Question / Help Gradual Audio/Video source desync (NOT an El Gato product)

[EDGAR_SEC]

First of all, this is not an El Gato device. It is an internal PCIe capture card (Datapath VisionDVI-DL).

I'm having this odd issue where an OBS's audio source becomes desynced from the video source slowly over time. At the start of a stream, everything is lined up properly. However, after around 2 hours, my viewers report the audio is 500-1000ms behind the video.

This is a dual PC setup with a separate mixer. The capture card in question is a Datapath VisionDVI-DL (which has no audio input of its own). The game audio is mixed in a Mackie DL1608 mixer and sent to the Line In on the motherboard of the stream PC. In OBS, I would then add my (Global) capture source, right click on the added source, and then select my Line In under "Audio Input Device." I do not have a "Desktop Audio Device" enabled, so this is the only way audio comes into the stream. After researching this issue, I tried enabling and setting the "Use Video Buffer" to 0 ms with no improvement at all. The log linked at the end of this post is with this 0 ms buffer set.

It seems I can reset the sync and fix it if I right click on the source, switch the audio from, "Output audio to stream only," to "Output audio to desktop," then save and close the window. Then I would right click on the source again and set "Output audio to stream only" again to fix the sync issue. However, the problem crops up again over the next 2 hours.

I've done a clean re-install of all the video capture device drivers (and this whole PC had Windows 10 recently clean installed on it after a reformat).

According to the OBS log, out of a total 544477 frames over last night's ~3 hour stream, only 1261 of those frames (0.2%) were late/skipped/dropped. OBS's log also seems to not recognize I have a second Xeon CPU installed as well.

I have also verified it is not the mixer introducing the gradual desync since the audio from that is fed into a separate headphone amp (via Y-cables) and I don't experience any desync in my headphones.

Any other troubleshooting ideas on how to fix this issue? Thanks

Log: http://pastebin.com/ix0mq13c

 

[TechnicalMonkey]

Since you have such a kick-ass streaming PC---damn e5-2699v3?!?, and you allegedly have 2 of them?!? (I'm just looking at what the log says don't hurt me :p), I am surprised that you are not trying to go for the holy grail of slower or veryslow presets (slow has been shown time and again to be a waste,) I would first make sure that I get all of my ducks in a row. I'll split this up in 2 short paragraphs with a conclusion.

I would say before getting into fixing the issue, I would make sure that I do these 2 things before anything else. First, make sure you use the rgb24 fourcc configuration. It helps a lot with the picture quality. Making sure you get the most out of your card. There post in here that go over why it is better than any YUV fourcc you can use right now. Second, I would check that you disable Aero checked for good performance measure, or better yet use windows basic mode so that you can have all that processing mostly if not all for OBS. It will greatly enhance the performance of this otherwise SUPREMELY MONSTER BOX!!!

The fixes that I would recommend to a fine intel user as your self with a BEAST GPU to render your stages would be 1 to use ThrottleStop. It works on Intel CPUs and is made to allow you to disable features that may or may not be easily available in your BIOS/UEFI (from here on I'll just call it BIOS) Things like C States Turboboost PROCHOT and others that may interfere with your performance. even causing frame drops, Just set it to take away all of the stuff that may alter the speed at which your CPU/s run at without having to go into the bios and shutting them off (if they are available there.) Second would be either to get MSI Afterburner or EVGA Precision X whatever the latest version is and enable KBoost. This feature is so that the GPU always runs at its set speed. In this case you just want to run your GTX 980 at it's full stock speed, and never slow down. Both of these programs should be running in the background minimized.

Now that I have that primer out of the way I would say that there are 2 things that I would recommend, and both I would use in your case in which I would suspect throttling and it might not be apparent, and I can be off base with these suggestions. However, I do feel that this subject is not talked enough, but if you feel that neither of these recommendations are not working for you, they are easily reversible. I would like to see what a stream on dual e5-2699v3 CPUs look like even if OBS seems to only recognize only one ATM. What is your channel, so I can check it out. Sorry if I posted to much, but I felt that it was necessary.

