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ITU601  

2011-04-06 23:45:35|  分类: 应用 |  标签: |举报 |字号 订阅

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ITU-R BT 601 4:2:2 Format

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Activity 2.1.1 Video Compression standards and technologies

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State-of-the-Art Abstract: D1 has been the first Digital Video Tape Recorder, working in components 4:2:2 and with no compression. Now it isn't alone because also D5 exists. Usually we refer to "D1" as the Standard Definition Digital Video Signal, Non-Compressed, with 4:2:2 format. But what's D1 4:2:2 format ? Recommendation ITU-R BT 601, formerly CCIR 601, describes the 4:2:2 digital video signal and another Recommendation, ITU-R BT 656 describes the interfaces both serial and parallel, used for transfering ITU-R BT 601 4:2:2 video signal among different video equipment. It's out of discussion the importance for Distributed Video Production of 4:2:2 format also as a quality reference.

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Back to Deliverable Structure Page

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The Video Tape Recorder D1 and other digital equipment work with the 4:2:2 digital signal format as described by Recommendation ITU-R BT 601.
The serial and parallel interfaces used for interconnecting such video equipment are described by Recommendation ITU-R BT 656.
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ITU-R BT 601 4:2:2 format
Video Signal
3 components
Luminance Y
Chrominance Cb, Cr
differentiation for 25 Hz countries and 30Hz countries.
25 frames per second (30 frames per second), that is 50 fields/s (60 fields/s)
625 lines/frame (525 lines/frame)
for luminance: 864 samples/line (858 samples/line), that means for both cases a sampling frequency of 13.5 MHz.
for chrominance: 432 samples/line (429 samples/line), that means for both cases a sampling frequency of 6.75 MHz.
sampling structure: orthogonal.
sample coding: uniform PCM either 8 bits or 10 bits.
quantization levels (for 8 bits samples) and analogical signal:
0 and 255 only for sync.
from 1 to 254 for video.
luminance: 16 = black, 235 = white
chrominance: 128 = no chrominance
The bit rate resulting is either 216 Mbps (for 8 bits samples as in D1-DTR), or 270 Mbps (for 10 bits samples as in D5-DTR).

Active Video
The active video is the part of the video signal that describes the image, in other words it's the video signal excluding the Vertical Blanking Interval and the Horizontal Blanking Interval.
576 lines/frame (480 lines/frame)
720 samples/line for luminance and 360 samples/line for chrominance.
The bit rate resulting is 165.9 Mbps for 8 bits samples.

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ITU-R BT 656
Parallel Interface
The Y, Cb, Cr signal of ITU-R 601 is multiplexed in the following way: Cb, Y, Cr, Y, Cb, Y, Cr, ..., producing the Parallel Digital Signal, that has 27MHz frequency.
The signal is driven to a bus of 11 pairs (10 for the data and 1 for the clock). Lines must be balanced ECL with characteristic impedance 100 ohms. Cables can be 50 m long without equalization (till 150 m otherwise). Connectors are type D 25 pins.
Serial Interface
The Parallel Digital Signal is converted to the Serial Digital Signal, that has 270 MHz frequency. The conversion includes a scrambling process, in order to reduce the DC components and make easier the clock reconstruction, and a Non Return to Zero Inverted coding, that make the signal insensible to polarity.
The cable is coax. 75 ohms, the connectors are BNC.
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Page edited by: Laurent Boch
Last update: August the 23rd 1996 

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