DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

DV HD HD stands for high definition. The “Blue Book” and the
IEC standards define an adaptation of DV coding at
50 Mb/s for consumer HDTV. At 30 Hz frame rate, the
system could be denoted 1024i30.00, or at 25 Hz
frame rate, 1152i25. The image arrays are, respectively,
1008×1024 and 1008×1152. Chroma is subsampled
3:1:1. This format has double the bit rate of SD,
double the tape speed, and consequently half the
program duration for tape of a given length. There is no
strong engineering argument that 1024i30 offers superior
performance to 720p60; however, the scheme was
developed during a time when Japanese manufacturers
denied the superiority of progressive scanning. DV HD
is unlikely to be commercialized: It is likely to be
rendered obsolete by direct recording of DTV MPEG-2
transport bitstreams as I outlined on page 427.
Professional DV variants
In Studio adaptation of DV technology, on page 425,
I outlined adaptations of the DV system for studio use.
DV25 is used for studio SDTV in D-7 (DVCPRO) and
DVCAM equipment.
DV50 has twice the data rate, twice as many macroblocks
per second (or per frame), and twice as many
superblocks per second (or per frame) as DV25. DV50
uses 4:2:2 subsampling; a CM contains just two luma
blocks instead of four. Space that in DV25 would have
been allocated to AC terms of the other two luma
blocks is available for overflow AC terms. The corresponding
DC terms, mode bits, and class bits are
reserved; the first four bits of DV25’s AC coefficient
spaces are filled with EOB symbols. The D-9 (Digital-S)
format records DV50 SDTV bitstreams onto 1 ⁄2-inch
tape in VHS-style cassettes. The DVCPRO50 format,
standardized in SMPTE’s D-7 series, records DV50 SDTV
bitstreams onto 6 mm tape in DVC-style cassettes.
DVCPRO P, sometimes denoted DVCPRO50 P, records
480p59.94 or 576p50, 4:2:0 video at 50 Mb/s, using
an adaptation of the DV50 system.
CHAPTER 39 DV COMPRESSION 469