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Author Topic: Latency "creeping"  (Read 727 times)

Stephen Swaffer

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Latency "creeping"
« on: April 27, 2020, 12:47:58 pm »

We are using Wirecast to stream.  Been working on a lot of things the last few weeks to make the live-stream better-and every service we get a little bit better but one thing that we can't seem to conquer is keeping audio and video in sync.  Testing outside of service with everything on we have no issues-but as the service progresses it gradually gets worse-both on FB and on our church online stream.  Video is HDMI into a converter to USB, audio is in to the iMac through a USB interface. iMac is about two years old-fastest processor/ssd available at the time.

We are trying to manage the local network-but would devices on the network have any impact on this?  I guess in the end I don't understand how things interact once the stream leaves Wirecast?
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Steve Swaffer

Erik Jerde

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Re: Latency "creeping"
« Reply #1 on: April 27, 2020, 01:00:38 pm »

We are using Wirecast to stream.  Been working on a lot of things the last few weeks to make the live-stream better-and every service we get a little bit better but one thing that we can't seem to conquer is keeping audio and video in sync.  Testing outside of service with everything on we have no issues-but as the service progresses it gradually gets worse-both on FB and on our church online stream.  Video is HDMI into a converter to USB, audio is in to the iMac through a USB interface. iMac is about two years old-fastest processor/ssd available at the time.

We are trying to manage the local network-but would devices on the network have any impact on this?  I guess in the end I don't understand how things interact once the stream leaves Wirecast?

When you test outside of the service are you doing an equal length test?

Im not surprised youre seeing drift.  Figuring out the cause is hard though.  Id be curious to know if it would do the same with an audio source embedded in the hdmi signal.

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Caleb Dueck

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Re: Latency "creeping"
« Reply #2 on: April 27, 2020, 04:17:56 pm »

Id be curious to know if it would do the same with an audio source embedded in the hdmi signal.

My first thought as well.
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Keith Broughton

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Re: Latency "creeping"
« Reply #3 on: April 28, 2020, 06:09:42 am »

When you test outside of the service are you doing an equal length test?

Im not surprised youre seeing drift.  Figuring out the cause is hard though.  Id be curious to know if it would do the same with an audio source embedded in the hdmi signal.
We have found that embedding audio into HDMI or SDI solves any kind of synch issues down stream.
« Last Edit: April 29, 2020, 06:17:23 am by Keith Broughton »
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Stephen Swaffer

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Re: Latency "creeping"
« Reply #4 on: April 28, 2020, 01:03:41 pm »

I've primarily worked on getting a good mix to the video guys-but I assume the easiest (best?) way to embed the audio in the HDMI is to run audio into the camera?

I know we are using more than one camera-so that might complicate things a bit unless Wirecast can utilize the same audio stream regardless of camera.
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Steve Swaffer

brian maddox

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Re: Latency "creeping"
« Reply #5 on: April 28, 2020, 02:46:22 pm »

I've primarily worked on getting a good mix to the video guys-but I assume the easiest (best?) way to embed the audio in the HDMI is to run audio into the camera?

I know we are using more than one camera-so that might complicate things a bit unless Wirecast can utilize the same audio stream regardless of camera.

The easiest way to embed audio into an existing system is via one of the cameras.  So long as you're going into line level input and such this works well.

I don't know about wirecast, but I know that the BMD stuff has an "audio follows video" option that you can uncheck so that the audio only comes from one source regardless of switching.
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brian maddox
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Caleb Dueck

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Re: Latency "creeping"
« Reply #6 on: April 28, 2020, 06:53:27 pm »

I've primarily worked on getting a good mix to the video guys-but I assume the easiest (best?) way to embed the audio in the HDMI is to run audio into the camera?

I know we are using more than one camera-so that might complicate things a bit unless Wirecast can utilize the same audio stream regardless of camera.

Camera audio is more for emergency backup.  Take your video mix feed from your video switcher or router and use an SDI or HDMI audio embedder.  Some video switchers have balanced or digital audio inputs already. 

It's like room mics in audio.  You wouldn't use a room mic instead of a console feed, so why use a camera instead of the video system feed?
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Mac Kerr

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Re: Latency "creeping"
« Reply #7 on: April 28, 2020, 08:00:03 pm »

Camera audio is more for emergency backup.  Take your video mix feed from your video switcher or router and use an SDI or HDMI audio embedder.  Some video switchers have balanced or digital audio inputs already. 

It's like room mics in audio.  You wouldn't use a room mic instead of a console feed, so why use a camera instead of the video system feed?

If the camera audio is embedded, why would you need another embedder.

Mac
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brian maddox

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Re: Latency "creeping"
« Reply #8 on: April 28, 2020, 09:02:12 pm »

Camera audio is more for emergency backup.  Take your video mix feed from your video switcher or router and use an SDI or HDMI audio embedder.  Some video switchers have balanced or digital audio inputs already. 

It's like room mics in audio.  You wouldn't use a room mic instead of a console feed, so why use a camera instead of the video system feed?

If by camera audio you mean the microphone ON the camera, then yes.  But i think the OP is referring to using the XLR inputs on a camera as an embed point.  This has a number of drawbacks, but can work fine if it's done correctly and even has teh advantage of limiting the amount of audio offset needed later for latency correction.

You are correct that the ideal way to do this is with an embedder downstream of the Video switcher, but sometimes you got to work with you've got.
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"It feels wrong to be in the audience.  And it's too peopley!" - Steve Smith

brian maddox
bdmaudio@gmail.com

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       ....for you are crunchy, and taste good with ketchup...'

Stephen Swaffer

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Re: Latency "creeping"
« Reply #9 on: May 05, 2020, 12:52:41 pm »

Thank you for the responses.  I appreciate all of them-and the spirit of helping make the best of what we have.  I know that a switcher and other equipment is the way to o-but as Brian said sometimes we have to make do with what we have.  Usually the end product is more about the skill and vision of the person than about the gear.  We never aspired to be a broadcast ministry (nothing against those that do).  Obviously current events have forced our hand-and maybe even caused us to re-think some things.  Still there is a desire to do the very best we can, but investing in better gear and researching the right solutions will take some time.


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Steve Swaffer

ProSoundWeb Community

Re: Latency "creeping"
« Reply #9 on: May 05, 2020, 12:52:41 pm »


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