Mastering Software Part 1 - Metering Levels and Loudness - Mastering Media Blog

Thursday, 15 May 2008

Mastering Software Part 1 - Metering Levels and Loudness

I mentioned the Orban Loudness Meter on the SOS forums, and thought it would be good to start a series of posts here on useful mastering software. So, first up - metering apps. Several of the best editing packages include decent metering, for example Wavelab, and Audacity, but here are a few personal favourites:
  •  Orban Loudness Meter Great (free!) utility includes a PPM meter, VU meter, ITU BS.1770 meter and CBS Technology Center loudness meter - it's fantastic to have access to these less common metering systems, which offer measurements of perceived loudness, which can be more useful than pure RMS. (Plus it runs well under Parallels on my MacBook Pro ;-) 
  • Pinguin Audio Meter Not free but comes in several flavours, the Pro version includes an incredibly detailed spectrum analyser, audio phase correlator (more in a later post), PPM & VU monitoring plus a specrogram. Interestingly, Pinguin have done research to suggest that RMS is the most reliable way of measuring perceived loudness.
  • Speaking of Spectrograms, there's Spectrogram - and Audacity has this capability, too.
  • Finally, the fantastic (Mac-only) AudioLeak - an Leq (Long-term Equivalent Level) Analyzer for audio files and sound input streams. Swiftly discover the average RMS of an audio file, and it's A-weighted counterpart. Just watch out - by default it displays a combined mono value which reads higher than other applications like Wavelab - I usually use the average of the left & right values - they should be almost identical if the L/R balance is right, anyway. Also great for DVD Producers wanting to find the right dialnorm setting for a Dolby Digital encode.
  • Update - here's another one - the SSL X-ISM meter. This is useful because it includes checking for inter-sample peaks. This is well-explained on the page I linked to, but briefly: strange as it may seem, when audio has been heavily limited and is peaking at (or very near to) zero, it is possible that the reconstructed analogue output actually peaks above zero. (In theory, up to 6 dB higher !) In cheaper players, MP3 encoders and other utilities, there is often no headroom allowed for this situation, and unwanted clipping can result. This meter will help you watch for this effect and avoid it. As a rule of thumb, don't allow your audio to peak higher that -0.3 dBFS.
Coming soon - how to choose a mastering studio.


omer said...

Hi Ian,
I'm an audio novice, and I started getting interested in the loudness war after reading about Death Magnetic and how Iron Maiden got their music butchered in their "enhanced" CDs. I found your blog and found it very informative, so I have a few questions:
1. Can you recommend a free/cheap software that can help me assess clipping (seeing or counting) and other loudness-war related artifacts in my music CDs and mp3s?
2. Can you recommend a CD-to-mp3/wmv ripping method (software+how-to) that will produce the closest-to-original music files?
3. Are you familiar with a website that posts examples of bands/CDs that are victims of the war, and should be avoided?

Thanks for your time!

omer said...

Almost forgot:
4. Can you recommend a tool that can "correct" clipping and restore dynamic range? I know real correction is impossible, but I hear there are software that estimate the clipped wave by interpolating etc...

Again, thanks!

ianshepherd said...

Hi Omer,

1. Audioleak - link in the post above. To get an idea what it's telling you, check this post. Any audio editor - for example Audacity - will allow you to look at waveforms and spot clipping.

2. ITunes does a reasonable job, and is free

3. You could try Justice For Audio ?

4. The only one I have used is Sonic Solutions - it is no longer in production, and used to cost tens of thousands of dollars, but when it works, it works. I've read good things about Izotope's software, but I haven't used it.

Hope that helps !


soundseller said...

just stumbled upon your blog.
Thanks for the SSL X-ISM info.
Would have gone past me otherwise.

ianshepherd said...

No problem, you're welcome !

vacuole said...

On Linux, there's jkmeter by Fons Adriaensen. This is a metering app with stereo and ambisonic support, K-14 and K-20 RMS as well as peak metering, clipping indicator, long-term peak, and a correlation meter. Connectivity is via JACK, and it's royalty-free and open-source (GPLv2).

Rafael said...

Isotope RX is awesome, spectral repair and declipper...

John Decade said...

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