Surround sound is an integral part of the home theater experience, and with that, there are lots of surround sound formats in use, depending on your audio system's capabilities, speaker layout, and content.

Probably the most used are formats that are part of the Dolby Digital family. In this article, we discuss three: Dolby Digital, Dolby Digital EX, and Dolby Digital Plus. These formats are commonly used on DVDs and streaming content and are also present as a supplemental selection in Blu-ray and Ultra HD Disc content.

What Dolby Digital Is

Dolby Digital is a digital audio encoding system designed for use on DVDs, Blu-ray, and Ultra HD Blu-ray Discs, and, in some cases, for TV broadcast and streaming content. This system provides efficient transfer for audio signals that may be composed of one, or more channels, that can be decoded by a home theater receiver or AV Preamp/Processor with a Dolby Digital decoder and distributed to one or more speakers.

Almost all home theater receivers in use have a built-in Dolby Digital decoder and all DVD, Blu-ray Disc, and Ultra HD Blu-ray Disc players are equipped with the ability to pass Dolby Digital signals via a technique referred to as bitstream to properly equipped receivers for decoding.

Dolby Digital is often referred to as a 5.1 channel surround system. However, the term 'Dolby Digital' refers to the digital encoding of the audio signal, not how many channels it has. Dolby Digital may also be referred to asDD, DD 5.1, AC3

• Monophonic: Represented by one or two speakers. However, with two speakers, both reproduce the same sound so the sound will appear to come from the space between the speakers.
• 2-Channels: Represented by two speakers - one on the left and on the right front of the listening position.
• 4-Channels: Represented by four speakers - Two placed on the left and right front of the listening position, and two on the left and right, and slightly behind the listening position.
• 5.1 Channels: Represented by five speakers (left, center, right, left surround, right surround), and a subwoofer (.1)

Dolby Digital EX

The Dolby Digital EX format adds a third surround channel that is placed directly behind the listener. The means that it is a 6.1 Channel system.

The six channels are represented by six speakers (left, center, right, left surround, center back, right surround), and a subwoofer (.1.).

This means that the listener has both a front center channel and, with Dolby Digital EX, a rear center channel. If you are losing count, the channels are labeled: left front, center front, right front, left surround, right surround, subwoofer, with a surround back center. A home theater receiver with a Dolby Digital EX decoder is required to access the full 6.1 channel experience.

However, if you have a DVD, or other source content, that contains 6.1 channel EX encoding and your receiver does not have an EX decoder, the receiver will default to Dolby Digital 5.1. What it does is sort out the extra EX information and distribute/mix it within a 5.1 channel sound field.

Usually, this means that the 6th (center back) channel is placed into both the left and right surround channels as a mono signal, which in turn creates a 'phantom' rear center back channel without having to have a physical rear center speaker.

This is not as accurate as a setup that includes a dedicated rear center channel speaker as the output level can't be adjusted independently of the left and right surround channels, but you are still able to hear the sound that was originally encoded for the center back channel.

Dolby Digital Plus

Dolby Digital Plus is a high definition digital-based surround sound format that supports up to 8-channels (7.1) of surround decoding. The channel distribution is as follows: front left, front center, front right, left surround, right surround, left surround back, right surround back, and subwoofer.

In addition, Dolby Digital Plus contains a standard Dolby Digital 5.1 bitstream that is compatible with standard Dolby Digital-equipped receivers. This means on a 5.1 channel receiver you will hear a 5.1 channel mix of the soundtrack, rather than a 7.1 channel mix. The surround back left and right channels are folded into the left and right surround channels.

Dolby Digital Plus is one of the several audio formats employed by Blu-ray Disc format. Dolby Digital Plus is compatible with the audio portion of the HDMI interface, as well as being applied in streaming and mobile audio applications. Dolby Digital Plus is also built into the Dolby Audio platform for Windows 10 and the Microsoft Edge browser.

Although Dolby Digital Plus has its own specific label designation, in many applications, Dolby Digital 5.1 and 6.1 (EX) are often referred to as just Dolby Digital.

No matter which format in the Dolby Digital family discussed above you have access to, the goal is to provide a room-filling surround sound listening experience that enhances the home theater viewing experience or a fuller audio experience from a compatible home theater receiver, PC, or portable device.

However, depending on your content and components, there are additional Dolby home theater audio formats to be aware of including Dolby TrueHD and Dolby Atmos.

It can also extract those compressed Bitstreamaudio such as Dolby Digital, AC3 and DTS 5.1 through its optical audiooutput for further decoding by your A/V receiver.

Uses for baking powder. This HDMI processor supports direct pass-throughof all HDMI 3D video and deep color content. The HDMI input supports resolutions up to 4Kx2K.

This device has an internal repeater function built in to make sure its HDMI output will pass the same sharp detailed images with original digital audio sound maintained all the way to the display or the receiver end.

No TV Hookup Required
The operation of this HDMI audio processor does not require HDMI hookup with a TV.

Theanalog audio output or optical audio output from the device remains coming through when the HDMI output of this device is not connected with a TV.

