Hello,
On Fri, Nov 26, 2021 at 05:14:31PM +0100, Ricardo Ribalda Delgado wrote:
> Hello Hans
>
> What if we make something like:
>
> #define UVC_STREAM_FID_UNINITIALISED (UVC_STREAM_FID + 1)
>
> and then use that define at the initialization and in decode_start() ?
> I think it will be clearer than the current comparison.
>
>
> Also you might want to wait to assign "stream->last_fid = fid;" until
> line 1106, because otherwise the "Dropping payload" will be triggered
> (I believe)
>
> Thanks!
>
> PS: You will get better response time if you email me at
> ribalda@xxxxxxxxxxxx , not much time recently for the personal email
> :(
>
> On Wed, Nov 24, 2021 at 11:49 AM Hans Verkuil wrote:
> >
> > When you start streaming from uvc, then the first buffer will
> > have sequence number 0 and the second buffer has sequence number
> > 2. Fix the logic to ensure proper monotonically increasing sequence
> > numbers.
> >
> > The root cause is not setting last_fid when you start streaming
> > and a new fid is found for the first time.
I can confirm the issue with my device, but this short explanation
doesn't really tell me where the problem comes from. Could you elaborate
on this, maybe with a detailed sequence ?
> > This patch also changes the initial last_fid value from -1 to 0xff.
> > Since last_fid is unsigned, it is better to stick to unsigned values.
Maybe U8_MAX then ?
> > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > ---
> > drivers/media/usb/uvc/uvc_video.c | 11 +++++++----
> > 1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index 9f37eaf28ce7..8ba8d25e2c4a 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -1055,7 +1055,10 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
> > * that discontinuous sequence numbers always indicate lost frames.
> > */
> > if (stream->last_fid != fid) {
> > - stream->sequence++;
> > + if (stream->last_fid > UVC_STREAM_FID)
> > + stream->last_fid = fid;
> > + else
> > + stream->sequence++;
> > if (stream->sequence)
> > uvc_video_stats_update(stream);
> > }
> > @@ -1080,7 +1083,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
> >
> > /* Synchronize to the input stream by waiting for the FID bit to be
> > * toggled when the the buffer state is not UVC_BUF_STATE_ACTIVE.
> > - * stream->last_fid is initialized to -1, so the first isochronous
> > + * stream->last_fid is initialized to 0xff, so the first isochronous
> > * frame will always be in sync.
> > *
> > * If the device doesn't toggle the FID bit, invert stream->last_fid
> > @@ -1111,7 +1114,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
> > * last payload can be lost anyway). We thus must check if the FID has
> > * been toggled.
> > *
> > - * stream->last_fid is initialized to -1, so the first isochronous
> > + * stream->last_fid is initialized to 0xff, so the first isochronous
> > * frame will never trigger an end of frame detection.
> > *
> > * Empty buffers (bytesused == 0) don't trigger end of frame detection
> > @@ -1895,7 +1898,7 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
> > int ret;
> >
> > stream->sequence = -1;
> > - stream->last_fid = -1;
> > + stream->last_fid = 0xff;
> > stream->bulk.header_size = 0;
> > stream->bulk.skip_payload = 0;
> > stream->bulk.payload_size = 0;
--
Regards,
Laurent Pinchart
