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Thank you!
Only thing is, how would we handle the fallback playout if running as an MPX-link?
I suppose I could put an extremely optimized breakaway-processor with the low cpu clipper and stereo generator, to handle the fallback 🙂.///Leif
No need to worry. Being in the red area does not necessarily mean distortion, and being in the blue area does not necessarily mean the level is too low. It’s just there as a guideline, as an aid if you’re broadcasting live and have an actual fader to control.
As long as you never have red flashing meters (clipping), it should be fine.
///Leif
Makes sense. I’ll put it in, but you will need a 2-instance license for BBP. Two 1-instance licenses will not do it as that requires two PCs.
Also, this does not work with BBP ASIO unless you have a card with an ASIO driver which can be opened by two programs at the same time. If you do, then this is already supported by BBP ASIO today, as you can choose MPX output channels individually.
Best regards,
///Leif[quote author=”yorkie98″]lost in the event of theft or communications authority raids[/quote]
I had to LOL at this 🙂. Okay, I see your point.
Seriously, I wouldn’t dream of changing a user again in this particular situation 🙂.
It would be interesting to run flac, the only problem is that it performs rather poorly on MPX signals. I use flac in mpxtool, and i’m lucky to achieve compression ratio 0.7. Flac compression usually achieves more like 0.4 with regular cd-quality audio — this is a huge difference.
Using MPEG-1 Layer 2 i was able to encode composite at 1.5mbps with barely 1% of overshoot, which would be completely acceptable performance wise, but still too hefty bandwidth-wise.
Composite does not need 192kHz — it would in fact be fine with 128kHz if carefully done. (15 kHz bandwidth is readily achievable at 32 kHz sampling rate, so 60 kHz is achiavable at 128 kHz sampling rate, and this covers MPX including RDS.)
It also doesn’t need 16-bit sampling. Not even on an awfully frigid day in hell will we achieve 100 dB SNR on the FM band during anything resembling normal circumstances. In fact, 12-bit sampling is enough, which gives us 72dB SNR. Considering that this -72dB noise floor is AFTER compression and clipping, we’re good.
128 kHz 12-bit 1-channel is 1.536 MBps. Literally half the size of 192 kHz 16-bit, and this is before even using a codec — this is still PCM.
I just did a test on this, and then FLAC’ed the result, and got a compression ratio of 0.57, above and beyond the downsampling already done. This meant that a 93mb flac file got down to 35mb.. That’s 1.15mbps, with no possibility of codec-induced overshoots or audible degradation.
Here’s what the result looks like:
Now, can a DSL line sustain 1.15mbps indefinitely without dropouts or glitches? Most cannot, I would think, but perhaps some can. Interesting thought.
This was reference settings though. More aggressive settings might use some more bits.
Edit: Here’s with more aggressive settings + RDS. 12-bit mpx audio, 128 kHz sampling, flac:
Total bitrate: 1.26 Mbps
10-bit (!!) mpx audio with RDS, 128khz sampling, flac:
The noise floor is a little higher than I’d ideally like, but considering the nature of FM, I’d accept it in a pinch — i doubt it would be audible in anything resembling normal circumstances.
Total bitrate: 1.0 Mbps
///Leif
That’s the colour coding to help you feed the correct input level.
Try to usually stay in the green zone. If you want more headroom (if you’re in the blue zone, barely reaching the green zone) you can adjust the ITU Ref Level to move the green zone downwards. This adjusts internal parameters (for example downward expanders) to suit your input level.
Best regards,
///LeifAnything is possible, but at this point I have to ask, what on earth for??
I mean, how often does one really have two FM transmitters with MPX inputs in one place? 🙂
Channel selection makes sense though — that’s not too hard to implement. I’ll look into it.
Best,
///LeifLack of bandwidth is only part of the problem.
No hardware supports MPX streaming, so you’d still need a computer at the transmitter site to receive the stream.
At that point, why not just run the processor on *that* computer instead? 🙂
///Leif
The carrier should really be able to basically disappear. The point where it completely nulls, that’s where you’re at +/- 75 kHz with the 31185hz bessel null tone.
I’m not sure why you’re not able to get it to null.
Check and make sure you’re really seeing the first null. Start by turning the exciter modulation level all the way down. You should see just the carrier, no sidebands.
Then, as you turn the modulation up, you should see sidebands appear and grow outwards, and you should be able to find the first null. That’s where you want to be
///Leif
Exactly what I’m planning to do. I just figured I’d ask 🙂.
Thanks, Sgeirk. Finally someone who’s reasonable!
///Leif
I think I know what the problem is.
Please delete dsphost.exe from the BreakawayBroadcast folder and then install the latest version again. If this file is still remaining from an older version, perhaps the installer didn’t overwrite it.
Best,
///LeifHi Yorkie!
There are professional sound cards where this would be possible, where L and R could show up as different devices. However, most sound cards do not support this.
///Leif
Hi Herman!
I listened to this song, and thought it sounded just great through eruption!
Could you elaborate?
Please provide clips from bbp (and a competing processor, and the original) and explain exactly what it is you don’t like, and i’ll be happy to listen and figure out a solution.
Best,
///LeifIt should be dead-on accurate! Bessel null is the most accurate way there is.
What preset are you using? Are you sure you nulled it properly? Please post a photo of the spectrum analyzer.
Best,
///LeifSorry Stavros, there is no way to make a cheap FM-exciter behave, no matter how much you EQ the signal. Believe me, I’ve tried.
If you care at all about getting a loud, powerful signal, the pre-requisite is to have an exciter that can pass 1 through 60 kHz flat. If the exciter has inferior performance, no audio processor in the world will help you.
On the other hand, you only need to replace the exciter, which is cheap. You can still use the same power amplifier, antenna, etc.
I recommend the Broadcast Warehouse PLL+ 1w. Impeccable performance, and it’s under 200 dollars.
Best,
///Leif
