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Dolby Surround games; primitive surround sound on SNES 
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Joined: Sat 11 Apr 2009, 01:26:03

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Post Re: Dolby Surround games; primitive surround sound on SNES
quequotion wrote:
We need an SNES Dolby Surround test rom.

Why? Just use any game that supports the type of audio output for your tests...

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Fri 18 Apr 2014, 16:56:24
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Post Re: Dolby Surround games; primitive surround sound on SNES
Franpa wrote:
Why? Just use any game that supports the type of audio output for your tests...
Mostly to reduce the hassle of setting up the test for each iteration, but more importantly because the games don't feature specific tools for debugging Dolby Surround problems (play individual channels, for example). I have no means to verify that a matrix-encoded surround signal is reaching the amp.

For example, i'd like to know if:

-It actually works but doesn't sound much different than ordinary stereo (need to check all four channels).
According to wikipedia, Dolby Stereo ("Dolby Surround" for consumer products) has four channels: L, R, Center (50%L&R), Surround (90% phase inverted, 50%L&R) with the Surround channel given some delay by the decoder. By checking each individual channel, inside the emulator, one could very quickly determine if the signal is going through.

-The matrix encoding is being distorted or stripped at some point along the chain (spu code -> pulseaudio driver -> pulseaudio (alsa intel hda driver) -> spdif -> amp).
The most likely culprits being higan's pulseaudio driver and the amp in my opinion. The ideal way to test this would be to dump the audio output at each stage for analysis. That would require a higan debugger (or at least an stdout audio driver) to dump raw audio ouput, a means to dump the output from higan's pulseaudio driver (a dummy pulseaudio daemon?), a means to dump the output from pulseaudio before it goes to the amp (this may be possible), and means to dump the audio from the amp before it goes to the speakers (there's a headphone jack..).

-The digital amp doesn't support this analog matrix encoding format (need other samples of Dolby Surround).
Supposedly Prologic II is backward compatible. One or both of Cinema / Music should work, at least when set manually, but most of the audio comes out of the center channel in either mode, with only whispery L&R and no audible Surround.

Does anyone have conclusive proof that Dolby Surround on the SNES has actually been heard on anthing other than original hardware and a 1980s amp?

Sat 19 Apr 2014, 13:58:18
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Post Re: Dolby Surround games; primitive surround sound on SNES
Further testing:

The OpenAL driver will output a 5.1 channel stream from higan. Testing with Jurrasic Park and Star Ocean confirms audio only on the L and R channels in "Surround" modes. None of the other drivers produce more than two channel output; which pulseaudio then stretches around 5.1 channels (probably C&LFE 50%R+50%L, R, L, R(delayed), L(delayed); doesn't sound like any high or low pass redirection or dsp is going on).

Sat 26 Apr 2014, 13:08:28

Joined: Thu 02 Jun 2011, 01:36:41

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Post Re: Dolby Surround games; primitive surround sound on SNES
The SNES games probably don't make the best use of it. I don't think I have any SNES games that have surround support or I'd test it on my system. I did the digital audio output mod on my SNES so it should be the best chance to get good results.

Sat 26 Apr 2014, 15:01:46

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Post Re: Dolby Surround games; primitive surround sound on SNES
CaptainJistuce wrote:
jebbyderinger wrote:
Yeah it won't work as Dolby Digital but most receivers can manually be set to Dolby Pro-Logic I believe.

I think it's a mandatory part of DD licensing, is also supporting DPL something-or-other.

Quote:
I tried it out years ago with Zsnes and was surprised to discover it worked quite well for a LOT of Snes games in fact there were very few where you didn't get some sort of positive effect. Despite very few games officially being endorsed by Dolby there is some fairly convincing surround sound in others.

You mean the ZSNES surround toggle?

We're talking about games that ACTUALLY have surround sound in them, not ZSNES hacking the audio to make sound come out the back.


