CONTENT
 CD Basics

 CD Audio

 CD-ROM

 DVDBasics

 DVD-Video

 DVD-ROM

 DVD-Audio

 DVD-Recordable

 Replication

 DigitalVideo

 Glossary


 
DVD-Audio audio coding title graphic

Audio Coding

DVD-Audio uses high resolution coding with lossless compression for the highest quality  multi-channel surround sound and maximum flexibility.

The DVD-Audio specification makes use of a scalable linear PCM multi-channel and stereo encoding format, down-mixing control and optional audio formats. The video objects use the same audio encoding as DVD-Video discs.
Parameter

Audio Object Video Object
Coding mode LPCM or MLP LPCM or Dolby Digital
Sampling frequency (kHz) 44.1/48/88.2/96/ 176.4/192 48/96
Bits per sample 16/20/24 16/20/24
Max channels 6 (@ 96 kHz) or
2 (@ 176.4/192 kHz)
6 or 8
Max bit rate  9.6 Mb/s 6.144 Mb/s

As this table shows, DVD-Audio offers sampling rates up to 192kHz for stereo audio and up to 6 channels at 96kHz maximum for surround sound. Audio bandwidths of up to 96kHz are therefore possible with signal to noise ratios up to 144 dB.

Channel Groups

The maximum data rate for the audio data is 9.6Mb/s, which means that the sampling frequency for multi-channel audio is limited to 96kHz or less. To make best use of the bandwidth available, multi-channel DVD-Audio can be encoded as two Channel Groups with different parameters (ie sampling frequency and quantisations) for each group. 

The channel groups can be used for any number of channels from three (L, R and C) upwards. Note that the sampling frequencies and quantisations (bits per sample) used must be as shown in the table below.
Parameter Channel Group 1 Channel Group 2
Sampling Frequency 48kHz 48kHz
96kHz 96 or 48kHz
44.1kHz 44.1kHz
88.2kHz 88.2 or 44.1kHz
Bits per sample 16 bits 16 bits
20 bits 20 or 16 bits
24 bits 24, 20 or 16 bits

For sampling frequencies of 176.4 and 192kHz the number of channels is two or less, so only one channel group can be used. Down-mixing Down-mixing of multi-channel audio to stereo is facilitated by the inclusion of down-mix coefficients to obtain best results. This technique is called Smart Content (System Managed Audio Resource Technique). 16 coefficient tables can be re-defined for each Album and the appropriate coefficient table selected from these 16 for each Track. All players must implement down-mixing.

Meridian Lossless Packing (MLP)

The use of 6-channel 96/24 audio with PCM encoding would imply a data rate of over 13 Mb/s, which is higher than the maximum of 9.6kHz allowable.  In addition the playing time would be only about 40 minutes for a DVD-5 disc.  Therefore some form of compression is needed to accommodate the highest quality in surround sound.  

For these reasons, the DVD Forum has chosen Meridian Lossless Packing (MLP), developed by Meridian Audio, a UK company committed to the highest quality digital audio. MLP is easy to implement and will not alter the decoded signal in any way.  Decoding MLP requires relatively little computing power even for six channels of 24-bit/96kHz audio. MLP also provides additional flexibility that allows, for example, quantisations in one-bit steps, eg 22 bits can be chosen where appropriate instead of 20 or 24, for optimal quality and playing time.

The possible sampling rates, quantisation and numbers of channels for both PCM and MLP audio are shown in

Sample Rate (kHz) Quantisation 2 ch 4 ch 6 ch
44.1/48 16 to 24 LPCM/MLP
96/88.2 16 LPCM/MLP
96/88.2 20 or 24 LPCM/MLP MLP
192/176.4 16 to 24 MLP No

Examples of typical playback times with MLP are shown below for high quality stereo, high quality surround sound and CD quality stereo.
Audio
channels
Configuration Playing Time
Single layer Dual layer
2 ch 192kHz, 24bits 120 mins 215 mins
6 ch 96kHz, 24bits 86 mins 156 mins
2 ch 44.1kHz, 16 bits 13 hours 23.6 hours

 

 

In this page:

Channel Groups

Meridian Loss-
    less Packing

 

 

 

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