BARIX EXTREMER 110

[RealityCheckr]

RealityCheckr , so i guess we're back to this setup. the Barix 1000 ,PCM mode, ubiquity power station 5 ethernets radios,short 1500 ft to tower, clear line of site, dedicated path, which la guy and i agree should work fine, Your thoughts,please.

Sounds quite reasonable.

Can't beat PCM . La Guy, does it both 24 bit and 16 bit resolution? Sometimes 24 bit can be useful.

Of course 4:1 compression is inaudible, and Layer 2 or APTX are both fine at those rates (APTX is more cascadable).

I am not familiar with power station 5, but I have seen good results with both Proxim and Motorola radios, and as you say, the path is short. Do you have a link handy?

The main thing to look at is packet loss rate which is more useful than bit error rate.

Regarding Ogg Vorbis. If the boxes did not have Layer 3, it might be useful, but since they do, there is no particular advantage. It is most definitely in the same class as AAC.

AAC+ is truly amazing, but should be used only where low bit rates are the only option.


Keep us posted.

 

[gtomas]

i bet if you took a cut off a cd,encoded it to ogg vorbis and aac, they would be so comparable you could not tell the difference.would Flac work just as well? good point about the ogg vorbis. is that the same codec that Otsjuke uses?

As Dana (LA_Guy) points out, FLAC is a lossless codec. The decoded file/stream is bit-identical to original as coding doesn't exploit psychoacoustic phenomena, only redundancy in the bit stream. Lossless codecs are completely transparent.

At higher bitrates, aoTuV implementation of Ogg Vorbis actually compares very well to AAC and other codecs. See this test.

SBR enabled codecs such as HE-AAC should only be used as a final codecs in services such as web streaming and/or digital radio. HE-AAC is a codec designed to operate at very low bitrates and although it does an amazing job there (if fed with uncompressed audio) it has it's drawbacks. Codecs such as HE-AAC shouldn't be used in any other point in transmission (including STL) except at the very end! If you want to use Barix units for STL, the absence of HE-AAC is not something that should worry you at all. It's a great codec for what it is intended to do. It's not great per se! If you have at least 96kbps of bandwidth for your STL, don't use HE-AAC.

A decent wireless point-to-point bridge will do 10Mpbs, which will carry two uncompressed audio channels without a hitch. If you're stuck with 1Mpbs, you'll have to encode, but make it 320kbps. Enlighten me, but I don't know of any dedicated wireless circuit that will require you to go lower than that...

There is a valid concern among broadcast professionals due to significant drop in audio quality as a result of people overly easy relying on audio coding. And not being aware of the issues such as codec cascading or even bitrate/quality trade-off. People just click encode, encode, encode, radio spots in particular get encoded every time an edit is being made. And they just click 128kbps everytime. If you ask them why did they choose 128kbps and not 320kbps instead, their eyes just glaze over... Sad.

We, as engineers, should know better than that! I would recommend two general rules when it comes to coding and broadcasting:

1) Avoid audio coding at all costs!
2) If you absolutely have to use lossy coding, use the highest bitrate possible!

Hope that answers your questions


Regards,
Goran Tomas

 

[Chuck]

1) Avoid audio coding at all costs!
2) If you absolutely have to use lossy coding, use the highest bitrate possible!

Hope that answers your questions


Regards,
Goran Tomas

Of course, you are right. If you have your own private link, higher bit rates are of little consequence. You might as well use them. Unfortunately, the problem I've encountered using the public Internet is interment occasions when a 1 mbs stream suddenly chokes down to 64K for a few seconds. That causes all kinds of problems, including buffering, stuttering and other things we'd rather not broadcast.

The obvious solution is to find a better Internet connection. Unfortunately, where I am (and where many Americans reside) that is not an option. Other than wireless cellular service or satellite, I have one ISP available to me. Setting up a private RF link has not worked either due to the area's topography. I don't see these problems improving in the near future.

