Package media provides means for querying information about audio and video data.
const ID3v1TagLength = 128
ID3v1TagLength is the length of an MP3 ID3v1 tag in bytes.
GetMPEGAudioDuration reads the first frame in r and returns the audio length with millisecond precision. Format details are at http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header.
HasID3V1Tag returns true if an ID3v1 tag is present at the end of r.