From 440d7034f09de014f96ec183cd59e2b43bcf75c7 Mon Sep 17 00:00:00 2001
From: Mark Nauwelaerts <mark.nauwelaerts@collabora.co.uk>
Date: Mon, 19 Mar 2012 12:01:40 +0100
Subject: flacparse: perform additional frame crc check if applicable

... such as a frame header parsing throwing some suspicious warnings.
So we can be a bit more convinced we determine the right frame end.

diff --git a/gst/audioparsers/gstflacparse.c b/gst/audioparsers/gstflacparse.c
index 942914e..ed4e733 100644
--- a/gst/audioparsers/gstflacparse.c
+++ b/gst/audioparsers/gstflacparse.c
@@ -381,7 +381,8 @@ typedef enum
 
 static FrameHeaderCheckReturn
 gst_flac_parse_frame_header_is_valid (GstFlacParse * flacparse,
-    const guint8 * data, guint size, gboolean set, guint16 * block_size_ret)
+    const guint8 * data, guint size, gboolean set, guint16 * block_size_ret,
+    gboolean * suspect)
 {
   GstBitReader reader = GST_BIT_READER_INIT (data, size);
   guint8 blocking_strategy;
@@ -575,6 +576,8 @@ gst_flac_parse_frame_header_is_valid (GstFlacParse * flacparse,
         /* TODO: can we know we're on the last frame, to avoid warning ? */
         GST_WARNING_OBJECT (flacparse, "Block size is not constant");
         block_size = flacparse->block_size;
+        if (suspect)
+          *suspect = TRUE;
       }
     }
   }
@@ -623,6 +626,7 @@ gst_flac_parse_frame_is_valid (GstFlacParse * flacparse,
   guint i, search_start, search_end;
   FrameHeaderCheckReturn header_ret;
   guint16 block_size;
+  gboolean suspect_start = FALSE, suspect_end = FALSE;
 
   buffer = frame->buffer;
   data = GST_BUFFER_DATA (buffer);
@@ -633,7 +637,7 @@ gst_flac_parse_frame_is_valid (GstFlacParse * flacparse,
 
   header_ret =
       gst_flac_parse_frame_header_is_valid (flacparse, data, size, TRUE,
-      &block_size);
+      &block_size, &suspect_start);
   if (header_ret == FRAME_HEADER_INVALID) {
     *ret = 0;
     return FALSE;
@@ -653,16 +657,23 @@ gst_flac_parse_frame_is_valid (GstFlacParse * flacparse,
 
   for (i = search_start; i < search_end; i++, remaining--) {
     if ((GST_READ_UINT16_BE (data + i) & 0xfffe) == 0xfff8) {
+      GST_LOG_OBJECT (flacparse, "possible frame end at offset %d", i);
+      suspect_end = FALSE;
       header_ret =
           gst_flac_parse_frame_header_is_valid (flacparse, data + i, remaining,
-          FALSE, NULL);
+          FALSE, NULL, &suspect_end);
       if (header_ret == FRAME_HEADER_VALID) {
-        if (flacparse->check_frame_checksums) {
+        if (flacparse->check_frame_checksums || suspect_start || suspect_end) {
           guint16 actual_crc = gst_flac_calculate_crc16 (data, i - 2);
           guint16 expected_crc = GST_READ_UINT16_BE (data + i - 2);
 
-          if (actual_crc != expected_crc)
+          GST_LOG_OBJECT (flacparse,
+              "checking checksum, frame suspect (%d, %d)",
+              suspect_start, suspect_end);
+          if (actual_crc != expected_crc) {
+            GST_DEBUG_OBJECT (flacparse, "checksum did not match");
             continue;
+          }
         }
         *ret = i;
         flacparse->block_size = block_size;
@@ -1322,7 +1333,7 @@ gst_flac_parse_parse_frame (GstBaseParse * parse, GstBaseParseFrame * frame)
       flacparse->offset = GST_BUFFER_OFFSET (buffer);
       ret =
           gst_flac_parse_frame_header_is_valid (flacparse,
-          GST_BUFFER_DATA (buffer), GST_BUFFER_SIZE (buffer), TRUE, NULL);
+          GST_BUFFER_DATA (buffer), GST_BUFFER_SIZE (buffer), TRUE, NULL, NULL);
       if (ret != FRAME_HEADER_VALID) {
         GST_ERROR_OBJECT (flacparse,
             "Baseclass didn't provide a complete frame");
-- 
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