BTS-3 — Television Broadcasting
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Broadcast Transmission Standard
Table of Contents
- Basic Standards
- Multichannel Television Sound Standards
- Vertical Blanking Interval Signal Standards
- Digital Data in the Video Portion of TV Transmissions
- 5.1 General
This document contains the standards governing TV broadcasting systems in Canada. The standards ensure satisfactory monochrome and colour television broadcasting services based on the 525 line NTSC colour system. The system is known as NTSC/M.top of page
2.1.1 Television stations are assigned channels with numbers and frequencies as designated in Table 2.1. The width of the television broadcast channel shall be 6 MHz. The visual carrier frequency shall be nominally 1.25 MHz above the lower boundary of the channel. The aural carrier frequency shall be 4.5 MHz above the visual carrier frequency.
|Channel No.|| Frequency Band
| Visual Carrier
| Aural Carrier
2.2.1 The number of scanning lines per picture (frame) shall be 525, interlaced two to one in successive fields.
2.2.2 The chrominance subcarrier frequency shall be 3.579545 MHz. The tolerance is ± 10 Hz and the rate of frequency drift shall not exceed 0.10 Hz per second.
2.2.3 The horizontal scanning frequency shall be 2/455 times the chrominance subcarrier frequency. This corresponds nominally to 15 570 Hz with an actual value of 15 734.264 ± 0.044 Hz.
2.2.4 The vertical scanning frequency is 2/525 times the horizontal scanning frequency. This corresponds nominally to 60 Hz with an actual value of 59.94 Hz.
2.2.5 The aspect ratio of the transmitted television picture shall be 4 units horizontally to 3 units vertically.
2.2.6 During active scanning intervals, the scene shall be scanned from left to right horizontally and top to bottom vertically, at uniform velocity.
2.2.7 The nominal and peak levels of the composite video signal expressed in % shall be as follows: (see Figure 1)
2.3.1 Line Synchronization. The details of the line synchronizing signal are given in Table 1, Figure 1 and Figure 5. The durations specified are measured between the half-amplitude points of the appropriate edges.
Nominal line period (μs)
|a||Line-blanking interval (μs)||10.2 to 11.4||10.9 ± 0.2|
Front porch (μs)
|1.27 to 2.54||1.27 to 2.22|
|d||Synchronizing pulse(μs)||4.19 to 5.71||4.7 ± 0.1|
|e||Built-up time (10 to 90 %) of the edges of the line-blanking pulse (μs)||≤ 0.64||≤ 0.48|
|f||Build-up time (10 to 90 %) of the edges of the line-synchronizing pulses (μs)||≤ 0.25||≤ 0.25|
2.3.2 Field Synchronization. The details of the field synchronizing signal are given in Table 2, Figure 2 and Figure 5. The durations specified are measured between the half-amplitude points of the appropriate edges.
|Symbol (Fig. 2)||Characteristics||M Monochrome||NTSC/M Colour|
|v||Field period (ms)||16.667||16.6833|
|j||Field-blanking interval (for H and a, see Table 1)||19 to 21H + a||19 to 21H + a|
|-||Build-up time (10 to 90 %) of the edges of field-blanking pulses (μs)||≤ 6.35||≤ 6.35|
|-||Interval between front edge of field-blanking interval and front edge of first equalizing pulse(μs)||1.5 ± 0.1||1.5 ± 0.1|
|l||Duration of first sequence of equalizing pulses||3H||3H|
|m||Duration of sequence of equalizing pulses||3H||3H|
|n||Duration of second sequence of equalizing pulses||3H||3H|
|p||Duration of equalizing pulse (μs)||2.3 ± 0.1||2.3 ± 0.1|
|q||Duration of field-synchronizing pulse (μs)||27.1 nominal||27.1 nominal|
|r||Interval between field-synchronizing pulse (μs)||4.7 ± 0.1||4.7 ± 0.1|
|s||Build-up time (10 to 90%) of synchronizing and equalizing pulses (μs)||≤ 0.25||≤ 0.25|
2.4.1 The equation of the composite colour signal is
EM= E'Y + [E'Qsin(ωt+33°) +E'I cos(ωt+33°)]
E'Y = 0.30E'R + 0.59E'G + 0.11E'B
E'Q = 0.41(E'B - E'Y) +0.48(E'R - E'Y)
E'I = -0.27(E'B - E'Y) + 0.74(E'R - E'Y)
The symbols in the above equations have the following significance:
EM = the total video voltage, corresponding to the scanning of a particular picture element, applied to the modulator of the visual transmitter.
