DVD-Audio for AES, INDIA
Presented by Mr. Victor Dantes
Yash Raj Films,
Mumbai, India.on 24th March 2007

DVD-Audio is a digital format for delivering very high-fidelity audio content on a DVD. The first discs entered the marketplace in 2000.

Audio specifications

DVD-Audio offers many possible configurations of audio channels, ranging from single-channel mono to 5.1-Channel Surround sound, at various sampling frequencies and sample rates. (The ".1" denotes a Low Frequency Effects channel (LFE) for bass and/or special audio effects.)
Compared to the compact disc, the much higher capacity DVD-A format enables the inclusion of either:

• Considerably more music (with respect to total running time and quantity of songs), or
• Far higher audio quality, reflected by higher linear sampling rates and higher bit-per-sample resolution, and/or
• Additional channels for spatial sound reproduction.

Different bit-rate/sampling rate/channel combinations can be used on a single disc. For instance, a DVD-Audio disc may contain a 96 KHz/24-bit 5.1-channel audio track as well as a 192 KHz/24-bit stereo audio track. Playback of either streams is in the audio options menu.  Also, the channels of a track can be split into two groups stored at different resolutions. For example, the front speakers could be 96/24, while the surrounds are 48/20.

Audio on a DVD-Audio disc can be stored in many different bit-rate / sampling rate / channel combinations:

Audio is stored on the disc in Linear PCM format, which is either uncompressed or losslessly compressed with Meridian Lossless Packing. The maximum permissible total bitrate is 9.6 Megabits per second. Channel / resolution combinations that would exceed this need to be compressed. In uncompressed modes, it is possible to get up to 96/16 or 48/24 in 5.1, and 192/24 in stereo. To store 5.1 tracks in 88.2/20, 88.2/24, 96/20 or 96/24 MLP encoding is mandatory.

Compression Ratios

MLP – Meridian Lossless Packing uses an average compression ratio of 1.85:1 – it is not possible to state exactly what the ratio is, because by it’s very nature as a true lossless system it uses a variable bit rate. Compression achieved is usually in the region of between 40 and 55% of the original file size but again, this really is heavily dependant on the content being compressed. Its licensing is administered by Dolby Labs, and it is the sole compression format allowed for use in a DVD-Audio disc.
The next 2 compression types are not strict DVD-Audio formats, but because it is a common practice to include a Video_TS as well as the Audio_TS to make the resulting disc playable in all DVD players and not just the special DVD-Audio types – I feel they are worth a mention here. 
DTS – Digital Theatre Systems uses a compression ratio of about 3:1 at an average date rate of 1.5 Mbps.  Due to less data compression DTS is better than Dolby Digital.
Dolby Digital – DD takes 6 channels of 48 KHz/24 bit and compresses at a ratio of about 11:1 to a max bit rate of 640 Kbps, although 384 is the average data rate presently being used.

Preamplifier / Surround Processor Interface

In order to play DVD-Audio, a preamplifier or Surround controller with six analogue inputs was originally required. Whereas DVD-Video audio formats such as Dolby Digital and DTS can be sent via the player's digital output to a receiver for conversion to analogue form and distribution to speakers, DVD-Audio could not originally be delivered via unencrypted digital audio link at sample rates higher than 48 KHz (i.e. ordinary DVD-Video quality) due to concerns about digital copying.
Since the launch back in 2000, things have changed – with the introduction of HDMI (High Definition Multimedia Interface) it is now perfectly possible to transmit the full 24/96 resolution 5.1 Surround mix from an HDMI equipped DVD player to an HDMI equipped AV Amplifier with no loss of resolution whatsoever. Additionally, several manufacturers have also implemented their own proprietary FireWire interfaces that will also allow digital transmission of the full resolution content from and to suitably equipped players and amplifiers.

Technical information on DVD-AUDIO

DVD-Audio has been specifically designed keeping high quality audio playback in mind. It offers increased bit depth and sampling frequencies, allowing you to hear music in a much more natural way than was ever possible with an ordinary Audio CD. This format gives you a higher dynamic range and extended frequency response as well as high resolution stereo and Surround sound that almost places you in the same room with the musicians that you are listening to.

With optional extras available, such as Song lyrics, Synopsis and Photo gallery, music never sounded or looked as good.

The highest possible quality is MLP (Meridian Lossless Packing), which is true lossless format offering bit-for-bit identical output to the studio masters at up to 24 bit / 96 KHz in 5.1 Surround Sound and 24 bit / 192 KHz in stereo. A DVD-Audio player is required to hear these MLP streams, and all DVD-Audio players are required to decode MLP streams.

DTS Digital Surround offers performance that is close to MLP lossless quality at resolutions of up to 24 bit / 96 KHz. World renowned for high quality 5.1 Surround Sound, DTS is rapidly becoming the format of choice for DVD-Video & Cinema.  A DTS capable DVD player or external decoder is required to hear these DTS streams, and they will of course be located in the Video_TS section of the disc as DTS – great as it is – is still a DVD-Video type format.

All DVD players are capable of decoding Dolby Digital. These streams have the lower bit rate of all the options normally included in DVD-Audio discs. Again, such content will be located in the Video_TS of the DVD-A disc.

