Perform some checks on the Xing header, and reject it if it looks funny,

which causes the code fall back to another code path to determine the
length of the file. This makes it so that NPR podcasts don't show up
as being 13 seconds long.

diff --git a/fileformats/mp3/parser/src/mp3parser.cpp b/fileformats/mp3/parser/src/mp3parser.cpp
index 6590925..ba8e59c 100644 (file)
--- a/fileformats/mp3/parser/src/mp3parser.cpp
+++ b/fileformats/mp3/parser/src/mp3parser.cpp
@@ -47,6 +47,9 @@
 // Initial search range, resetted to the file size once valid mp3
 // frame is found
 #define KMAX_INITIAL_SEARCH_FILE_SIZE_IN_BYTES  500000
+// If the Xing header reports a size that is smaller than the file length
+// by this much, consider the Xing header invalid.
+#define XING_SIZE_FUZZINESS 0.90
 
 /***********************************************************************
  * Global constant definitions
@@ -1074,6 +1077,32 @@ bool  MP3Parser::DecodeXINGHeader(uint8 *XingBuffer,
     {
         mp3XingHD.bytes = SwapFileToHostByteOrderInt32(pBuf);
         pBuf += 4;
+
+        if (head_flags & FRAMES_FLAG)
+        {
+            // check if the number of frames and the number of
+            // bytes roughly match up
+            int bytesperframe = mp3XingHD.bytes / mp3XingHD.frames;
+            // 52 and 1440 are the minimum and maximum number of bytes per frame for
+            // a compliant mp3 stream (8kbps@22050Hz and 320kbps@32000Hz respectively)
+            if (bytesperframe < 52 || bytesperframe > 1440)
+            {
+                head_flags = mp3XingHD.flags = 0;
+            }
+        }
+        if (iLocalFileSize != 0)
+        {
+            // check if the number of bytes and the file size roughly
+            // match up
+            if (mp3XingHD.bytes > iLocalFileSize)
+            {
+                head_flags = mp3XingHD.flags = 0;
+            }
+            if (mp3XingHD.bytes < iLocalFileSize * XING_SIZE_FUZZINESS)
+            {
+                head_flags = mp3XingHD.flags = 0;
+            }
+        }
     }
 
     if (head_flags & TOC_FLAG)
@@ -1091,7 +1120,10 @@ bool  MP3Parser::DecodeXINGHeader(uint8 *XingBuffer,
         mp3XingHD.vbr_scale = SwapFileToHostByteOrderInt32(pBuf);
         pBuf += 4;;
     }
-    iNumberOfFrames = mp3XingHD.frames;
+    if (head_flags & FRAMES_FLAG)
+    {
+        iNumberOfFrames = mp3XingHD.frames;
+    }
     return true;
 }