EasyEDID Switch For Audio Output Mode
Thisunit is featured with EDID switch on the front panel for manually selectingbetween various audio output modes:

• TV Mode: Switch to TV mode for the HDMI source to output audio according to what the TV or AV receiver can support.
• Bitstream Mode: HDMI source will output bit-stream audio such as AC3, Dolby 5.1, DTS 5.1, which will be extracted and routed through its optical audio output.
• LPCM 7.1CH Mode: all 3.5mm audio ports output LPCM 7.1CH sound. Optical port output 2 channel PCM digital audio.
  [Note]: Depending on the input audio format, the unit may not output audio through all output port. For Example, the optical output port will have no audio when the input audio format is more than LPCM 7.1CH.

HDMI LPCM 5.1 7.1 Audio Decoder
This HDMI audio decoder is a great device for decoding the LPCM 5.1 and 7.1 surround sound outputfrom devices such as PS4, Wii U, Blue-ray player, etc into 7.1 and 5.1discrete channel sound through its front left/right, center/subwoofer, rear left/right and rearcenter left/right ports to deliver a directional and more realistic effect.Source player and DVDdisc must have the capability of providing multi-channel audio output for thisprocess.

The decoded analog audio output from this device produces an accurate duplicate of sound whichis bit-for-bit identical to the studio master, so listening at home is the ultimate home cinema experience.[Note]: Dolby TrueHD or DTS-HD Master Audio can only passed through the HDMI output with no decoding and no conversion.

Discrete Channel Sound
This HDMI audio processor decodes LPCM 5.1 or 7.1 audio and outputs through 4 of its 3.5mm audio terminals usingoptional splitters/cables (not included)

• FL/FR OUT: front left and front right audio outputs
• LFE/FC OUT: subwoofer and center audio outputs
• RL/RR OUT: rear left and rear right audio outputs
• RLC/RRC OUT: rear left center and rear right center audio outputs

HDMI To Optical Audio Output
This HDMI audio converter can extract the compressed Dolby Digital, AC3and DTS 5.1 and route through its optical audio out.

Source player and DVDdisc must have the capability of providing multi-channel audio output for thisprocess. [Note]: The optical output port will have no audio when the input audio format isLPCM 7.1 or 5.1CH.

InternalHDMI Repeater Function
This HDMI audio processor has repeater built in which can automaticallyequalizes and compensates for HDMI signal loss during the cable run and alsoextends the cable reach to maximum distance with the same signal qualitymaintained all the way and delivered to the end HD display.

Compliance With New HDMI 1.3 For HD Video/Audio
This device is fully complaint with the new HDMI 1.3 and HDCP 1.2 standard.

• Great digital to analog audio decoder solution for transcoding uncompressed digital LPCM 7.1 or 5.1 channel sound into analog surround format for existing analog amplifier or receiver.
• Extract compressed digital Bitstream audio such as Dolby Digital, AC3 and DTS 5.1/7.1 embedded in HDMI feed and output through its optical audio output for further decoding by downstream device.
• Supports uncompressed LPCM 7.1, LPCM 5.1 and PCM in analog output through the multi-channel 3.5 output ports.
• Deliver 7.1 and 5.1discrete channels through its front left/right, center/subwoofer, rear left/right and rearcenter left/right channel to deliver a directional and more realistic effect
• Supports compressed audio such as Dolby Digital, AC3, DTS 5.1 and PCM 2CH through optical audio output.
• Easy EDID dip switch selection so users can easily control their HDMI source to send the desired digital audio format for decoding or conversion.
• No HDMI output with TV is required when receiving audio at the analog or optical audio output.
• Supports all HDTV resolutions including 4K, 2K, 1080p, 1080i, 720p, 576p and 480p. Output resolution follows input.
• Fully compliant with HDMI 1.3, HDCP 1.2 and DVI 1.1 standards.
• Supports HDMI audio sampling rates up to 192 kHz.
• Supports optical (S/PDIF) digital audio sampling rates up to 192 kHz.
• Supports high-bit-rate (HBR) audio.
• Its built-in repeater function helps devices regenerate and equalize the HDMI output signal to be same with sharp detailed images with original audio sound quality.
• Supports 12-bit per channel (36-bit all channel) deep color and 3D .
• Supports HDMI CEC (Consumer Electronics Control) bypass.

• Video Bandwidth: 300Mbps / 10.2 Gbps
• Input Port: HDMI female x 1
• Output Port:
  • HDMI female x 1
  • Toslink x 1
  • 3.5mm x 4
• HDMI Audio Sampling Rate: 192 kHz max
• Optical S/PDIF Audio Sampling Rate: 192 kHz max
• HDMI Audio Format Support:
  • LPCM 2CH, LPCM 5.1/7.1CH
  • Dolby Digital 5.1 and DTS 5.1
  • Dolby TrueHD, and DTS-HD Master Audio [Pass-Through Only]
• Analog Audio Output Format Support: 6-channel or 8 channel audio decoded from the LPCM 5.1 or 7.1 input
• Optical Audio Output Format Support:
  • LPCM 2CH
  • Dolby Digital and DTS
• Power Supply: DC 5V, 2A

• HDMI LPCM audio processor
• Power adapter
• User manual