A surroundreceiver is able to provide sound in surround quality as Dolby Digital. A stereoreceiver will as it say only provide stereo sound.

How do you choose the right THX Certified products for your listening environment?To help you find the right products for your room, THX has established performance categories based on the size of specific listening areas. For example, a THX Select2 Certified AV receiver is engineered for rooms with a viewing distance* of approximately 10 – 12 feet from the display to the primary seating position. By contrast, THX Ultra2 Certified products are engineered for rooms with a viewing distance of 12 feet and beyond.

HDMI (High-Definition Multimedia Interface) is the first and only industry-supported, uncompressed, all-digital audio/video interface. By delivering crystal-clear, all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable. HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby® TrueHD and DTS-HD Master Audio™ with bandwidth to spare to accommodate future enhancements and requirements.With the launch of HDMI version 1.3, HDMI continues to increase its overall functionality to meet the needs of the High-Definition marketplace. HDMI 1.3 will include the following new features:Higher speed: HDMI 1.3 increases its single-link bandwidth from 165MHz (4.95 gigabits per second) to 340 MHz (10.2 Gbps) to support the demands of future high definition display devices, such as higher resolutions, Deep Color™ and high frame rates. In addition, built into the HDMI 1.3 specification is the technical foundation that will let future versions of HDMI reach significantly higher speeds.Deep Color™: HDMI 1.3 supports 30-bit, 36-bit and 48-bit (RGB or YCbCr) color depths, up from the 24-bit depths in previous versions of the HDMI specification.Lets HDTVs and other displays go from million of colors to billions of colors.Eliminates on-screen color banding, for smooth tonal transitions and subtle gradations between colors.Enables increased contrast ratioCan represent many times more shades of gray between black and whiteAt 30-bit pixel depth, a four times improvement would be the minimum, and the typical improvement would be eight times or more.Broader color space: HDMI 1.3 removes all limits on color selectionNext-generation “xvYCC” color space supports 1.8 times as many colors as existing HDTV signalsLets HDTVs display colors more accuratelyEnables displays with natural, vivid colorsNew mini connector: With small portable devices such as HD camcorders and still cameras demanding seamless connectivity to HDTVs, HDMI 1.3 offers a new, smaller form factor connector option.Lip Sync: Because consumer electronics devices are using increasingly complex digital signal processing to enhance the clarity and detail of the content, synchronization of video and audio in user devices has become a greater challenge and could potentially require complex end-user adjustments. HDMI 1.3 incorporates an automatic video/audio synching capability that allows devices to perform this synchronization automatically with total accuracy.New lossless audio formats: In addition to HDMI’s current ability to support high-bandwidth uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new, lossless compressed digital audio formats Dolby TrueHD and DTS-HD.

DVD-Audio is an extension of the highly popular DVD format, distinguished by its capability for delivering a new standard of quality previously unavailable in packaged audio media. A highly compelling feature of DVD-Audio is its multichannel (5.1) audio capability. DVD-Audio also includes a host of value-added multimedia features not previously available on compact disc.

Dolby® TrueHD is Dolby’s next-generation lossless technology developed for high-definition disc-based media. Dolby TrueHD delivers tantalizing sound that is bit-for-bit identical to the studio master, unlocking the true high-definition entertainment experience on next-generation discs. When coupled with high-definition video, Dolby TrueHD offers an unprecedented home theater experience that lets you enjoy sound as stunning as the high-definition picture. Features * 100 percent lossless coding technology. * Up to 18 Mbps bit rate. * Supports up to eight full-range channels of 24-bit/96 kHz audio.* * Supported by High-Definition Media Interface (HDMI™), the new single-cable digital connection for audio and video. * Supports extensive metadata including dialogue normalization and dynamic range control. *Dolby TrueHD can support more than eight audio channels. HD DVD and Blu-ray Disc standards currently limit their maximum number of audio channels to eight. Benefits: * Delivers enthralling studio-master-quality sound that unlocks the true high-definition entertainment experience on next-generation discs. * Offers more discrete channels than ever before for impeccable surround sound. * Compatible with the A/V receivers and home-theaters-in-a-box (HTIBs) of today and tomorrow. * Dialogue normalization maintains the same volume level when you change to other Dolby Digital and Dolby TrueHD programming. * Dynamic range control (Night mode) enables you to customize audio playback to reduce peak volume levels (no loud surprises) while experiencing all the details in the soundtrack, enabling late-night viewing of high-energy surround sound without disturbing others. * Selected as the mandatory format for HD DVD and as an optional format for Blu-ray Disc.

