[Qemu-devel] [PATCH] hw/usb/dev-audio.c: make USB audio card sound perfect

[Programmingkid]

The USB audio card would not play audio well because its buffer was too small. 
Increasing it made it play perfectly. All the crackling and dropouts are gone.  

Signed-off-by: John Arbuckle <address@hidden>

---
This patch was tested on qemu-system-ppc running Linux and qemu-system-i386
running Windows XP. Windows XP sound output thru the USB audio card sounded
perfect. Linux did improve in sound quality, but it still wasn't perfect. I
think there are problems with the hcd-ohci.c file. The Mac OS 10.2 guest in 
qemu-system-ppc did not play sound due to USB issues unrelated to this patch. 

 hw/usb/dev-audio.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/hw/usb/dev-audio.c b/hw/usb/dev-audio.c
index f092bb8..e4e4989 100644
--- a/hw/usb/dev-audio.c
+++ b/hw/usb/dev-audio.c
@@ -88,6 +88,7 @@ static const USBDescStrings usb_audio_stringtable = {
 #define USBAUDIO_PACKET_SIZE     192
 #define USBAUDIO_SAMPLE_RATE     48000
 #define USBAUDIO_PACKET_INTERVAL 1
+#define BUFFER_MULTIPLIER        32
 
 static const USBDescIface desc_iface[] = {
     {
@@ -664,7 +665,7 @@ static const VMStateDescription vmstate_usb_audio = {
 static Property usb_audio_properties[] = {
     DEFINE_PROP_UINT32("debug", USBAudioState, debug, 0),
     DEFINE_PROP_UINT32("buffer", USBAudioState, buffer,
-                       8 * USBAUDIO_PACKET_SIZE),
+                       BUFFER_MULTIPLIER * USBAUDIO_PACKET_SIZE),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
1.7.5.4