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參數(shù)資料
| 型號： | VPX3214C |
| 廠商： | Electronic Theatre Controls, Inc. |
| 英文描述： | Video Pixel Decoders |
| 中文描述： | 視頻解碼器像素 |
| 文件頁數(shù)： | 15/80頁 |
| 文件大?。?/td> | 752K |
| 代理商： | VPX3214C |
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VPX 3220 A, VPX 3216 B, VPX 3214 C
PRELIMINARY DATA SHEET
MICRONAS INTERMETALL
15
2.4.2. Compression 24
8 bits
A variant of the time-honored DPCM coding technique
is available to compress the 24-bit YCbCr 4:4:4 signal to
an 8-bit per pixel signal. The technique combines differ-
ential coding, companding, and adaptive subsampling
of the chrominance. For the most natural image materi-
al, the resulting bandwidth savings are purchased at a
modest loss of amplitude resolution, which appears
mostly as high frequency noise. Signals encoded in this
form are readable by decoders, which are embedded in
commercially available ICs (RAMDACs, back-end ana-
log encoders, etc...).
Different techniques are used to code the luminance and
the two chroma signals. For the luma, the difference be-
tween 8-bit luma value and a computed reference is
companded to a 5-bit value for transmission. The com-
puted reference is simply the 8-bit value of the nearest
horizontal neighbor as it appears at the decoder. Each
decoded luminance sample is therefore used as a pre-
diction for the next pixel. This, in turn, requires that the
encoder contains almost a complete decoder as a sub-
set.
The chrominance samples are encoded in a similar
fashion. The samples of each chrominance component
are ordered into non-overlapping groups of four. For
each group, one of the four samples is selected as a rep-
resentative value. For each representative pixel, the rel-
ative position and companded differential amplitude are
computed for transmission. The position data is relative
to the beginning of the group and is encoded as a 2-bit
word. The difference between the 8-bit value of the sam-
ple and the decoded reference value of the previous
group is companded to a 5-bit word.
2.4.3. Inverse Gamma Correction
Today, most broadcast video sources anticipate the dis-
play on conventional CRTs by predistorting the RGB sig-
nals with a gamma function (shown below)
I’ = cI
γ
+
I
0
γ
c, I
0
=
constants
I
{R, G, B}...
linear intensity
2.2
However, for video processing in a computer, linear
space (no gamma distortion) is often the representation
of choice. The VPX provides two options for gamma re-
moval. Both conform to the basic formula:
I = I’
(1
/γ)
These two
γ
–1 functions are realized as fixed entries in
ROM. The first table compensates for a
γ
= 1.4. The se-
cond table compensates for a
γ
= 2.2.
2.4.4. Alpha Key
A 1-bit threshold select signal can be generated for ev-
ery pixel in the YCbCr 4:4:4 signal. Using six registers,
an upper and a lower threshold is separately defined for
each of the Y, C
b
, and C
r
components. These six register
values define a cube in YC
b
C
r
space. Equality is always
included in comparison. For each pixel, an alpha bit is
generated, which signals whether the pixel lies inside or
outside this cube. A 3-point horizontal median filter is
available to mitigate the effects of impulse noise.The al-
pha signal is fed out through the alpha pin, which is in
turn multiplexed with JTAG TDO function (see chapter
5, sections 5.1. and 5.3.). When there is no JTAG activ-
ity, the TDO pin is used for the alpha signal. Polarity of
this signal (high active or low active) can be pro-
grammed using I
2
C.
2.4.4.1. Alpha Key as Static Control Signal
The alpha pin can also be used as a static control signal.
When doing so, all comparators have to be set to their
respective maximal or minimal values.
YMIN = 00
YMAX = FF
UMIN = 80
UMAX = 7F
VMIN = 80
VMAX = 7F
In this case, the alpha signal will always be correct and
the output state (high or low) can be selected through the
polarity bit (keyinv bit in FORMAT register).
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| VPX3224D | Video Pixel Decoders |
| VPX3224E | Video Pixel Decoders |
| VPX322XE | Video Pixel Decoders |
| VQ1000J | N-Channel Enhancement-Mode MOSFET Transistor(最小漏源擊穿電壓60V,夾斷電流0.225A的N溝道增強型MOSFET晶體管) |
| VQ1000J | N-Channel 60-V (D-S) MOSFET |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| VPX3214C(PLCC44) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Decoder Circuit |
| VPX3214C(QFP44) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Decoder Circuit |
| VPX3216B | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video Pixel Decoders |
| VPX3216B(PLCC44) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Decoder Circuit |
| VPX3216B(QFP44) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Decoder Circuit |
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