I/OMagic PC PVR
User’s Guide
- 46 -
gives you more control over the amount of hard disk used. DVD video quality
usually uses VBR or variable bitrate.
Video Bitrate
Measured in kilobytes per second, the higher the bitrate the more memory
consumed but with better quality.
Frame Rate
The frame rate is measured by frames per second (FPS) during recording. The
more frames the better for capturing video content with motion.
GOP (Group of Pictures) Pattern
A MPEG compression technology, GOP concept reduces the temporal
redundancy across frames (from frame to frame) for video content. There are
three types of frames involved in the GOP concept:
• I-Frame (Intra pictures): I-frame is typically the first frame of each
GOP, is moderately compressed, and serves as the reference points for
random access and can be likened to images.
• P-Frame (Predicted pictures): P-frames are coded with reference to
past pictures, predict in a forward direction and significantly
compressed.
• B-Frame (Bi-directional pictures): B-frames' predictions are forward,
backward and bi-directional, which is relative to the other I-frames
and P-frames. Compression is at a high level.
Audio Compression
The default, Layer 2, contains more efficient codes for representing bit
allocation and performs better than Layer 1. Possible applications for this
layer are the storage of audio sequences and content on CD-ROM or VCD
audio tracks.
Audio Mode
Stereo (default) includes two independent channels but bitrate remains
constant while the channels' split may vary. The encoder uses this flexibility
to improve quality by allocating more bits to the channel with the higher
dynamic signal. Stereo is best for audio quality at higher bitrates.
Audio Bitrate
Like its video counterpart, this too is measured in kilobytes per second
(kbps). The higher the bitrate, the more hard disk it will use but with better
quality.