DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

D-12 (DVCPRO HD) The DV standard was adapted to accommodate
1080i30 HDTV signals downsampled to 1280×1080
image format (or 720p60 downsampled to 960×720),
with 4:2:2 chroma subsampling in the downsampled
domain, compressed to a bit rate of about 100 Mb/s
(DV100). This format was introduced by Panasonic as
DVCPRO HD, and was later standardized as SMPTE
D-12; it shares many of the mechanical and signal
processing elements of the DV25 and DV50 formats.
The “blue book” and the IEC standard for DVC, both
referenced earlier, define an adaptation of DV coding at
50 Mb/s for consumer HDTV. Details will be presented
in Consumer DV variants – SD, LP, SDL, HD, on
page 468. The format is unlikely to be commercialized;
it is likely to be rendered obsolete by direct recording
of DTV broadcast MPEG-2 transport bitstreams.
Consumer bitstream recording – DV ATV, DV DVB
The ATSC bitstream, to be outlined in Digital television
broadcast standards, on page 587, has a data rate of
about 19.39 Mb/s. A scheme has been defined to map
two 188-byte ATSC transport packets onto five sync
blocks of a modified DV25 stream. A comparable
scheme has been defined to record DVB bitstreams.
An MPEG-2 transport stream is not designed to be
robust in the presence of channel errors. ATSC and DVB
have standardized schemes to augment the transport
stream with error checking and correction (ECC) information.
For DV recording, the transport stream is
augmented by an ECC scheme suitable for videotape.
Unlike a DV-encoded bitstream, an MPEG-2 bitstream
does not provide for picture-in-shuttle. DV standards
provide modest capacity in the recorded bitstream to
store trick mode at low speed (TPL) and trick mode at
high speed (TPH) data. The on-tape location of this data
is chosen to enable recovery during slow-speed play
(TPL) and during shuttle (TPH). Consumer recorders are
supposed to extract, encode, and record data from
MPEG I-frames. The standards do not specify exactly
what data is to be recorded, so such data is unlikely to
be interchangeable among different manufacturers.
CHAPTER 35 VIDEOTAPE RECORDING 427