OpusDecoder produces degraded audio quality

[appujet]

Bug

OpusDecoder produces unclear/muffled audio when decoding real-world Opus
packets encoded by the reference C libopus (e.g. WebM/Opus).

Reproduce

let mut decoder = OpusDecoder::new(48000, 2).unwrap();
let mut pcm = vec![0.0f32; 960 * 2]; // 20ms stereo @ 48kHz
decoder.decode(&libopus_packet, 960, &mut pcm).unwrap();
// → audio plays but sounds unclear/distorted