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SingMai Electronics

PT9 User Manual Revision 0.3

Page 16 of 38

utilize this to help separate the chroma and luma where they overlap (the chroma information will
have this phase relationship, the high frequency luma information will not).

The PAL subcarrier is shifted 270° in phase every line of a field, so over a two lines of field it will be
180° phase shifted. If we add these two lines together it will cancel the chroma and reinforce the
luma. This ‘line-comb’ filter can recover the full luma bandwidth, but only under certain conditions.

If there is a vertical transition in the image (one line of one colour, another of a different colour)
then the line comb will fail (giving what are called, ‘hanging dots’). Similarly if there are diagonals
in the image then the line comb will fail. In each case the failure can result in higher levels of
chroma, giving the familiar shimmering cross-colour effects on high frequency luma structure, as
shown in Figure 10.

Figure 10 Zone plate image after line comb decoding.

To separate the luma and chroma almost perfectly, a frame comb decoder can be used. The 3D
frame comb decoder, because it is combing spatially aligned images, does not suffer from the
problems of the 2D line comb decoder (where the comb taps are separated by a number of lines).
This can be seen in the frame comb decoded image of the zone plate in Figure 11.

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Содержание PT9

Страница 1: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 1 of 38 PT9 Multi standard Video Encoder with cross colour reduction User Manual Revision 0 3 9th June 2018 ...

Страница 2: ...evisions Date Revisions Version 19 11 2015 First draft 0 1 29 08 2017 Revisions to comb filter Cross colour reduction description added Pre emphasis added Cross luma reduction removed Additions to technical description 0 2 09 06 2018 Minor correction to Table 8 0 3 ...

Страница 3: ...registers 23 11 Default Register Settings 25 12 Interfacing to a DAC 27 13 Specification 28 14 Measurements 29 Tables Table 1 PT9 Altera FPGA resource requirements 5 Table 2 PT9 module heirachy 6 Table 3 Input Output signals 7 Table 4 BT656 Signal Levels 9 Table 5 BT656 test waveform 525 line 10 Table 6 BT656 test waveform 625 line 10 Table 7 Register descriptions 22 Table 8 Default Register setti...

Страница 4: ...l timing 23 Figure 16 PAL BG horizontal timing 24 Figure 17 Interfacing to a DAC 27 Figure 18 NTSC Vertical blanking interval 29 Figure 19 NTSC Horizontal Timing 30 Figure 20 NTSC 75 Colour bar 30 Figure 21 NTSC Chroma Luma delay 31 Figure 22 NTSC K Factor 31 Figure 23 NTSC Multiburst No sinx x correction 32 Figure 24 NTSC Noise Spectrum Black 32 Figure 25 NTSC Noise Spectrum luma ramp 33 Figure 2...

Страница 5: ...coder The encoder can also be set to a free run mode in which it ignores the BT656 timing information and data and uses the clock input to generate a black and burst output Control and status registers are written to and read from using a conventional 8 bit wide microprocessor interface The Altera FPGA usage taken from the SM05 evaluation board compilation statistics is shown in Table 1 Logic Elem...

Страница 6: ...der v is the top level module of the hierarchy six of the other modules are instantiated from it Top level 2nd level 3rd level 4th level PT9_encoder v PT9_Register_control v PT9_BT656_receiver v PT9_SPG v PT9_Subcarrier_gen v PT9_ROM v PT9_Chroma_modulator v PT9_output_proc v PT9_Comb_filter v ram_infer_generic v Table 2 PT9 module heirachy ...

Страница 7: ...to ground logic 0 RESETn Asynchronous active low reset signal Asserting this input sets all the control registers to their default value and resets all registers A 5 0 Control address bus input used to select the control register to be written to read from Din 7 0 Control data input bus PT9_CSn Control chip select input active low Used in combination with the WRn input to control writing to the co...

Страница 8: ...ock2x Clock2x_sig input Clock2x_sig BT656_data BT656_data_sig input 9 0 BT656_data_sig RESETn RESETn_sig input RESETn_sig A A_sig input 5 0 A_sig Din Din_sig input 7 0 Din_sig PT9_CSn PT9_CSn_sig input PT9_CSn_sig PT9_WRn PT9_WRn_sig input PT9_WRn_sig PT9_Register_out PT9_Register_out_sig output 7 0 PT9_Register_out_sig CVBS_out CVBS_out_sig output 9 0 CVBS_out_sig Comp_Sync Comp_Sync_sig output C...

Страница 9: ... 663 64 Green 578 215 137 Magenta 426 809 887 Red 326 361 960 Blue 164 960 439 Black 64 512 512 10 bit YCbCr signal Levels 75 0 75 0 Y Cb Cr White 940 512 512 Grey 721 512 512 Yellow 646 176 567 Cyan 525 625 176 Green 450 289 231 Magenta 335 735 793 Red 260 399 848 Blue 139 848 457 Black 64 512 512 Table 4 BT656 Signal Levels The resulting nominal output levels for a 100 PAL colour bar input are s...

