HIGH DEFINITION part one. by Allen Dyke

Allen Dyke
Carrying on from Ray Liffen’s very interesting talk on High Definition (HD), I would like to explain more about Blu-ray discs. Ray unfortunately glossed over this area of HD leaving many with unanswered questions and possibly more confusion. Blu ray is not a film recording format but a disc format like CD and DVD.It uses a blue laser to read and write as opposed to the red laser of CD and DVD. This blue laser is capable of a better focus being more precise and therefore packing more data onto the disc.A Single layer disc can store up to 25 GB and a dual layer can store up to 50 GB. The discs are specific for each type and therefore not interchangeable. Blu-ray movie; this is the name of any professional film /movie which is released on Blu-ray.
The main film is recorded in high definition 1920-1080pixels. It is quite common for the preliminary titles etc to be recorded in standard definition 720-576 mpeg2 (PAL) or 640-480 mpeg2 (NTSC) (the same as standard DVD movies) There are three HD recording formats used for video. The choice of usage is up to the movie company and film distributor. They are: -MPEG2 HD, VC1, and AVCHD. MPEG2 HD is the older format of the three and is basically a beefed up version of mpeg2 SD (As used in standard definition DVD movie and by Freeview for television.). Very hungry on storage using around30/40mbits per second. HD Camcorders using mini dv tapes use this format at 1440-1080 pixels and a bit rate of25mbps.VC1 is the newest format, which is the development from Microsoft's Windows media video 9. VC1 is often calledwmv9-advanced profile. Most movies are around 20/25mb persec. AVCHD is the third format. This format was developed some5 years ago. This is the format also used by camcorder manufactures for their latest HD domestic camcorders. They use the SD card as a storage medium as well as internal solid state memory and hard drives. Most movies on Blu-ray are around 20/25mbps.SOUNDFilm distributors for Blu-ray movies use the following, Dolby Digital, or AC-3, is the common version containing up to six discrete channels of sound. The mode in common usage involves five channels for normal-range speakers (20 Hz –20,000 Hz) (right front, centre, left front, right rear and left rear) and one channel (20 Hz –120 Hz) for the subwoofer for low-frequency effects. Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz, and is Lossy i.e. like mp3 sound where during compression information is thrown away. This sound system is also used on some consumer HD camcorders. DTS (also known as Digital Theatre System, is a multi-channel digital surround sound format up to 6 channels used for both commercial/theatrical and consumer grade applications. It is used for in-movie sound both on film and on DVD. The overall performance of the previous two systems is virtually identical Dolby True HD is an advanced lossless (complete, nothing thrown away.) multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc. It is the successor to the AC-3 Dolby Digital surround sound codec which is used as the audio standard for Blu-ray & DVD movie discs. DTS-HD Master Audio is a lossless audio codec created by Digital Theatre System. It was previously known as DTS++. It is an extension of DTS which, when played back on devices which do not support the Master Audio or High Resolution extension, degrades to a 1.5 Mbit/s "core" track which is Lossy. DTS-HD Master Audio is at present, an optional audio format for Blu-ray Disc movies. Home movies usually use mpeg2 sound with mpeg2 video, AAC sound is usually used with mpeg4 video compression. PCM also known as WAV which is uncompressed digital audio is used in DV recordings within a SD camcorder and also standard CD music discs. In the next newsletter, I will explain the number of frames/scans used per second for Blu-ray, TV, and DVD. Also, the difference between transport, elementary, and programme streams. This will lead on to later in the year, when I will explain how we can record/burn our own homemade HD videos onto Blu-ray or to standard DVD disc using the Blu-ray file structure to play on a Blu-ray player.

Allen Dyke

ED: AAC =Advanced Audio Coding, PCM = Pulse-code modulation

SECOND TAKE April 2009

High Definition Video a quick look
SSD versus HDD
MP3 / FLAC Sound Compression
High Defintion
Part One
Cleaning Hard Drives
Hard Drive Installation
A Novel Camera Support
Adding Filters
Create a Freeze Frame
Correcting Synch Errors
Change Capture Location