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