Страница 10: ... 1716 515 line or 1728 625 line samples in a multiplexed Cb Y Cr Y sequence Each sample of each element should be clocked at 27MHz For 525 line standards the elements should be selected according to the following table Line No s Pattern Element 4 19 264 265 F0V1 1 1 3 266 282 F1V1 2 20 263 75 Bars F0 3 283 525 75 Bars F1 4 Table 5 BT656 test waveform 525 line For 625 line standards the elements sh...

Страница 11: ...T656 formatted data stream and associated 27MHz clock If the input is 8 bits the bottom 2 bits should be tied to logic 0 The 656 interface block identifies and extracts the TRS codes from the stream and de multiplexes and co times the Y Cb Cr data This module also detects the line standard of the input BT656 video which can be used to auto select the output video standard PT9_SPG v The clock frame...

Страница 12: ...onse with a Gaussian response see Figure 4 Figure 4 Chroma modulation filter The filtered Cb and Cr signals are then scaled multiplied by the sin and cos waveforms from the subcarrier generator and added to generate a composite chroma signal The resulting U sin 2πfsc t and V cos 2πfsc t data is added together to create the chrominance signal which has blanking added as well as programmable gain PT...

Страница 13: ...equency boost network at the receiver decoder To provide better compensation the PT9 has a pre emphasis filter that is matched to response of typical coaxial cable e g RG 59 The filter provides a high frequency boost whose amplitude is controllable via a register The response of this filter is shown in Figures 7 and 8 It is possible when used with the SingMai video decoders that this frequency com...

Страница 14: ...th a line comb video decoder A description of its operation may be found in Chapter 7 The comb filter module also provides compensating delays for the chroma components ram_infer_generic v This module is a generic single port RAM that is used in the comb filter module InphaseFilterFrequencyResponse FrequencyinMHz Magnitude in dB 0 1 2 3 4 5 6 14 12 10 8 6 4 2 0 2 InphaseFilterFrequencyResponse Fre...

Страница 15: ...ate the luma from the composite signal we could employ a low pass filter that blocks all frequencies above 3MHz This will result in clean luma i e with no chroma crosstalk but we have reduced the luma bandwidth of the signal by nearly one half This approach is even more detrimental for NTSC where the subcarrier is at 3 58MHz still with a 1 3MHz bandwidth so the resulting luma bandwidth would be on...

Страница 16: ...e image one line of one colour another of a different colour then the line comb will fail giving what are called hanging dots Similarly if there are diagonals in the image then the line comb will fail In each case the failure can result in higher levels of chroma giving the familiar shimmering cross colour effects on high frequency luma structure as shown in Figure 10 Figure 10 Zone plate image af...

Страница 17: ...the case for the SingMai PT9 encoder and the PT4 line comb decoder The line comb decoded image using this technique is shown in Figure 12 As you can see the cross colour is almost completely removed compared with the image in Figure 10 yet because only the high frequency luma is combed we still preserve as much picture detail as possible compared with for example a simple notch filter Of course th...

Страница 18: ... Revision 0 3 Page 18 of 38 Figure 12 Zone plate image line comb decoded from PT9 encoder Figure 13 NTSC zone plate with line comb decoder Left conventional encoder line comb decoder Right PT9 encoder with conventional line comb decoder ...

Страница 19: ...ed the required register address and the data for this register set up The PT9_WRn input must then be driven low and high again On the rising edge of this pulse the data is latched into the address selected The PT9_CSn should then be returned high For the write to occur reliably the address A 5 0 and data Din 7 0 must be stable and valid during the low to high transition of the PT9_WRn pulse The a...

Страница 20: ...cted manually 0 via Bit 5 or via the line standard detection of the BT656 input 525 or 625 line 1 Default value 1 5 If bit 6 0 this bit selects the output line standard 4 Selects either PAL NTSC output 0 or PAL N PAL M output 1 5 4 Line standard detect bit 6 1 or bit 5 bit 6 0 Bit 4 0 0 NTSC M Default 0 1 PAL M 1 0 PAL 1 1 PAL N 3 0 Not used 01 Control 2 R W Control status register 7 6 Not used Si...

Страница 21: ...tively H blank end H blank start 1 27MHz is the blanking width nominally 52us 11 bit value Hblankend2 2 0 Hblankend1 7 0 12 H blank end 2 R W 13 Pedestal start 1 R W Delay between H Phase reset and start of pedestal insertion for 525 line standards only Increments of 1 27MHz Maximum value 1715 11 bit value Pedestalstart2 2 0 Pedestalstart1 7 0 14 Pedestal start 2 R W 15 Pedestal end 1 R W Delay be...