 

[EDGAR_SEC]

Thanks for the response! I'll definitely test out some of your suggestions since I'm striving to achieve the best picture quality on Twitch. :)

I don't think enabling KBoost would do much for me since according to Jim, the GPU in OBS is only used to compose the scene. Even when I was running a 5960X in my older stream PC, a GTX 750 Ti would never ramp up more than 30% usage under OBS load.

No idea why the CPU might be throttling since total usage on the system with the current settings I'm using to iron out kinks in this new build (1080p/60fps/Medium) show less than 17% CPU usage while streaming. I highly doubt thermal throttling since the CPUs are under water and haven't had any sort of Vcore increase applied from stock. I was able to get a 104 BCLK OC on them though.

The reason I never went to the slower presets yet is due to the experience I (and other users I've talked to) have where OBS 32-bit and 64-bit ignore the resources available on the CPU: https://obsproject.com/forum/threads/36-core-stream-pc-and-memory-crashes.36718/#post-166447

In fact, here is a screenshot showing what happens (all this load is only on CPU0 while CPU1 remains idle):

It seems I have a terrible habit of running into issues that no one ever has a solution for. This is the price of being on the bleeding edge. :|

Anyway, my twitch url is: http://www.twitch.tv/edgar

...and yes, I'm pretty sure it is a dual Xeon rig ;)

 

[TechnicalMonkey]

KBoost would not run up your percentages, just the working frequency if the 980x is used to running at low speeds (like when it is NOT gaming.) So you would not see a higher percentage on GPU, but a lower percentage. The whole idea for the 2 apps is to make sure that you can run at the fastest clock speed with any processing load not just the heaviest. Running slow or throttling from low speed to other medium speeds may cause these drops to happen. It certainly did with me.

 

[FerretBomb]

Just a quick mention, DVI absolutely DOES support audio. And the DVI-DL does not carry the 'does not support audio' notation on the Datapath website that the E2(S) does. It's entirely possible that you could send your audio over the capture card, and keep everything in-sync that way. Not sure if you're using your mixer for things other than the game audio though.

Entirely possible that your sound card and cap card may be falling off-timestamp relative to one another. I was having this issue with my system, as I'd tweaked the CPU frequency a bit in a way the system REALLY didn't like; presented as a slow drift replaced with microstuttering when 'use video timestamps as a base for audio' was checked.
Here's the link Jim sent me, that nailed the problem down in my case: http://forum.exkode.com/index.php?topic=324.0
Run it for 5 minutes, should be seeing no more than 20ms offset, preferably single-digit. I was into the high hundreds of ms.

If you use a microphone plugged into the streaming PC, and a webcam, does your lip-sync drift similarly, or just the game audio? Have you tried setting your Line In as your System (or Mic) audio device in Settings rather than in the source properties? Rather than leaving buffering at 0, try setting it to 1. It's fixed a few issues in the past that persisted otherwise.

Oh, and DO NOT DISABLE AERO. Please don't tell people to turn it off, TechnicalMonkey. It's really bad advice when it comes to OBS, as OBS can use the Aero buffers to accelerate captures significantly. Even if it didn't, the performance hit is so small on a non-potato PC that it's not worth mentioning.
This was valid back in the Vista days. Not so much any more.

 

[EDGAR_SEC]

Just a quick mention, DVI absolutely DOES support audio. And the DVI-DL does not carry the 'does not support audio' notation on the Datapath website that the E2(S) does. It's entirely possible that you could send your audio over the capture card, and keep everything in-sync that way. Not sure if you're using your mixer for things other than the game audio though.

The microphone, Gaming PC, and Auxiliary all feed into the mixer. The mixer then outputs via XLR cables to a J Iso (http://www.radialeng.com/jisoproiso.php) which then has a 3.5mm cable coming out of it plugged into the Line In on the Stream PC's motherboard. I'll poke around in the Datapath config program and see if I can hopefully capture audio directly through it the same way it works on those Micomsoft cards.

