm{Tcl}}{\mathrm{\times \; 40\; \times 10}}^{\mathrm{-3}}$

$=\frac{{\mathrm{n\; .\; f}}_{\mathrm{sc\; .}}{\mathrm{M\; .\; 40\; \times \; 10}}^{\mathrm{-3}}}{m}$

$=\frac{n}{m}\mathrm{\times \; M\; \times \; 177344.75}$

N must be the integer that satisfies following formula.

During M=1, promptly 1 frame internal clock pulse signal is continuous, m/n=12/11,16/11,20/11 etc., bit rate at this moment is respectively 4.836675MHz, 6.44890MHz, 8.061125MHz during 54 possible microseconds of the multichannel of PAL signal, it is impossible making the demultiplexing of 272+8+16=296 bit.

During M=2, it is continuous promptly making clock pulse signal in 2 frames, m/n=12/11,14/11,16/11 etc.Here, except that m/n=14/11, the situation continuous with maintenance in above-mentioned 1 frame is identical.Under the m/n=14/11 situation, its bit rate is 5.6427875MHz, approximately equates with the bit rate 5.727MHz of Japanese text broadcast.During about 54 microseconds, realize that the bit number of multichannel is 304.7 bits, 296 necessary bits are bit rates of realizing abundant multichannel.

1 row of PAL signal just in time is 64 microseconds.Therefore, realize that in 1 row the bit number of multichannel is:

64 * 5.6427875=361.1384 bit approximates 364 bits of Japan.Use this bit rate, per 296 bits in 1 row are realized the clock pulse demultiplexing of continuous phase; After 8 row, the phase place of foremost bit is offset 1 bit approximately.Bit number behind 1 frame is 225711.5 bits, after 2 frames, than the 1st vertical shift 0.5 bit phase.After the 3rd frame, be same-phase.

As mentioned above, in the TV signal of pal mode, realize the demultiplexing of letter signal, can obtain the very strong error correcting capability identical with Japanese standard, 14/11 the frequency of colour being paid carrier wave is a good method as bit rate.

In pal mode,, can realize the demultiplexing of text broadcast at 8 row-25 row and its corresponding vertical blanking period.Yet, when from 8 row when carrying out the word group signal demultiplexing of 272 bits successively, owing to the word group cycle is decided to be 272 bits, all some skews in turn of multichannel position of each row (with reference to the 2nd figure).Its side-play amount is 0.8616 bit.Therefore, the side-play amount to 25 row is

0.8616 * 17=14.6472 bit

Corresponding time quantum is

14.6472×1/5.6427875＝2.595738365

(microsecond)

Thereby, only, have temporal rich amount in the decline of the demultiplexing word group signal of initial eighth row; If the demultiplexing word group signal of each row all is that per 362 bits carry out demultiplexing, also is easy to handle at receiving terminal then.

At this moment, till the last bit of the top bit to the of eighth row demultiplexing 25 row demultiplexings, from the colleague, its total length is:

（296+14.6472）/5.6427875＝55.05208197

(microsecond)

Because the colored burst signal of pal television signa is 10 microseconds, and 1 row is 64 microseconds, demultiplexing time 54 microseconds at most only then.As seen, above-mentioned side-play amount has surpassed 54 microseconds, can not realize demultiplexing by present situation.

When being the cycle with 361 bits, (with reference to the 3rd figure) only advanced phase place of 0.1384 bit of each row then when word group signal is carried out demultiplexing.At this moment, go from 18 of eighth row to the 25 row:

（296+17×0.1384）/5.6427875＝52.87330065

(microsecond)

In 54 microseconds.Yet because colored burst signal is 10 microseconds, the time of demultiplexing, rich amount was:

(54-52.8978275=1.1021725 microsecond)

This is not impossible, and just rich amount is few.

Original 1 block length, 296 bits are:

296 * 1/5.6427875=52.45634361 (microsecond)

The situation of above-mentioned the 3rd figure is:

(52.87330065-52.45634361=0.41695704 microsecond)

Only lacked a little.

Compare with " Ceefax " shown in the 6th figure

(52.87330065-51.89189189=0.98140876 microsecond)

Prolonged less than 1 microsecond than it.Roughly the same with the block length of Ceefax.

