WaveformData class final Visualizer and analysis

Mono min, max and RMS amplitude envelope of the audio currently loaded.

Emitted on PlayerStream.waveform for the loaded track. The track is mixed down to mono and binned into a fixed ~2000-entry envelope. A local file is decoded in the background: partial envelopes (decoding true) come first, then the final one. An HTTP file that plays from its start is decoded the same way from mpv's cache as it downloads. Other network sources grow with playback (unfilled bins in filled), and a live stream is a sliding window of up to 131072 bins.

Bin i spans the time slice [start + i / bins * duration, start + (i + 1) / bins * duration). min and max hold the lowest and highest sample value seen in each bin, range [-1.0, +1.0], and rms the root mean square of the bin. On loud, heavily limited masters the peaks sit near full scale for most of the track, so drawing rms as the body of the waveform, with the peaks as a lighter outline, keeps the sections readable.

For a normal (known-length) track start is zero and duration is the whole track, so bins map onto [0, duration]. For a live stream (live == true) there is no total length: the envelope is a sliding window kept in lockstep with the demuxer's seekable cache, so start is the absolute media time of bin 0 (the oldest still-cached moment) and duration is the span currently held (it grows while you listen and only drops its oldest bins once the demuxer evicts that audio from its back-buffer). The newest bin is "now". Map bins with start and duration in absolute media time and you can scrub anywhere the cache still covers.

Example: paint a bar per bin:

player.stream.waveform.listen((wave) {
  if (wave == null) return;
  for (var i = 0; i < wave.bins; i++) {
    final yMin = wave.min[i] * canvasHeight / 2;
    final yMax = wave.max[i] * canvasHeight / 2;
    // draw bar i from yMin to yMax …
  }
});