From: Clemens Ladisch <clemens@ladisch.de>
To: tiwai@suse.com
Cc: Jiada Wang <jiada_wang@mentor.com>,
perex@perex.cz, o-takashi@sakamocchi.jp,
alsa-devel@alsa-project.org, apape@de.adit-jv.com,
linux-kernel@vger.kernel.org
Subject: Re: [alsa-devel] [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize
Date: Tue, 6 Dec 2016 13:11:13 +0100 [thread overview]
Message-ID: <8ec36827-450e-ff5a-5183-75b31ec95dc3@ladisch.de> (raw)
In-Reply-To: <20161206054615.29187-2-jiada_wang@mentor.com>
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
next prev parent reply other threads:[~2016-12-06 12:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-06 5:46 [PATCH 0/2 v2] usb-audio misc fix Jiada Wang
2016-12-06 5:46 ` [PATCH v2 1/2] ALSA: usb-audio: more tolerant packetsize Jiada Wang
2016-12-06 7:13 ` Takashi Iwai
2016-12-06 12:11 ` Clemens Ladisch [this message]
2016-12-06 5:46 ` [PATCH 2/2] ALSA: usb-audio: avoid setting of sample rate multiple times on bus Jiada Wang
2016-12-06 15:02 ` [PATCH 0/2 v2] usb-audio misc fix Takashi Iwai
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