User`s guide

Creating DTV Clips 55
The DVMHD supports all of the following Main Profile High Level DTV
video formats:
Format Size Chroma
Format
Aspect
Ratio
Scan
Type
Frame Rates
1080i
(Note 1)
1920x1080 4:2:0 16x9 Interlaced 23.976,24, 25
29.97, 30
720p
(Note 2)
1280x720 4:2:0 16x9 Progressive 50, 59.94, 60
480p
720x480 4:2:0 4x3 Progressive 59.94
NTSC
720x480 4:2:0 4x3 Interlaced 29.97
PAL
720x576 4:2:0 4x3 Interlaced 25
Note 1: All 1080i encodings are displayed at either 25, 29.97 or 30fps.
Note 2: All 720p encodings are displayed at either 50, 59.94 or 60fps.
Audio Format
The DTV standard specifies Dolby Digital AC-3 audio encoding to provide
multichannel digital audio for every DTV program. The AC-3 stream provides
“5.1” channels of audio – five (Front Left, Front Right, Surround Left, Surround
Right, and Center) at full bandwidth and one bandwidth-limited Low Frequency
Effects (LFE) channel.
As of version 2.13 of the DVMHD operating system, standard, 2-channel,
MPEG-1 Layer 2 audio streams can be used as well.
The DTV Bitstream
In order for the audio and video program material to be decoded and presented
together, the two streams must be “multiplexed” to form a single bitstream for
transmission. The ATSC decided that the MPEG-2 Transport Stream
specification was an appropriate format for the DTV bitstream, with the
constraint that streams transmitted via UHF (off-air antenna) would be
multiplexed at a maximum of 19.39Mb/s, and streams transmitted over cable
would be at a maximum of 38.8Mb/s. In addition to these two “vsb” bitrates,
the DVMHD supports all other stream bitrates between 10Mb/s and 50Mb/s.