fix: Calculate bitrate from actual file size instead of API value

The API returns theoretical max bitrate (e.g., 1411kbps for FLAC), but files
may be compressed (e.g., 960kbps). Calculate real bitrate from downloaded
file size and duration to ensure Telegram displays accurate values.

Author: Lemonawa

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "music163bot-rust"
-version = "1.1.9"
+version = "1.1.10"
 edition = "2024"
 license = "WTFPL"
 

Cargo.toml

@@ -820,6 +820,24 @@ async fn download_and_send_music(
 
     // Get file size for database (async to avoid blocking)
     let audio_file_size = audio_buffer.size().await as i64;
+    let duration_sec = (song_detail.dt.unwrap_or(0) / 1000) as i64;
+
+    // Calculate actual bitrate from file size and duration
+    // API's song_url.br is often theoretical (e.g., 1411kbps for FLAC) but
+    // actual file may be compressed (e.g., 960kbps). Use real calculated value.
+    let actual_bitrate_bps = if duration_sec > 0 {
+        (8 * audio_file_size) / duration_sec
+    } else {
+        // Fallback to API value if duration is missing
+        song_url.br as i64
+    };
+
+    tracing::info!(
+        "Bitrate - API: {} bps, Calculated from file: {} bps (duration: {}s)",
+        song_url.br,
+        actual_bitrate_bps,
+        duration_sec
+    );
 
     // Create song info for database
     let mut song_info = SongInfo {
@@ -834,8 +852,8 @@ async fn download_and_send_music(
         music_size: audio_file_size,
         pic_size: 0,
         emb_pic_size: 0,
-        bit_rate: song_url.br as i64,
-        duration: (song_detail.dt.unwrap_or(0) / 1000) as i64,
+        bit_rate: actual_bitrate_bps,
+        duration: duration_sec,
         file_id: None,
         thumb_file_id: None,
         from_user_id: msg.from.as_ref().map_or(0, |u| u.id.0 as i64),