L64105 LSI Logic Corporation, L64105 Datasheet - Page 407

• Manufacturer Part Number: L64105
• Description: Mpeg-2 Audio/video Decoder
• Manufacturer: LSI Logic Corporation

Numerics
B
Appendix B
Glossary of Terms and
Abbreviations
3:2 Pulldown
B Picture
bap
Film material digitized at 24 pictures per second forms an
excellent source for the MPEG video bitstream. To
display 24 frame-per-second video at the television frame
rate of 30 frames-per-second, 3:2 pulldown is necessary.
A single frame of 24 frames per second video is
displayed three times at the television field rate of 60
fields-per-second, followed by the next frame displayed
two times. This pattern of three and then two repeated
frames continues. The net result is that a total of two
frames of 24 frame-per-second video is displayed over a
period of five television field times, or 5/60ths (1/12th) of
a second. This result is exactly the same amount of time
occupied by two frames of 24 frame per second video
(2/24 = 1/12).
Bidirectionally Predictive-Coded Picture
B pictures in an MPEG bitstream are pictures that are
predicted from an I or P (anchor) picture and are
compressed by coding the differences between the B
picture and the referenced I or P picture.
bit allocation pointer
The outputs of the bit allocation computation in the Dolby
Digital Decoder are a set of bit allocation pointers (baps),
one for each coded mantissa. The bap indicates the
quantizer used for the mantissa and how many bits in the
bitstream were used to encode each mantissa.
B-1