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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>
38 lines
1.4 KiB
C
38 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __USBAUDIO_ENDPOINT_H
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#define __USBAUDIO_ENDPOINT_H
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#define SND_USB_ENDPOINT_TYPE_DATA 0
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#define SND_USB_ENDPOINT_TYPE_SYNC 1
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struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
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struct usb_host_interface *alts,
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int ep_num, int direction, int type);
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int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
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snd_pcm_format_t pcm_format,
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unsigned int channels,
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unsigned int period_bytes,
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unsigned int period_frames,
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unsigned int buffer_periods,
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unsigned int rate,
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struct audioformat *fmt,
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struct snd_usb_endpoint *sync_ep);
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int snd_usb_endpoint_start(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_activate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_release(struct snd_usb_endpoint *ep);
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void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep);
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int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
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void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
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struct snd_usb_endpoint *sender,
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const struct urb *urb);
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#endif /* __USBAUDIO_ENDPOINT_H */
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