The beginning of each word group can change.For example: the row of the 9th behind the eighth row, its clock pulse series can be since 361 bits, and the 10th row can be since 362 bits.

Like this, the situation that the clock pulse series of each row begins at 361 bits, and the clock pulse series of each row is under the situation that 362 bits begin, clock pulse series to initial multichannel has phase deviation, because the situation to 362 bits has 6-7 skew doubly, then can after 6-7 is capable, sneak into 1 word group the word group of the clock pulse series that begins behind 362 bits to the row of the clock pulse series that begins at 361 bits.

Above-mentioned explanation is with whole object of action that may demultiplexing during the vertical recurrence, so under the situation of restriction multichannel row, the demultiplexing of 361 bits or 362 bits is fine certainly.

Yet under the above-mentioned situation, the colored carrier wave of paying does not have affluence yet, can shorten the information unit of 372 bits, for example can make unit length be:

272-8=264 (bit)

272-16=256 (bit)

The information bit of (272,190) symbol is 190 bits, owing to do not have byte unit, if be taken as

272-6=266 (bit)

272-14=258 (bit)

Then information bit is respectively 184 bits=23 bytes, and 176 bits=22 bytes are easy-to-use.In this case, can be by the interval of above-mentioned 361 bits or 362 bits, configuration is from the signal of clock pulse series in each row.

Multichannel method in the vertical blanking of 1 frame zero hour has been described above, but must have considered the vertical blanking problem of next.The number of the row of next beginning is the 313rd row, and then possible multichannel row is 17 row since the 321st row.Its relation is shown in the 4th figure.

But when 361 bits or 362 bits, if next word group is continuous, then 321 are about to produce significantly skew, and this is inappropriate.Therefore, after the clock pulse of certain certain-length that regulation begins from eighth row, carry out demultiplexing.Next realizes multichannel since the 633rd row, at this moment also is to carry out after the clock pulse of another certain-length.In this case, with respect to the field of beginning, the phase place of clock pulse signal only is offset 0.5 bit.This is because the 14/11 * fsc that determines is that 2 frames were 1 cycle here.

The 4th figure is benchmark with the eighth row, and the bit clock pulse skew of 321 row of next is:

313 * 64 * 5.6427875=113036.3192(bit)

Behind next 312 row be:

312 * 64/5.6427875=112675.1808(bit)

Therefore, behind 1 frame when same the skew of punctuate be:

(113036.3192+112675.1808=225711.5 bit)

With time representation, the following skew of 1 bit base is respectively:

0.05656778675 microsecond, 0.03204090177 microsecond, 0.08860868852 microsecond.

Therefore, if the clock pulse of the multichannel word group signal of the 313rd row series phase place is decided to be the 113036th clock pulse, again at 112674.5 bits (i.e. 1 frame) afterwards the phase place (promptly behind 1 frame) behind 312 row, make the phase place of bit clock pulse move half bit, phase place has just become continuously in 1 frame period so.

The 5th figure represents the relative position of each word group signal.

The 1st figure represents to produce the circuit of TV signal of the present invention.Among the figure: the 101st, colored carrier wave (4.43361875MHz) signal of paying, the 102nd, be the frame pulse of clock pulse phase deviation half bit that makes every frame, the 103rd, the horizontal-drive signal of Accounting Line Number, the 104th, from the lteral data of computer output, the 105th, the TV signal of common pal mode, the 106th, the specification signal of the capable number of appointment multichannel row, the 107th, frequency dividing circuit, the 108th, the phase difference detecting circuit, the 109th, frequency dividing circuit, the 110th, voltage controlled oscillator (VCO), the 111st, the phase-adjusting circuit of adjustment clock pulse phase place, the 112nd, make the phase conversion circuit of clock pulse phase deviation half bit in every frame, the 113rd, with the dma controller of markers from memory 114 sense datas, the 114th, temporarily store the memory of dateout, the 115th, the address of control storage 114 and control signal, the 116th, multichannel block count certificate, the demultiplexing device that 117 nominated bank that are illustrated in TV signal carry out demultiplexing.

The working condition of signal generator below is described.

