Question / Help Sync video/audio from two wifi sources on a budget. Is it even possible?

[dinki]

Hey guys. I'd like to stream some events from my kid's school. I have this crazy idea that I can use a phone or a web cam for the wide shot feeding OBS with an RTSP stream over wifi. I can do this (tried with a Wyze cam), but the audio is horrible. I'd like to add another wifi source to get sound only off the mixing board. I'm guessing I can use the same sort of RTSP camera source on another phone plugged directly into the board.

The big question is how do I sync the audio to the video? I know I can set an audio offset in OBS but will this be different for every event? Will this drift over the course of the hour long program? I'd like to be able to set this up and have one of the teachers be able to turn it on and off without needing me to set things up every time.

Is it possible to do this on such a low budget or am I just dreaming?

 

[Narcogen]

There are too many variables unaccounted for to be able to answer meaningfully without actually being in your situation.

To me this scenario sounds possible but unlikely.

The only way anyone could answer would be to have all the specifics of your situation-- what model of phones, what applications, what networking equipment, what audio mixer, etc... and the purpose of gathering that information would be to duplicate the situation and test whether or not it's possible.

If you're lucky, the amount of delay would be relatively constant, at least within the context of a single event as long as all equipment works correctly and predictably, and you could compensate with audio offset.

You might want to at least consider using NDI over wifi instead of RTSP; at least with that source type in OBS you'll have a choice of sync types (network/source/internal) that might have some impact on whether or not things stay in sync. If your network is fast enough this should be pretty low latency (about 1 second or less).

 

[dinki]

Apologies for the lack of detail. I didn't want to go into great detail if this was not at all possible but from the sounds of it it may be. Here's a bit more:

OBS machine: Windows 7 connected via school WIFI
Main Camera: Google Pixel Android phone running some sort of IP Camera software (trying to determine what would work best) over school wifi
Audio source: Another Android phone running same IP Camera software but only using audio portion (or some other to be determined audio streaming software that someone might suggest) connected to sound board via analog output to headphone/mic jack of the phone over school wifi

I did see some videos where someone used the NDI app and it seemed to have low latency. Would I be able to use two phones with the NDI app and sync them better/easier? Could I use NTP on the phones and computer to keep the all clocks the 'same' and then use one of the sync types you mentioned from the NDI add on? Which option would I choose for this type of set up?

Thanks for your input. I will certainly add more detail if needed. Do understand that I am trying to see if this is feasible so some of my answers as to specific software using may not be concrete and that I am soliciting advice on this as well.

 

[Narcogen]

Just to clarify: I am not actually asking for some more detail, because if even if I got it, the only way I (or almost anyone else who hasn't already done this same exact thing) could answer the question of whether or not it could be done would be to go ahead and do it.

That said, is it absolutely necessary that the connection to the sound board be via wifi from a cellphone? Presumably your computer running OBS and the sound board are both in known, fixed positions, surely a wire is a better idea?

And as far as I know there's no way when using OBS with NDI to explicitly use NTP for sync. You'd just choose "internal" and the PC running OBS would use its own clock.

 

[dinki]

You're absolutely right that a wire would be better and I do fully understand that. Logistics do not allow for this however.

Can you speak to my question about the NDI app and the syncing of the sources? I think that may be the key to getting this to work.

 

[Narcogen]

You don't set sync on NDI sources, you set it in OBS. If you use Source, it will use the clock from the device sending the signal. If you use Internal, it will use the clock of the PC running OBS.

Which performs best for you on your particular network with your particular PC and which particular NDI apps you choose on your particular phones will depend on the above factors and can only be reliably determined by trial and error.

I would guess that Internal for all sources is the way to go, and if you're lucky, the delay caused by the network will be consistent and can be compensated for with an audio offset. It would also have a LOT to do with whether or not the wifi network you're using is accessible to people in the venue. If you're using a public network in an auditorium with a room full of people with phones that are connecting to that network... then this may be less likely to work.

Good luck!

 

[dinki]

Thanks for the information. Certainly something I can try. The network is a private network only used by the school faculty and students so it would not be being used heavily at the time of the broadcast as all faculty and students will be in attendance.

You mention which particular NDI apps I choose. Is there a comprehensive list of these posted somewhere? I'm particularly interested in Android but may be able to acquire some iOS phones as well.

 

[Narcogen]

https://www.newtek.com/software/ndi-camera/