MP3Gain is an implementation of ReplayGain. Depending on the audio file format, the process may also be lossy in the sense that it could irreversibly push a signal above the format's maximum amplitude (resulting in clipping) or below the minimum (resulting in silence). For example, MP3 and AAC files can only be losslessly modified in 1.5 dB steps. Limitations of the audio file format may prevent precise (finely tuned) gain adjustments with this method. If no "undo" info is saved somewhere, it may not be possible to restore the original audio data. In this scenario, only one type of ReplayGain (Track Gain or Album Gain) can be applied. In the audio data method, the file's actual audio data is modified so that its natural/default playback volume is at the target level. And there's no standard for where and how ReplayGain info is stored each implementation uses different formats and puts the info in different locations.
#Mp3 gain normalizer how to
Not all audio players/decoders know how to read and use ReplayGain information stored in metadata. If audio data was also changed, the metadata can contain "undo" info. The volume-change information can be very precise. In the metadata method, information on both types of ReplayGain (Track Gain and Album Gain) can be stored. There are advantages and disadvantages to both methods. Some modify the audio data itself, and optionally use metadata as well. Most use metadata to indicate the level of the volume change that the player should make. There are different ReplayGain implementations, each with its own uses and strength. Some recommend using a compressor/limiter DSP to prevent or reduce clipping, regardless of whether it was caused by ReplayGain. Some have a "prevent clipping" feature to reduce the amount of ReplayGain adjustment to whatever amount would keep clipping from occurring, based on peak info stored in the file's metadata (thus reducing the effectiveness of ReplayGain). Some have a "pre-amp" feature which reduces (or boosts) the original audio's level by a certain amount before doing whatever is needed for ReplayGain. Implementations deal with the risk of clipping in different ways. Whether this distortion is audible depends on the sounds in question, and the listener's sensitivity. That is, upon playback, the volume of a quiet song is increased, so the parts of the song with above-average loudness, especially in the bass frequencies, will exceed the limits of the format and will be distorted. ClippingĪudio is generally recorded such that the loudest sounds don't clip, but the use of ReplayGain can cause clipping if the average volume of a song is below the target level. The target loudness of almost all ReplayGain utilities is 89 dB SPL when replayed in an SMPTE RP 200 calibrated system (an early departure from the proposal, endorsed by its author ) - the ReplayGain proposal and SMPTE recommendation are 6dB lower. The result is that Replay Gained waveforms are usually more uniformly amplified than peak-normalized waveforms. the RMS power after applying an "equal loudness contour"), and then adjusts the amplitude of the waveform accordingly. The ReplayGain technique measures the effective power of the waveform (i.e. Peak normalization merely ensures that the peak amplitude reaches a certain level. ReplayGain is different from peak normalization.
This is especially important when listening to classical music albums, because quiet tracks need to remain a certain degree quieter than the louder ones. This is called 'Album Gain' (or 'Audiophile Gain' in earlier parlance). It also allows the loudness of a specific sub-collection (an "album") to be consistent with the rest of the collection, while allowing the dynamics from song to song on the album to remain intact. This is called 'Track Gain' (or 'Radio Gain' in earlier parlance). ReplayGain allows the loudness of each song within a collection of songs to be consistent. It defines an algorithm to measure the perceived loudness of audio data. ReplayGain is the name of a technique invented to achieve the same perceived playback loudness of audio files.
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