4.1

Chapter 4 Advanced adjustments 40
•
Two Pass VBR: This mode uses two passes—one pass to analyze the entire source video
stream, and a second pass to compress the le. This mode takes longer and provides a
better-quality le than the one-pass modes, and is recommended for source media les with
a substantial dierence between the most and the least complex scenes.
•
Two Pass VBR (Best): This mode provides the best possible quality output, and outstanding
quality at bit rates of 3 to 3.5 Mbps and above for HD and SD video.
•
Motion estimation: This pop-up menu sets the amount of motion processing that will be
performed on the le. There are three options:
•
Good: The fastest processing setting. Use this setting when there is relatively low motion
between frames. In general, use Good with the one-pass encoding modes.
•
Better: Provides very good results even in the presence of complex interlaced motion. In
general, use Better with Single Pass VBR (Best) and Two Pass VBR (Best).
•
Best: The slowest processing setting. Use for the most complex motion and for interlaced
source les. In general, use the Best mode to maximize quality when using Single Pass VBR
(Best) or Two Pass VBR (Best).
•
GOP structure: This property is available only when the “Frame rate” property is set manually
(does not use Automatic).
Note: Automatically determined properties, including the “Frame rate” property mentioned
above, are assigned by Compressor based on your source media le. Therefore, "Automatic”
properties are strongly recommended.
Compressor provides three methods of grouping frames, or “pictures,” in encoded video: as
I-frames (intra-frames), P-frames (predictive frames), and B-frames (bi-predictive frames). The
“GOP structure” pop-up menu includes several methods of combining frames:
•
IP: Use IP only if your media contains fast motion that isn’t encoded with sucient quality
using an IBBP or IBP structure.
•
IBP: Use IBP only if your media contains fast motion that isn’t encoded with sucient quality
using an IBBP structure.
•
IBBP: Recommended for majority of MPEG-2 encoding situations.
Note: For most MPEG-2 encoding situations intended for use on a DVD, choose IBBP as the
GOP structure setting, and a GOP size of 15 for NTSC, or 12 for PAL.
•
GOP size: This property is available when the “Frame rate” property is set manually (does not
use Automatic).
Note: Automatically determined properties, including the “Frame rate” property mentioned
above, are assigned by Compressor based on your source media le. Therefore, "Automatic”
properties are strongly recommended.
This slider species how many frames are contained within a GOP (group of pictures). The
values available in the slider are are determined by the GOP structure property (described
above). The maximum GOP size you can choose within Compressor is 15 frames (NTSC) or 12
frames (PAL and 720p). The minimum GOP size for all video formats is 6 frames (closed GOP) or
7 frames (open GOP).
•
Automatically select bit rate: Select this checkbox to have Compressor automatically compute
the best bit rate for the output le, based on the duration of the source le. To manually adjust
the bit rate, deselect the checkbox and drag the “Average bit rate” and “Maximum bit rate”
sliders (or enter values in the adjacent elds).
•
YUV 422 color encoding: This property appears in most built-in settings that output MPEG-2
les. Select this checkbox to use YUV 422 color encoding for superior chroma quality.
67% resize factor