USB frame rate is slightly lower than 1kHz: ie. ~950Hz.
Thus usb-audio device is not able to perform a simple audio playback
without underruns on audio backend.
eg. "-device pci-ohci,id=ohci -device usb-audio,bus=ohci.0" vs PulseAudio
backend. more than 50 underruns are observed per second.
Update ohci_sof_time computation, using QEMU_CLOCK_VIRTUAL in
ohci_usb_start(), and increment by usb_frame_time in ohci_sof()
makes USB frame rate close to 1kHz.
This way, no audio underrun are observed during audio playback.
Signed-off-by: Miguel GAIO <mgaio35@gmail.com>
Message-Id: <20180927151936.3647-1-mgaio35@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
a60f39a468