Algorithms to measure audio programme loudness and true-peak audio level

Scope This Recommendation specifies audio measurement algorithms for the purpose of determining subjective programme loudness, and true-peak signal level. The ITU Radiocommunication Assembly, considering a) that modern digital sound transmission techniques offer an extremely wide dynamic range; b) that modern digital sound production and transmission techniques provide a mixture of mono, stereo and multichannel formats and that sound programmes are produced in all of these formats; c) that listeners desire the subjective loudness of audio programmes to be uniform for different sources and programme types; d) that many methods are available for measurement of audio levels but that existing measurement methods employed in programme production do not provide indication of subjective loudness; e) that, for the purpose of programme exchange, it is essential to have a single recommended algorithm for objective estimation of subjective loudness; f) that future complex algorithms based on psychoacoustic models may provide improved objective measures of loudness for a wide variety of audio programmes; g) that digital media overload abruptly, and thus even momentary overload should be avoided, considering further h) that peak signal levels may increase due to commonly applied processes such as filtering or bit-rate reduction; j) that existing metering technologies do not reflect the true-peak level contained in a digital signal since the true-peak value may occur in between samples; k) that the state of digital signal processing makes it practical to implement an algorithm that closely estimates the true-peak level of a signal; l) that use of a true-peak indicating algorithm will allow accurate indication of the headroom between the peak level of a digital audio signal and the clipping level,