RingBuffer: Optimize readahead buffer to completely fill if readblock…

…size > totfree.

This allows the readahead buffer to fill if the readblocksize is greater than buffer free by temporarily reducing the read size to a size that will fit. With this change the buffers reach 99% for all videos.

mythtv/libs/libmythtv/ringbuffer.cpp

@@ -734,8 +734,7 @@ void RingBuffer::run(void)
 
         // These are conditions where we don't want to go through
         // the loop if they are true.
-        if (((totfree < readblocksize) && readsallowed) ||
-            (ignorereadpos >= 0) || commserror || stopreads)
+        if ((ignorereadpos >= 0) || commserror || stopreads)
         {
             ignore_for_read_timing |=
                 (ignorereadpos >= 0) || commserror || stopreads;
@@ -752,12 +751,16 @@ void RingBuffer::run(void)
             totfree = ReadBufFree();
         }
 
+        const uint KB32 = 32*1024;
         int read_return = -1;
-        if (totfree >= readblocksize && !commserror &&
+        if (totfree >= KB32 && !commserror &&
             !ateof && !setswitchtonext)
         {
             // limit the read size
-            totfree = readblocksize;
+            if (readblocksize > totfree)
+                totfree = (int)(totfree / KB32) * KB32; // must be multiple of 32KB
+            else
+                totfree = readblocksize;
 
             // adapt blocksize
             gettimeofday(&now, NULL);
@@ -792,7 +795,7 @@ void RingBuffer::run(void)
                     readtimeavg = 225;
                 }
             }
-            ignore_for_read_timing = false;
+            ignore_for_read_timing = (totfree < readblocksize) ? true : false;
             lastread = now;
 
             rbwlock.lockForRead();