HD audio situation for 780g/790g/8200/G45 - AVS Forum
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post #1 of 8 Old 08-11-2008, 08:07 PM - Thread Starter
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Lost my posts from earlier so I'm asking again. Based on what I've read so far, I would like to confirm the following with the experts here :-

- there is no way to get 8ch LPCM over HDMI (TrueHD etc) due to Windows not having a PAP

- 780g and 790g only support 2ch LPCM over HDMI, Nvidia and Intel chipsets support 8ch

My receiver and tv do not have HDMI, I will use DVI+SPDIF.

- is it correct that with 780/790g, I am not guaranteed to get 5.1 over SPDIF?

- G45 does support this. DTS-I will convert all kinds of sources (like stereo) to 5.1 digital and HD audio will also be downsampled and be 5.1 over SPDIF.

- There is no way to output 5.1 LPCM as SPDIF does not support this.

If these are correct then my choices are limited to Nvidia/G45 as I do not want to get analogue audio out of the HTPC.

Thanks for your replies.
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post #2 of 8 Old 08-11-2008, 08:46 PM
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Quote:
Originally Posted by Defcon View Post

Lost my posts from earlier so I'm asking again. Based on what I've read so far, I would like to confirm the following with the experts here :-

- there is no way to get 8ch LPCM over HDMI (TrueHD etc) due to Windows not having a PAP

- 780g and 790g only support 2ch LPCM over HDMI, Nvidia and Intel chipsets support 8ch

My receiver and tv do not have HDMI, I will use DVI+SPDIF.

- is it correct that with 780/790g, I am not guaranteed to get 5.1 over SPDIF?

- G45 does support this. DTS-I will convert all kinds of sources (like stereo) to 5.1 digital and HD audio will also be downsampled and be 5.1 over SPDIF.

- There is no way to output 5.1 LPCM as SPDIF does not support this.

If these are correct then my choices are limited to Nvidia/G45 as I do not want to get analogue audio out of the HTPC.

Thanks for your replies.

I have no problem doing 5.1 with my Gigabyte GA-MA78GM-S2H DVI & SPDIF (Optical) thru my HK AVR347. I am now doing it with HDMI.
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post #3 of 8 Old 08-11-2008, 09:21 PM
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You can get Dolby Digital 5.1 over SPDIF. It is compressed with a max bitrate of 640kbps. You will not get 8ch LPCM over SPDIF.

Here is a good article on audio:

http://forum.blu-ray.com/showthread.php?t=41820



Quote:
Originally Posted by Defcon View Post

Lost my posts from earlier so I'm asking again. Based on what I've read so far, I would like to confirm the following with the experts here :-

- there is no way to get 8ch LPCM over HDMI (TrueHD etc) due to Windows not having a PAP

- 780g and 790g only support 2ch LPCM over HDMI, Nvidia and Intel chipsets support 8ch

My receiver and tv do not have HDMI, I will use DVI+SPDIF.

- is it correct that with 780/790g, I am not guaranteed to get 5.1 over SPDIF?

- G45 does support this. DTS-I will convert all kinds of sources (like stereo) to 5.1 digital and HD audio will also be downsampled and be 5.1 over SPDIF.

- There is no way to output 5.1 LPCM as SPDIF does not support this.

If these are correct then my choices are limited to Nvidia/G45 as I do not want to get analogue audio out of the HTPC.

Thanks for your replies.

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post #4 of 8 Old 08-11-2008, 09:33 PM - Thread Starter
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renethx said this -
http://www.avsforum.com/avs-vb/showt...9#post13368419

Quote:


There are several HD-DVD/Blu-ray Disc movies, sources with multi-channel PCM, downloaded videos with multi-channel mpeg-1 audio, WMV-HD movies, or multi-channel WMA music, etc. that result in only 2-channel S/PDIF. The following is the statistics concerning BD movies based on the following database:

Unofficial Blu-ray Audio and Video Specifications Thread.

- If the main audio track is LPCM, then the probability is very low (< 3%). The majority include DD 5.1 as the secondary soundtrack.

