What Is Blu-ray?

How it fits into the home theater experience

Blu-ray is one of two high-definition disc formats introduced to consumers in 2006. Along with its rival, HD-DVD, Blu-ray aimed to expand the depth, color, and detail of the images viewers see. While HD-DVD was discontinued in 2008, Blu-ray and DVD are still in use. Here's a look at Blu-ray's history and where it stands today.

Official Blu-ray Disc Logo
Blu-ray Disc Association

Blu-ray vs. DVD

DVD technology greatly improved on previous formats, such as VHS and Laserdisc, in terms of the TV viewing and listening experience. Still, DVD isn't a high-definition format, and its limitations became more noticeable as HDTV emerged, TV screen sizes increased, and video projectors become more common.

Blu-ray aimed to answer DVD's shortcomings, allowing viewers to see more depth, a wider range of color shades, and more image detail.

DVD utilizes red laser technology, while the Blu-ray Disc format uses blue laser technology and sophisticated video compression to achieve high-definition video playback on a standard DVD-sized disc.

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 gives the disc more capacity, allowing for the storage of high-def video.

Blu-ray also provides more audio capacity than the DVD format. While DVD supports Standard Dolby Digital and DTS audio, Blu-ray supports these formats and more, with up to eight channels of uncompressed audio in addition to video content.

Standard Dolby Digital and DTS audio are referred to as "lossy" audio formats because they're more highly compressed in order to fit onto a DVD.

Blu-ray Disc Format Specifications

Here's a look at the Blu-ray format's specifications:

Disc Storage Capacity for Pre-recorded (BD-ROM) Playback Material

  • Single-layer: 25 GB
  • Dual-layer: 50 GB

Disc Storage Capacity for Recording

  • Single-layer: 25 GB
  • Dual-layer: 50 GB

There are two types of recordable Blu-ray Discs: BD-R (Blu-ray Disc Record Once) and BD-RE (Blu-ray Disc Re-writable). Standalone consumer Blu-ray Disc recorders aren't available in the U.S.

Data Transfer Rate

Blu-ray's data transfer rate is 36 to 48 Mbps on average, with capabilities up to 54 Mbps. This exceeds the 19.3 Mbps transfer rate approved for HDTV broadcasting.

Video Specifications

Blu-ray is compatible with full MPEG2 encoding, as well as MPEG4 AVC (also known as H.264) and VC1 (based on the Microsoft Windows Media Video format). Video resolutions from 480i to 1080p (in either 2D or 3D) can be implemented at the content producer's discretion.

Audio Specifications

Only Dolby Digital, DTS, and uncompressed PCM are required on all players. Other formats, including Dolby Digital Plus, Dolby TrueHD, and DTS-HD Master Audio, are optional. 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 and 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, everything but HDMI was eliminated. To use any Blu-ray Disc player made since 2013, your TV must have an HDMI input to view video content.

Internet and Network Connectivity

The Blu-ray format supports networking and internet capabilities, and most players also now have a built-in Wi-Fi connection option. Most Blu-ray Disc players also provide internet streaming capabilities, such as access to Netflix, Vudu, Hulu, and Amazon Video.

Backward Compatibility Support

The Blu-ray Disc format isn't compatible with previous formats, so you can't play a Blu-ray Disc on a DVD or CD player. However, Blu-ray Disc players can play DVDs and CDs, and some can play more 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 they're constructed to fit more information and support native 4K resolution playback (this isn't the same as 4K upscaling). Ultra HD Blu-ray also offers other video enhancement capabilities, such as wide color gamut and HDR.

You can't 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 Discs, DVDs, and CDs, and most can stream internet content.

Blu-ray and Ultra HD-Blu-ray can also be used with 4K Ultra HD TVs. For more information, learn what you need to know before buying a Blu-ray player, what types of Blu-ray players are best, and how to set up a Blu-ray player.