Entirely possible that your sound card and cap card may be falling off-timestamp relative to one another. I was having this issue with my system, as I'd tweaked the CPU frequency a bit in a way the system REALLY didn't like; presented as a slow drift replaced with microstuttering when 'use video timestamps as a base for audio' was checked.
Here's the link Jim sent me, that nailed the problem down in my case: http://forum.exkode.com/index.php?topic=324.0
Run it for 5 minutes, should be seeing no more than 20ms offset, preferably single-digit. I was into the high hundreds of ms.

EDIT: I'm running this on the stream PC right now. I'll report back with my findings.

If you use a microphone plugged into the streaming PC, and a webcam, does your lip-sync drift similarly, or just the game audio? Have you tried setting your Line In as your System (or Mic) audio device in Settings rather than in the source properties? Rather than leaving buffering at 0, try setting it to 1. It's fixed a few issues in the past that persisted otherwise.

I don't use a webcam, but I have every single audio source (including the mic) directly plugged into the mixer. I'll try setting the buffer to 1ms to test it out.

Oh, and DO NOT DISABLE AERO. Please don't tell people to turn it off, TechnicalMonkey. It's really bad advice when it comes to OBS, as OBS can use the Aero buffers to accelerate captures significantly. Even if it didn't, the performance hit is so small on a non-potato PC that it's not worth mentioning.
This was valid back in the Vista days. Not so much any more.

I still have Aero enabled and figured it would be such an infinitesimally small performance hit on the resources for this Stream PC anyway. ;)

Also Ferret, thank you for another quality post!

 

[EDGAR_SEC]

So @FerretBomb I ran that program you mentioned for a whole 4h30min stream and the offset for the audio Line In was -7 milliseconds. This time, I also used the 64-bit version of OBS (where the log also shows it only recognizes one CPU, but that's another story).

Interestingly enough, if you do a Ctrl+F for:

Audio timestamp for device 'Datapath VisionDVI-DL Video 01' was behind target timestamp by

you can see several instances in the log file where it shows the audio gets delayed by 490ms, or 300ms, or anything off timestamp. Every single time my viewers noticed, I made sure to do the right click and output source audio to desktop then reversing it back to stream only. After a few minutes, audio would become desynced again.

I also tried it with a different input line: a PCIe sound card instead of the Line In I had been using on the motherboard. I still had the same issues.

Anyway, here is the latest log from my 4.5hr stream just now. Hopefully someone can help me solve this. Thanks!

New log: http://pastebin.com/FaQLxUn0

 

[FerretBomb]

Ah, then the problem I was having isn't the one you are.

Have you tried setting your line-in as the Mic audio device, and setting the capture card to Disabled?

The error seems to point at a problem with your sound card though, given that it's falling behind in timestamps. Checked for newer drivers (I assume you installed the mobo's driver package, and aren't using the Windows built-ins)? Tried grabbing a cheap USB sound card to test?

Just a sanity-check; which version of Windows 10 are you using? I'd assume it to be Pro or better (given that you said it worked in XSplit). If it's Home though, MS locked off multi-CPU capability (but possibly not recognition; their posted info is very contradictory).

If I were in your shoes and the system is a new build, I'd consider a nuke-and-pave. Full format, clean installs, drivers and OBS only. Possibly a rollback to Win7 or 8 if I had a spare copy lying around, to rule out an early-adopter teething issue with 10 (heck knows I've seen enough of them at work). If it still presented, I'd be looking at the motherboard itself with a hairy eyeball. They can get out the door with subtle issues.
Have you tried running under OBS-MP? Does it have the same fall-behind issue there? Just trying to come up with stuff you could try on your end, before possibly needing to ask @Jim or one of the other devs... they have a lot of stuff on their plate, even if catching weird edge-cases can help point out potential code issues if they're OBS-side.

 

[EDGAR_SEC]

Have you tried setting your line-in as the Mic audio device, and setting the capture card to Disabled?

That will be the next thing I test tomorrow.