Pay carrier wave frequency divider 107 and, obtain the 5.6427875MHz signal by the colour of pal television signa by the PLL circuit that VCO110 forms.This signal is adjusted into the phase place of data output signal by phase regulator 111.Then, this signal is offset half bit by frame pulse on every frame, and every frame word group signal is exported with identical markers with respect to the horizontal synchronization markers.

, synchronous this output by frame markers and row as clock pulse signal, control dma controller 113, such with above-mentioned markers dateout, address signal and control signal output from dma controller 113 are come.

According to the signal from dma controller 113, output has been stored in the data in the memory 114, by demultiplexing device 117, the TV signal demultiplexing of the row of appointment.On the other hand, because clock pulse series, framing code also are the signals stipulated rather than from memory 114 outputs, so can export from read-only storages such as ROM.

What the 1st figure represented is basic comprising, and memory dateout 116 is to the input of demultiplexing device 117, because the effect of (not shown)s such as cosine decline filter, frequency band is restricted.

The following describes receiving system.

The 7th figure is an embodiment of text broadcast signal receiving device of the present invention.201 is by aforementioned method of the present invention letter signal to be carried out the signal that demultiplexing is handled on pal television signa among the figure, and bit rate is (14/11) * fsc.Here fsc is the colored carrier frequency of pal television signa

fsc＝4.43361875 MHz

Yet the bit rate of letter signal is 5.6427875 MbPS.

The 202nd, the colored carrier reproducing circuit of paying from the colored burst signal of the multichannel of each row, by the APC circuit, is paid carrier wave 4.43361875MHz signal as the colour of continuous signal output regeneration.

The 203rd, colored carrier frequency is by the frequency dividing circuit of 1/11 frequency division.Therefore, frequency dividing circuit 203 output signal frequency are: 0.40305625 MHz.

The 204th, produce VCO205 phase of input signals comparison circuit.The output frequency of VCO205 is 5.6427875MHz, presses 1/14 frequency division by frequency dividing circuit 206.Therefore, frequency dividing circuit 206 output signal frequency are all 0.40305625MHz with frequency dividing circuit 203 output signal frequencies.

The output signal of VCO205 is input to phase option circuit 207, prepares the signal of various phase places, and for example, phase place can respectively be offset 10ns.

The 208th, the extraction circuit of clock pulse series.The frequency of clock pulse series of signals 209 is identical with the output signal frequency of VCO205, from the various phase signals of phase option circuit, selects the signal near clock pulse series of signals 209 phase places, as signal 210 outputs.That is, signal 210 and clock pulse series of signals 209 are the synchronous signals of general phase.

The 211st, the vertical synchronizing signal detecting circuit particularly only detects the 1st circuit.By linage-counter 213, from the multichannel timing signal of the 2nd of framing code generation circuit 214 output.

The 212nd, horizontal synchronization timing signal generation circuit produces the signal of count line pulse.

The 215th, detect the circuit of input signal framing code, produce the input signal of framing code generation circuit 214.This framing code generation circuit 214 is according to the signal of the row of nominated bank's counter 213 output signals 217; and the identification signal 209 that has or not of clock pulse signal 210, multichannel row, framing code detecting signal 215 etc., receive the place ahead, the rearward protect of framing code.According to the markers of this framing code generation circuit output 216,, only correctly take the data division (data set that framing code is later) of word group signal (output of word group signal detection circuit 217) by data sampling circuit 218.

According to the 7th figure, phase option circuit 207, should be in the 1st auto-reverse 180 ° of phase places, yet, also can force 180 ° of phase places of conversion by the output of vertical synchronizing signal detecting circuit 211.

The 8th figure is the detailed circuit diagram of the framing code generation circuit 214 of the 7th figure.The 301st, pal television signa, 302 is reverse in the 1st clock pulse signals of 180 ° of phase places of signal 210(that the 1st figure produces), capable and the gate signal of 312-329 between the departure date of 8-25 of 303 expression multichannels, 304 is gate signals of 8 row, the 305th, the framing code detecting circuit, 306 is 361 bit counter, the 307th, the AND circuit, 308 is 113036 bit counter, the 309th, the AND circuit, the 310th, overlap detecting circuit, the 311st, coincidence impulse not, the 312nd, coincidence impulse, the 313rd, coincidence counter not, the 314th, coincidence counter, the 315th, coincidence counter output signal not, the 316th, the coincidence counter output signal, the 317th, the AND circuit, the 318th, the AND circuit, the 319th, from the framing timing signal of internal counter, 320 is 113036 counter output signals, the 321st, and framing markers output signal.