Dolby® Digital Plus is the next-generation audio technology for all high-definition programming and media. It combines the efficiency to meet future broadcast demands with the power and flexibility to realize the full audio potential of the upcoming high-definition experience. Built on Dolby Digital, the multichannel audio standard for DVD and HD broadcasts worldwide, Dolby Digital Plus was designed for the delivery formats of the future, but remains fully compatible with all current A/V receivers. With Dolby Digital Plus, you get even higher quality audio, more channels, and greater flexibility. Amaze your ears. Features * Multichannel sound with discrete channel output. * Channel and program extensions can carry multichannel audio programs of up to 7.1 channels and support multiple programs in a single encoded bitstream. * Outputs a Dolby Digital bitstream for playback on existing Dolby Digital systems. * Supports data rates as high as 6 Mbps. * Bit rate performance of at least 3 Mbps on HD DVD and up to 1.7 Mbps on Blu-ray Disc. * Accurately reproduces what the director and producer intended. * Interactive mixing and streaming capability in advanced systems. * Supported by HDMI™, the new single-cable digital connection for high-definition audio and video. Benefits * Can deliver 7.1 channels and beyond of enhanced-quality audio at up to 6 Mb * Allows multiple languages to be carried in a single bitstream. * Offers audio professionals new creative power and freedom. * Compatible with the millions of home entertainment systems equipped with Dolby Digital. * No latency or loss of quality in the conversion process. * Maintains high quality at more efficient broadcast bit rates (200 kbps for 5.1-channel audio). * Selected by the Advanced Television Systems Committee (ATSC) as the standard for future broadcast applications; named as an option by the Digital Video Broadcasting (DVB) Project for satellite and cable TV. * Selected as the mandatory audio format for HD DVD and as an optional audio format for the Blu-ray Disc.

Star Wars:Episode I was the first film to use an additional rear channel routed to the array of speakers along the back wall of a cinema. In the cinema, this center surround channel is not discrete, but is matrixed into the left surround (LS) and right surround (RS) channels. Embedded in the soundtrack print master, this matrixed channel works with all cinema digital sound formats. DTS calls this process Extended Surround, or "ES." When the film soundtrack is transferred to DVD, the matrixed center surround channel again automatically appears in the 5.1-channel soundtracks on the disc. With its greater bandwidth, DTS is also able to offer a fully discrete center surround channel, which can be recovered by a new generation of decoders. These soundtracks are fully compatible with existing 5.1-channel DTS decoders, which decode the center surround channel information to be heard in and between the LS and RS speakers. Thus "ES" is the general term for DTS tracks with a center surround channel, and "ES 6.1 discrete" is the particular case where the center surround channel is discrete. About DTS in Consumer Electronics Products * The center surround channel is always matrixed into the LS and RS channels. * A discrete center surround channel can optionally be encoded. * A DTS-ES 6.1-discrete decoder will play the discrete center surround channel and will subtract the discrete center surround channel from the matrixed LS and RS channels. * Any DTS-ES track, discrete or not, is fully compatible with 6.1-matrix decoders because the matrixed tracks are always present. * Any DTS-ES track is fully compatible with 5.1 decoders because the center surround channel information is matrixed into the LS and RS channels and will be heard in and between the LS and RS speakers. Hardware features: Devices carrying the logo handle DTS 6.1 Matrix and DTS 6.1 Discrete decoding, and offer DTS 5.1 capabilities.

Dolby Digital EX takes the Dolby Digital 5.1-channel setup one step further with an additional center surround channel (reproduced through one or two speakers) for extra dimensional detail and an enveloping surround sound effect. Feature films originally released in Dolby Digital Surround EX (the cinema version) carry the encoded extra surround channel in their subsequent DVD releases, as well as onto 5.1-channel digital satellite and TV broadcasts. If your home theater system has a receiver or preamp/processor with Dolby Digital EX decoding and speakers to support 6.1 or 7.1 playback, you can hear Surround EX soundtracks as they were meant to be heard, with the increased realism created by the extra surround channel. As in the cinema, with regular 5.1-channel Dolby Digital playback no sonic information is lost (although you'll miss out on the heightened realism). Current Dolby Digital Surround EX soundtracks contain a digital flag that can automatically activate the EX decoding in a receiver or preamp/processor. For titles released prior to late 2001, however, you need to turn on the EX decoding manually.

DTS Digital Surround is the standard for providing 5.1 channels of discrete digital audio in consumer electronics products and software content.

