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HMP8117 Datasheet(PDF) 8 Page - Intersil Corporation |
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HMP8117 Datasheet(HTML) 8 Page - Intersil Corporation |
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8 / 45 page  8 FN4643.3 April 19, 2007 remove high-frequency Y data. This may make a noisy image more pleasing to the user, although softer. Coring of the high-frequency Y data may be done to reduce low-level high frequency noise. Coring of the Y data may also be done to reduce low-level noise around black. This forces Y data with the following values to a value of 0: coring = 1: ± 1 coring = 2: ± 1, ± 2 coring = 3: ± 1, ± 2. ± 3 High-frequency components of the luminance signal may be “peaked” to control the sharpness of the image. Maximum gain may be selected to occur at either 2.6MHz or the color subcarrier frequency. This may be used to make the displayed image more pleasing to the user. It should not be used if the output video will be compressed, as the circuit introduces high-frequency components that will reduce the compression ratio. The brightness control adds or subtracts a user-specified DC offset to the Y data. The contrast control multiplies the Y data by a user-specified amount. These may be used to make the displayed image more pleasing to the user. Finally, a value of 16 is added to generate a nominal range of 16 (black) to 235 (white). CbCr Processing The CbCr data is low-pass filtered to either 0.85MHz or 1.5MHz. Coring of the CbCr data may be done to reduce low-level noise around zero. This forces CbCr data with the following values to a value of 128. coring = 1: 127, 129 coring = 2: 126, 127, 129, 130 coring = 3: 125, 126, 127, 129, 130, 131 The saturation control multiplies the CbCr data by a user- specified amount. This may be used to make the displayed image more pleasing to the user. The CbCr data may also be optionally multiplied by the contrast value to avoid color shifts when changing contrast. The hue control provides a user-specified phase offset to the color subcarrier during decoding. This may be used to correct slight hue errors due to transmission. YCbCr Output Format Processing Y has a nominal range of 16 to 235. Cb and Cr have a nominal range of 16 to 240, with 128 corresponding to zero. Values less than 1 are made 1 and values greater than 254 are made 254. While BLANK is asserted, Y is forced to have a value of 16, with Cb and Cr forced to have a value of 128, unless VBI data is present. RGB Output Format Processing The 4:2:2 YCbCr data is converted to 4:4:4 YCbCr data and then converted to either 15-bit or 16-bit gamma-corrected RGB (R ′G′B′) data. While BLANK is asserted, RGB data is forced to a value of 0. 15-Bit R ′G′B′ The following YCbCr to R ′G′B′ equations are used to maintain the proper black and white levels: R ′ = 0.142(Y - 16) + 0.194(Cr - 128) G ′ = 0.142(Y - 16) - 0.099(Cr - 128) - 0.048(Cb - 128) B ′ = 0.142(Y - 16) + 0.245(Cb - 128) The resulting 15-bit R ′G′B′ data has a range of 0 to 31. Values less than 0 are made 0 and values greater than 31 are made 31. The 15-bit R ′G′B′ data may be converted to 15-bit linear RGB, using the following equations. Although the PAL specifications specify a gamma of 2.8, a gamma of 2.2 is normally used. The HMP8117 allows the selection of the gamma to be either 2.2 or 2.8, independent of the video standard. for gamma = 2.2: for R ′G′B′ < 0.0812*31 R = (31)((R ′/31)/4.5) G = (31)((G ′/31)/4.5) B = (31)((B ′/31)/4.5) for R ′G′B′ >= 0.0812*31 R = (31)(((R ′/31) + 0.099)/1.099)2.2 G = (31)(((G ′/31) + 0.099)/1.099)2.2 B = (31)(((B ′/31) + 0.099)/1.099)2.2 for gamma = 2.8: R = (31)(R ′/31)2.8 G = (31)(G ′/31)2.8 B = (31)(B ′/31)2.8 16-Bit R ′G′B′ The following YCbCr to R ′G′B′ equations are used to maintain the proper black and white levels: R ′ = 0.142(Y - 16) + 0.194(Cr - 128) G ′ = 0.288(Y - 16) - 0.201(Cr - 128) - 0.097(Cb - 128) B ′ = 0.142(Y - 16) + 0.245(Cb - 128) The resulting 16-bit R ′G′B′ data has a range of 0 to 31 for R′ and B ′, and a range of 0 to 63 for G′. Values less than 0 are made 0; R ′ and B′ values greater than 31 are made 31, G′ values greater than 63 are made 63. The 16-bit R ′G′B′ data may be converted to 16-bit linear RGB, using the following equations. Although the PAL specifications specify a gamma of 2.8, a gamma of 2.2 is normally used. The HMP8117 allows the selection of the gamma to be either 2.2 or 2.8, independent of the video standard. HMP8117 |
Similar Part No. - HMP8117_07 |
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Similar Description - HMP8117_07 |
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