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 <hverkuil@xxxxxxxxx> 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.
>
> 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.
>
> 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;
> --
> 2.33.0
>
--
Ricardo Ribalda