E'Y = the gamma-corrected voltage of the monochrome (black and white) portion of the colour picture signal, corresponding to the given picture element.
E'Q, E'I = the amplitude of the two orthogonal components of the chrominance signal corresponding respectively to narrow-band and wide-band axes.
E'R, E'G, E'B = the gamma-pre-corrected primary signals corresponding to red, green and blue signals during the scanning of the given picture element.
ω = the angular frequency and is 2π times the frequency of the chrominance subcarrier.
The portion of the complete equation between the brackets represents the chrominance subcarrier signal that carries the chrominance information. The phase reference in the EM equation is the phase of the burst i.e. 180° as shown in Figure 3. The burst corresponds to amplitude modulation of a continuous sine wave.
2.4.2 The equivalent bandwidth assigned before modulation to the colour difference signals E'Q and E'I are as follows:
Q - channel bandwidth:
At 400 kHz, less than 2 dB attenuation
At 500 kHz, less than 6 dB attenuation
At 600 kHz, equal to or greater than 6 dB attenuation
I - channel bandwidth:
At 1.3 MHz, less than 2 dB attenuation
At 3.6 MHz, equal to or greater than 20 dB attenuation
2.4.3 The gamma-corrected voltages E'R, E'B and E'B are suitable for a colour picture tube having primary colours with the chromaticities in the CIE (Commission internationale de l'éclairage) system of specification as follows: The assumed transfer gradient (gamma exponent) of the receiver for which the primary signals are pre-corrected is 2.2.
2.4.4 The radiated chrominance subcarrier vanishes on the reference white of the scene. The numerical values of the signal specification assume that this condition will be produced as CIE Illuminant C (x = 0.310, y = 0.316).
2.4.5 E'Y, E'Q, E'I and the components of these signals shall match each other in time to 0.05 μs.
2.4.6 The angles of the subcarrier measured with respect to the burst phase, when reproducing saturated primaries and their complements at 75% of full amplitude, shall be within ± 10 degrees and their amplitudes within 20% of the values specified above. The ratios of the measured amplitudes of the subcarrier to the luminance signal for the same saturated primaries and their complements shall fall between the limits of 0.8 and 1.2 of the values specified for their ratios.
2.4.7 The type of subcarrier modulation produced by the chrominance components shall be suppressed carrier amplitude modulation of two subcarriers in quadrature.
2.4.8 The bandwidth of the chrominance sidebands relative to the subcarrier frequency shall be:
The amplitude of the chrominance subcarrier shall be
G = [(E'I)2 + (E'Q)2]½
2.4.9 The chrominance subcarrier shall be synchronized by a subcarrier burst on the horizontal blanking back porch. The start of the subcarrier burst shall be 4.71 to 5.71 μs (5.3 μs nominal) after the front edge of horizontal sync. and at least 0.38 μs after the trailing edge of the horizontal sync. signal. The duration of the subcarrier burst shall be 2.23 to 3.11 μs (9 ± 1 cycles).
2.4.10 The peak-to-peak value of the chrominance subcarrier burst shall be 4/10 of the difference between blanking level and peak white level. The phase of the chrominance subcarrier burst shall be 180° relative to the (E'B - E'Y) axis (see Figure 3). The chrominance subcarrier shall be blanked following each equalizing pulse during the broad synchronizing pulses in the field-blanking interval (See Figure 5).
2.5.1 The frequency spacing of the radiated signal is shown in Figure 4. The nominal radio-frequency channel bandwidth shall be 6 MHz. The sound carrier relative to the vision carrier shall be 4.5 MHz. The nearest edge of the channel relative to vision carrier shall be -1.25 MHz. The nominal width of the main sideband and the vestigial sideband shall be 4.2 and 0.75 MHz respectively.
