Reece Dunn : dsound: Correct the dsound fraglen calculations.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: ce06de420874b9983324508f8257a580fee341ca
URL:    http://source.winehq.org/git/wine.git/?a=commit;h=ce06de420874b9983324508f8257a580fee341ca

Author: Reece Dunn <msclrhd at googlemail.com>
Date:   Mon Dec 22 13:33:43 2008 +0000

dsound: Correct the dsound fraglen calculations.

---

 dlls/dsound/primary.c |   23 ++++++++++++++---------
 1 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/dlls/dsound/primary.c b/dlls/dsound/primary.c
index 661cd8c..5812f00 100644
--- a/dlls/dsound/primary.c
+++ b/dlls/dsound/primary.c
@@ -46,19 +46,24 @@ WINE_DEFAULT_DEBUG_CHANNEL(dsound);
  */
 DWORD DSOUND_fraglen(DWORD nSamplesPerSec, DWORD nBlockAlign)
 {
-    DWORD fraglen = 256 * nBlockAlign;
+    /* Given a timer delay of 10ms, the fragment size is approximately:
+     *     fraglen = (nSamplesPerSec * 10 / 1000) * nBlockAlign
+     * ==> fraglen = (nSamplesPerSec / 100) * nBlockSize
+     *
+     * ALSA uses buffers that are powers of 2. Because of this, fraglen
+     * is rounded up to the nearest power of 2:
+     */
 
-    /* Compensate for only being roughly accurate */
-    if (nSamplesPerSec <= 26000)
-        fraglen /= 2;
+    if (nSamplesPerSec <= 12800)
+        return 128 * nBlockAlign;
 
-    if (nSamplesPerSec <= 10000)
-        fraglen /= 2;
+    if (nSamplesPerSec <= 25600)
+        return 256 * nBlockAlign;
 
-    if (nSamplesPerSec >= 80000)
-        fraglen *= 2;
+    if (nSamplesPerSec <= 51200)
+        return 512 * nBlockAlign;
 
-    return fraglen;
+    return 1024 * nBlockAlign;
 }
 
 static void DSOUND_RecalcPrimary(DirectSoundDevice *device)