For people in my situation, a decent sounding low bit rate codec looks very appealing.

 

[RolfTaylor]

1) Avoid audio coding at all costs!
2) If you absolutely have to use lossy coding, use the highest bitrate possible!

Hope that answers your questions


Regards,
Goran Tomas

Of course, you are right. If you have your own private link, higher bit rates are of little consequence. You might as well use them. Unfortunately, the problem I've encountered using the public Internet is interment occasions when a 1 mbs stream suddenly chokes down to 64K for a few seconds. That causes all kinds of problems, including buffering, stuttering and other things we'd rather not broadcast.

The obvious solution is to find a better Internet connection. Unfortunately, where I am (and where many Americans reside) that is not an option. Other than wireless cellular service or satellite, I have one ISP available to me. Setting up a private RF link has not worked either due to the area's topography. I don't see these problems improving in the near future.

For people in my situation, a decent sounding low bit rate codec looks very appealing.

Well said Goran.

But there is a huge difference between 1 mbps and 64 kbps. 256 kbps does not require anything particularly fancy with regards to codecs.

And, in most cases, buffering will solve the problem of occasional bottlenecks.

Try setting your rcv buffer to max and set the prepacketized bit rate to something on the order of 256 kbps and see how that works. This is a much better option than going to a lower bit rate.

You should also consider a larger packet size, since this will reduce your packet rate.

Ideally any IP codec should allow adjustment of

-Coded audio bit rate = delay vs bit rate

-Packet size (packetized bit rate) = delay vs overall bandwidth

-Rcv buffer size. = delay vs robustness

-Codec type, sample rate, and mode (e.g mono/stereo/joint stereo). quality vs coded audio bit rate

These parameters will allow for optimal operation. In some cases operation is automatic, but if you cannot adjust them one way or the other, you are going to be rather limited.

Rolf Taylor

Applications/Support Engineer

APT North America

 

[LA_Guy]

La Guy, is there psycho-acoustic error concealment on these products, or simply FEC or packet re-transmission schemes?

Rolf Taylor

Applications/Support Engineer

APT North America Laguy did you get a response from Zurich on the post about using pcm for stl on the 1000 model barix?

There is error concealment in the units (similar to that now used in the Exstreamer 100).

 

[LA_Guy]

RealityCheckr , so i guess we're back to this setup. the Barix 1000 ,PCM mode, ubiquity power station 5 ethernets radios,short 1500 ft to tower, clear line of site, dedicated path, which la guy and i agree should work fine, Your thoughts,please.

Sounds quite reasonable.

Can't beat PCM . La Guy, does it both 24 bit and 16 bit resolution? Sometimes 24 bit can be useful.

The Exstreamer 1000 will only do 16 bit PCM. There's a good reason. Barix DOES think out of the box, and what they're trying to do (and succeeding, based upon sales numbers) is provide high quality performance for a reasonable cost. Though adding all this stuff would be nice, it increases cost. Barix hired me to both do tech support and provide them guidance on what the USA broadcast market wants (and doesn't want). For example, notably absent in the Exsreamer 1000 is all the raw TCP, Raw UDP, SIP , G-711 and other formats that are in the 100 series boxes. We took them out because they aren't really used by the USA broadcast market. We left in PCM, BRTP, RTP and HTTP.

If you need or want all the other stuff, our competitors have it (at over double the price). On the other hand, if you want outstanding, reliable performance at a great price, (and with great tech support!), Barix is your only real choice.

 

[gunterm]

What is the range of a dedicated wireless link? Are we talking wifi here or another standard?

 

[littlejohn]

Length? We get something over 20 miles using Western Microwave "Lynx" brand spread spectrum link radios. Aren't cheap, but they are rock solid. They offer 2.4 and 5.8GHz boxes, with up to 8 T1 paths per box. A four foot dish at each end is sufficient so far. They must, however, have line of sight. Basically point and forget.