| Message ID | 20161206054615.29187-2-jiada_wang@mentor.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 06 Dec 2016 06:46:14 +0100, Jiada Wang wrote: > > From: Andreas Pape <apape@de.adit-jv.com> > > since commit 57e6dae1087b ("ALSA: usb-audio: do not trust too-big > wMaxPacketSize values"), the expected packetsize is always limited > to nominal + 25%. It was discovered, that some devices have a much > higher jitter in used packetsizes than 25% which would result in BABBLE > condition and dropping of packets. > A better solution is so assume the jitter to be the nominal packetsize: > -one nearly empty packet followed by a almost 150% sized one. > > V2: changed to assume max frequency is +50 of nominal packetsize. Clemens, are you OK with this change? Takashi > > Signed-off-by: Andreas Pape <apape@de.adit-jv.com> > Signed-off-by: Jiada Wang <jiada_wang@mentor.com> > --- > sound/usb/endpoint.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c > index c470251..a2931f4 100644 > --- a/sound/usb/endpoint.c > +++ b/sound/usb/endpoint.c > @@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep, > ep->stride = frame_bits >> 3; > ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0; > > - /* assume max. frequency is 25% higher than nominal */ > - ep->freqmax = ep->freqn + (ep->freqn >> 2); > + /* assume max. frequency is 50% higher than nominal */ > + ep->freqmax = ep->freqn + (ep->freqn >> 1); > /* Round up freqmax to nearest integer in order to calculate maximum > * packet size, which must represent a whole number of frames. > * This is accomplished by adding 0x0.ffff before converting the > -- > 2.9.3 >
Jiada Wang wrote: > since commit 57e6dae1087b ("ALSA: usb-audio: do not trust too-big > wMaxPacketSize values"), the expected packetsize is always limited > to nominal + 25%. It was discovered, that some devices Android audio accessory > have a much > higher jitter in used packetsizes than 25% which would result in BABBLE > condition and dropping of packets. > A better solution is so assume the jitter to be the nominal packetsize: > -one nearly empty packet followed by a almost 150% sized one. > > V2: changed to assume max frequency is +50 of nominal packetsize. > > Signed-off-by: Andreas Pape <apape@de.adit-jv.com> > Signed-off-by: Jiada Wang <jiada_wang@mentor.com> Acked-by: Clemens Ladisch <clemens@ladisch.de> > --- a/sound/usb/endpoint.c > +++ b/sound/usb/endpoint.c > @@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep, > ep->stride = frame_bits >> 3; > ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0; > > - /* assume max. frequency is 25% higher than nominal */ > - ep->freqmax = ep->freqn + (ep->freqn >> 2); > + /* assume max. frequency is 50% higher than nominal */ > + ep->freqmax = ep->freqn + (ep->freqn >> 1); > /* Round up freqmax to nearest integer in order to calculate maximum > * packet size, which must represent a whole number of frames. > * This is accomplished by adding 0x0.ffff before converting the
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index c470251..a2931f4 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -632,8 +632,8 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep, ep->stride = frame_bits >> 3; ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0; - /* assume max. frequency is 25% higher than nominal */ - ep->freqmax = ep->freqn + (ep->freqn >> 2); + /* assume max. frequency is 50% higher than nominal */ + ep->freqmax = ep->freqn + (ep->freqn >> 1); /* Round up freqmax to nearest integer in order to calculate maximum * packet size, which must represent a whole number of frames. * This is accomplished by adding 0x0.ffff before converting the