Hi Ricardo, Thank you for the patch. On Wed, Mar 15, 2023 at 02:30:15PM +0100, Ricardo Ribalda wrote: > With UVC 1.5 we get as little as one clock sample per frame. Which means > that it takes 32 frames to move from the software timestamp to the > hardware timestamp method. > > This results in abrupt changes in the timestamping after 32 frames (~1 > second), resulting in noticeable artifacts when used for encoding. > > With this patch we modify the update algorithm to work with whatever > amount of values are available. > > Tested-by: HungNien Chen <hn.chen@xxxxxxxxxxxxx> > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> > --- > drivers/media/usb/uvc/uvc_video.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c > index 4d566edb73e7..6d0243ea0e07 100644 > --- a/drivers/media/usb/uvc/uvc_video.c > +++ b/drivers/media/usb/uvc/uvc_video.c > @@ -754,10 +754,10 @@ void uvc_video_clock_update(struct uvc_streaming *stream, > > spin_lock_irqsave(&clock->lock, flags); > > - if (clock->count < clock->size) > + if (clock->count < 2) > goto done; > > - first = &clock->samples[clock->head]; > + first = &clock->samples[(clock->head - clock->count + clock->size) % clock->size]; > last = &clock->samples[(clock->head - 1 + clock->size) % clock->size]; > > /* First step, PTS to SOF conversion. */ > @@ -772,6 +772,17 @@ void uvc_video_clock_update(struct uvc_streaming *stream, > if (y2 < y1) > y2 += 2048 << 16; > > + /* > + * Have at least 1/4 of a second of timestamps before we > + * try to do any calculation. Otherwise we do not have enough > + * precision. This value was determined by running Android CTS > + * on different devices. Either a blank line for a new paragraph, or no line break. > + * Dev_sof runs at 1KHz, and we have a fixed point precision of s/Dev_sof/dev_sof/ Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > + * 16 bits. > + */ > + if ((y2 - y1) < ( (1000 / 4) << 16)) > + goto done; > + > y = (u64)(y2 - y1) * (1ULL << 31) + (u64)y1 * (u64)x2 > - (u64)y2 * (u64)x1; > y = div_u64(y, x2 - x1); > -- Regards, Laurent Pinchart