The error seems to point at a problem with your sound card though, given that it's falling behind in timestamps. Checked for newer drivers (I assume you installed the mobo's driver package, and aren't using the Windows built-ins)? Tried grabbing a cheap USB sound card to test?

I'm running the latest mobo and integrated motherboardaudio drivers. :) I had the same issue when using a PCIe soundcard though. I'll pick up a cheap USB sound card and test it with that next.

Just a sanity-check; which version of Windows 10 are you using? I'd assume it to be Pro or better (given that you said it worked in XSplit).

Windows 10 Pro. I've run Cinebench as well to verify all 36 cores/72 threads can be loaded.

If I were in your shoes and the system is a new build, I'd consider a nuke-and-pave. Full format, clean installs, drivers and OBS only. Possibly a rollback to Win7 or 8 if I had a spare copy lying around, to rule out an early-adopter teething issue with 10 (heck knows I've seen enough of them at work). If it still presented, I'd be looking at the motherboard itself with a hairy eyeball. They can get out the door with subtle issues.

This will definitely be on my list of things to try out.

Have you tried running under OBS-MP? Does it have the same fall-behind issue there? Just trying to come up with stuff you could try on your end, before possibly needing to ask @Jim or one of the other devs... they have a lot of stuff on their plate, even if catching weird edge-cases can help point out potential code issues if they're OBS-side.

Wish I could run multiplatform, but it doesn't accept a canvas larger than 1920x1080 as I have outlined in a thread I posted a few weeks ago regarding OBS Classic not utilizing the second CPU. I'll try to work something up to see if I can get Multiplatform to function.

I also plan on using a Micomsoft capture card to test. Thanks again for the other great suggestions.

 

[FerretBomb]

Actually, on looking through the logs again... have you tried it without VB-Audio loaded?

Sounds good; what res are you trying to run at by the way? Log seemed to indicate 1080p. The SC512 does top out at 1080p@60 too, unless you're planning to use an overlay to fill extra space on a 1440+ canvas? Should help rule out the VisionDVI-DL as the culprit though. Also have to admit curiosity about the 61fps rate from the log; just proof-of-concept?

 

[TechnicalMonkey]

I guess things might have changed... I will compare running with Aero on again, or maybe I confuse it with the transparency option? All I know is that I still get huge gains in Switching/Mixing when I'm not using this transparency, and have the GPU running at its stock speed, not when the GPU is trying to decide wether it wants to run at the lowest to the highest and everything in between CONSTANTLY.

I use a set up that is more like one computer just for capturing and mixing the sources into said stages much like a real AV production switch, and a second PC just solely for the sake of encoding and sending to the channel of my choice. In the future I hope to push this more by streaming uncompressed/compressed RGB 4:4:4 (if possible) to a the streaming box running NGINX with x264 and transcode on the fly to an ideal rate and quality for streaming. I'm surprised that you are not looking at this kind of option as you might be able to get higher quality from your stream.

I'll stop here and see what you guys think.

 

[EDGAR_SEC]

Actually, on looking through the logs again... have you tried it without VB-Audio loaded?

Yes, I have tried it with VoiceMeeter disabled. I don't think it would matter too much anyway since OBS on the stream PC doesn't use any of the VoiceMeeter sources as an input or output in any shape or form.

Sounds good; what res are you trying to run at by the way? Log seemed to indicate 1080p. The SC512 does top out at 1080p@60 too, unless you're planning to use an overlay to fill extra space on a 1440+ canvas? Should help rule out the VisionDVI-DL as the culprit though.

Trying to output 1080p. I was just setting a 1080p canvas (instead of a 1440p canvas) to test proof of concept and to help stamp out issues in both OBS1 and OBSMP. I just need to find a console game to stream for a few hours. Too bad none currently pique my interest.

Also have to admit curiosity about the 61fps rate from the log; just proof-of-concept?

