The primary goal of mastering for mobile devices and apps is to ensure that the audio sounds its best when played back on these devices, taking into account their specific playback characteristics and limitations.

High-resolution audio formats are not typically a challenge when mastering for mobile devices and apps, as these devices typically support lower-resolution formats due to bandwidth and storage limitations.

The recommended loudness level for audio mastered for mobile devices and apps is -16 LUFS, as specified by the ITU-R BS.1770 standard.

FLAC is a lossless audio codec, while MP3, AAC, and Opus are lossy codecs. Lossy codecs are typically preferred for streaming audio on mobile devices and apps due to their smaller file sizes.

Dithering is a process that adds a small amount of random noise to the audio signal before quantization, which helps to reduce quantization noise and improve the overall sound quality.

Reverb is not typically used as a mastering technique for mobile devices and apps, as it can add unnecessary space and muddiness to the audio.

A limiter is used to prevent clipping, which occurs when the audio signal exceeds the maximum amplitude level and causes distortion.

WAV is a lossless audio format, while AIFF, MP3, and AAC are lossy formats. Lossy formats are typically preferred for mastering audio for mobile devices and apps due to their smaller file sizes.

Metadata provides information about the audio file, such as the title, artist, album, and genre. This information is important for organizing and identifying audio files on mobile devices and apps.

Physical media, such as CDs and DVDs, are not typically used for distributing audio mastered for mobile devices and apps, as these devices do not have physical media drives.

Testing mastered audio on a variety of mobile devices and apps helps to ensure that the audio sounds its best and is compatible with different playback systems.

Bit depth is not typically used as a metric to evaluate the quality of mastered audio for mobile devices and apps, as these devices typically support lower bit depths due to bandwidth and storage limitations.

Perceptual coding is a technique used to reduce the file size of audio files while maintaining the perceived quality of the audio.

While a spectrum analyzer can be useful for analyzing the frequency content of audio, it is not typically used as a primary tool for mastering audio for mobile devices and apps.

Staying up-to-date with the latest trends and technologies in mastering for mobile devices and apps helps to ensure that mastered audio is compatible with the latest devices and platforms and meets the evolving needs of listeners.