In thousands of cinemas and millions of homes worldwide, Dolby® Digital is the reigning standard for surround sound technology in general and 5.1-channel surround sound in particular. Dolby Digital is a highly sophisticated and versatile audio encoding/decoding technology. Dolby Digital technology can transmit mono, stereo (two-channel), or up to 5.1-channel surround sound (discrete multichannel audio). The superior coding efficiency of Dolby Digital-and its ability to deliver high-quality discrete multichannel audio without compromising video quality-has made it the designated audio standard for DVD worldwide. Dolby Digital is also the preferred multichannel audio standard for direct broadcast direct to home satellite and digital cable systems. Nearly 60 million digital cable and satellite set-top boxes are currently in use worldwide supported by over 30 million audio/video receivers equipped with 5.1-channel Dolby Digital decoding. Virtually every DVD-Video player sold today offers a two-channel mixdown of the Dolby Digital 5.1 movie soundtrack as well as a digital output for connection to a 5.1-channel audio/video receiver. In the film industry, the Dolby Digital soundtrack is optically encoded right on the filmstrip, in the space between the sprocket holes. Placing the soundtrack directly on the film allows it to coexist with the analog track, a cost-effective and simple solution for film distributors and theatre owners. The sprocket hole area has also proven highly resistant to wear and tear, so that a soundtrack encoded in Dolby Digital will remain free of pops and hiss for the useful life of the print. The sound information contained in each of the six available channels is distinct and independent. These six channels are described as a "5.1-channel" system, because there are five full-bandwidth channels with 3 Hz to 20 kHz frequency range for Front Left and Right, Center, and Surround, plus one "Low Frequency Effects" (LFE) subwoofer channel devoted to frequencies from 3 to 120 Hz.

Dolby® Pro Logic® IIx - The age of 7.1 surround sound for the home is here. But it's not just reserved for DVD movies encoded in Dolby Digital EX. With Dolby Pro Logic IIx, any movie, CD, TV program or video game can be enjoyed through this enhanced surround sound technology. Pro Logic IIx is the first and only technology to expand any existing stereo- or 5.1-channel audio for a 6.1- or 7.1- channel playback, creating a seamless, natural surround soundfield that immerses you in the entertainment experience.Dolby® Pro Logic® II technology processes any high quality stereo (two-channel) movie and music audio into five playback channels of full-bandwidth surround sound. A matrix surround decoding technology, Dolby Pro Logic II detects the directional cues that occur naturally in stereo content and uses these elements to create a five-channel surround sound playback experience. It's ideally suited for home theater systems, PCs, game consoles, and multichannel in-car audio systems (as Dolby Pro Logic II Surround). Dolby Pro Logic II is fully compatible with all Dolby Pro Logic technologies. It provides optimal audio for playback in a 5.1-channel home theater system for the thousands of videocassettes and TV programs encoded in four-channel Dolby Surround (the encoding counterpart to Dolby Pro Logic's decoding technology. Dolby Pro Logic II also enables video game consoles to encode five-channel surround sound information into a stereo signal with virtually no impact on the console's CPU, which means all this extra audio won't slow your game down. Dolby Pro Logic II can bring new life to your CD collection. Play your music through your home theater system, and you'll hear seamless, natural sound with new depth and detail – it's almost like hearing a newly remastered CD. In addition to enhancing playback, Dolby Pro Logic II can be used to encode TV programming to deliver a surround sound experience for viewers with stereo TV systems. Dolby Surround is the consumer version of the original Dolby multichannel analog film sound format (Dolby analog and Dolby SR [Spectral Recording]). When a Dolby Surround soundtrack is produced, four channels of audio information—Left, Center, Right, and Mono surround—are matrix-encoded onto two audio tracks. These two tracks are then carried on stereo program sources such as videotapes and TV broadcasts into the home, where they can be decoded by Dolby Pro Logic® to recreate the original four-channel surround sound experience. A result of Dolby's expertise in matrix surround processing, Dolby Pro Logic was the foundation for multichannel home theater, and was the reference decoder for creating the surround sound audio tracks in thousands of commercially available videocassettes, laser discs, DVDs, and television programs. With the introduction of the Dolby Digital multichannel film sound format, Dolby Digital has replaced Dolby Surround as the preferred technology to deliver multichannel audio to consumers via DVD-Video, digital television, and games. However, every Dolby Digital decoder also provides a Dolby Pro Logic-compatible stereo signal on its analog outputs.