DD is different than Dolby Surround though. DD is Dolby Digital which the SNES doesn't support since it can in no way output a digital audio signal (unless hacked). Also I didn't use ZNES surround I took the stock stereo signal over RCA cables into a Marantz 6.1 receiver and switched it to Dolby Pro Logic (I believe I also tried S/PDIF). I've tried this with real SNES hardware & N64 as well. I've tried a number of games including those branded "Dolby Surround" like Jurassic Park 1 & 2 and Super Turrican 2. After trying these games I thought I'd try others. Some games have zero benefit from enabling Dolby Pro Logic but what I was surprised to discover was that many games not officially endorsed by Dolby supported some sort of believable separation. Whether this was done intentionally or is just chance based on how the technology works I have no idea but there were definitely titles that benefited and those that didn't. It was years ago now and I had planned on creating a list but I've forgotten which games were worth trying and which weren't.

quequotion wrote:
Further testing:

The OpenAL driver will output a 5.1 channel stream from higan. Testing with Jurrasic Park and Star Ocean confirms audio only on the L and R channels in "Surround" modes. None of the other drivers produce more than two channel output; which pulseaudio then stretches around 5.1 channels (probably C&LFE 50%R+50%L, R, L, R(delayed), L(delayed); doesn't sound like any high or low pass redirection or dsp is going on).


I'm not sure this will get you anywhere since the SNES doesn't do any surround sound processing, it's just a pure stereo signal that Dolby Pro Logic extrapolates a 4.0 signal from on the receiver end. If you could somehow run "Dolby Pro Logic" on the stereo signal coming from Higan and before outputting 5.1 by the Open AL driver you would be able to capture the differences in the channels.

Caedhros wrote:
The SNES games probably don't make the best use of it. I don't think I have any SNES games that have surround support or I'd test it on my system. I did the digital audio output mod on my SNES so it should be the best chance to get good results.


The digital audio output still won't give you Dolby Digital but it will give you clean PCM audio which you should still be able to enable Dolby Pro Logic on. Everyone needs to understand that from the SNES -> Gamecube the only way to get Surround Sound is with a receiver that supports Dolby Pro Logic. You can't hack in a SPDIF output and get anything other than a stereo signal.

Tue 06 May 2014, 20:35:08
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Post Re: Dolby Surround games; primitive surround sound on SNES
Dolby Digital does not merely require a digital output, but also an AC3/DD encoder of some sort.

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Wed 07 May 2014, 00:34:59

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Post Re: Dolby Surround games; primitive surround sound on SNES
jebbyderinger wrote:
The digital audio output still won't give you Dolby Digital but it will give you clean PCM audio which you should still be able to enable Dolby Pro Logic on. Everyone needs to understand that from the SNES -> Gamecube the only way to get Surround Sound is with a receiver that supports Dolby Pro Logic. You can't hack in a SPDIF output and get anything other than a stereo signal.


Correct, and that was the idea behind me doing the mod on my system. I know very well it won't magically give AC3 audio.

On a related note, I looked into doing a similar mod on N64, but since the games generate sample rates all over the place, it won't work reliably, as most SPDIF receivers only go down to ~32KHz, and many N64 games go well under that.

Wed 07 May 2014, 04:17:40

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Post Re: Dolby Surround games; primitive surround sound on SNES
jebbyderinger wrote:

DD is different than Dolby Surround though. DD is Dolby Digital which the SNES doesn't support since it can in no way output a digital audio signal (unless hacked).

Quite so. What I was saying, which I thought was abundantly clear, is that it's not MOST Dolby Digital recievers that also do Pro-Logic decoding, but ALL of them. Because Dolby won't LET people do DD without also doing Pro-Logic, so digital recievers handle analog surround just fine.


Quote:
Also I didn't use ZNES surround I took the stock stereo signal over RCA cables into a Marantz 6.1 receiver and switched it to Dolby Pro Logic (I believe I also tried S/PDIF). I've tried this with real SNES hardware & N64 as well. I've tried a number of games including those branded "Dolby Surround" like Jurassic Park 1 & 2 and Super Turrican 2. After trying these games I thought I'd try others. Some games have zero benefit from enabling Dolby Pro Logic but what I was surprised to discover was that many games not officially endorsed by Dolby supported some sort of believable separation. Whether this was done intentionally or is just chance based on how the technology works I have no idea but there were definitely titles that benefited and those that didn't. It was years ago now and I had planned on creating a list but I've forgotten which games were worth trying and which weren't.
It was chance. Pro-Logic includes surround "faking" for pure stereo content.

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Wed 07 May 2014, 07:46:57

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Post Re: Dolby Surround games; primitive surround sound on SNES
King Arthur's World is another one with Surround in it, and it has a sound test for instant gratification.

Tue 13 May 2014, 15:06:21
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Post Re: Dolby Surround games; primitive surround sound on SNES
JILost wrote:
King Arthur's World is another one with Surround in it, and it has a sound test for instant gratification.
Do you mean the "Presented in Dolby Surround" wha~~~ wha~~~ wha~~~ ?

