Blu-ray Disc (BD)

Updated - June 2, 2010

Background

In the first half of the last decade Sony and Toshiba, each joined by several other companies were developing high definition optical disc technologies that relied on the use of a blue laser to pack the needed additional data capacity need for high definition video onto an optical disc (as compared red lasers used for DVDs).  Ultimately Toshiba, and its partners that held several of the key patents for conventional DVDs, built their HD optical disc as an extension to the design of conventional DVDs.  This group won approval from the DVD patent licensing organization, the DVD Consortium - subsequently renamed the DVD Forum, for their alternative for a HD optical disc.  This format became known as HD-DVD and was introduced to consumers in 2006.  After about 1 1/2 years of marketing HD-DVD, Toshiba, as well as other manufacturers, withdrew that format from the marketplace

Sony, along with several partner companies, developed their own HD optical disc format that while their discs may appear similar to DVDs and HD-DVDs, they use a substantially different structure for storing the data on the disc.  This format is much less tied to the DVD technology, and less encumbered by the existing DVD related patents, than is the HD-DVD format.  Sony and their partners named their HD optical disc format "Blu-ray Disc" (BD) and created a new standards and licensing organization called the Blu-ray Disc Association.

The Blu-ray Disc (BD) technology supports multiple data layers and the current discs and players support two data layers.  BD uses a blue laser whose shorter wavelength (as compared to the red laser used for DVDs) allows for more data storage on each layer of the disc. The BD format allows for higher data density per layer (approx. 25 GB per layer for BD as compared to less than 5 MB per layer for DVD).  BD has adopted three alternative video encoding techniques (i.e. video codecs).  Each of these 3 video codecs is capable of producing excellent results as long as the video is encoded at high enough data rate.  However, the most efficient codec can produce equivalent results to the least efficient at less that one half of the data rate.  The 3 video codecs supported by BD are:

All of the BD players support the same baseline Dolby Digital and DTS surround sound formats, as used on DVDs.  The new, higher fidelity, Dolby surround formats are Dolby Digital Plus and Dolby Digital TrueHD, with TrueHD being the highest fidelity Dolby format as it provides lossless compression (i.e, decoded output is bit-for-bit identical to the original master recording).  DTS has also developed two new formats under the overall name DTS-HD.  These are "DTS-HD High Resolution Audio" and "DTS-HD Master Audio" (with DTS-HD MA being the highest fidelity DTS format as it provides lossless compression).  A third lossless audio format found on some BDs is Linear Pulse Code Modulation (LPCM), which is an uncompressed format.  The highest fidelity advanced formats require data rates too high to be passed over conventional digital optical connections to an external Audio/Video Receiver (AVR) or processor.  As a result, the various disc player manufacturers are offering alternative methods to getting this improved audio out of their disc players.  All current BD players offer undecoded "bitstream" output of the digital audio data stream via the HDMI interface (along with the Video data) and the advanced audio is only enabled when connected to a new generation of AVR that includes HDMI inputs as well as decoding for the advance audio format.  A second alternative is to provide, within the disc player, the decoding of the advanced audio formats and to then encode the audio as linear Pulse Code Modulation (PCM) and output then the PCM audio via the HDMI, along with the digital video (the original PlayStation 3 only offered this option as it did support bitstream mode for output of the lossless audio fomats).  This mode is compatible with many lower-end AVRs build after 2005 that have HDMI inputs that can accept PCM audio, but the AVR does not have any capability for decoding the new advanced Dolby and DTS audio formats.  A third alternative is to have the disc player decode the advanced audio format then perform the digital to analog conversion and provide discrete analog outputs for each of the channels (either 5.1 or 7.1 channels). This allows use with older AVRs that lack HDMI inputs.

For more technical details on the BD disc format and technology check this link:  Blu-ray Disc  

