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| author | Alexander Tsoy <alexander@tsoy.me> | 2020-04-24 05:24:48 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-06-25 15:32:53 +0200 |
| commit | 2d50acd7dbd0682a56968ad9551341d7fc5b6eaf (patch) | |
| tree | be98df32feb2a93f5fe248c9505718163c1ea23e /sound/usb/endpoint.h | |
| parent | f35713ba67d07e974d141d7891cfc5509672c0da (diff) | |
| download | linux-stable-2d50acd7dbd0682a56968ad9551341d7fc5b6eaf.tar.gz linux-stable-2d50acd7dbd0682a56968ad9551341d7fc5b6eaf.tar.bz2 linux-stable-2d50acd7dbd0682a56968ad9551341d7fc5b6eaf.zip | |
ALSA: usb-audio: Improve frames size computation
[ Upstream commit f0bd62b64016508938df9babe47f65c2c727d25c ]
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 <alexander@tsoy.me>
Link: https://lore.kernel.org/r/20200424022449.14972-1-alexander@tsoy.me
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'sound/usb/endpoint.h')
| -rw-r--r-- | sound/usb/endpoint.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sound/usb/endpoint.h b/sound/usb/endpoint.h index 63a39d4fa8d8..d23fa0a8c11b 100644 --- a/sound/usb/endpoint.h +++ b/sound/usb/endpoint.h @@ -28,6 +28,7 @@ void snd_usb_endpoint_release(struct snd_usb_endpoint *ep); void snd_usb_endpoint_free(struct snd_usb_endpoint *ep); int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep); +int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep); int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep); void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep, |