fix(analysis): render full-track spectrograms

2026-07-28 23:08:59 +02:00 · 2026-07-23 18:24:14 +07:00
parent 5856729e9a
commit 0cbe51ad19
2 changed files with 632 additions and 431 deletions
@@ -0,0 +1,168 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/widgets/audio_analysis_widget.dart';
+
+void main() {
+  group('audio spectrogram filter', () {
+    test('keeps source rate and uses a full-range float pipeline', () {
+      final filter = buildAudioSpectrogramFilter();
+
+      expect(filter, contains('[0:a:0]aformat=sample_fmts=fltp'));
+      expect(filter, contains('s=1600x800'));
+      expect(filter, contains('scale=log'));
+      expect(filter, contains('fscale=lin'));
+      expect(filter, contains('win_func=hann'));
+      expect(filter, contains('drange=120'));
+      expect(filter, contains('limit=0'));
+      expect(filter, isNot(contains('pan=')));
+      expect(filter, isNot(contains('aresample')));
+    });
+
+    test('can render one source channel without app-specific branching', () {
+      final filter = buildAudioSpectrogramFilter(channel: 1);
+
+      expect(filter, contains('[0:a:0]pan=mono|c0=c1,'));
+      expect(filter, contains('aformat=sample_fmts=fltp'));
+    });
+
+    test('processes the complete source without resampling or downmixing', () {
+      final arguments = buildAudioSpectrogramArguments(
+        inputPath: 'source.flac',
+        outputPath: 'spectrum.rgba',
+      );
+
+      expect(arguments, containsAllInOrder(['-i', 'source.flac']));
+      expect(arguments, containsAllInOrder(['-frames:v', '1']));
+      expect(arguments, containsAllInOrder(['-pix_fmt', 'rgba']));
+      expect(arguments, isNot(contains('-t')));
+      expect(arguments, isNot(contains('-ss')));
+      expect(arguments, isNot(contains('-ar')));
+      expect(arguments, isNot(contains('-ac')));
+    });
+  });
+
+  group('broadband spectral cutoff', () {
+    const width = 200;
+    const height = 800;
+    const nyquist = 96000.0;
+
+    test('ignores a narrow ultrasonic pilot above a 22 kHz music band', () {
+      final rgba = _blankRgba(width, height);
+      _paintFrequencyBand(
+        rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+        lowHz: 0,
+        highHz: 22000,
+        intensity: 220,
+      );
+      _paintFrequencyBand(
+        rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+        lowHz: 53880,
+        highHz: 54120,
+        intensity: 255,
+      );
+
+      final cutoff = estimateBroadbandSpectralCutoffHz(
+        rgba: rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+      );
+
+      expect(cutoff, isNotNull);
+      expect(cutoff!, inInclusiveRange(21000, 23500));
+    });
+
+    test('retains genuine broadband ultrasonic content', () {
+      final rgba = _blankRgba(width, height);
+      _paintFrequencyBand(
+        rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+        lowHz: 0,
+        highHz: 48000,
+        intensity: 180,
+      );
+
+      final cutoff = estimateBroadbandSpectralCutoffHz(
+        rgba: rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+      );
+
+      expect(cutoff, isNotNull);
+      expect(cutoff!, inInclusiveRange(47000, 49500));
+    });
+
+    test('does not report an isolated line as a broadband cutoff', () {
+      final rgba = _blankRgba(width, height);
+      _paintFrequencyBand(
+        rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+        lowHz: 53880,
+        highHz: 54120,
+        intensity: 255,
+      );
+
+      final cutoff = estimateBroadbandSpectralCutoffHz(
+        rgba: rgba,
+        width: width,
+        height: height,
+        maxFrequencyHz: nyquist,
+      );
+
+      expect(cutoff, isNull);
+    });
+
+    test('rejects invalid or incomplete images', () {
+      expect(
+        estimateBroadbandSpectralCutoffHz(
+          rgba: Uint8List(3),
+          width: 1,
+          height: 1,
+          maxFrequencyHz: nyquist,
+        ),
+        isNull,
+      );
+    });
+  });
+}
+
+Uint8List _blankRgba(int width, int height) {
+  final rgba = Uint8List(width * height * 4);
+  for (var offset = 3; offset < rgba.length; offset += 4) {
+    rgba[offset] = 255;
+  }
+  return rgba;
+}
+
+void _paintFrequencyBand(
+  Uint8List rgba, {
+  required int width,
+  required int height,
+  required double maxFrequencyHz,
+  required double lowHz,
+  required double highHz,
+  required int intensity,
+}) {
+  for (var y = 0; y < height; y++) {
+    final frequency = (height - y - 0.5) / height * maxFrequencyHz;
+    if (frequency < lowHz || frequency > highHz) continue;
+    for (var x = 0; x < width; x++) {
+      final offset = (y * width + x) * 4;
+      rgba[offset] = intensity;
+      rgba[offset + 1] = intensity;
+      rgba[offset + 2] = intensity;
+    }
+  }
+}