Wacom CTF-220 User Manual download pdf (Page 27)

Issue

10.04.A

XT[2] Series DISK RECORDER

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Version 10.04 - Hardware Technical Reference

EVS Broadcast Equipment

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January 2011

IMPORTANT RECOMMENDATIONS

• For 6-channel configuration, maximum bitrates for Avid DNxHD® or Apple

ProRes 422 should be 220Mbps (NTSC) or 185Mbps (PAL).

• “Super Motion + 1 Cam” configuration (i.e. 1 Super Motion REC + 1 Std REC +

1 Super Motion PLAY + 1 Std PLAY): maximum bitrates for Avid DNxHD® or

Apple ProRes 422 should be 145Mbps (NTSC) or 185Mbps (PAL).

• When using the Avid DNxHD® codec, we advise to work at 100Mbps if the

picture quality is satisfactory Æ the XT[2] can sustain 6 local channels + 5

network transfers.

1.8.8 RAID LEVEL: 3

The Video Raid uses striping process across 5 disk drives. The video and audio

data is striped over the first 4 drives while the parity information is saved on the

fifth drive. If one drive is damaged, the Video Raid can use the parity information

to recover the missing information, so that operation can continue seamlessly

without bandwidth loss.

For more information on online rebuild, refer to the section dedicated to this

subject in the XT Technical Reference manual.

1.8.9 INTERPOLATION

The playing back of smooth slow motion pictures carries specific issues: since

some fields must be repeated at regular interval to provide the video at the

playback speed required by the operator, parity violation appears regularly on the

output video signal. This issue is specific to interlaced formats (525i, 625i and

1080i) and does not concern progressive formats (720p and 1080p).

If O and E represent respectively the odd and even fields of a standard video

signal (50/60 Hz), we have:

The original video signal:

O E O E O E O E O E O E O E O E

The output video signal at 50% speed:

O O

E E O O E E O O E E O O E E

The output video signal at 33% speed:

O O O E E E O O O E E E O O O E

The output video signal at 25% speed :

O O

O O E E E E O O O O E E E E

Fields with parity violation are shown in bold, underlined letters. As it appears

from the above table, whatever the playback speed (with the exception of the

normal 100% playback speed), a number of fields violate the normal parity of the

output signal. This parity violation induces a 1-line shift of the field, resulting in a

vertical jitter of the picture. The jitter frequency depends upon the chosen

playback speed.

To avoid this phenomenon and provide a stable output picture, EVS developed 2

types of line interpolator: 2-line and 4-line interpolators. The interpolation process

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Wacom CTF-220 User Manual Page 27

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