With digital 5.1 output, I can hear it pan around from left to right all the way to the rear speakers, and pavumeter shows it panning pretty far, but it doesn't really pan from front (left, right) to back (surround) as I can hear, nor does pavumeter show that (which may be normal).

UPDATE: I tried another test with digital stereo output. Switching the receiver to either ProLogic II option manually, I was again able to hear the sound pan left and right on the rear speakers, but somewhat differently than with 5.1 output. The audio seems to be stretched evenly between each front and rear speaker, so it moves from side to side.

This game has a Sound menu as well, which like all other game sound menus of the time is primarily for entertainment; it has a switch for surround and it can play a list of bgm and sfx but only in stereo.

What would be useful is an in-game surround debug menu that would output samples encoded for the Left, Center, Rear, and Surround channels on queue... perhaps I will have to learn to program SFC games...

EDIT: Added some details.


quequotion


Sun 18 May 2014, 15:38:40
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Post Re: Dolby Surround games; primitive surround sound on SNES
jebbyderinger wrote:
If you could somehow run "Dolby Pro Logic" on the stereo signal coming from Higan and before outputting 5.1 by the Open AL driver you would be able to capture the differences in the channels.


This may be the point of the whole thread; even if higan (it's spu and audio driver), does faithfully output the matrix-encoded stereo signal it may still be lost in the transition to digital output in pulseaudio.

I've tested both digital stereo (which should still be the original stereo signal when decoded) output and digital 5.1 AC3 (which probably needs some Dolby Surround -> discrete channels transcoding in pulseaudio) output. With digital stereo, the "Presented in Dolby Surround" sound effect in King Arthur's World makes no use of the rear speakers, unless ProLogic II is enabled manually, and then it sounds like expanded stereo. With digital 5.1, it pans left and right all the way around, but doesn't seem to make use of the surround channel independently from the front channels.

UPDATE: I'm beginning to think it may actually work with digital stereo output from pulseaudio and the receiver set to Prologic II (Cinema and Music sound the same...) but the difference between Dolby Surround and a stereo signal stretched around 5.1 channels is very little, aside from the subwoofer. Still, it would be nice to have conclusive proof.

Sun 18 May 2014, 16:13:33

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Post Re: Dolby Surround games; primitive surround sound on SNES
Emulation should give exactly the same effect as long as the audio is generated the same as the real console. Prologic will never give the same level of channel separation as discrete 5.1 audio. Original Prologic was only designed for right/center/left/rear setup. Prologic2 is supposed to to the full 5 channel setup, but still not as good as discrete. In the early 90's when this stuff was made, they probably didn't even have a surround setup at the dev studio to test it.

On newer stuff it's different though. Rogue Squadron 2 on Gamecube was made with Prologic2 in mind, and it works pretty good there last time I tried it(almost 10 years ago).

Sun 18 May 2014, 18:42:33
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Post Re: Dolby Surround games; primitive surround sound on SNES
Caedhros wrote:
Emulation should give exactly the same effect as long as the audio is generated the same as the real console. Prologic will never give the same level of channel separation as discrete 5.1 audio. Original Prologic was only designed for right/center/left/rear setup. Prologic2 is supposed to to the full 5 channel setup, but still not as good as discrete. In the early 90's when this stuff was made, they probably didn't even have a surround setup at the dev studio to test it.

On newer stuff it's different though. Rogue Squadron 2 on Gamecube was made with Prologic2 in mind, and it works pretty good there last time I tried it(almost 10 years ago).
Yeah, I'm thinking running Dolby Surround encoded audio through a ProLogic II decoder doesn't really improve anything either; it certainly doesn't activate the LFE (since nothing's encoded for it of course).

The best thing to do would be analog matrix encoding detection and discrete channel upmix in either alsa or pulseaudio...


quequotion


Mon 19 May 2014, 05:15:00

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Post Re: Dolby Surround games; primitive surround sound on SNES
Be aware that games that were never intended to be surround can have amazing separation, in part due to the simplicity of old video game music

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Mon 19 May 2014, 06:40:53
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Post Re: Dolby Surround games; primitive surround sound on SNES
panzeroceania wrote:
Be aware that games that were never intended to be surround can have amazing separation, in part due to the simplicity of old video game music

Yet another reason why I don't trust my ears as a measure of whether or not surround sound is working; unless I can hear sound from the rear speakers explicitly.

Mon 19 May 2014, 07:23:10
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