What Is Blu-ray?

Everything you need to know about Blu-ray

Official Blu-ray disc logo
Official Blu-ray disc logo. Blu-ray Disc Association

Blu-ray is one of the two major High Definition disc formats (the other being HD-DVD) that were introduced to consumers in 2006 to expand the depth, color, and detail viewers could see in images. The intention was to replace the DVD standard in the U.S. and World market. However, on February 19, 2008, HD-DVD was discontinued, with Blu-ray taking the lead for HD playback, but DVD is still also in use.

Blu-ray vs. DVD

Blu-ray builds on the foundation established by DVD in the quest for a higher-quality TV viewing and listening experience. Although DVD is much better than previous formats, such as VHS and Laserdisc, it is not a high definition format. With the advent of HDTV, the trend for larger TV screen sizes, and an increased use of video projectors, the limitations of DVD quality become more noticeable.

Blu-ray enables viewers to see more depth, a wider range of color shades, and more detail in the image than from DVD.

Where DVD utilizes Red Laser technology, the Blu-ray Disc format utilizes Blue Laser technology and sophisticated video compression to achieve high definition video playback on the same size disc as a standard DVD.

A blue laser light beam is narrower than a red laser, which means it can focus more precisely on a disc surface. Taking advantage of this, the "pits" on the disc where information is stored can be made much smaller. This means more "pits" can be placed onto a Blu-ray disc than a DVD. Increasing the number of pits creates more storage capacity on the disc, which is needed for the additional space required for high definition video.

In addition to increased video capacity, Blu-ray also provides more audio capacity than DVD. Instead of just including Standard Dolby Digital and DTS audio that is used on DVD (which are referred to as "lossy" audio formats because they are more highly compressed in order to fit onto a DVD disc), Blu-ray has the capacity to hold those formats and more, with up 8 channels of uncompressed audio in addition to video content.

Blu-ray Disc Format Specifications

  • Disc Storage Capacity for Pre-recorded (BD-ROM) Playback Material: Single-layer (25GB) - Dual-layer (50GB)
  • Disc Storage Capacity for Recording: Single-layer (25GB) — Dual-layer (50GB). There are two types of recordable Blu-ray Discs, BD-R (Blu-ray Disc Record Once), and BD-RE (Blu-ray Disc Re-writable).  Be aware that standalone consumer Blu-ray Disc recorders are not available in the U.S.
  • Data Transfer Rate: 36 to 48 Mbps (Megabits per Second) average — capable of up to 54MPS. This exceeds the 19.3 Mbps transfer rate approved for HDTV broadcasting. This means that Blu-ray not only handles a lot more information than DVD but can also handle more information than HDTV television broadcasts are capable of.
  • Video Specifications: Compatible with full MPEG2 Encoding, as well as MPEG4 AVC (also known as H.264), and VC1 (based on the Microsoft WMV - Windows Media Video format). Resolutions from 480i to 1080p (in either 2D or 3D - 3D compatibility on some players was added in 2010) can be implemented at the content producer's discretion.
  • Audio Specifications: Only Dolby Digital, DTS, and Uncompressed PCM are required on all players. The following audio formats are optional - Dolby Digital Plus, Dolby TrueHD, DTS-HD Master Audio. However, almost all Blu-ray Disc players made since 2008 incorporate Dolby TrueHD/DTS-HD Master Audio onboard decoding, undecoded bitstream output, or both. In addition, most Blu-ray Disc players are also compatible with Dolby Atmos and DTS:X immersive surround sound audio encoding.
  • Audio/Video Connectivity: Blu-ray supports audio output from players via analog, digital optical/coaxial and HDMI connectivity. When players were first introduced, video output was allowed via composite, S-video, component, and HDMI - but as of 2013 all video connection support via composite, S-video, and component video was eliminated. This means that for any Blu-ray Disc player made from 2013 on, your TV must have an HDMI input in order to view video content. Also, there are a decreasing number of players that offer analog or digital optical audio outputs.
  • Internet/Network Connectivity: Although the Blu-ray format supports networking and internet capabilities (BD-Live), built-in networking and ethernet ports on individual Blu-ray Disc Players are only required on players made after November 2007. Most players also now have a built-in WiFi connection option. Also, although not required as a part of the Blu-ray specifications, most Blu-ray Disc players also provide internet streaming capabilities, such as access to Netflix, Vudu, Hulu, Amazon Video, etc.
  • Backward Compatibility Support: Although the Blu-ray Disc format is not compatible with previous formats - in other words, you cannot play a Blu-ray Disc on a DVD or CD player, but all Blu-ray Disc players can play DVDs and CDs, and some can play additional disc and USB-based media file formats.

Ultra HD Blu-ray

In late 2015, the Ultra HD Blu-ray disc format was introduced. This format uses the same size discs as Blu-ray, but are constructed so that they can fit more information that supports native 4K resolution playback (this is not the same as 4K upscaling provided on some standard Blu-ray Disc players), as well as other video enhancement capabilities, such as wide color gamut and HDR.

You cannot play an Ultra HD Blu-ray Disc on a standard Blu-ray Disc player, but Ultra HD Blu-ray Disc players can play standard Blu-ray, DVD, and CD discs, and most can stream content from the internet — all at the manufacturer's discretion.

The Bottom Line

Blu-ray is a disc-based video format that is suitable for viewing on HDTVs and can also be used with 4K Ultra HD TVs as well, although the newer Ultra HD Blu-ray format meets those needs even better.

For more details on Blu-ray, go beyond the specifications discussed above and check out what else you need to know, what to buy, and how to set-up a Blu-ray Disc Player.