Powerware Model V-2000B - Manual (Page 86)

84 = System Configuration
Use Sample Rate Conversion with any 48K signal that is not referenced to either the same
source as genlock, or the digital outputs of the Image Server.
Bit-for-Bit ® Recording & Playback
The recording, storage, and playback of audio program material such as Dolby®-E, Dolby
Digital (AC-3), or DTS® requires that upon playout the data stream be identical to the original.
Do not use the audio sample rate converters when working with these encoded audio formats.
The Image Server and a Dolby encoder must be supplied with the same genlock signal.
Audio Sync Reference
The audio sample rate is derived from the selected video sync reference. Audio is recorded at a
nominal 48K sample rate, so the 0.1% pull-down for 29.97 NTSC is taken into account when
generating the audio sample rate for color NTSC. There is no drop frame issue for PAL servers.
Time Code Source
This function selects the time code source for newly recorded clips. A time code value is
obtained from the selected input source at the start of a new recording. Choose VITC, LTC, or
Manual input source. For manual, enter the desired time value for the first frame of the
recording in the Starting Time Code entry field.
The selected time code source value can be viewed in the Channel 1 CVBS Time Code burn-in
window when E-E mode is monitoring the input source and no clip is cued. When recording
begins, E -E mode switches the monitor from the input to the disk and the Time Code burn-in
window shows the current time code position.
MPEG-2 Profiles
Select either Main Profile @ Main Level (4:2:0), or 4:2:2 Profile @ Main Level for the
recording.
GOP Structure
GOP structure defines the MPEG Group of Pictures coding as combinations of I, P, and B
frames. The allowable combinations are presented in a drop-down list. I-Frame only encoding
will produce the least compressed picture and requires the most hard disk space. However, I-
frame encoding facilitates frame-accurate editing. For broadcast-quality resolution, I-frame
encoding should be considered at 20 or 25 Mb/sec. When frame-accurate edits are required
for production work, an I-frame GOP structure should be selected. Very low bit rates should
never be employed with I-frame encoding.
Long-GOP video recorded with P and B frames produces superior image quality for a given
data rate, compared to I-frame. Most broadcasters go to air with 10 or 12 Mb content, having
medium-length GOPs.
Encode Mode
Image Servers employ Variable Bit Rate (VBR) MPEG-2 encoding. For almost all broadcast
applications, VBR encoding produces superior results than its alternative, Constant Bit Rate.