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From: Takashi Iwai <>
To: Alexander Tsoy <>
Cc: Gregor Pintar <>,, Roope Salmi <>
Subject: Re: [PATCH 1/2] ALSA: usb-audio: Improve frames size computation
Date: Fri, 24 Apr 2020 08:28:02 +0200
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, 24 Apr 2020 04:24:48 +0200,
Alexander Tsoy wrote:
> For computation of the the next frame size current value of fs/fps and
> accumulated fractional parts of fs/fps are used, where values are stored
> in Q16.16 format. This is quite natural for computing frame size for
> asynchronous endpoints driven by explicit feedback, since in this case
> fs/fps is a value provided by the feedback endpoint and it's already in
> the Q format. If an error is accumulated over time, the device can
> adjust fs/fps value to prevent buffer overruns/underruns.
> But for synchronous endpoints the accuracy provided by these computations
> is not enough. Due to accumulated error the driver periodically produces
> frames with incorrect size (+/- 1 audio sample).
> This patch fixes this issue by implementing a different algorithm for
> frame size computation. It is based on accumulating of the remainders
> from division fs/fps and it doesn't accumulate errors over time. This
> new method is enabled for synchronous and adaptive playback endpoints.
> Signed-off-by: Alexander Tsoy <>

Applied to for-next branch now.



  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-24  2:24 Alexander Tsoy
2020-04-24  2:24 ` [PATCH 2/2] ALSA: usb-audio: Remove async workaround for Scarlett 2nd gen Alexander Tsoy
2020-04-24  6:28   ` Takashi Iwai
2020-04-24 15:21   ` Gregor Pintar
2020-04-24  6:28 ` Takashi Iwai [this message]
2020-04-24  9:19 ` [PATCH 1/2] ALSA: usb-audio: Improve frames size computation Pavel Hofman
2020-04-24  9:29   ` Alexander Tsoy
2020-04-24  9:39     ` Pavel Hofman
2020-04-24 15:02 ` Gregor Pintar
2020-04-24 16:43   ` Alexander Tsoy
2020-04-25 16:50     ` Gregor Pintar
2020-04-25 18:09       ` Gregor Pintar

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