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ADV7341 数据表(PDF) 61 Page - Analog Devices |
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ADV7341 数据表(HTML) 61 Page - Analog Devices |
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61 / 108 page  Data Sheet ADV7340/ADV7341 Rev. C | Page 61 of 108 The hue adjust value is calculated using the following equation: Hue Adjust (°) = 0.17578125° (HCRd − 128) where HCRd is the hue adjust control register (decimal). For example, to adjust the hue by +4°, write 0x97 to the hue adjust control register. 97 x 0 151 128 17578125 . 0 4 = ≈ + d where the sum is rounded to the nearest integer. To adjust the hue by −4°, write 0x69 to the hue adjust control register. 9 6 x 0 105 128 17578125 . 0 4 = ≈ + − d where the sum is rounded to the nearest integer. SD BRIGHTNESS DETECT Subaddress 0xBA The ADV7340/ADV7341 allow monitoring of the brightness level of the incoming video data. This feature is used to monitor the average brightness of the incoming Y signal on a field-by- field basis. The information is read from the I2C and, based on this information, the color saturation, contrast, and brightness controls can be adjusted (for example, to compensate for very dark pictures). The luma data is monitored in the active video area only. The average brightness I2C register is updated on the falling edge of every VSYNC signal. The SD brightness detect register (Subad- dress 0xBA) is a read-only register. SD BRIGHTNESS CONTROL Subaddress 0xA1, Bits[6:0] When this feature is enabled, the SD brightness/WSS control register (Subaddress 0xA1) is used to control brightness by adding a programmable setup level onto the scaled Y data. This feature can be enabled using Subaddress 0x87, Bit 3. For NTSC with pedestal, the setup can vary from 0 IRE to 22.5 IRE. For NTSC without pedestal and for PAL, the setup can vary from −7.5 IRE to +15 IRE. The SD brightness control register is an 8-bit register. The seven LSBs of this 8-bit register are used to control the brightness level, which can be a positive or negative value. For example, to add a +20 IRE brightness level to an NTSC signal with pedestal, write 0x28 to Subaddress 0xA1. 0 × (SD Brightness Value) = 0 × (IRE Value × 2.015631) = 0 × (20 × 2.015631) = 0 × (40.31262) ≈ 0x28 To add a –7 IRE brightness level to a PAL signal, write 0x72 to Subaddress 0xA1. 0 × (SD Brightness Value) = 0 × (IRE Value × 2.075631) = 0 × (7 × 2.015631) = 0x(14.109417) ≈ 0001110b 0001110b into twos complement = 1110010b = 0x72 Table 50. Sample Brightness Control Values1 Setup Level (NTSC) with Pedestal Setup Level (NTSC) Without Pedestal Setup Level (PAL) Brightness Control Value 22.5 IRE 15 IRE 15 IRE 0x1E 15 IRE 7.5 IRE 7.5 IRE 0x0F 7.5 IRE 0 IRE 0 IRE 0x00 0 IRE −7.5 IRE −7.5 IRE 0x71 1 Values in the range of 0x3F to 0x44 may result in an invalid output signal. SD INPUT STANDARD AUTODETECTION Subaddress 0x87, Bit 5 The ADV7340/ADV7341 include an SD input standard autodetect feature. This SD feature can be enabled by setting Subaddress 0x87, Bits[5: 1]. When enabled, the ADV7340/ADV7341 can automatically identify an NTSC or a PAL B/D/G/H/I input stream. The ADV7340/ADV7341 automatically update the subcarrier frequency registers with the appropriate value for the identified standard. The ADV7340/ADV7341 are also configured to correctly encode the identified standard. The SD standard bits (Subaddress 0x80, Bits[1:0]) and the subcarrier frequency registers are not updated to reflect the identified standard. All registers retain their default or user- defined values. Figure 65. Examples of Brightness Control Values NTSC WITHOUT PEDESTAL NO SETUP VALUE ADDED POSITIVE SETUP VALUE ADDED 100 IRE 0 IRE NEGATIVE SETUP VALUE ADDED –7.5 IRE +7.5 IRE |
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