What Is Gapless Playback? Why Albums Break

The one-paragraph version

Some albums are not a collection of songs — they are one continuous recording that happens to have track markers in it. A live set, a DJ mix, most classical recordings, Dark Side of the Moon. Without gapless playback, a player inserts a fraction of a second of silence at every track boundary, and the record stops being what it was. Gapless playback removes that.

Why the gap exists at all

Two separate causes, which is why fixing one does not always fix the problem.

The buffering gap. A naive player finishes decoding track one, tears down the audio pipeline, opens track two, fills a buffer, and starts again. The gap is however long that takes. A gapless player decodes ahead and hands the audio device a continuous stream across the boundary — the next track is already buffered before the current one ends.

The encoder padding gap. This one is specific to MP3 and it is not the player's fault. MP3 encodes in fixed blocks of 1,152 samples. A track almost never divides evenly, so the encoder pads the beginning and end with silence to fill the last block. Play the file back honestly and you hear the padding.

The fix is metadata: LAME encoders write a header recording exactly how many padding samples to skip at each end. A player that reads it can trim them and join the tracks correctly. A player that ignores it cannot, no matter how good its buffering is.

Lossless formats do not have this problem at all. FLAC, ALAC, WAV and APE store an exact sample count, so there is nothing to guess and nothing to pad. If gapless matters to you, this is a genuine practical argument for a lossless library — not a subjective one about sound quality.

Testing whether your player really does it

Vendors claim gapless more often than they deliver it. The test takes two minutes:

1. Find an album you know is continuous. Dark Side of the Moon, any live recording, an electronic mix.
2. Play it across a track boundary you know well.
3. Listen for a click, a stutter, or silence where the music should carry through.

If you want to be rigorous, do it twice — once with a lossless copy and once with an MP3 copy of the same album. A player that is gapless on FLAC and gappy on MP3 is not reading the LAME header, which tells you exactly which half of the problem it solved.

What tends to break it

• Streaming from a network share with a buffer sized for one track at a time. This is the most common cause of a player that is gapless locally and gappy from a NAS.
• Bluetooth, sometimes. The codec negotiation can insert its own discontinuity independent of the player.
• An equalizer or DSP chain that resets between tracks rather than running continuously.
• Shuffle. Gapless between two unrelated tracks is not a feature, and a good player does not try.

Gapless in Trove

Trove plays gapless across every format it supports, including MP3 with LAME headers, and including when the tracks are streaming from a WebDAV or SMB share — the decoder reads ahead across the track boundary rather than restarting at it. Gapless playback is in the free app, along with every format, the 10-band equalizer, playback speed and the sleep timer.

Related terms

• FLAC — the format that makes gapless a non-problem
• DSD — SACD reissues of continuous albums are the hardest case
• WebDAV — where gapless most often quietly stops working