Video encoding
Encoding the video information for all DVD disc formats follow the same lines as those for standard and high-definition digital television described in previous chapters. The traditional DVD-video format uses MPEG-2 data compression techniques including temporal and spatial compression as well as DCT and entropy coding. HD DVD and BD formats support MPEG-2 as well as MPEG-4, AVC (advanced video coding H.264) and SMPTE VC-1 (Microsoft Windows’ media Video Codec). MPEG-4 and AVC (H.264) have been discussed in detail in Chapter 5.
VC-1 is a data compression procedure and is published and approved by SMPTE (Society of Motion Picture and Television Engineers) uses similar compression techniques to AVC. It was developed well after MPEG-2 and has benefited from the lessons learned. It employs many of the same advanced coding techniques as those used in AVC (temporal and spatial, block motion compensation, integer transforms and the use of a loop filter) and thus is able to achieve similar coding efficiencies. VC-1 is less complex than AVC and hence it is faster to decode with a Windows-based software (WMV9) that can be used on a 2–3 GHz personal computers. VC-1 has a number of profiles: simple (up to 384 Kbps), Main (2, 10 and 20 Mbps) and advanced (10, 20, 45 and 135 Mbps).
Audio encoding
DVD-video discs may incorporate up to eight audio streams; each one can convey mono or multi-channel audio using one of three coding techniques:
● MPEG-2 audio.
● Dolby Digital (also known as AC-3).
● Linear pulse code modulation (LPCM).
Both MPEG-2 (described in Chapter 6) and AC-3 coding involve audio compression to reduce the data bit rate. LPCM does not include any form of data compression and thus it has the highest quality and the greatest bit rate requirements.
HD DVD and Blu-ray formats support an enhanced set of audio encoding over and above those available for DVD-video. These include digital theatre system (DTS) which is optional in the DVD format but is mandatory for HD DVD and BD under a name DTS-HD constant bit rate (CBR). DTS- HD variable bit rate (VBR) is optional. Other audio-encoding techniques include Dolby TrueHD (previously called meridian lossless packing, MLP), Dolby Digital Plus, AAC, MP3 and WMA Pro with sampling rates of 48, 96 and 192 kHz.