How to detect silence in audio files?

Android detect silence in MP3 files

• Is there a way to detect silence at the start/end in mp3 files? I want to write a player which cuts the silence in real time. e.g. there is a song which has at the start and end a few milliseconds silence, the player should start play the song from the moment when the silence finishes and should end the song if there is only silence to the end. I think teh best is, that the player cuts the song in real time before it plays it.

• Answer:

  I have solved this type of problem before (automatically detecting the end of a song) by searching for silence. Basically, the algorithm is to decode/generate the audio stream and then find the silence. What does silence look like? First, consider what the audio looks like. The raw PCM data will be an array of amplitude values over time. The amplitude values lie within a range and silence is represented by the midpoint of that range. Thus, if the audio decoder gives you an array of signed, 16-bit values, the range is -32768..32767, with a center value of 0. Thus, to find when the song actually starts, look for the first non-zero value. This isn't perfect since silence might float around the center value. So run some experiments to find the "silence threshold" that is right for you. For finding the true end of the song, you will need to decode ahead a little bit and detect when you have, perhaps, 1/2 second of samples that fall below your silence threshold.