HD Audio Information.

Confused about all the HD options? Don’t worry most people are, there are two important things to know when picking a media player for its audio abilites those are Downmixing and Passthrough (or often called bitstream). These two options are explained later on but for now lets go over the different HD audio types.

Our thanks to http://www.iboum.com for the write up and continued efforts in providing neutral points of view on media players as well as a great comparison grid (go on check it out!).

HD-Audio Explained
The advent of HD video content has seen a corresponding switch to HD-Audio. You will see much mention of the various confusing standards. This page attempts to explain in relatively easy to understand terms what it’s all about. Two competing companies have issued standards for HD-Audio, Dolby and DTS (Digital Theatre System), these will be dealt with in turn.

Dolby Digital (Also known as AC-3)
Dolby Digital is a required standard of both Blu-Ray and DVD and the most widely supported HD-Audio format, being supported by all the Media Players on our site. It is a ‘lossy’ format so is of a lesser quality than the original cinema/studio original. Surround sound up to 5.1 channel is supported. The Dolby Digital audio track can either be decoded (downmixed) to stereo in the Media Player or digitally bitstreamed direct (passthrough) to a compatible receiver (via TOSLINK/Coaxial/HDMI) for decoding.

Dolby Digital Plus (E-AC3)
Dolby Digital Plus is an enhanced version of Dolby Digital offering higher bit-rates and the possibility for 7.1 surround sound. Although better quality than Dolby Digital, it is still a ‘lossy’ format. Dolby Digital Plus is little used and has largely been passed over in favour of higher quality lossless formats.

Dolby TrueHD
Dolby TrueHD is a lossless compression format giving audio identical to the original studio recording. It can handle 14 separate channels for surround sound. Dolby TrueHD is completely separate from Dolby Digital AC-3, so files carrying TrueHD audio must also carry a separate AC-3 track to make them playable on non TrueHD players. Dolby TrueHD can either be downmixed in the player to an analogue format, or bitstreamed via HDMI 1.3 or higher* to a compatible receiver. A hardware bug prevents any Realtek based player from passing full Dolby TrueHD, making the Sigma chipset players your only choice for Dolby TrueHD passthrough.
*TOSLINK or Coaxial S/PDIF cannot carry a TrueHD signal because the S/PDIF standard was finalised long before lossless HD-Audio was envisaged (despite S/PDIF being theoretically able to cope with the bandwidth). HDMI 1.3 or higher is therefore the only way to pass Dolby TrueHD audio.

The majority of players we sell can downmix Dolby TrueHD

DTS (Digital Theater System)
DTS is a required standard of both Blu-Ray and DVD players and is widely regarded to produce audio quality superior to Dolby Digital. Up to 5.1 channel surround sound is supported. DTS is a ‘lossy’ compression standard so the audio is of a lesser quality than the original studio recording. Until recently many Media Players did not support DTS so you would get no audio at all when playing back files with a DTS audio track (many .mkv files). The DTS audio track can either be decoded (downmixed) in the Media Player to stereo or digitally bitstreamed direct (passthrough) to a compatible receiver (via TOSLINK/Coaxial/HDMI) for decoding. Any decent new Media Player will be able to both downmix and passthrough DTS.

The majority of players we sell can downmix and passthrough DTS.

DTS-HD HR (High Resolution / DTS+)
DTS-HD High Resolution is an enhanced version of DTS offering higher bit-rates and better compression. Up to 7.1 channel surround sound is supported. It is still a ‘lossy’ format and is not widely used, having been largely passed over in favour of lossless formats. DTS-HD HR uses a core+extension format so if your player doesn’t support DTS-HD HR then the DTS core can be extracted.

DTS-HD MA (Master Audio / DTS++)
DTS-HD Master Audio is a lossless compression format giving audio identical to the original studio recording. It supports up to 8 channels for surround sound. Unlike Dolby TrueHD, DTS-HD MA works in a core+extension configuration so players that do not support it can extract the DTS core audio. DTS-HD MA can either be downmixed to an analogue format if supported by the player, or bitsreamed via HDMI 1.3* to a compatible receiver. A hardware bug prevents any Realtek based player from passing full DTS-HD MA, making the Sigma based players your only choice for DTS-HD MA passthrough.
*TOSLINK or Coaxial S/PDIF cannot carry a DTS-HD MA signal because the S/PDIF standard was finalised long before lossless HD-Audio was envisaged (despite S/PDIF being theoretically able to cope with the bandwidth). HDMI 1.3 or higher is therefore the only way to pass Dolby TrueHD audio.

So what is downmixing and passthrough?

Downmix is where the HD digital audio from a movie (as covered above) is converted on the fly into an analogue format by a media player before being sent to your amp and TV. As an example a lot of Blu-ray ISO rips will have HD audio but most users will only have the two speakers that are built into the TV instead of a 7.1 surround sound setup – so downmxing is perfect and allows the audio to come out of the two speakers. If downmixing was not supported you wouldn’t hear anything.

Passthrough (or bitstream) is where the HD digital audio is sent directly to an amp and the amp processes the signal and sends it out to the TV or speaker setup. Now not all amps are born equal so check yours can handle the HD audio formats. Most amps will process the signal better than a media player as that is what they are designed to do.

What’s this I keep reading about Sigma V Realtek for HD audio?

There are two big players in the media player market Sigma and Realtek, these guys make the hardware and software and then sell it to all the other companies to chuck in a box and rebrand the software as they see fit.

It seems that none of the Realtek 1073 / 1283 chipset players such as Xtreamer / Playon HD / Mede8er will ever support lossless HD-Audio passthrough (basically no DTS HD MA and Dolby Digital HD audio output as a bitstream) This is because the hardware on the Realtek boards cannot play it back. I expect this to change when new Realtek players are released using a new chipset (and possibly BBC IPlayer support!)

Now a lot of media players have advertised these features as “coming soon” and we have done our best (always) to tell people the Sigma players are better at the HD audio side of things.

This is not the end of the world the actual number of people who want to use these features are pretty small so I wouldn’t panic The Mede8er and PlayOn still get great reviews and are some of our highest sellers be sure to read our blogs monthly “best media player” post for the latest best buy.