There have been a lot of questions about audio support for the new HD-A1 and HD-XA1 HD DVD players from Toshiba. It seems to be a source of much more confusion than the video side. There is good reason for this as the audio possiblities are much more complex than they were for DVD. A glance at the attached PDF which is page 59 of the A1 manual illustrates this fact.
Since the same questions keep getting asked and answered in new threads, I thought I would try to summarize some of the information which has been posted. I'm not an expert or insider and some of this info may not be 100% correct. If any of this is incorrect or you have better information, please post a reply or PM me and I will update it. Some of this information may apply to future HD-DVD and Blu-ray players as well.What Are These New Surround Sound Formats?
Both the HD-A1 and HD-XA1 support onboard decoding for the following audio formats which are part of the HD-DVD specification. Note that the manuals do not mention support for DVD-Audio or SACD and it has been confirmed they will not play them.
- Dolby Digital
- Dolby Digital Plus (new)
- Dolby TrueHD (new) - lossless. Getting 5.1 channels requires firmware 2.0 or higher. Earlier firmware was 2 channel output only and 5.1 channel TrueHD soundtracks were down mixed to left and right only.
- DTS-HD (new) - name for a collection of DTS formats (see more details below). Lossless is supported (Master Audio), but the manual says "DTS Core Only" so they probably will not decode the new DTS-HD lossless
The formats marked as (new) were not available on standard DVDs. All HD DVDs are required to have at least a DD+ soundtrack. TrueHD and DTS-HD are optional. They all support higher bitrates and audio quality, but the maximum bitrates are too high for the coaxial or Toslink optical S/PDIF connection that you use with your current DVD player. They also cannot be decoded by current processors or receivers so even if S/PDIF could pass these bitstreams it wouldn't do any good. So how can you get access to the improved sound quality of these new formats?
Since both players have internal decoders all the supported formats listed above can be decoded and output as 5.1 channel digital LPCM over the HDMI connection. They also have 5.1 channel 24/192 DACs (Digital to Analog Converters), so the LPCM can be converted to 5.1 channel analog audio and passed over the 6 RCA jacks. 5.1 channel analog inputs have become fairly common in receivers to support DVD-Audio and SACD players, but HDMI is only on newer units. HDMI 1.0 and lower supports only 2 channel PCM. HDMI 1.1 supports up to 8 channels of PCM but does not require that a receiver handle 8 channels to claim it is HDMI 1.1. Check your manual or contact the manufacturer. It could be 5.1 or 7.1. Most current receivers are 5.1.
The players can also output standard DD or DTS over S/PDIF, but the new formats must be transcoded or re-encoded to one of these standard formats to be passed over S/PDIF. However, the data rate can be up to 640 kbps for DD and 1500 kbps for DTS which is higher than most DVDs used. So you can still get higher quality sound from these new formats with S/PDIF.
The April 2006 issue of Home Theater magazine has an article titled "Surround Revisited". It has some details on the new formats. If you don't want to buy it, you can read it in about 5-10 minutes at the book store. Here are a few quotes I found interesting.
|Dolby Digital Plus is billed as an extension of Dolby Digital. For backwards compatibilty with the Dolby Digital equipment in 30 million surround receivers and 60 million set top boxes, Dolby Digital Plus signals are converted to Dolby Digital at the relatively high data rate of 640 kilobits per second (Dolby Digital usually operates at 192 to 448 kbps) through S/PDIF outputs, better known as digital optical and coaxial.
So it sounds like DD+ can be converted to the highest bitrate standard DD pretty easily for those who don't have a receiver with HDMI or 5.1 analog audio inputs. All of the lauch titles include DD+. However, the launch titles use something called Advanced Content (more details later) and for this type of content the players re-encode the PCM to standard DTS at 1.5 Mbps. So you must at least have a receiver which will accept DTS to get 5.1 channels over SPDIF.
|DTS-HD is the latest wrinkle in DTS branding. Not so much an extension as a consolidation, it includes all the Coherent Acoustics formats - DTS, DTS ES Discrete, DTS ES Matrix, DTS Neo:6, and DTS 96/24 - plus a new lossless format that supports up to 7.1 channels and a sampling frequency of 192 kHz.
So DTS-HD is not necessarily lossless like DD TrueHD, although it can be. However, the manual clearly says in several places that they support "DTS core only". It is unclear at this time what this means. Some posters in these forums have said it means no lossless support. Others have said it means 5.1 channels only (no 6.1 or 7.1) but can be lossless. We may not know for sure until someone releases a disk with lossless DTS-HD. If you are interested in this topic you might want to start reading at this post in another thread
If you are interested in the supported bit rates, you might want to check out this thread
.What Are My Connection Options?
The audio connection options for multichannel sound and supported formats will be the following, listed first choice to third choice. Use the first one that your receiver supports.
HDMI Connection (version 1.1)
- All formats supported by the player's internal decoder (see above) can be converted to 5.1 channel digital LPCM and sent over HDMI
- If you set Digital Out HDMI to Auto the new formats will be decoded and output as PCM. Standard DD and DTS from DVDs will be passed as bitstream.
- If you set Digital Out HDMI to PCM, all formats will be decoded and output as PCM, even std DD and DTS from DVDs.
- Your reciever may apply speaker settings, bass management and surround processing to the 5.1 channel digital PCM input. If this is the case you should not need to set these in the player although someone did report that the speaker settings do affect HDMI as well as the analog outputs. So if the balance from the Toshiba is different than other sources you might be able to tweak it. Usually it is best to set the Toshiba to all speakers large, all levels at zero and distances at the default.
