I'm trying to set up a WiFi-network that can deliver real-time audio for live musicians, with minimal latency. I've had trouble with audio crackling/noise with cheap off-the-shelf routers.
The WiFi-network do not need access to internet, it should be a isolated network with only necessary features. Password protection might be good, but I don't think the network needs any other internal security features enabled (or does it?).
The WiFi signal should be strong and far-reaching enough to cover a stage and have enough mbps for up to 8 devices at the same time. Some off-the-shelf routers recommended for this purpose has like 6 antennas, though I don't know if numbers of antennas really matter or if it's a marketing technique (quality vs quantity is still relevant with antennas?)
My questions are;
What hardware do you suggest for this?
Will OpenWRT fit this task?
Is it possible to create a DIY WiFi generation 6 device with OpenWRT? If so, how; what specific parts do I need?
This has very little to do with OpenWRT/routing. You are basically asking how to build a well functioning WiFi network. I recommend following enterprise WiFi practices:
No 2.4, only 5GHz. Multiple wired Access Points, 20MHz width with non-overlapping channels.Also, forget 802.11ax, most devices do not support it.
I think it has a lot to do with OpenWRT. As far as I know, there exists no router on the consumer market that is not designed to connect to internet, so those are probably bloated with uneccesary software and features I don't need. But I'm not an expert on routers. I don't know programming, and I don't know OpenWRT. I know OpenWRT is not designed for a isolated WiFi network, but as far as I know there exists no software that is. My question is really, with OpenWRT, my router can be set-up just fine without internet access? some consumer routers need internet access to be set up
No, you do not understand. What you call a "router" is basically multiple things. A routing device, a smart switch and an access point. Functionality you are talking about only needs Access point functionality.
Whether AP runs OpenWRTY or not is not so important. And yes, you can use OpenWRT router as Access Point...just ignore port called "WAN" and wire it through one of LAN ports.
That being said, the much more important part in your application will be to use multiple Access Points (OpenWRT or not) and wire them via Ethernet. The whole "Open"-part of OpenWRT will not be used...it will not route anything...it will be a dumb bridge between WiFi and wired LAN.
openwrt is about customizing network devices to perform to specific needs so I think this is a perfectly fine question for this forum. Yes openwrt will work fine without internet access. However...
I don't know if there is off the shelf software you plan to use or not, but the problem of transporting audio at high reliability and low latency over WiFi is not trivial. For example packet loss is inevitable on WiFi so your software should be sending duplicate packets if you don't want scratchy audio. Also the software needs to know what to do with those dup packets... Jitter buffers need to be nonexistent because live musicians can easily detect 5ms latency. So the project is mostly about either software development or at least knowing what off the shelf software already does what is needed
The network part of your quest is mostly "find best AP's you can use" which is the easy part. Hard part is to write software to synchronize and de-jitter audio packets.
Sonos uses its own bastardized 802.11 custom protocol to make sure all speakers are synchronized (but they still suffer some delay in order to make sure audio is in sync.
Only way to have perfect sync is analog FM radio...
opus codec could encode high quality audio at say 150kbps so times 8 is 1.2Mbps. the slowest modern wifi signal is 6Mbps.
If you choose to use something like raw 16 bit CD samples at 44.1khz this is 44100*2*8 = 705600 bits per second, so 8 of those is 5.6Mbps. But to get low latency will require you to have substantially above that, so you can probably do well with something like 12Mbps or above... this is all year 2000 era wifi speeds.
Speed isn't the issue, and neither is range (unless your stage is football field sized). What's the big issue is interference from other radio sources, latency, and packet loss.
If you're relatively physically isolated from other wifi, and operating on 5Ghz, you're good with a single wifi access point somewhere at the back of the stage, pretty much anything that exists. The hard part is writing software to encode/decode/transmit the audio reliably.
My suggestion would be something that encodes in opus, then sends an RTP stream with duplicate packets, and reassembles on the other end with 1 packet jitter buffer. even that will I fear be rather too much latency for musicians in the same room. Normally opus would use 20ms packet spacing, so you're going to be having 20 to 40ms latency. MIDI keyboardists start to complain about delay at about 5-10ms latency between pressing the key and hearing the sound as far as I know.
for a song with 100 beats per minute, an 1/8th note duration is 75ms so playing with a 40ms delay is like being a 1/16th note behind all the time.
Yes. I'm using off-the-shelf software for this. If I'm correct, then a router, access point and a routing device all need the same hardware, so it's not really possible to assemble (hardware) a great access point that doesn't work as a router? cus functionality all depends on the software/firmware/os?
Gotcha, so assuming you have the off the shelf app, I think all you really need is a single openwrt device set it up to use 5Ghz with 20Mhz or 40 MHz channel width, on a channel that has no major interference. You might benefit from disabling connection rates below 12Mbps. If you can get the software to tag packets with DSCP it might help to tag them appropriately
The software I use, others have successfully used with low-latency on expensive off-the-shelf routers. However, my cheap router caused audio issues, but no latency issues. Therefore I conclude that it does matter what router I use, and I'm looking for an answer to what exactly makes one router function well and not another. It might be hardware, or it might be os/software, I guess.
This indicates packet loss. Packet loss will be affected by the radio environment, and that's more important than which router you use. If you compare your colleagues at studio X with a different router to yourself at studio Y with your router, it might well be more important where and what neighbors there are with what wifi and which channel you use etc than what device you use.
Asus device (maybe 90$), can't remember the model name, I don't have it now. Firmware was vendor firmware.
I'm looking if maybe the Raspberry Pi 4 will be a good option for trying to build a first router. If I try out a Raspberry Pi 4 with OpenWRT, the build in wireless chipset has built in both a receiver and transmitter/antenna? So if I create a WiFi-network in OpenWRT software, it uses the wireless chipset to broadcast the WiFi? If this is true, then I guess that this wireless chipset will have less range and be less powerful than with a dedicated antenna. Does it exist dedicated antenna I can connect to a USB-port or other port, that will increase the signal strength? In theory, should I get a better WiFi with Raspberry Pi 4 and a connected external antenna, than a medium-priced off-the-shelf router?
My optimal solution would be to use software on my Mac to create a WiFi network, and use a dedicated external antenna on my Mac. However for this I'm lacking the correct software, antenna. I don't think it exist a turn-your-mac-into-a-router-software and it's hard to find any information on the web about this. OpenWRT can not run be run inside a virtual machine, or installed on my Mac anyhow? Cus if I already got all hardware parts inside my Mac to set up a good WiFi, then I shouldn't need to buy more hardware?
WiFi is junk on the pi. Its a great router but terrible as an access point. I would tend to recommend a gl-inet travel router, easy to transport around, comes with a custom openwrt preinstalled and the advanced config button takes you to luci.
As of today you still haven't explained why you need a "router"? The task of a router is to transfer packages between different IP Networks which in the situation you explained is not the case. What you need is one or more Access Points and if more the one Access Points you need a switch (not a router) and you may want to have a DHCP/DNS server for convenience.
access points can not function without a router, cus it can't set up it's own network? The best device would probably be a hybrid-device that maybe doesn't exist. It should be an access point and able to set up it's own network without functionality to connect to other networks, only a pc.
