Index: libsndfile-1.0.17/src/flac.c
===================================================================
--- libsndfile-1.0.17.orig/src/flac.c
+++ libsndfile-1.0.17/src/flac.c
@@ -57,7 +57,7 @@ flac_open (SF_PRIVATE *psf)
 ** Private static functions.
 */
 
-#define ENC_BUFFER_SIZE 4096
+#define ENC_BUFFER_SIZE 8192
 
 typedef enum
 {	PFLAC_PCM_SHORT = 0,
@@ -204,13 +204,24 @@ flac_buffer_copy (SF_PRIVATE *psf)
 
 	if (pflac->ptr == NULL)
 	{	/*
+		**	frame->header.blocksize is variable and we're using a constant blocksize
+		**	of FLAC__MAX_BLOCK_SIZE.
+		**	Check our assumptions here.
+		*/
+		if (frame->header.blocksize > FLAC__MAX_BLOCK_SIZE)
+		{	psf_log_printf (psf, "Ooops : frame->header.blocksize (%d) > FLAC__MAX_BLOCK_SIZE (%d)\n", __func__, __LINE__, frame->header.blocksize, FLAC__MAX_BLOCK_SIZE) ;
+			psf->error = SFE_INTERNAL ;
+			return 0 ;
+			} ;
+
+		/*
 		**	Not sure why this code is here and not elsewhere.
 		**	Removing it causes valgrind errors.
 		*/
 		pflac->bufferbackup = SF_TRUE ;
 		for (i = 0 ; i < frame->header.channels ; i++)
 		{	if (pflac->rbuffer [i] == NULL)
-				pflac->rbuffer [i] = calloc (frame->header.blocksize, sizeof (FLAC__int32)) ;
+				pflac->rbuffer [i] = calloc (FLAC__MAX_BLOCK_SIZE, sizeof (FLAC__int32)) ;
 			memcpy (pflac->rbuffer [i], buffer [i], frame->header.blocksize * sizeof (FLAC__int32)) ;
 			} ;
 		pflac->wbuffer = (const FLAC__int32* const*) pflac->rbuffer ;