gateOptInAudio function

ResolvedAudioMix? gateOptInAudio({ required Widget composition, required bool encode, required bool warn, required int fps, required int frameCount, required void warnSink(String message), required String platformLabel, Export? export, })

The one audio-drop policy the on-device and in-browser renderers share.

Audio is opt-in where the encode runs on the user's device: with encode false, a Video that declares Audio yields no mix and warns once through warnSink (unless warn silences it), naming the platform via platformLabel ("on-device", "in-browser"). A non-MP4 export cannot carry audio, so it also yields no mix, with its own warning. A non-Video composition or one with no declared audio yields null silently.

With the opt-in on and an MP4 target, returns the ResolvedAudioMix the renderer stages into its encoder.

Implementation

ResolvedAudioMix? gateOptInAudio({
  required Widget composition,
  required bool encode,
  required bool warn,
  required int fps,
  required int frameCount,
  required void Function(String message) warnSink,
  required String platformLabel,
  Export? export,
}) {
  if (composition is! Video) return null;
  final mix = resolveAudioMix(video: composition, fps: fps, totalFrames: frameCount);
  if (mix.isEmpty) return null;
  if (!encode) {
    if (warn) {
      warnSink(
        'This Video declares ${mix.tracks.length} audio track(s), but '
        '$platformLabel audio is off, so the MP4 will be silent. Pass '
        'audio: true to encode it, or warnOnDroppedAudio: false to silence '
        'this warning.',
      );
    }
    return null;
  }
  if (export != null && export.mode != ExportMode.mp4) {
    if (warn) {
      warnSink(
        'Audio is only muxed into MP4 renders; this ${export.mode.name} export '
        'drops the ${mix.tracks.length} declared audio track(s).',
      );
    }
    return null;
  }
  return mix;
}