- Some have reported getting sound from their rear speakers (7.1) using their receiver's surround fields (Dolby Pro Logic II) in the posts below, but this is not 7.1 discrete channels. The rear channel sound is created from the 5.1 channel output.
5.1 Channel Analog Audio Connection (6 RCA)
- All formats supported by the player's internal decoder (see above) are decoded to PCM then converted to 5.1 channel analog audio.
- Should be full bandwidth analog since spec sheets say "Multi-Channel 24-bit/192kHz Audio DACs"
- Speaker setup and bass management depends on receiver capabilities, but most do not support processing of analog inputs. So you might want to use the 5.1 Speaker setup in the player's Setup menu to configure it correctly for your speakers.
- There are problems with the internal test tones in the player. The 5 channel level is very loud and the LFE is much lower. If possible, you should use test tones from a setup disk such as Avia or Video Essentials to set the speaker levels. There is much discussion of this topic below.
- Some people with 7.1 channel analog inputs use RCA splitters to feed the left and right surround signals to the corresponding rear speakers as well.
S/PDIF Coaxial or Toslink (optical) Digital Audio Connection (same as current DVD players)
Are There Audio Differences Between the HD-A1 and HD-XA1?
- If SPDIF Audio Output is set to Bitstream (the default) you will get the new formats either transcoded or re-encoded to standard DD or DTS. The format depends on the disc, but the launch titles all use "Advanced Content" which is re-encoded to DTS at 1.5 Mbps by the XA1 and A1. See the "Advanced Con." row in the attached table for details.
- If SPDIF Audio Output is set to Bitstream (the default) standard DD or DTS streams on DVDs will be passed as that bitstream.
- You can only get 2 channel PCM over SPDIF. If you set SPDIF Audio Output to PCM, you will only get 2 channels. See the attached table.
Early on there was much speculation about audio differences between the A1 and XA1 due mostly to what was not mentioned in the advertised specs versus what was mentioned. The A1 spec sheet contained much less detail. Now that the A1 is shipping, it seems to have all of the audio features listed on the XA1 spec sheet.Should I Wait for Next Generation Players and Receivers That Support HDMI 1.3?
Many people in these forums suggest waiting for HDMI 1.3 devices because it can pass the new formats as a bit stream for external decoding. The HD-A1 and HD-XA1 players are HDMI 1.1 and as of today there are no receivers or processors which support 1.3. So you might be wondering if it is better to wait until players and receivers that support 1.3 become available. A personal choice, but this information may help you decide.
Posts in these forums indicate that the chip sets for HDMI 1.3 will be released in April of 2007, so there will likely be no players or receivers that support it until sometime after that.
The November 2005 issue of Widescreen Review
had a very good article titled "Dolby Audio Coding for Future Entertainment Formats" which indicated that using an external decoder might not be desirable. If you are really interested in this topic, I would recommend reading the full article. If you subscribe to their web site you can download the full article as a PDF file. Here is a quote from that article.
|The implications of this decoding within the player are significant. New features can be created for a given title long after the discs have shipped. More importantly, the fact that players will be mixing the audio internally means that it will no longer be possible (or necessary) to output raw audio bitstreams from the player as is typical with DVD-Video. As a result, consumers can no longer assume that every player will work with every A/V receiver. Two methods already exist for reproducing the high-resolution soundtracks of next-generation optical formats through your A/V receiver or audio processor...
The article goes on to discuss the multi-channel analog audio and multi-channel digital LPCM over HDMI connection options and says "A connection through either of these existing interfaces will let you experience the full potential of the high-resolution audio delivered on next-generation optical formats."
It also discusses re-encoding the PCM signal to standard Dobly Digital for output to a current DD receiver or processor over S/PDIF and says "In many instances, the audio quality you will experience from this connection may be better than what you would experience during playback of standard-definition DVD-Video discs, especially if the native signal on the disc is Dolby TrueHD or high-bit-rate Dolby Digital Plus." This is because most standard DVDs do not use the maximum quality (bits/kHz) supported by DD and DTS to save space on the disk for extras. These new players should be able to downconvert the new formats to the highest supported standard DD and DTS quality.
All of the April 18 launch titles use something called "Advanced Content" so the most important row in the audio output tables may be the one for "Advanced Con.". The soundtracks on these discs is decoded to PCM and goes through a mixer where other audio (such as the menu selection sounds or future content) can be added. The resulting mix can be output directly as 5.1 channel PCM or analog, but to get a multichannel bitstream it is re-encoded to DTS then sent to the receiver to be decoded again. It's too early to know if all future HD DVD players and discs will be like this, but it does hint that future players with HDMI 1.3 might re-encode the PCM to DD+, TrueHD or DTS-HD to provide a bitstream output. If this is true, the ability to send these bitstreams over HDMI offers no advantage, in fact it would be undesirable. You might as well send the PCM over HDMI and not bother with another encode/decode step which can potentially degrade the audio.
Standard DVD created the mindset that to get the best audio quality you must pass the raw digital audio bitstream to a high quality external decoder. But the WSR article indicates that with the new HD-DVD and Blu-ray players there will be advantages to having the player decode and mix the audio. So for those wanting the highest quality sound, the audio capabilities of the player may become more important and external decoding in the receiver/processor will no longer be required.
Given all of that, there may be no reason to wait for HDMI 1.3 to get better audio. You should be able to get higher quality sound from these new formats now. With currently available HDMI 1.1 connections you can have a single cable passing high quality multi-channel digital sound to your receiver or processor.
HD-A1 audio output settings - page 59.pdf 142.6025390625k . file