comments

diff --git a/src/libFLAC/stream_decoder.c b/src/libFLAC/stream_decoder.c
index f377080..e09db2f 100644 (file)
--- a/src/libFLAC/stream_decoder.c
+++ b/src/libFLAC/stream_decoder.c
@@ -2141,6 +2141,19 @@ FLAC__bool read_frame_header_(FLAC__StreamDecoder *decoder)
         * Note that along the way as we read the header, we look for a sync
         * code inside.  If we find one it would indicate that our original
         * sync was bad since there cannot be a sync code in a valid header.
+        *
+        * Three kinds of things can go wrong when reading the frame header:
+        *  1) We may have sync'ed incorrectly and not landed on a frame header.
+        *     If we don't find a sync code, it can end up looking like we read
+        *     a valid but unparseable header, until getting to the frame header
+        *     CRC.  Even then we could get a false positive on the CRC.
+        *  2) We may have sync'ed correctly but on an unparseable frame (from a
+        *     future encoder).
+        *  3) We may be on a damaged frame which appears valid but unparseable.
+        *
+        * For all these reasons, we try and read a complete frame header as
+        * long as it seems valid, even if unparseable, up until the frame
+        * header CRC.
         */
 
        /*