From 8f96da8b2000fcf43d1c19ed3b9ae84b74c26284 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=B2=81=E6=A0=91=E4=BA=BA?= <lu.shuren@um-react.app>
Date: Mon, 31 Mar 2025 08:53:24 +0900
Subject: [PATCH] fix: better mp3 detection; drop mp1/mp2 format test

---
 um_audio/src/lib.rs        |  8 ++++++++
 um_audio/src/sync_frame.rs | 18 ++++++++++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/um_audio/src/lib.rs b/um_audio/src/lib.rs
index f4af545..05f0454 100644
--- a/um_audio/src/lib.rs
+++ b/um_audio/src/lib.rs
@@ -103,4 +103,12 @@ mod tests {
         let result = detect_audio_type(mp3_data).expect("failed to parse mp3");
         assert_eq!(result, AudioType::MP3);
     }
+
+    #[test]
+    fn test_mp3_invalid_data() {
+        let mut mp3_data = [0; 4096];
+        mp3_data[0..4].copy_from_slice(&[0xff; 4]);
+        let result = detect_audio_type(&mp3_data).expect("failed to parse mp3");
+        assert_eq!(result, AudioType::Unknown);
+    }
 }
diff --git a/um_audio/src/sync_frame.rs b/um_audio/src/sync_frame.rs
index 45ee29a..b717554 100644
--- a/um_audio/src/sync_frame.rs
+++ b/um_audio/src/sync_frame.rs
@@ -1,11 +1,21 @@
 pub const SYNC_FRAME_TEST_SIZE: usize = 0xff;
 
 pub fn is_mp3(magic: u32) -> bool {
-    // Frame sync should have the first 11 bits set to 1.
-    const MP3_AND_MASK: u32 = 0b1111_1111_1110_0000u32 << 16;
-    const MP3_EXPECTED: u32 = 0b1111_1111_1110_0000u32 << 16;
+    // Check for 11-bit sync word, followed by 2 bits of version, and 2 bits of layer.
+    // MPEG Version: MPEG Version 2 (ISO/IEC 13818-3) or MPEG Version 1 (ISO/IEC 11172-3)
+    const MP3_AND_MASK: u32 = 0b1111_1111_1111_0110u32 << 16;
+    const MP3_EXPECTED: u32 = 0b1111_1111_1111_0010u32 << 16;
 
-    (magic & MP3_AND_MASK) == MP3_EXPECTED
+    if (magic & MP3_AND_MASK) != MP3_EXPECTED {
+        return false;
+    }
+
+    // Check for bitrate index and sampling rate frequency index.
+    let bitrate = ((magic >> 12) & 0b1111) as u8;
+    let sampling_rate = ((magic >> 10) & 0b11) as u8;
+
+    // They should not be all 1s.
+    bitrate != 0b1111 && sampling_rate != 0b11
 }
 
 pub fn is_aac(magic: u32) -> bool {