The Overload pop-up - How can overloads happen?


The overload warning pop-up

The overload warning pops up when the file conversion produces results which exceed maximum digital value (0dBFS) by a margin determined by a value on the settings page. By default this value is 2dB; a good choice for general use. However recordings and mastering engineers may want to set this much lower; perhaps +0.1dBFS.*

*Note that overload setting may not be set negative to 0dBFS.

How can overloads happen?

The FRANCINSTIEN and the Bride of FRANCINSTIEN process are both equal energy processes. Being the result of a simulated interchannel crosstalk, energy may be exchanged between the channels, but there is no gain in the system. Because of this, these processes will very rarely produce clipping

The same is not true of other processes. Here, there is gain in the system and, depending on the nature of the input file, these may produce values above 0dBFS when converted back to a PCM file. This is especially true of the Blumlein delta process which "expects" to see input files from closely spaced microphones. Input files derived from other microphone arrangements, or from panned stereo may have substantial interchannel differences at low frequencies which will produce very high amplitude LF energy after conversion. (Note that the clipping does not happen within the program itself; where floating point values ensure that the audio can never overload. It is only when these values are converted back to the signed integer format of an audio file that the clipping can occur.)

The Stereo Lab program offers you the option to reduce the amplitude of the input file when clipping occurs. The gain reduction is based on the severity of the clipping in the output file.

A special situation exists in the case of converting Quadraphonic or Ambisonic tracks or when up-converting to 5.1 from stereo. In these cases, there are output options to produce multiple audio files; either in groups of two (stereo files) or as mono files. In this situation, all files are calculated and the maximum overmodulation is indicated in the dialogue. In the case where gain reduction is selected, this gain reduction will be applied to all files equally so as to preserve the correct channel balance.



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