- If the main audio track is DTS-HD Master Audio, the probability is 0% as DTS-HD MA includes DTS as the core stream.

- If the main audio track is Dolby TrueHD, the probability is high (> 50%). The number of movies with Dolby TrueHD is very small (only ~30 titles right now), but will surely increase in future. Spider-Man 3 is a typical example which includes LPCM 5.1 as the secondary audio so that you can't get surround sounds from S/PDIF without DTS Connect or DDL.

Spider-Man 3
Main Audio Track: Dolby TrueHD 5.1
Secondary Audio Track: LPCM 5.1 4.6Mb/s 16-bit
- One third of the BD movies still have DD 5.1 or DTS as the main soundtrack.

Conclusion

DTS Connect (or DDL) is a must if you want to get 5.1 S/PDIF from every source.

I know DD 5.1/DTS are over SPDIF. My question was whether 780/790g can do this for all sources, based on above quote I am not sure.
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post #5 of 8 Old 08-11-2008, 09:45 PM
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Quote:
Originally Posted by Defcon View Post

renethx said this -
http://www.avsforum.com/avs-vb/showt...9#post13368419



I know DD 5.1/DTS are over SPDIF. My question was whether 780/790g can do this for all sources, based on above quote I am not sure.

I have not heard of anything not being able to output S/PDIF in many years. It is a very basic format. The software product used to play back the film should be able to downconvert to S/PDIF.

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post #6 of 8 Old 08-11-2008, 10:05 PM
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Quote:
Originally Posted by Defcon View Post

renethx said this -
http://www.avsforum.com/avs-vb/showt...9#post13368419



I know DD 5.1/DTS are over SPDIF. My question was whether 780/790g can do this for all sources, based on above quote I am not sure.

Sorry, your question wasn't very clear to me. The interest in 780g was that it could possibly send Dolby TrueHD over HDMI, so it was confusing that you're asking about SPDIF support.

If you use SPDIF and the source that your playing has a DD5.1 or DTS track then that audio will be sent over SPDIF providing your media player sends it.

Unfortunately not all hi-def content has a DD5.1 track. Some hi-def (Blu-Ray/HD-DVD) content uses DD+ instead of DD5.1 as a low end track and this can not be sent over SPDIF (instead 2 channel LPCM is sent).
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post #7 of 8 Old 08-11-2008, 10:27 PM
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Quote:
Originally Posted by butters2006 View Post

Sorry, your question wasn't very clear to me. The interest in 780g was that it could possibly send Dolby TrueHD over HDMI, so it was confusing that you're asking about SPDIF support.

If you use SPDIF and the source that your playing has a DD5.1 or DTS track then that audio will be sent over SPDIF providing your media player sends it.

Unfortunately not all hi-def content has a DD5.1 track. Some hi-def (Blu-Ray/HD-DVD) content uses DD+ instead of DD5.1 as a low end track and this can not be sent over SPDIF (instead 2 channel LPCM is sent).

Well actually DD+ is a bad example because DD+ decoders have algorithms to convert down to DD with as little loss as possible and so you do indeed get a DD output from DD+ tracks.
Source

A better example would be a DTS-HD Master Audio or TrueHD track, these are all decoded into multi-channel LPCM which S/PDIF cannot transport. S/PDIF is limited to 2 channels of LPCM.
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post #8 of 8 Old 08-11-2008, 10:31 PM
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Quote:
Originally Posted by Defcon View Post

renethx said this -
http://www.avsforum.com/avs-vb/showt...9#post13368419



I know DD 5.1/DTS are over SPDIF. My question was whether 780/790g can do this for all sources, based on above quote I am not sure.

Now you're question is a bit ambiguious. Are you asking if all audio from your PC can be sent over S/PDIF? The answer is yes. Think of S/PDIF as a 2-channel raw (LPCM) digital audio transport. It can transport raw (or decoded) stereo audio, or it can transport pre-compressed audio tracks from DVDs (DD and DTS).

So anything that is decoded into sound inside the PC... i.e. playing an MP3, playing a game, etc. is now raw audio that Windows mixes and outputs. S/PDIF is only capable of outputting 2-channels of raw audio.
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