On Tue, Sep 22, 2015 at 07:32:01PM -0400, Programmingkid wrote: > 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 <[email protected]> > > --- > 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),
I'm not familiar with the code but I guess this also increases audio latency by a factor of 4 (8 -> 32). Gerd might have an opinion on whether that is okay or not. Stefan