Well, in similar I-find-odd-bugs-or-limitations fashion, I experienced this issue on the old 5960X stream PC (and probably still on the new stream PC): https://obsproject.com/forum/thread...-missed-frames-preventing-fluid-motion.21144/

I set a 61fps capture because I was thinking that jitter might just be capture signal aliasing due to running Vsync in game. Needless to say, this didn't solve the problem either. ;)

---

I actually picked up a USB soundcard (Soundblaster Omni 5.1) and the audio desync issue persists, yet with a one hour timeframe now before noticeable desync occurs. This is an improvement from the ~30min period with the on-board audio however.

In the VOD from last night, you can see where the audio desync occurred here: http://www.twitch.tv/edgar/v/19210810?t=1h40m09s

At the end of the stream, you can see the desync has decreased: http://www.twitch.tv/edgar/v/19210810?t=2h07m00s

Now that I think about it, I used to also have these gradual desync issues over time with my old 5960X stream PC (completely different machine) with any capture card that didn't have it's own audio input. At the time I was still using OBS1 64-bit and 32-bit (with both the Datapath or the Micomsoft). However, the desync would take maybe 4 hours before it would be noticeable.

 

[FerretBomb]

Yes, I have tried it with VoiceMeeter disabled. I don't think it would matter too much anyway since OBS on the stream PC doesn't use any of the VoiceMeeter sources as an input or output in any shape or form.

Ah, OK. Was suggesting it as I've had programs that weren't in use, but still managed to monkey with hardware and software, even if they weren't active. Figured VM might have been hooking the audio hardware in the background and triggering an aggregating wait-state delay somehow. Tried it turned off, or with VM entirely uninstalled?

Trying to output 1080p. I was just setting a 1080p canvas (instead of a 1440p canvas) to test proof of concept and to help stamp out issues in both OBS1 and OBSMP. I just need to find a console game to stream for a few hours. Too bad none currently pique my interest.

Kind of a dearth of good ones lately, yep. One of my go-to games for testing is Super Stardust Ultra, if you like twin-stick shooters. Lots of on-screen action, with 3D mode support for the future. Journey HD has a lot of subtle stuff.

Well, in similar I-find-odd-bugs-or-limitations fashion, I experienced this issue on the old 5960X stream PC (and probably still on the new stream PC): https://obsproject.com/forum/thread...-missed-frames-preventing-fluid-motion.21144/

I set a 61fps capture because I was thinking that jitter might just be capture signal aliasing due to running Vsync in game. Needless to say, this didn't solve the problem either. ;)

I've run into the same problem. It seems to be an issue with direct OBS capture more than anything else; not sure why, but it happens with every video card I have (I've not tried it with the Datapath Native source plugin as it seems to have broken). I've been using a workaround though... just capturing with AmaRec 2.20c (2.31 has an audio warping problem) and fullscreening it, then capturing that with a DWM Game Capture. Improves the smoothness greatly. Here's an example running 720p@60 with this method: http://www.twitch.tv/ferretbomb/v/18161479
OBS-direct looks herky-jerky as heck.

I actually picked up a USB soundcard (Soundblaster Omni 5.1) and the audio desync issue persists, yet with a one hour timeframe now before noticeable desync occurs. This is an improvement from the ~30min period with the on-board audio however.
...
Now that I think about it, I used to also have these gradual desync issues over time with my old 5960X stream PC (completely different machine) with any capture card that didn't have it's own audio input. At the time I was still using OBS1 64-bit and 32-bit (with both the Datapath or the Micomsoft). However, the desync would take maybe 4 hours before it would be noticeable.

Interesting. That kind of makes me wonder about VM again, but it's mostly brainstorming. Did you have that installed on the older system too? Something that's messing with all audio devices on the system.
Yeah, keeping audio sync across sources is why my Datapath E2 isn't being used; just sitting in the machine and waiting until I grab an HDMI camcorder or DSLR with video mode and HDMI. Less of a pressing issue when you already get to deal with cam/mic sync.

