Commit fd1a5059 authored by Andreas Pape's avatar Andreas Pape Committed by Takashi Iwai
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ALSA: usb-audio: more tolerant packetsize

since commit 57e6dae1

 ("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: default avatarAndreas Pape <>
Signed-off-by: default avatarJiada Wang <>
Acked-by: default avatarClemens Ladisch <>
Signed-off-by: default avatarTakashi Iwai <>
parent 1e2e3fe4
......@@ -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
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