- This topic has 14 replies, 4 voices, and was last updated 15 years ago by
.
-
Posts
-
Welcome to the MpxTool forum!
In the name of maintainability, we’ve moved the MpxTool forum from mpxtool.com to claessonedwards.com. This way, BBP + MpxTool users don’t need to register twice, and it’ll be much easier to keep track of both forums.
Upcoming new features for the next MpxTool version:
Online activation — No more hardware ID necessary!
ITU Loudness MeterBest,
///LeifWhat is the purpose of MpxTool? I’ve read many references to it here in the forums, but I’ve yet to figure out just what it’s used for. ❓
Excellent question, AuBadge 🙂.
It’s a program for recording / playing back / comparing / analyzing MPX files, as well as real-time analysis.
MPX is the underlying analog encoding system used in FM Stereo Radio. Being able to work with MPX audio on a computer takes a lot of the guess work out of calibrating the audio chain at a radio station (whether a big "real" station, or your own transmitter for experimentation).
To record MPX, you’d need MpxTool full version ($199), a 192 kHz capable sound card, and a tuner modified for MPX output.
However, to play / analyze / compare MPX, all you need is the free version and ANY sound card. 192 kHz not necessary! All decoding is done in software, and you get an oscilloscope, spectrum analyzer and modulation monitor — replacing hardware that costs thousands and thousands of dollars.
If you for example download one of the MPX recordings I made during my last travel, and play it back, it will sound EXACTLY like it would if you were there, listening with a good radio. Thus, you can accurately compare what radio sounds like in different cities — even if you’re thousands of miles from the city. All you need is the MPX.
Is it useful? For most people, no — definitely not. However, for anyone interested in audio processing, it’s invaluable. I couldn’t live without it — in fact, that’s why I wrote it, since nobody else had. 😉
At some point in the distant future I’ll implement RDS decoding. RDS is captured in the files, the subcarrier is right there (as well as SCAs on certain stations), MpxTool just doesn’t decode it yet.
Best,
///LeifThanks for that explanation, Leif; I feel better now. 😀
For a while there, I thought I was missing out on something everyone should have![quote author=”Leif”]Upcoming new features for the next MpxTool version:
Online activation — No more hardware ID necessary!
ITU Loudness Meter[/quote]
That sounds great, but may I submit my own wish list for your consideration? It’s just a few things that should be reasonably straightforward…* The ability to take a 192 kHz composite source file and decode it to a de-emphasized L/R 44.1 kHz WAV file, at full processing speed… mostly so I could take one of the processing tests or airchecks, burn the "as-received" audio to a CD, and then listen to it on my home stereo system, on the same equipment I use to listen to my local radio stations, to get an equal comparison. Right now I could have a program recording MPXtool’s demodulated audio in the background as it plays an MPX file, but that must be done in real-time and involves going through the sound card mixer, which may degrade audio quality.
* The ability of the "Stats" panel to keep a running tally of the highest peak level measured during the current session (recording or playback), so I don’t have to always keep my eye on the meter to catch overshoots.
* The ability to "zoom in" on the 0-20 kHz audio baseband of the composite spectrum, to get a better look at the shape of the processor’s low-pass filter.
* Finally, the ability to turn off the built-in 18.5 kHz brickwall filter when in L/R input mode, to get a look at how deep the processor’s own notch around the pilot is.
Hopefully that’s not too much on your plate! 😉
-Kevin
Hi Kevin!
quote :The ability to take a 192 kHz composite source file and decode it to a de-emphasized L/R 44.1 kHz WAV file, at full processing speed…Done!
http://mpxtool.com/files/mpxdec.zip
I had already written an mpx decoder utility, but it didn’t have sample rate conversion (so it would only output 48k from a 192k file). I added that, cleaned up the command line interface, and here is!
It’s a command line utility — completely free.
quote :The ability of the “Stats” panel to keep a running tally of the highest peak level measured during the current session (recording or playback), so I don’t have to always keep my eye on the meter to catch overshoots.Good idea. Will do for the next version.
quote :The ability to “zoom in” on the 0-20 kHz audio baseband of the composite spectrum, to get a better look at the shape of the processor’s low-pass filter.Sorry, I’m gonna have to veto this one for now — the way the code is written it’d be a major pain in the neck to do zoom, and besides, you see it quite clearly as it is.
quote :Finally, the ability to turn off the built-in 18.5 kHz brickwall filter when in L/R input mode, to get a look at how deep the processor’s own notch around the pilot is.This actually exists already. Open mpxtool.ini in notepad, search for "StereoCoder", and change lowpass from 1 to 0.
3 out of 4 ain’t bad, eh? 🙂
///Leif
[quote author=”Leif”]3 out of 4 ain’t bad, eh? 🙂[/quote]
Fair enough! 🙂 And now that I think of it, viewing the decoded L/R audio in Adobe Audition’s spectrum analyzer would give me a perfect view of the audio passband, anyway. 😉..or just view the decoded L/R in MpxTool. That IS in fact an option, if you haven’t already found it. Right-click the spectrum analyzer 🙂.
How’s the command line tool working out for you?
///Leif
[quote author=”Leif”]Yeah, it’s only for us cool geeks, it’s too much for you, don’t even try it 😉 🙂.
///Leif[/quote]
Ok, Ok, I get it 😆
I’m happy enough when the music I stream sounds awesome; I don’t need to know how it happens, as long as it happens. I’ll let you "cool geeks" handle the mechanism which helps me to do that. Fair enough?
[quote author=”Leif”]How’s the command line tool working out for you?[/quote]
It does the trick… thanks! 🙂It’s interesting to realize how much more detail I can hear when playing the MPX clips on a hi-fi audio setup in a quiet environment… for example, I can now clearly hear the Omnia 6EX’s HF hole punching in the "torture test"… I thought that was only a problem with the Omnia.One, but especially at 32:53 I can really hear how the 6EX ducks down the treble and then takes several seconds to slowly recover. 😮
I don’t mean to bash Omnia’s flagship product just based on this one particular artifact, but even on much less expensive processors running presets that are more aggressive, I don’t hear similar problems with HF ducking and hole punching. 😳
Indeed, Kevin.
The O6EXi in particular does several more strange things in the torture test. Stereo image shifts, compressor-trying-to-climb-over-a-hill phenomenon (i named that myself, I have no better name for it, but it’s extremely audible in the first couple of verses of "my heart will go on"), wideband ducking to prevent too much distortion (dixie chicks clip), for example. Try to catch’em all 😉.
///Leif
- You must be logged in to reply to this topic.