Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Streaming How to check if your Sooloos network is 'bit perfect'

The following are instruction on how to check that your Sooloos network is 'bit perfect'. I have used the term 'bit perfect' to describe the network passing audio data unchanged between consecutive runs. ie it tests for random deviations in audio data passed over the network that may lead to claims of audio differences.

The test scenario presented is a very basic scenario to show the basics of capturing and comparing Sooloos audio data. The test scenarios could be extended to make greater comparisons than shown, for example:

• Different HH members use their own equipment on their own equipment to import a single copyright free reference test file. This would highlight any differences in import methods, store and core hardware and network topology between members equipment.
• Comparing files ripped as FLAC or WAV.

The following involves a technical 'can do' approach and whilst I have hopefully presented the instructions in relatively easy manner, it is probably not for the technically naive. The processes that we will be undertaking is generally termed network sniffing and we will be capturing data off the network and saving in a fairly raw form.

The approach also assumes that the network traffic between Sooloos core and audio endpoint is accessible. Network switches, by design, isolate data between ports so it is not possible for one port to intercept data solely being transferred between two other ports. To achieve this trick, you either need to step back into the past and use a network hub or have access to a smart or managed switch that has a function for port monitoring or mirroring. All is not lost if you do not have either of these as you can use Control:Mac, Control:PC running as an audio endpoint on the same machine as the network sniffer to achieve. Control:Web cannot be used as it uses a different network protocol.

Pre requisites:

• Sooloos store and core
• Sooloos audio endpoint (or Control:Mac/PC)
• Smart or managed switch (optional)
• About half hour of your time

There are many way to achieve this, but I will demonstrate using freely available software and a standard Mac. The process is equally valid for a PC or otherwise, but choice of software will be vary slightly.

Steps:

Download and install Wireshark. Wireshark is a very highly regarded network sniffer and is available for free from www.wireshark.org for different platforms.



When wireshark is first opened, it asks you to select a network interface from which to capture the network packets. You wish to select the hardwired ethernet connection which will differ from machine to machine. On my Mac en0.en1 is the wireless connection.



You should now see your screen rapidly filling with network data. If not, then you need to check what you are connected to. If sniffing from a broadcast type network, such as wireless or powerline, you may need to track down the capture option for promiscuous mode and toggle its setting. This will allow you to capture traffic destined for other machines.



As we are only interested in Sooloos audio traffic, we need to setup a filter to only show us network audio data. Each packet of Sooloos audio data is UDP traffic approx 4000 bytes long with data that contains the string "Sooloos AESPDATA". As 4000 bytes is typically too long for a single network packet, the network automatically splits it across smaller packets. Thankfully wireshark can detect this and treat the different packets as one.

So filter out unwanted traffic, we set up a filter:

udp && data contains "Sooloos AESPDATA"

Then hit Apply. Watch out for case sensitive and double characters in operators. Also "Sooloos AESPDATA" is all uppercase but HHer BB converts it Sooloos to lower case.

If running simultaneous audio to more than one zone, you can append "&& IP.addr == 192.168.1.30" i.e.

udp && data contains "Sooloos AESPDATA" && IP.addr == 192.168.1.30

to the filter where 192.168.1.30 should be replaced by the IP address of the audio endpoint that you wish to monitor. This will only report on traffic to/from that endpoints IP address.

All other data disappears. If you were not playing any Sooloos audio, then you will probably have a blank display. Go into Control:XX and play something to the audio endpoint that you are monitoring. You should then see the audio packets being shown on the screen.



We are now in the position to capture Sooloos audio data.

We will be performing the capture process twice, on the same track of music. In Control:XX, stop the music then start a fresh capture with Wireshark using the three icons at the top or the capture menu. You may be prompted to save the previous capture. Select continue without saving unless you want to save the audio capture file.

At this point, the screen should be blank. With control:xx, play the track of music either for a fixed duration or until the end of the track. Now stop the capture in wireshark - the icon with the x on it. Now, to let wireshark know that we are only interested in the captured audio data, select 'edit/mark all displayed packets'. The packets on screen will go black.

We now need to export the audio data in a human readable form. Go to file/export/plain text file. Enter a filename, select 'marked packets only' for the range and make sure that only 'packet bytes' is selected for the format.



OK. You now have the PCM data for the track that you played saved in human readable ASCII format.

Repeat the same process using exactly the same track but making sure that you save under a different file name as the next stage, we will be comparing the two files.

This bit differs between OS versions, installed programs and user preferences. Im going to use OSX terminal for an example. Basically, we will be comparing the two files and hopefully explaining away the differences.



In OSX, use the built in diff commans from command line:
$ diff capture1.dat capture2.dat -y -W 180 > comparisonfile

Now view the comparison file:
$ more comparison file

Yes, I know I could have combined the two steps by piping direct to more



We are expecting to have thousands of differences, but hopefully the differences are fully explainable. As we are looking at the raw data from the network packets, it will have the IP and UDP headers included, which will have different sequence numbers, CRC's and port numbers (Sooloos uses dynamically assigned ports). But there should be no other differences.

Thankfully OSX diff puts a change bar '|' next to lines that differ, which makes them easy to spot. Other programs show differences in other ways, the following from filemerge supplied with OSX XCode developers IDE is even more helpful.



This test should conclusively show if the integrity of Sooloos audio data is maintained between subsequent plays of the same audio track and for those who have a more complex Sooloos system than I have, if network data is identical when the runs occur with different power supplies, fixed/dynamic IPs, core or store in one room then another etc.

Thanks very much for doing this Ian. I'll definitely investigate (bit of painting to do first...).

Ian,

You're a genius.

Will this enable me to track down my media not playing issue as well, do you think?

Wireshark is a very powerful piece of software and it's ability to track down issues as down to user and external equipment.

At basic level (I think by default) wireshark will flag erroneous packets in red. So if you get lots of those, network looks suspect. wifi will do this when marginal.

At more complex level, you can run two wireshark captures on different ends of a network, and get it to check that what goes in on one end comes out of the other within specic time constraints. But to do that, you need to be able to monitor ports at either side. Can't remember if your switches can do that. This allows you to check for dropped packets.

Sticking Control:Mac/PC on same port as audio endpoint and comparing captures should however tell you whether network is transparent or not. It will also give a basic indication if your randomly dropping packets. If you do find issues, then joining Sooloos core and Control:XX only by crossover network cable will tell you if it's Sooloos fault or network issue.

Ian,

You might like to edit your first post.

The filters appear to need to be: udp && data contains "Sooloos AESPDATA" as per your screenshot, noting the upper and lower case letters. If you use "UDP" for example I get an error message.

Edit: In the filter the word Sooloos needs to be all in capitals as per the screenshot.

As Ian points out later in this thread, UBB is messing up the exact capitalization necessary to get Wireshark to work.

Thanks. Also noticed that UBB is converting uppercase Sooloos to mixed case Sooloos so added a note about that.

Hi Ian,

An excellent post, very clear and concise, a great candidate for the WiKi once the dust has settled.

Regards,
Carl

LOVE this post Ian!
Thanks for your time and effort here.
/Marcus

I tried it and everything as described until I put the filter on and then I got nothing in the report screen. I figured out the caps letter problem but must be doing something wrong with the filter phrase.

Have you applied the filter?

Are you playing a song on Sooloos? You get nothing if Sooloos is not playing.

After starting the program and selecting the correct connection I get a ton of posts as described. Then I apply the filter and nothing. Yes I use Control:PC to play a CD on the MS600 zone in my office where the computer with the snoop program is installed.

Try playing music to the Control:PC zone.