Original File Length (OFL) for mp3, mp3PRO and Other Audio Codecs
When audio signals are encoded and decoded with typical "lossy" data compression codecs, then it is expected that the decoded audio signals are almost never identical to the original signals. What is often overlooked is, that the decoded audio signals are also typically no longer time-aligned with the original signals. It is shown how these small timing errors are due to the block structure of data processing and to the look-ahead needed for psychoacoustic models. For audio codecs based on the ISO/IEC MPEG standards a solution is introduced which restores the original timing. This "OFL" feature is available in the latest implementations of the mp3PRO audio codec.
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