The action of circuit shown in the 8th figure is described below in order.

In initial condition, by the timing signal that framing code detecting circuit 305 detects, by gate circuit 309, after this 361 bit counter 306 that reset, by 361 bit counter, 306 counting clock pulse signals 302, produce inner framing code signal 319.Only capable and 312-329 moved between the departure date counter 306 at the 8-25 of multiple signals.

The output of internal counter output signal 319 and framing code detecting circuit 305 often compares.Here, whether expression letter signal 303 signal of demultiplexing, can be by detecting in the clock pulse series.

By overlapping detecting circuit 310 output signal relatively, as not coincidence signal 311 and coincidence signal 312.When coincidence counter 314 countings were over, coincidence signal 311 1 did not arrive, and by signal 317 coincidence counter 314 is resetted.That is, coincidence counter 314 calculates continuous coincidence number, through 3 continuously after, when framing code just can receive with same phase place, will export and count the signal 316 that is over and export.Coincidence counter 313 does not calculate continuously not coincidence number, when signal 315 outputs, coincidence counter 314 is made zero.

According to the markers of the 1st foremost multichannel row framing code of gate signal 304, the 2nd foremost resets, and counts 113036 bits, by the output of counter, 361 bit counter 306 is resetted, and produces inner framing code.

Eighth row of gate signal 303,304 shown in the 8th figure or the 312nd row can be thought a multiple signals top row.

According to the circuit of the 8th figure, received the framing code of the multichannel 296 bit letter signals on pal television signa really.

The capable number of above-mentioned eighth row etc. is that the method for counting according to the 4th figure provides.

Letter signal shown in the 7th figure is listed as by (272,190) symbol substitution, takes out the information of 190 error-free bits.CPU explains the information of 190 bits, represents literal, figure on CRT.

By above explanation as can be known, the present invention really can be according to the clock pulse frequency of multichannel letter signal and the relation of colored carrier frequency on pal television signa, target regeneration when realizing clock pulse signal and framing on receiver.

For example, above-mentioned clock pulse signal frequency is taken as (14/11) fsc, every the framing markers (40ms) of 1 TV signal, make clock pulse phasing back, be offset half bit, making the top markers of word group signal is consistent every 40ms, therefore, the easier Signal Processing of carrying out of receiver.

Like this, can be the same with Japanese text broadcast signal, realize the demultiplexing of 1 word group, 296 bits, can be suitable for (272,190) symbol with very strong error correcting capability.The signal that only is receiver takes out the mode difference, in addition, can use the integrated circuit of developing as the text broadcast of Japan.In addition, also can the symbolization method.

Claims (4)

1, a kind of method that transmits the text broadcast signal comprises:

From pal television signa, take out the colored carrier signal of paying;

Generation becomes the letter signal of simple integer ratio to use with this signal clock pulse signal;

It is characterized in that:

From specific vertical blanking period, the signal of following 296 bits of sequential delivery; As the 16 synchronous bit clock trains of impulses of clock pulse, target 8 bit framing codes during as framing, the information of 190 bits, the 82 bit parity signal that calculate from this 190 bit information.

2, the method in the claim 1 is characterized in that described ratio of integers is 14/11.

3, be used for receiving the device of the text broadcast signal in the claim 1, it is characterized in that comprising:

The colour of regenerating is paid the device (202) of carrier signal;

Pay carrier signal with colour and multiply by 14/11 device, text broadcast of its regeneration use with the signal of clock pulse series with frequency, it comprises that one is paid the frequency dividing circuit (203) that carrier signal is divided into 1/11 component with colour, a phase-comparison circuit (204), a voltage-controlled oscillator (205), a frequency divider (206) that produces 1/14 component;

The device (207) of the signal of selection and clock pulse series homophase, it uses the clock signal of this signal as the text broadcast signal.

4, be used for receiving the device of the text broadcast signal in the claim 3, thereby it is characterized in that every certain markers, the reliability that receives framing code so just is provided the multiplexed device that detects framing code of framing code.

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