Страница 22: ...NTSC output only 11 bit value NTSCHue2 2 0 NTSCHue1 7 0 1 LSB 0 176deg 2A NTSC Hue 2 R W Proc amp control 2B Sync Scaling 1 R W Output composite sync level nominally Sync scaling 256 results in sync output between 16 sync bottom and 256 sync top 9 bit value SyncScaling2 0 SyncScaling1 7 0 2C Sync Scaling 2 R W 2D Burst Scaling 1 R W Burst amplitude 9 bit value BurstScaling2 0 BurstScaling1 7 0 2E ...

Страница 23: ...gMai Electronics PT9 User Manual Revision 0 3 Page 23 of 38 10 Horizontal timing registers Figures 15 and 16 show the timing specifications for NTSC and PAL BG respectively Figure 15 NTSC horizontal timing ...

Страница 24: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 24 of 38 Figure 16 PAL BG horizontal timing ...

Страница 25: ...9 254 254 254 04 H Phase 2 5 5 5 5 5 5 05 V Phase 1 112 112 112 9 9 9 06 V Phase 2 2 2 2 2 2 2 0B H Sync start 1 32 32 32 32 32 32 0C H Sync start 2 0 0 0 0 0 0 0D H Sync end 1 159 159 159 159 159 159 0E H Sync end 2 0 0 0 0 0 0 0F H blank start 1 20 20 20 20 20 20 10 H blank start 2 1 1 1 1 1 1 11 H blank end 1 0 0 0 0 0 0 PAL I front porch is 1 65µs 12 H blank end 2 0 0 0 0 0 0 13 Pedestal start...

Страница 26: ...aling 1 140 140 140 31 31 31 30 UV Scaling 2 3 3 3 4 4 4 31 Sync Offset 1 8 8 8 8 8 8 32 Sync Offset 2 0 0 0 0 0 0 33 VBI Scaling 1 63 63 63 128 128 128 34 VBI Scaling 2 1 1 1 1 1 1 35 Y Pedestal 0 0 0 24 24 0 The pedestal register only operates for NTSC M and PAL M 36 Y Offset 1 64 64 64 64 64 64 37 Y Offset 2 0 0 0 0 0 0 38 Luma Scaling 1 62 62 62 142 142 142 39 Luma Scaling 2 1 1 1 1 1 1 3E CVB...

Страница 27: ...the PT9 encoder The digital composite video output and the 27MHz clock can be used to directly drive a DAC the SM05 board uses an ADI AD9706 12 bit DAC for this purpose The output of the DAC is filtered and buffered The SM05 DAC schematic is shown if Figure 17 Full details for the SM05 may be found here http www singmai com Modules SM05 html Figure 17 Interfacing to a DAC ...

Страница 28: ...d be 250ns Sync Pulse amplitude 300mV 40IRE Luminance white bar amplitude 700mV 100IRE Vertical Sync Group 7 5 lines 9 lines No of equalizing pulses 5 5 6 6 Chrominance Phase error 1deg 1 5deg Subcarrier Frequency 4 43361875MHz PAL 3 58205625MHz PAL N 3 5795455MHz NTSC 3 5756118MHz PAL M Colour Frame duration 8 fields 4 fields 8 fields for PAL M Burst start 5 64us 5 31us 5 3us for PAL N Burst dura...

Страница 29: ...ch provided the 10 bit BT656 input to the PT9 encoder The composite digital output was converted to analogue using an Analog Devices AD9706 12 bit digital to analogue converter top 10 bits driven The output from the DAC was amplified and filtered using an ADA4412 amplifier with the filter bandwidth set to 27MHz and the composite measurements were performed on a Tektronix VM700 measurement set Figu...

Страница 30: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 30 of 38 Figure 19 NTSC Horizontal Timing Figure 20 NTSC 75 Colour bar ...

Страница 31: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 31 of 38 Figure 21 NTSC Chroma Luma delay Figure 22 NTSC K Factor ...

Страница 32: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 32 of 38 Figure 23 NTSC Multiburst No sinx x correction Figure 24 NTSC Noise Spectrum Black ...

Страница 33: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 33 of 38 Figure 25 NTSC Noise Spectrum luma ramp Figure 26 PAL Vertical blanking interval ...

Страница 34: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 34 of 38 Figure 27 PAL Horizontal timing Figure 28 PAL 75 Colour bars ...

Страница 35: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 35 of 38 Figure 29 PAL Chroma Luma delay Figure 30 PAL K factor ...

Страница 36: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 36 of 38 Figure 31 PAL Multiburst no sinx x correction ...

Страница 37: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 37 of 38 Figure 32 PAL Noise spectrum black ...

Страница 38: ...SingMai Electronics PT9 User Manual Revision 0 3 Page 38 of 38 Figure 33 PAL Luma non linearity ...

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