About the mpeg format – Apple Final Cut Express HD User Manual
Page 973
Chapter 69
Exporting Sequences for DVD
973
XII
 Add compression and chapter markers in Final Cut Express HD to help control the
encode quality and make creating chapter selection menus easier. MPEG encoders,
such as the one used by iDVD, can use these markers to customize the MPEG encoding
process, directing the encoder to concentrate on those areas of the video that are the
hardest to encode. See “
Compression Markers to Your Sequence
” on page 974 for more information.
All video in iDVD projects is automatically converted to the MPEG-2 format before the
DVD is burned.
About the MPEG Format
MPEG-2 is an internationally accepted compression standard developed by the Motion
Picture Experts Group (MPEG). MPEG-2 allows you to create broadcast-quality video files
and was designed to support high-resolution, high bit-rate video. It is the video
compression format used for high-quality video titles on DVD and home satellite dish
systems. All DVD players contain the hardware required for MPEG-2 playback.
MPEG encoding is based on eliminating redundant video information, not only within a
frame, but over a period of time. In a shot where there is little motion, such as an
interview, most of the video content does not change from frame to frame, and MPEG
encoding can compress the video by a huge amount, with little or no perceptible
quality loss. In shots with lots of action or a moving camera, MPEG encoding will not be
able to compress the video as much without sacrificing quality. Choosing encoder
settings that provide acceptable results at each extreme can be challenging.
MPEG encoders create I-frames, also known as keyframes or reference frames, that
store complete image frames. In between these frames are P- and B-frames that only
store information relating to what has changed since the last I-frame. In most cases,
the encoder adds an I-frame every half-second. Any sudden transitions that occur
between the I-frames can lead to encoding artifacts in the video. See “
” on page 976 for information on adding I-frames to reduce
these artifacts.