skip over packets without frames when initializing the decoder

Author: jgraef

src/decoder/symphonia.rs

@@ -113,8 +113,8 @@ impl SymphoniaDecoder {
                 continue;
             }
 
-            match decoder.decode(&current_span) {
-                Ok(decoded) => break decoded,
+            let decoded = match decoder.decode(&current_span) {
+                Ok(decoded) => decoded,
                 Err(e) => match e {
                     Error::DecodeError(_) => {
                         // Decode errors are intentionally ignored with no retry limit.
@@ -124,6 +124,15 @@ impl SymphoniaDecoder {
                     }
                     _ => return Err(e),
                 },
+            };
+
+            // Loop until we get a packet with audio frames. This is necessary because some
+            // formats can have packets with only metadata, particularly when rewinding, in
+            // which case the iterator would otherwise end with `None`.
+            // Note: checking `decoded.frames()` is more reliable than `packet.dur()`, which
+            // can resturn non-zero durations for packets without audio frames.
+            if decoded.frames() > 0 {
+                break decoded;
             }
         };
         let spec = decoded.spec().to_owned();