 

[EDGAR_SEC]

Ah, OK. Was suggesting it as I've had programs that weren't in use, but still managed to monkey with hardware and software, even if they weren't active. Figured VM might have been hooking the audio hardware in the background and triggering an aggregating wait-state delay somehow. Tried it turned off, or with VM entirely uninstalled?

Tried with is disable/off and with the drivers uninstalled. No improvement.

I've run into the same problem. It seems to be an issue with direct OBS capture more than anything else; not sure why, but it happens with every video card I have (I've not tried it with the Datapath Native source plugin as it seems to have broken). I've been using a workaround though... just capturing with AmaRec 2.20c (2.31 has an audio warping problem) and fullscreening it, then capturing that with a DWM Game Capture. Improves the smoothness greatly. Here's an example running 720p@60 with this method: http://www.twitch.tv/ferretbomb/v/18161479
OBS-direct looks herky-jerky as heck.

Yup! No one ever seemed to find a fix for this one either. Last I checked the Datapath Plugin didn't really work with Multiplatform or OBS64bit either. On top of that, it wouldn't allow you to assign an Audio device to it like you could if it was just added as a regular capture device.

Interesting. That kind of makes me wonder about VM again, but it's mostly brainstorming. Did you have that installed on the older system too? Something that's messing with all audio devices on the system.
Yeah, keeping audio sync across sources is why my Datapath E2 isn't being used; just sitting in the machine and waiting until I grab an HDMI camcorder or DSLR with video mode and HDMI. Less of a pressing issue when you already get to deal with cam/mic sync.

Yes, it happened before Voicemeeter was ever installed (8 month period) and after Voicemeeter was installed (6 month period).

---

Just finished another stream, this time with VM disabled. (OBS Legacy 64-bit)

At the start of the stream, it is all synced up: http://www.twitch.tv/edgar/v/19341805?t=30s

Halfway through, it's offset again by ~200ms: http://www.twitch.tv/edgar/v/19348692?t=49m55s

It was still ofset around ~200ms at the end of the stream, but my VOD was muted, so I can't really show it.

I also was able to get OBSMP (64-bit) to not crash. I opened up one of the logs and saw that it still would only recognize one CPU and was only showing 18 cores and 36 threads. So I'm guessing it's definitely something with the way OBS (even the MP) is written since those cores are recognized and used in other programs like Cinebench. Hopefully Jim and the rest of the wizards can figure out why it doesn't show up even in the MP version.

Looks like I might have hit a dead end in troubleshooting. Any suggestions on what the next step might be? I'm predicting using a different capture device (and assigning audio to it) will produce the same results. Thanks again for all the help so far.

I'm considering installing GameShow (that new streaming program from Telestream, the makers of WireCast) and seeing if the second CPU is recognized in that.

 

[MrTeaTime]

Bit unrelated but i dont come across dual xeon systems that often, especially people using them in game context environments.

You tried firing up some games on that beast and seeing how it performs compared to the main pc?

Also whats the quality like when streaming.

 

[EDGAR_SEC]

Bit unrelated but i dont come across dual xeon systems that often, especially people using them in game context environments.

You tried firing up some games on that beast and seeing how it performs compared to the main pc?

Also whats the quality like when streaming.

Never bothered to play any games on it since the gaming PC is a 5960X with quad Titan Xs. Why would I ever think the Stream PC could keep up?

For stream quality, you could just look at one of the VOD links above or this link: http://www.twitch.tv/edgar/v/19348692?t=1h35m15s

Keep in mind that stream just linked was done with pretty modest settings on the stream PC since I'm trying to troubleshoot all sorts of issues right now. It would look much better if I pushed the stream pc harder.

 

[MrTeaTime]

Never bothered to play any games on it since the gaming PC is a 5960X with quad Titan Xs. Why would I ever think the Stream PC could keep up?

For stream quality, you could just look at one of the VOD links above or this link: http://www.twitch.tv/edgar/v/19348692?t=1h35m15s

Keep in mind that stream just linked was done with pretty modest settings on the stream PC since I'm trying to troubleshoot all sorts of issues right now. It would look much better if I pushed the stream pc harder.

