diff --git a/mythtv/libs/libmythtv/ringbuffer.cpp b/mythtv/libs/libmythtv/ringbuffer.cpp
index 8dd1a67..70164a4 100644
--- a/mythtv/libs/libmythtv/ringbuffer.cpp
+++ b/mythtv/libs/libmythtv/ringbuffer.cpp
@@ -40,6 +40,7 @@ const int  RingBuffer::kDefaultOpenTimeout = 2000; // ms
 const int  RingBuffer::kLiveTVOpenTimeout  = 10000;

 #define CHUNK 32768 /* readblocksize increments */
+#define MAXBLOCK (256*1024) // Maximum buffer size

 #define LOC      QString("RingBuf(%1): ").arg(filename)

@@ -376,6 +377,7 @@ void RingBuffer::CalcReadAheadThresh(void)
         readblocksize = rbs;
     else
         readblocksize = max(rbs,readblocksize);
+    readblocksize = min(MAXBLOCK, readblocksize);

     // minumum seconds of buffering before allowing read
     float secs_min = 0.35;
@@ -820,6 +822,8 @@ void RingBuffer::run(void)
                     int old_block_size = readblocksize;
                     readblocksize = 3 * readblocksize / 2;
                     readblocksize = ((readblocksize+CHUNK-1) / CHUNK) * CHUNK;
+                    readblocksize = min(MAXBLOCK, readblocksize);
+
                     LOG(VB_FILE, LOG_INFO, LOC +
                         QString("Avg read interval was %1 msec. "
                                 "%2K -> %3K block size")
@@ -838,6 +842,7 @@ void RingBuffer::run(void)
                             .arg((readblocksize+CHUNK)/1024)
                             .arg(readblocksize/1024));
                     readtimeavg = 225;
+                    readblocksize = min(MAXBLOCK, readblocksize);
                 }
             }
             ignore_for_read_timing = (totfree < readblocksize) ? true : false;