Opus streaming support in mAirList 4.3


I have just uploaded Build 1830 of mAirList 4.3 beta which supports streaming and file creation (for Mixdown and VT) in Opus format.

If you haven’t heard about Opus, it’s a new low-latency but very high quality audio codec: http://www.opus-codec.org

The new build ships with opusenc.exe which is the command line encoder used to create the streams and .opus files. For streaming, you need Icecast2 version 2.4 beta, older versions such as 2.3 don’t support Opus yet.

Opus streams are in VBR mode by default; this is important to know, because it may lead to the connection being dropped if there is more than 10 seconds silence. Why is that? At the beginning of a silent part in the signal, the codec sends a packet saying “here comes silence” to the decoder, and then no packets at all until there is non-silence again. This causes the TCP connection to drop. The only workaround right now is to use constant bitrate encoding, which can be enabled by entering “–hard-cbr” as the encoder options.

Opus can now also be used in Mixdown and VT output file generation. Just select it from the list where you set the output file type.

If you want to play .opus files, you need the free BASSOPUS plugin from www.un4seen.com (copy to plugins\bass folder inside mAirList program folder).

Let me know if there are any issues.



I’ve tried streaming from one pc to another and the audio quality sounds good. The biggest problem is finding a decent player. Firefox will play Opus streams but the GUI is very very basic. I’ve tried to download other players but have been pestered by other programs/malware that seem to download as well! Any recommendations?

A good source of Opus streams is here http://www.absoluteradio.co.uk/listen/labs.html#opus allowing you to compare different bit rates.

Try VLC, it worked for me.

Allan: that’s a fascinating page from Absolute Radio. They seem to be the sole UK commercial broadcaster taking a genuine interest in open source streaming technologies, and I like the way their page is written.

I idly wonder if this is partly because they are owned by the Times of India group and not by Bauer? And of course, the other benefit is that open source products don’t attract a licensing fee nor any initial cost. Always a plus for any broadcaster, from largest to smallest.

I think Opus may well be the future for streaming if the beta-but-rock-solid Absolute Radio streams are anything to go by. I can also confirm that the latest VLC (2.0.6 “twoflower”) plays the stream; it took from one to four seconds here in Edinburgh, Scotland to connect and start playing audio. I’d describe the 24kB stream quality as ‘AM,’ and the the 64kB one as ‘FM+.’ The 96kB version of some streams did have dropouts here, but this is a home WiFi connection currently sharing with two other PCs, a Skype call on one and video streaming on the other, so that dropout may be a local bandwidth issue. :smiley:


Happy to hear about the implementation, Torben.

@ Cad

Though it’s an official internet standard since September 2012, there isn’t a really good support so far.I’ve tried VLC on PC and Android. It worked good. But sometimes it crashes. Especially in the beta Android VLC app.

There is a 3rd party plugin for Winamp, which you can find in the official winamp forum. I can’t recommend it at the moment. It’s more than a try and error thing.
Mozilla works best so far for me. All the other browsers don’t work, though Chrome should have a support for it.

I’m really hoping that this standard is gaining access to all areas really fast. Compared to mp3 and its highs especially, it beats the well known old standard by far, though it doesn’t need so much data.

Hi Cad. You may have seen their Labs page and news which is updated every now and again with interesting projects.

We’ve tried a few outside broadcasts using Opus and have been very impressed with the results, even at fairly low bit-rates. Using VNC or remote desktop to control mAirList and Opus for speech it came across quite well - especially with a pretty low latency (and two old PCs).

Great to see Opus in mAirList - it’ll be really interesting to see how adoption develops.

Thanks, I eventually found a clean version of VLC.

I’ve carried out some tests which have me puzzled to say the least.
The set up is a mairlist home studio installation encoding via LAN into a netgear router out via LAN to the receiving PC. A distance of 10metres at most!

I set up an mp3 stream at 80kb, joint stereo, sampled at 44100. Receiving PC using winamp, stable with audio in/out delay of 3seconds. Changed to VLC, again stable but with a delay this time of 9 seconds.

The second test was using Opus: VLC stuttered the audio initially and finally played. The delay 9 seconds, but the stream did have random drop outs. I changed the player to Firefox and the stream was stable with a delay of about 6 seconds.

I compared VLC and winamp on an external mp3 source, both were stable with the same audio in/out delay of 8 seconds. The source is streamed from mailist pro to an icecast server and then out to the internet.

I listened using VLC to some of the absolute radio Opus streams and they seem stable.