Stereo Tool

I have an application at a tx site where we orginally intended to receive our program link 24/7 via winamp using VAC and ST-SA. There will also be a remotely triggered 'ID player' on the pc to play short station identifications (cold vocal only) over the intro of songs. The ID application will also feed VAC1, so VAC1 effectively mixes both sources into ST-SA;

- Winamp (normal output 44.1 KHz) > VAC1
- ID player (normal output 44.1 KHz) > VAC1
- VAC1 > ST-SA (MPX output 192 kHz) > Fm tx

The problem with this approach is long term sync/drift issues in the Winamp player, so instead of using ST-SA, I'd instead like to use the new FM sync feature in the ST-DSP version;

- Winamp with ST-DSP (MPX output 192 kHz) > FM tx

The problem with that approach is that I then have no insert/mix point to feed the local ID Player into ST. Any suggestions? If it's not possible, could an Aux Input be easily added to ST-DSP version to allow another source to be mixed in? Cheers AJ

You could use an audio player with sound card input (Winamp with http://home.hccnet.nl/th.v.d.gronde/dev ... index.html , SAM, ...)

I should probably also enable the sync correction in the stand alone version to compensate for drift, but that requires more testing and I'm not going to do this now anymore (new version is nearly ready for release).

Can you please elaborate on that idea. Are you thinking two players, the first playing back the main program stream, feeding the line input of the 2nd player with ST-DSP? So how would that work, as the first player would not be running ST, so would drift. (nor could first player run ST, as FM sync only outputs to MPX device).

If just one Winamp player, you can't have two sources (playback stream and line input) active at once can you? Cheers AJ

You have more then 1 problem...

- You must use 48kHz for input, Don't worry, winamp will work just fine. All you need is to make sure that ST is FIRST started!
Then you can start winamp and your next play-program.

- Second, i guess you are making link connection with shoutcast or icecast server and winamp as RX player. If so, that will NEVER work longer then few days without, first drops and finally stops. Reason, because Winamp, when there is no more buffer, does not know to start again. You can make playlist with same stream over and over and loop ON. Sometimes it will go to next one in list and sometimes it will just stop and you need to manualy press stop and play again.

You don't need ST's sync function at all and it will not help you at all. Winamp will anyway make shorter and shorter latency and after few days, will stop!

You need other solution, other then winamp and sc or ic server. Something that will never make shorter or longer latency, something that will, if network error occures, will start to drop, and when network is ok again to continue with same latency without to stop..

Hi Bojcha,

Thanks for that. The streaming encoder is Orban Opticodec working in RTP/UDP Multicast mode. This feeds a satellite (one way) link.

We find that some pc's receiving the stream using Winamp, stay very *roughly* in sync, while others have a ~0.2 second gap/glitch an hour (when player/device is playing fast), while others accumulate an extra few seconds a day in their buffer (when player/device is playing slow).

I don't quite understand why you say we don't need ST FM sync feature. From what I understand of how it works, it is exactly what we need to keep each site playing at the same (long term) speed with same amount of data in its buffer, and avoid all gaps irrespective of the local sound card clock drift.

FM sync feature is the only way I can see to solve our issue (other to GPS clock encoder and all decoders, which is not viable).

Winamp will typically run continuously for many weeks or even months at a time, but we have an app that instantly sends a play command to winamp should it ever stop playing (e.g. during satellite sun transit interference).

ok, now i know that there is more then one transmitter site.

Yeah I overlooked something indeed. If you are using an ESI Juli@ card I know how to fix it... With other cards it's more difficult.

I wonder (Bojcha you have played with this a lot) - is it somehow possible to have VAC behave unaware of sampling rates? So basically, anything you send to it is delivered to the next program in the chain, but if you send nothing the other side will keep waiting?

Solution with ESI card:
- Signal receiving Winamp sends output to digital out, which is wired back to the input. And this first Winamp performs the sync
- Extra signal also sent to this output
- Stereo Tool stand alone takes (via DirectWire in the Juli@ driver) the digital output and processes it and sends the MPX signal to analog output.

Although I'm not 100% sure if this will function if the FM output written to the digital ports is running at 192 kHz.

So if the first winamp is to perform the FM sync, it must be running ST-DSP (presumably with all audio processing disabled) , which will then only output an FM MPX signal as I understand it. If that MPX output is looped back via Julia to an ST-SA input, how does ST-SA deal with a MPX input?

I could see how this could work if ST-DSP could do a normal (non-MPX) output with FM SYNC enabled, but it can't can it?

Yes it can. Just enable FM but nothing INSIDE it. It will then just upsample the audio but still give you 2 channels (stereo) of normal audio.

By the way, if you wouldn't have a Juli@, this might be an option: Running the synchronization mechanism TWICE... First time to handle input sync, 2nd to handle VAC vs sound card sync.

Confirmed. You learn something new everyday! Useful - Thanks.
I have a Julia, but the tricky bit is I want to process two FM services on the pc. At present ST does not allow sound card sharing (like BBP; tx1 MPX - Julia L, tx2 MPX R), and two Julia cards won't work in the one pc. I'm waiting on a demo Marian card (still no local stock in country at moment) as I understand they have true multiple client drivers, and audio routing capabilities similar to Julia. In total though, would require 4 ST instances on the pc (albeit one per stream just doing FM sync), so will be interesting to see how this works. I'll let you know.

If I do need VAC (and two steps of sync correction), that suggests the second step would not be via ST-SA, but ST-DSP in winamp. As I understand it, the line input plugin for winamp does not properly/reliably handle setting the input source to anything other than the windows default device, which would rule out processing two separate stations on the one pc. So hopefully a Marian card will allow me to route to ST-SA.
Yes that would be useful for many everyday applications. If I run into trouble, I'll wait for sync correction to be added to the SA version, although unless it will allow the input of an output device (like VAC), I assume I may still need two steps of sync correction enabled (winamp stream playback and then after the VAC pipeline). But at least I'd only need one step per station requiring a Winamp instance!

FM sync is a very cool feature Hans. I didn't even know it was on your to do list when it suddenly appeared out of nowhere in the DSP version.

Thanks for the advice. AJ