BD Comes to Market

Samsung was the first manufacturer to bring a BD player to market, in June 2006.  Blu-ray Disc had its share of problems with first generation hardware and software.  A number of manufacturers had planned to introduce their initial BD players in the May/June 2006 time frame.  However, only Samsung actually had a player in production by that time (in June 2006, one month later than they has previously announced).  Also the only manufacturer of the pre-recorded discs (i.e., movies) at the BD introduction was Sony and for the first several months they were only able to manufacturer single layer discs authored using MPEG-2 encoding.  This combination of the lowest capacity disc (i.e., single layer) format and the least efficient encoding technique (i.e, MPEG-2) resulted in discs with generally inferior quality, as compared to the initial HD-DVD releases or later BD releases. In some cases the initial Sony manufactured discs also had relatively low quality transfers from the original film which further contributed to poor video quality on certain of the initial BD releases.  However, by the end of 2006 BD manufacturers had overcome most of the startup problems.  The BD format saw other manufactures (Panasonic, Pioneer, Sony) introduced their first generation of players in late 2006 and the production of 2-layer BD discs began was well as the use of the more advanced video codecs (e.g, AC-1).  Sony also introduced in November 2006 the Playstation 3 that supported playback of BD software.  Also Samsung issued a firmware update to their first generation BD player in Oct. 2006 that corrected their player's biggest technical issue and this brought its level of performance in line with their competitors 1st generation BD players. While the quality of film transfers still varies by title, there has been a general improvement, especially as compared to some of the earliest BD releases.  

All BD players can provide high definition video output in the 720p, 1080i  and 1080p HD formats.    Most movies are recorded on BDs in a 1080p format at 24 frames per second (referred to as 1080p/24) to match the 24 frame per second rate of motion picture film.  The 1st generation Samsung player (as well as the 1st generation Panasonic BD player) used an internal chip set that only decoded to 1080i format.  Therefore, these manufacturers included an additional signal processing chip in their BD players to perform de-interlacing back to 1080p/60 format for output from the player via the HDMI interface.  Thus, the recorded 1080p/24 information was converted to 1080i/60 then converted again to 1080p/60.  The 1st generation Pioneer and Sony BD players introduced at the end of 2006 employed a chip set that could directly output 1080p/60, thus eliminating the additional conversions associated with interlacing and de-interlacing.  All of the current generation of BD players (since 2007) can directly decode and output video in 1080p/24 format.

BD Profiles

All BD players available since 2008 support at least the new BD Profile 1.1 (called "Bonus View") requirements.  Such profile 1.1 players must implement additional features, beyond the previous Profile 1.0 players, including support for "picture in a picture" (PIP), support for secondary audio decoding and include as a minimum 256 MB of 'persistent' memory.  These new features were mandated by the Blu-ray Disc Association through an updated "BD profile" (i.e., essentially an updated specification of the minimum required functions for BD players).  All new BD players receiving approval from the Blu-ray Disc Association after October 2007 were required to support this updated BD Profile version 1.1.  The optional BD Profile 2.0 (also called "BD-Live") requires players include a high speed internet connection (Ethernet and/or wireless) and additional memory for supporting web-enabled features to be included on some BD disc titles.  All current BD players, except the lowest-end budget models, support BD Profile 2.0 features.

Blu-ray 3D

In December 2009 the Blu-ray Disc Association released an update to the Blu-ray  Disc specification that added an optional capability for 3D content and playback.  Panasonic and Samsung were the first two manufacturers to begin selling Blu-ray 3D players.  Sony is offering certain Blu-ray Disc player models that are "3D Ready" and will become 3D capable with a firmware update planned for release in the 3rd quarter of 2010.  Also all existing PlayStation 3 models can be upgraded via a planned firmware update to become capable of playing Blu-ray 3D titles.  By the end of 2010 most of the Blu-ray Disc player manufacturers are expected to offer at least one model that is 3D capable.  

Blu-ray 3D players are required to support output of the 3D content using the HDMI output in a "Frame Packing" format as defined in the HDMI version 1.4 specification.  Blu-ray 3D when placed in a regular Blu-ray Disc player will play as would a non-3D disc (i.e., 3D discs are backward compatible with existing BD players).  The new HDMI Frame Packing format used for 3D includes support for the following 3D output video resolutions and frame rates:

• full 1080p resolution for each right/left images with refresh rates of 23.98/24 Hz.

• full 720p resolution for each right/left images with refresh rates of 59.94/60 Hz.(e.g., North America) or 50 Hz (e.g., Europe)

Notes:  

1. A Blu-ray 3D player is only required to output in the format recorded on the 3D disc and the vast majority of Blu-ray 3D discs will be recorded in the 1080p format.  

2. Frame Packing essentially places two full resolution HD images into one "super sized" frame for transmission across HDMI. When used for 1080p, the right and left images are placed one above the other into a "super sized" frame that is 2205 pixels vertical by 1920 pixels horizontal with a 45 x 1920 pixel active blanking area separating the two images. More information is HERE).

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