hi martin,

recently i have noticed that is some problem in time code behind vmix and FMLE. some unsync problems was detected here...

we use vmix up to 4h per service at our church and sometimes, i don`t know why, we see some audio drift or some delay at video.

regards,
melody
www.espiritosanto.cc

edit: we are currently using wowza on our server.

Hi James,

The vMix Virtual Audio Capture is designed to stay in sync, so if you are having issues with that option, could you send a sample video clip?

Thanks,

Martin
vMix

The only thing running on the system is vMix and 2 instances of FMLE (High speed, 500kbps and low speed 300kbps). I have had 4 instances of FMLE running, fed by vMix on my laptop before, and did not have sync issues - however I was not using a live source, just a video file. I'm trying to narrow the issue down, and I'm beginning to think it's just a frame rate issue. I will be running tests again later today, and will post the results then.

The file from last night, is posted here (350MB):

http://www.jamesdeane.co.../mars20120125-1800-2.flv

This is using Vmix video and Stereo Mix, as posted in my first post. the actual content starts at 32:12; we start our live stream about 30 minutes before a show starts.

I will run a test this afternoon using audio delay and the vMix virtual Audio, and send that over. The file we had where the audio was early, was corrupt, so I'll have to try and recreate that effect.

I appreciate the help.

I'm running my live test now, same show as last night from memory on the XDCAM deck. So far, so goo, as far as Sync goes, 10 minutes into the stream, using Virtual Audio Capture.

http://www.snwebcastcent...s/jamesdeane/flash-test/

(this will likely stop/start/die as I reset the stream and poke around)

I am getting a terribly scratchy sound, which is not on the source, or on the encoder - just on the final product. Need to see what that's about

Hi James,

As mentioned, if you are seeing a small delay with the vMix Virtual Audio Capture than that is expected for capture sources.
This can be offset by changing the Audio Delay setting in the settings for the external output so the final video in FMLE is correct.

You will need to use the vMix Virtual Audio Capture for your tests though as the "Stereo Mix" depends entirely on the sound card and is not very reliable.

Then, I will need to see if the audio drifts in the recording or has a constant delay, if the delay is constant it is easily fixed by changing the audio delay in the vMix settings.

Regards,

Martin
vMix

Thanks for all the information.

I solved the issue late last night, and I didn't get a chance to post until now.

The Decklink Audio is ONLY 48kHz; so I had to set all the audio card settings to 48kHz as well (default was 44.1). I am using the Stereo Mix as Audio source in FMLE.

I have been streaming for 90 minutes this morning with perfect sync.

Might be a good idea to allow 48kHz/44.1kHz switch for Virtual Audio.

I'm transferring the files from testing, but I will be posting the "scratchy" clip in about an hour.

I'm experiencing the same issue. I'm using a BM Deckling HD Extreme 3D, capturing audio/video in vmix with audio 48khz (no other options). I tried using Stereo Mix as well as the vmix audio capture. The sync keeps getting worse the longer it runs (in FMLE and vmix itself), it's probably the same issue as mentioned in this post.

Are you taking in JamesDeane's suggestion in the near future and offer 48/44.1 capability for your virtual audio capture? Or what is the recommended way to avoid this problem.

Thanks already for your answer

Scratchy

Set all your internal playback sound card settings to 48kHz - this should help.

Once we did that, and used the vMix virtual audio, we have not had a single issue with audio drift

I've been fiddling around with the machine, but I never got the drift to disappear completely. Here's some details about the machine:

Shuttle XPC SH67H7
i7 CPU
16GB Memory
SSD Drive
Realtek ALC 888 Sound
Intel GMA 3000
BM Decklink Extreme 3D
Windows 7 64 fully patched
FMLE / Drivers up to date

What I've done after:
- Disable Sound in Bios and use Virtual Sound Card
- Make sure sound devices are set to 48khz and capturing is happening at 48khz
- Chucked in an ATI graphic card
- Used an Osprey 700e capture card

Audio/Video inputs I use: HD/SD-SDI / various signals

The drift varied depending on the setup, the BM capture card with disabled Audio (just virtual sound card) brought me to a drift of about 100ms/hour, other setups had a slightly higher drift.

I do use the machine to encode with FMLE without vmix and experience no drifting audio.

The Blackmagic Drivers (9.5) installed virtual speakers, after disabling the audio in the machine's bios that was the only listed playback device. I did try to use virtual sound card from e2esoft as well, but the drift actually increased with that.

FMLE encoding with no audio drift was done with Decklink Video Capture / Decklink Audio Capture.