Both Audio_TS & Video_TS folders can cause confusion among some consumers. Most DVD-Audio discs are playable in all DVD players and not just DVD-Audio players. This is where these folders become important. The High Resolution (MLP Lossless streams, Multichannel PCM streams etc.) are all located in the Audio_TS, and the DTS / Dolby Digital streams are located in the Video_TS. Each folder is actually a different type of disc – and well-authored DVD-Audio titles will usually contain a combination of both types thus ensuring the disc will play on ALL DVD players, and not just DVD-Audio players. A brief example of how the hierarchy works could be as follows.

When a disc is first loaded into an AUDIO capable DVD player, it will look for the file Audio_TS.IFO which should be located in the Audio_TS folder. If it cannot find this file, it will then look instead for the Video_TS.IFO file which will be located in the Video_TS.

A VIDEO capable DVD player will skip the first step, and instead will automatically look for the Video_TS.IFO file. For this reason, most content creators will include a Video_TS on their discs, so that the same disc is playable on all DVD players.

For users without a Surround Sound setup, discs are also been encoded with a separate stream in MLP (Meridian Lossless Packing) to playback all songs in Stereo format, at 24 bit / 48 KHz, playable only on DVD-Audio players. Alternately, there is also an option to playback all songs in PCM Stereo, at 16 bit / 48 KHz which can be played back on all DVD players. This option is as good as listening to an Audio CD in Stereo format.

The DVD-Audio format hence brings to listeners the very best listening experience possible, through pristine quality sound, re-mastered in 5.1 Surround Sound as well as Stereo.

Not only that – a well thought out & authored DVD-Audio/Video disc is the universal disc that we have all been waiting for. It can literally be “all things” on the same disc.

As an example, you can have the following content:

1. Video_TS
2. 16/48 LPCM Stereo
3. 24/48 Dolby Digital at up to 5.1 channels
4. 24/96 DTS at up to 5.1 channels
5. Audio_TS
6. High Resolution Stereo at up to 24/192
7. High Resolution Surround at up to 24/96

Additionally, when correctly authored, the Video_TS content is also accessible from the menu system of the Audio_TS as well. The importance of this cannot be overstated as it means one player can access every piece of content on the disc, or in the worse case scenario (which would be a straightforward stereo DVD-Video player with no Surround set up) the end user can still access the 16/48 LPCM Stereo stream – which is higher quality than an ordinary RedBook CD.

DVD AUDIO PREPARATION PROCESS

1. HAVE ACCESS TO ALL OPEN TRACKS OR PRE-MIXES

2. LYRICS SHEET

3. HI-RES 300 DPI IMAGES FOR EACH SONG

4. SYNOPSIS OF THE FILM

5. CREDIT

6. AUDIO INFO SHEET

Attempt a new mix for all songs in 5.1 Surround Sound. Since we are attempting a music mix only, where no screen is involved on which to focus, it leaves us with no exit sign effect to worry about, like in a film situation. For music only DVD discs, it’s possible to utilize the Surround sound speakers for more creative purposes/uses.

Multi-channel sound is used to enhance the listening experience, and helps to deepen music and involve the audience further. 

Surround sound works because of the 4 ways we humans perceive sound:

1. AUDIBLE PERIPHERY – Each ear functioning as an independent receiver.

2. SPATIAL PERCEPTION – Perceiving the various sound elements in space, as placed in the Surround mix.
   
3. BINAURAL PERCEPTION – Hearing the same sound with both ears.

4. COGNITIVE PERCEPTION – How well we perceive and localize sounds.

TIPS FOR SURROUND SOUND MIXING

1. Better perception of object and sound locations. Listeners more readily identify the general direction from which sounds are initiated.

2. A different loudness balance over stereo playback. The volume can be lower yet provide more enjoyment due to perception of placement of sound.

3. More accurate perception of tone due to the additional placement options of sound sources.

4. Significantly greater perception of ambience. The ambience can be more immersed in the listening field.

5. More involved listener perception of sound points. Keep in mind that more speakers equals greater perceptive involvement.

6. A greater awareness of the quality of the mix, both individual components and as a whole.

Surround Sound projects are built through volume and placement to immerse your listening audience into a unique aural environment and experience.

Tonal based effects such as EQ work on the frequency content of the audio.

Time based effects such as reverbs/delays give us a sense of space.

Modulation based effects such as flange, chorus& phase change the effect over time.

Dynamics based effects essentially compression, reduce the dynamic range of an audio file.

Lastly Pitch based effects alter the original frequency of a file

MIDDLE OF THE BAND SURROUND MIX

Here the band is spread all over the room using the five main speakers, thus putting the listener in the center of the band performing, enveloping him with the sound. This results in a much more dramatic soundstage that is
far bigger sounding than the stereo CD that we are used to listening. 

SOUNDSTAGE / LIVE PERFORMANCE MIX

Here the band is spread across the front three speakers LCR, thus giving the listener an image that he is sitting in a live performance before a soundstage.  Usually the LS/RS are reverb/delay returns, original audience and room sounds / ambience which will be as heard in a live performance.

DHOOM:2 was the first Hindi film DVD-Audio to be released in India by Yash Raj Music, and distributed worldwide. 

Experience true Surround Sound on a DVD-Audio Disc. 

The future is here… GO DVD-AUDIO NOW!