Great stuff. thanks! - Mark On Sat, Apr 12, 2008 at 7:56 AM, Fons Adriaensen <fons@xxxxxxxxxxxxxxx> wrote: > The first (beta) release of Jmeters is available at > <http://www.kokkinizita.net/linuxaudio/downloads> > > Jmeters is a Jack multichannel audio level meter app. > It looks very similar to meterbridge since it uses the > same pixmaps. > > This first release offers VU, PPM and stereo versions of the > same. The stereo versions have two indicator needles on the > same scale. I've never seen a twin VU, but stereo (or M/S) > PPMs *do* exist. Later releases will add bargraph meters, > digital peak indicators for the analog ones, and a stereo > correlation meter. > > The main difference to meterbridge is that Jmeters has the > correct ballistics for both the VU and the PPM. > > The VU meter measures the average of the absolute value of > the signal, 'average' meaning a second order filter that > reaches 99% in 300ms and overshoots between 1.0 and 1.5%. > It is calibrated to indicate 0dB for a sine wave at -10dB > w.r.t. digital full scale (which is +/-1 peak in this case). > > The particular VU scale used is not entirely linear and > starts at -20dB (it's one designed for a passive VU meter > with a diode bridge), so the meter will not move at all > for inputs below that level. Later versions may use a > VU scale designed for an active meter which doesn't have > this threshold. > > The PPM is a pseudo-peak meter. It will indicate 80% of > the steady-state value for a 10ms burst, and fall by 24db > in 2.8s. Each scale division (1..7) represents 4dB. It is > calibrated to indicate '7' (+12 dB on the EBU scale) for > 0dB FS. > > For speech and music with distinct short peaks the PPM > will usually indicate higher. For music with continuous > long notes, and for heavily compressed signals the VU > indicates higher. Both meters require some 'getting used > to' in order to read them correctly. > > You can modify the calibration by using the -g(ain) option, > but it should normally not be necessary. > > > Enjoy ! > > > -- > FA > > Laboratorio di Acustica ed Elettroacustica > Parma, Italia > > Lascia la spina, cogli la rosa. > > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user > _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