Yeah i had a lookie at your stream, i take it your running audition or some other software that can do real time noise removal on the stream pc to strip background noise from the mic line.

Either that or you're some tech wizard who knows a hardware solution that i should pick the brains of ;) haha.

But yeah good shit, cant wait to see what happens when you manage to fix this cpu limit bs.

 

[Boildown]

Just a note that I use a DVI-DL and haven't had any audio-video sync issues. If you count the time in which I had a E1S Datapath card, I haven't had this problem in around 2 years of use.

The Datapath native drivers only work with the original OBS in 32-bit mode, they were never written for 64-bit and the author seemed to indicate he wasn't interested in re-doing them for MP. I use these drivers and have my 1080p screen duplicated, sending 120Hz to both my gaming monitor and the DVI-DL.

I run Windows 7 Pro on my encode PC, which is "just" an i7 2600k, with a mild OC to 4.3GHz. I keep Aero off in Windows and off in OBS. Audio is just my surround front right and front left (using a Y-splitter cable) plugged into the Line In of a Soundblaster card. GPU is a GTX 750Ti.

I routinely did encodes of over 3 hours straight, I think I did a few of over 8 hours before, playing Planetside 2. Haven't had this problem. Full specs on my Twitch page in my sig.

I think the biggest difference between our two setups is the Windows version. There's no reason I know of why you should have Windows 10 on your encode PC. Windows 10 should be classified as an experimental OS. In reality it probably should have a Windows Server installation, but failing that, Windows 7 is just fine.

I would put Windows 7 on it and simplify the setup by bypassing the mixer, just put audio right into the line in of your Soundblaster card, and see if the problem goes away. If the problem goes away with a barebones setup, then add things in one at a time, testing at each step, until the problem comes back, at which point you know where the fault lies.

 

[EDGAR_SEC]

Yeah i had a lookie at your stream, i take it your running audition or some other software that can do real time noise removal on the stream pc to strip background noise from the mic line.

Nope, all hardware based. All six of my inputs have one of these per input with appropriate ground/lift/pad: http://www.sweetwater.com/store/detail/ProAV2

From the mixer, the sound is then output into one of these which lowers the level an acceptable amount for a PC soundcard: http://www.bhphotovideo.com/c/product/536104-REG/radial_engineering_r800_1025_j_iso_stereo_4_db.html

If I crank the volume all the way up, there is literally no hum or distortion. You can't even tell the speaker/headphones are on. It's like sound magically comes out of nowhere.

The mixer (a Mackie DL1608) has realtime gating, EQ, compression, etc. Great mixer, only "problem" is that you can only control it with an iPad: https://youtu.be/ylR33R-i3sg?t=56

 

[EDGAR_SEC]

I think the biggest difference between our two setups is the Windows version. There's no reason I know of why you should have Windows 10 on your encode PC. Windows 10 should be classified as an experimental OS. In reality it probably should have a Windows Server installation, but failing that, Windows 7 is just fine.

The old stream PC was Windows 8. The one before that (a 4770K) was Windows 7 (I already had the Datapath card then). Same issue persisted when I look back at some of my old VODs (I've locally recorded every single one of them). Seems the older the stream PC, the longer it could
go before noticeable desync.

Windows 7 also has a RAM limit of 192GB. We could debate the merits of Windows Server 2012, but that's a topic for a different thread.

Simplify the setup by bypassing the mixer, just put audio right into the line in of your Soundblaster card, and see if the problem goes away. If the problem goes away with a barebones setup, then add things in one at a time, testing at each step, until the problem comes back, at which point you know where the fault lies.

Removing the mixer from the chain would be pointless as far as troubleshooting goes since I can monitor the Mixer output and everything on it stays in sync. The only audio passed into the stream PC is via the Line In on the Soundblaster (or mobo) straight from the mixer.

This desync doesn't occur for me if I use Xsplit. If it doesn't pop up either when I try it with GameShow this weekend, I'm going to be pretty certain it's OBS itself.