Optical Disc Formats for Audio Reproduction and Recording 114930.8.1 File Organization
Two types of DVD-Audio are defined. An Audio-Only
disc contains primarily LPCM music content; it can
optionally include still pictures (one per track), text
information, and a visual menu. In an Audio-Only disc,
data is contained in the DVD-Audio zone. The
AUDIO_TS directory (folder) contains menu and pre-
sentation data. An Audio Manager defines file types and
organizes audio and video data. Audio data, such as lin-
ear PCM, is contained in an Audio Title Set (ATS.)
An Audio with Video (AV) disc can contain motion
video content formatted as a subset of the DVD-Video
format. DVD-Audio players without video capability
can play back the audio contents and audio components
of video contents of DVD-Audio AV. They can play
selected audio components on DVD-Video VAN. In an
AV disc, audio data is contained in an Audio Title Set
and video data in a Video Title Set. The Audio Manager
and Video Manager define file types and organize audio
and video data. Both menu and program data is
included. The Audio Manager can control a subset of
the DVD-Video data. Using Link Info a DVD-Audio
player can play audio components of video contents. A
DVD-Audio disc can be partially compatible with a
DVD-Video player if the disc contains a stereo LPCM
or Dolby Digital version of the album in the Video Title
Set subdirectory of the disc. Universal DVD players can
play all DVD-Audio and DVD-Video.
The presentation data for audio tracks is contained in
AOB (Audio Object) files. Each AOB contains PCM
data as well as optional audio data such as Dolby
Digital. Optional nonaudio data such as still images are
contained in ASV (Audio Still Video) files. The presen-
tation data for video tracks is contained in VOB (Video
Object) files. VOB files contain interleaved MPEG-2
data as well as audio data. Files needed to play back an
audio track are located in the AUDIO_TS folder; files
for video tracks are in the VIDEO_TS folder (also
containing a VMG).
On many DVD-Audio, a track comprises one song.
A disc can also contain up to nine groups per album (an
album comprises one disc side). A group is essentially a
playlist that contains up to 99 different tracks (each with
up to 99 indices). A track may be included in more than
one group. Users select a group and tracks within that
group. This navigation is supported by the AMG (Audio
Manager). The SAMG (Simple Audio Manager) is
similar to a CD’s TOC and contains a list of tracks (up
to 314). Every disc includes a SAMG for track-based
navigation. Simple players only recognize the SAMG
and cannot recognize the AMG; these players have only
two channel audio output and no video output. AMG
players with video outputs read the AMG/AVTT (audio
with video) section of the AMG. AMG players without
video output read the AMG/AOTT (audio only) section.
In this way, discs are compatible with players with
widely different features. Fig. 30-15 summarizes the
principal data elements found on a DVD-Audio.30.8.2 Contents and FeaturesThe DVD-Audio format supports a variety of coding
methods and recording parameters. Optional audio cod-
ing methods include Dolby Digital, MPEG-1, MPEG-2
with/without extension bit stream, DTS, DSD, SDDS,
and MLP. Linear PCM (LPCM) tracks are mandatory
on all discs; all DVD-Audio players must support MLP
decoding. Unlike some 5.1 channel systems (Dolby
Digital, MPEG) the LPCM coding used in DVD-Audio
does not band-limit the LFE channel; it is a full-band-
width channel. DVD-Audio is a scalable format and
gives flexibility to content providers. When LPCM cod-
ing is used, the number of channels (1 to 6), the word
length (16, 20, 24 bit), and the sampling frequency
(44.1, 48, 88.2, 96, 176.4, or 192 kHz) are all allowed.
At the highest sampling frequencies of 176.4 kHz and
192 kHz, only two channel playback is possible. The
audio coding options and the number of disc layers cre-
ate a range of playback times. For example, a stereo
LPCM program on a data layer might play for 258 min-
utes or 64 minutes, depending on its recording parame-
ters. Similarly, different configurations of multichannel
recordings will yield a range of playing times, as shown
in Fig. 30-16. Use of MLP lossless compression, or
lossy compression, increases playing times as well.
Audio channels are placed in two Channel Groups
(CG). Examples of channel assignments are shown in
Fig. 30-17. The grouping hierarchically lists mixes thatElement Outline of ContentsSAMG Navigation information for simple audio player,
which has only two-channel audio output
AMG Information to navigate entire disc, may include
optional text manager
AMG menu video object set for visual menu
ASVS Information to navigate still pictures
Audio still video object set for still pictures
ATS Information to navigate ATS
Audio object set for audio data and optional RTI of
audio tracks
VMG Information to navigate video part
VTS Information to navigate VTS
Video object set for video/audio data of video tracks
Figure 30-15. Data elements found in a DVD-Audio.