Command line

• Since 19/11/2013 the source code of this loudness meter is available for free (under GPLv3 license) in the GitHub repository: https://github.com/jordicenzano/JOCLoudnessOpen.git

Introduction

The JOCLoudness application is a windows console applications that loads a wave file (.wav) and give us the following data of the file:

• Integrated loudness
• Vector of short term loudness
• Vector of momentary loudness
• Vector and maximum true peak level
• Loudness range value

Input parameters

Loudness Configuration file

The input configuration file is a .ini file (text format). The values that you can set in config file are explained in the following table:

(*) The ITU-R BS1770-2 and ITU-R BS1770 indicates the pre and rlb filter coefficients referred to a sampling frequency of 48KHz. If the input audio file has a different audio sampling frequency and the coefficients are set in auto mode the application calculates the filter coefficients in order to keep the filter weighting curve characteristics.

In the following table you can dowload 3 diferent config example file:

Accepted input wave (.wav) formats

Output wave (.wav) format

EBU gives a set of audio file to test the implementation of loudness meter, and also gives the expected results and tolerances. If the results of the JOCLoudness meter are according to the expected EBU results we can say that the JOCLoudness meter meets the minimum requirements to be EBU compliant.

In the following tables we can see that the results obtained by JOCLoudness meter are perfecly inside EBU tolerances:

Minimum EBU Tech 3341 requirements for loudness measure:

Minimum EBU Tech 3342 requirements for loudness range (LRA) measure:

Viewing those results we can say that JOCLoudness meter meets the minimum requirements to be EBU compliant, and this is indicated by EBU R128 compliant logo:

JOCLoudness implementation details

This application is completely developed in ansi C++ using the ITU, EBU, ATSC standards, and WAV specs as reference. Only tipical C++ ansi libraries (math, stdio, list, vector, etc…) was used, all application modules are implemented from zero: WAV reader, WAV writer, IIR filters, FIR filters, etc…

This gives the following advantages to this application:

• Portable source code (Linux, MAC os, etc…)
• Easy deployment (no dependencies)
• Easy error correction (no strange code from others)
• Very easy to improve

On the other hand, the bad point of absolutely the self made application are:

• More work 🙂

The architecture that the JOCLoudness was made allows to transform, in an easy way, the command line application in a real time loudness meter application.

In the following figure we can see the general block diagram of JOCLouness used in R128 (EBU mode):

The wavreader reads the integer or float samples from the wav file and it transforms them into double, the double precision (64b) samples are sent to channel mapper who allocates the channels according to readmapchanel config parameter. For each channel the samples are sent to channel proc. module (see below). The samples processed by channel proc. module are multiplied by a factor (specified in ITU-R BS.1770-2 recommendation), then are added and sent to the output data file. TO calculate I (integrate loudness) value the same samples are sent to Gate module (see below).

In the following figure we can see a detailed block diagram of channel proc. module:

When a sample enters in channel proc. module it’s sent to 4 different modules:

Following the ITU-R BS.1770-2 recommendation to calculate the true peak level, first it oversamples the signal (put zeros), and after that the signal enters into a low pas filter (LFP) to reconstruct them, and finally apply an algorithm to extract the true peak value.

• Loudness momentary calculation (M)

First we filter the entering samples with the PRE filter, after that the signal is filtered by RLB filter, and in the last step MeanFast does a mean of a number of samples specified intrinsically in config parameters.

• Loudness short term calculation (ST)

It does the same as Loudness momentary module, only change the parameters used to do the final mean.

• Loudness range calculation (LRA)

It does the same as Loudness momentary module, only change the parameters used to do the final mean.

To get Integrate Loudness value we need to apply a gate specified in the ITU-R BS.1770-2, in the following fgure can see a block diagram of gate module:

Future work

• Improve speed of low pass filter (LPF) of oversampler of TP meter (Done in JOCLoudnessDS).

Download JOCLoudness (win version)

(Tested with: Windows XP SP3, Windows 7 (32b and 64b))

• Here you can find a link to download the exe file:  JOCLoudness.exe
• Or you can download a zip that contains: JOCLoudness.exe , example.bat, totest.wav, and and 3 different config files:  JOCLoudness.zip

If you use the Example.bat remember to set PATH var to app directory!!!