[grc] [Stubblefield] Using a digital stream as STL toLPFM transmitter site

[Michael D. Brown]

I believe in using your own infrastructure whenever possible.  In most cases, two STL hops will will work where one hop does not.  For this application, the most basic Barix units can work fine as codecs, and they sound very good in linear PCM.
 
Dealing with two separate ISPs can be a nightmare.
 
IMHO, it's risky using Barix boxes (or any other fixed algorithm codec) on the public internet, for a primary STL.  And the Barix MP3 implementation is poor.
"Smarter" variable bit-rate hardware, and those that incorporate AAC/HE-AAC modes, are a better choice (e.g.: Comrex BRIC Link; Tieline Bridge-IT).
 
 
mb
 

Michael D. Brown
Brown Broadcast Services, Inc.


 

 


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From: Stubblefield [mailto:stubblefield-bounces at lists.prometheusradio.org] On Behalf Of Bill Putney
Sent: Thursday, September 29, 2016 6:07 PM
To: Stubblefield
Cc: GRC List
Subject: Re: [Stubblefield] Using a digital stream as STL toLPFM transmitter site


Line of sight implies a radio link. You've already said there's a hill in the way. 

I assume from what you've said you're going to try to use public Internet. Having two separate ISPs involved multiplies the possible maintenance issues because neither ISP controls the entire link. You can't call and tell them to just fix it. They won't trade trouble tickets and they may not even have a direct connection between each other. 

If you're going to do this I'd recommend getting MTR for Windows, Mac or Linux and test the link from end to end for at least a day. You'll need an IP address of something at the transmitter end you can ping from the studio end. MTR will give you details for each device the connection passes through and will tell you if there are dropped packets. There shouldn't be any. If the packet loss is 5% or more for any section of the connection I wouldn't use Internet as the STL. You should look at the jitter information MTR gives you too. High jitter indicates there are network errors being corrected that don't cause dropped packets but cause a stuttering data flow. That won't be good for your audio because the codec at the transmitter end will run out of data and go silent. 

Bill Putney - WB6RFW
Chief Engineer
KPTZ - Port Townsend, WA 


PP-SEL/A&P-IA

(360)  <tel:(360)%20379-6886> 379-6886

"...you know me to be a very smart man. Don't you think if I were wrong, I'd know it?" -Sheldon Cooper


On Sep 29, 2016, at 16:32, Danny <danny at wspj.org> wrote:



If line of sight link means a dedicated internet connection between the 2 locations, then no. This will be an internet link with or without the Barix boxes. Our studio uses Verizon FIOS and the transmitter site Time Warner Roadrunner broadband.



From: Stubblefield [mailto:stubblefield-bounces at lists.prometheusradio.org] On Behalf Of Will Floyd
Sent: Thursday, September 29, 2016 7:27 PM
To: Stubblefield
Cc: GRC List
Subject: Re: [Stubblefield] Using a digital stream as STL to LPFM transmitter site



The Barix boxes are basically little computers that convert analog audio to digital or the opposite. So yes, another little computer like a Raspberry Pi or a big desktop can accomplish those tasks. The benefit of the Barix boxes is that they are easy to set up, and cheaper than other broadcast quality CODECs.



It's unclear from your email if you are using a line of sight link or the Internet to connect your studio to the transmitter. Generally, a line of sight link is more desirable because it is a more direct path that is immune to problems with the wider Internet and more secure. It's worth noting that if you are using the Internet for the connection it might be worth looking into a CODEC with some additional features.



On Thu, Sep 29, 2016 at 5:09 PM, Danny <danny at wspj.org> wrote:

Our LPFM transmitter site is 6+ miles from our studio without a clean line-of-sight because of hills. So, to save time and money, we’ve been expecting to use a pair of Barix boxes to move a digital stream from our studio to our transmitter.  But a couple of our key people think we can skip using one or both Barix boxes.



Specifically, the person who maintains the Icecast server that hosts our webcast feels confident he can create a second private stream of much higher quality that can take the place of the need for a Barix box at the studio end and another person thinks we can use a “headless internet radio player” on a Raspberry Pi instead of a Barix box at the transmitter site. He’s looking at https://www.raspberrypi.org/forums/viewtopic.php?t=43108  especially noting this setup has auto-run upon reboot, which is what we want. This is a key person of ours with lots of experience using the Raspberry Pi.



Are one or both of them missing something with these suggestions? Will these be viable and reliable ways to avoid paying $1,200 for a pair of Barix boxes?



Thanks!

Danny

WSPJ-LP Syracuse NY


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Will Floyd
Technical Director | Prometheus Radio Project
 <mailto:will at prometheusradio.org> will at prometheusradio.org | 215.727.9620 x524

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