2.5.2 The minimum attenuation of the vestigial sideband shall be:
20 dB at -1.25 MHz
42 dB at -3.58 MHz
2.5.3 The type and polarity of the vision modulation shall be C3F negative.
2.5.4 The levels in the radiated signal expressed in % of peak carrier shall be:
2.5.5 The precorrected group delay of the radiated signal shall be 0 nanosecond to 3 MHz and decreases linearly to 170 nanoseconds at 3.58 MHz. The tolerance on the group delay shall be as shown in Figure 6.
2.5.6 The type and polarity of the sound modulation shall be F3E.
2.5.7 The peak frequency deviation of the sound carrier shall be ± 25 kHz for monophonic inputs and ± 75 kHz for stereophonic or composite inputs.
2.5.8 Pre-emphasis having a time constant of 75 μs shall be used.
2.5.9 The effective radiated power of the aural transmitter shall not be less than 10% nor more than 20% of the peak radiated power of the visual transmitter.top of page
3.1.1 The modulating signal for the main channel shall consist of the sum of the stereophonic (biphonic, quadraphonic, etc.) input signals.
3.1.2 The instantaneous frequency of any baseband subcarrier shall, at all times, be within the range of 15 kHz to 120 kHz. Either amplitude or frequency modulation of the subcarrier may be used.
3.1.3 One or more pilot subcarriers between 16 kHz and 120 kHz may be used to switch a TV receiver between the stereophonic and monophonic reception modes or to activate a stereophonic mode indicator, and one or more subcarriers between 15 kHz and 120 kHz may be used for any other authorized purpose. However stations transmitting the BTSC system of stereophonic sound and audio processing shall transmit a pilot subcarrier at 15 734 Hz ± 2 Hz. Other methods of multiplex subcarrier or stereophonic aural transmission systems shall limit energy at 15 734 Hz ± 20 Hz, to no more than ± 0.125 kHz aural carrier deviation.
3.1.4 Aural baseband information above 120 kHz shall be attenuated 40 dB referenced to 25 kHz main channel deviation of the aural carrier.
3.1.5 When transmitting MTS, the main channel of the aural transmission shall meet the standards of System NTSC/M and those contained in the appropriate Radio Standards Specification for the transmitting equipment involved.
3.1.6 Multiplex subcarrier or stereophonic aural transmission systems shall be capable of producing and shall not exceed ± 25 kHz main channel deviation of the aural carrier.
3.1.7 The arithmetic sum of non-multiphonic baseband signals between 15 kHz and 120 kHz shall not exceed ± 50 kHz deviation of the aural carrier.
3.1.8 Total modulation of the aural carrier shall not exceed ± 75 kHz.
3.1.9 During any mode of transmission, monophonic, stereophonic, multiplex, the spectrum of the radiated signal or occupied bandwidth of the aural transmitter shall be within the following limits:
- not greater than -25 dB, when referred to the level of the unmodulated carrier, for any frequency removed from the carrier by between 120 kHz and 240 kHz;
- not greater than -35 dB, when referred to the level of the unmodulated carrier, for any frequency removed from the carrier by between 240 kHz and 600 kHz.
3.2.1 Television broadcast stations may transmit stereophonic sound by employing a subcarrier on the aural carrier. The main channel modulating signal shall be the stereophonic sum signal; the subcarrier modulation shall be the stereophonic difference encoded signal.
3.2.2 The subcarrier shall be the second harmonic of the pilot signal which is transmitted at a frequency equal to the horizontal line rate of 15 734 Hz ± 2 Hz. If the station is engaged in stereophonic sound transmission accompanied by monochrome picture transmission, this horizontal scanning frequency shall be employed.
3.2.3 The subcarrier shall be double sideband amplitude modulated with suppressed carrier and shall be capable of accepting a stereophonic difference encoded signal over a range of 50 - 15 000 Hz.
3.3.1 Television broadcast stations may transmit a subcarrier carrying a second audio program.
3.3.2 The subcarrier frequency shall nominally be equal to the fifth harmonic of the horizontal line rate.
3.3.3 The second program encoded signal shall frequency modulate the subcarrier to a peak deviation of ± 10 kHz.
3.3.4 The second audio program (SAP) subchannel shall be capable of accepting second program encoded signals over a range of 50 - 10 000 Hz.
3.3.5 The modulation of the aural carrier by the second audio program subcarrier shall not exceed ± 15 kHz deviation.
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