Network Transmission

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Network Transmission

Peter Hoskin-2

Hi,

 

I work as a volunteer technical officer at a not-for-profit FM radio broadcaster.

 

I’m writing mainly for advice in solving issues that will soon be an issue in the future as there doesn’t seem to be any software based solutions.

 

Typically a radio broadcaster will have a studio and a remote transmitting site and will use microwave or telephone carrier based connectivity to send audio to the transmitter site. This is called STL. Radio stations often broadcast time information and therefore want low delay transmissions. There is an increased use of what the radio broadcast industry is calling STL-IP or Studio to Transmitter Links over IP networks. With the adoption of digital broadcasting such as DAB+, STL-IP is becoming the norm and appears to be a requirement to gain access to DAB+ transmitters in many cases.

 

Typically STL-IP is used with a dedicated hardware device that uses AAC codecs, has an Ethernet port, supports multicast, and has a routing table capable of failing over to alternate IP pathways. The transmission standard is open and Wikipedia has details on this at http://en.wikipedia.org/wiki/Audio_over_IP

 

STL-IP devices are inherently expensive. The lowest cost installations I know of cost around $4,000 AUD for hardware. There is the potential for a developer implementing a software based solution to seek substantial funding from radio broadcasters.

 

There have been efforts in the JACK project to produce network based operation, so I thought I’d open discussion here on how STL-IP could be implemented on Linux. Such an implementation should outperform any existing network based solution in JACK by far.

 

Regards,

Peter Hoskin


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Re: Network Transmission

Christoph Kuhr
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Hash: SHA1

On 01.10.2011 14:21, Peter Hoskin wrote:

> Hi,
>
>
>
> I work as a volunteer technical officer at a not-for-profit FM radio
> broadcaster.
>
>
>
> I'm writing mainly for advice in solving issues that will soon be an
> issue in the future as there doesn't seem to be any software based
> solutions.
>
>
>
> Typically a radio broadcaster will have a studio and a remote
> transmitting site and will use microwave or telephone carrier based
> connectivity to send audio to the transmitter site. This is called
> STL. Radio stations often broadcast time information and therefore
> want low delay transmissions. There is an increased use of what the
> radio broadcast industry is calling STL-IP or Studio to Transmitter
> Links over IP networks. With the adoption of digital broadcasting
> such as DAB+, STL-IP is becoming the norm and appears to be a
> requirement to gain access to DAB+ transmitters in many cases.
>
>
>
> Typically STL-IP is used with a dedicated hardware device that uses
> AAC codecs, has an Ethernet port, supports multicast, and has a
> routing table capable of failing over to alternate IP pathways. The
> transmission standard is open and Wikipedia has details on this at
> http://en.wikipedia.org/wiki/Audio_over_IP
>

Did you have a look at Ravenna?
http://ravenna.alcnetworx.com/

I think its quite a good solution and an open source implementation for
linux is already in developement.

bye
Ck

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Re: Network Transmission

Paul Davis
In reply to this post by Peter Hoskin-2
On Sat, Oct 1, 2011 at 8:21 AM, Peter Hoskin <[hidden email]> wrote:

> There have been efforts in the JACK project to produce network based
> operation, so I thought I’d open discussion here on how STL-IP could be
> implemented on Linux. Such an implementation should outperform any existing
> network based solution in JACK by far.

I am not competent to remark on the rest of your post, but this claim
above is, to put it mildly, a bit strong. There have been projects
done with JACK and Internet2 that far exceed what any current
commercial entity could pull off (e.g. 24 channels of 96kHz floating
point audio, long haul across north america).

no doubt there are interesting "different" kinds of network audio that
remain to be done with JACK.
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Re: Network Transmission

Fred Gleason-2
In reply to this post by Peter Hoskin-2
On Oct 1, 2011, at 08:21 44, Peter Hoskin wrote:

> Typically STL-IP is used with a dedicated hardware device that uses AAC codecs, has an Ethernet port, supports multicast, and has a routing table capable of failing over to alternate IP pathways. The transmission standard is open and Wikipedia has details on this at http://en.wikipedia.org/wiki/Audio_over_IP

I'm not sure that JACK would be the optimum point in the software stack in which to implement something like this as the introduction of bit-rate reduction in the data path will inherently increase latency, sometimes dramatically.


> STL-IP devices are inherently expensive. The lowest cost installations I know of cost around $4,000 AUD for hardware. There is the potential for a developer implementing a software based solution to seek substantial funding from radio broadcasters.

The primary cost driver for these systems is the licensing of the relevant patents (Dolby Laboratories in the case of AAC).  This is not something that making the code "open source" will circumvent.  Low latency codecs that are also open source (such as CELT) are still in the early stages of development and not really ready for prime time at the moment.

Cheers!


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