Video duration inconsistent with Capture duration

Hi, All:
our device is an USB Video Device compliant with USB Video Class V1.0.
After loaded the Microsoft InBox UVC driver, the video preview function is OK.
But when capture video, then playback it, the capture duration is
inconsisten with video duaration.
for the UVC descriptor, he uncompressed YUY2 frame type decriptor
report the each frame interval is 30fps, and our device acturally output
25fps.

But When capture the video using AMCAP or Ulead, there are no any
dropped counts reported by the software/uvc driver. I think it is the main
reason which lead to inconsistence.
So whether there are some bugs about MS Inbox UVC 1.0 Driver? Who can
give me some suggestion about how to compute the dropped counts?

Thanks in advance.

attached the UVC descriptor.

BR
Zhihua

Mini UVC UAC <> wrote:
>
> our device is an USB Video Device compliant with USB Video Class V1.0.
>After loaded the Microsoft InBox UVC driver, the video preview function is OK.
>But when capture video, then playback it, the capture duration is
>inconsisten with video duaration.
> for the UVC descriptor, he uncompressed YUY2 frame type decriptor
>report the each frame interval is 30fps, and our device acturally output
>25fps.

That's a problem, don't you think? Do you report actual timestamps in your
headers?

> But When capture the video using AMCAP or Ulead, there are no any
>dropped counts reported by the software/uvc driver. I think it is the main
>reason which lead to inconsistence.
> So whether there are some bugs about MS Inbox UVC 1.0 Driver? Who can
>give me some suggestion about how to compute the dropped counts?

Why do you think there are bugs? No frames were dropped. You are just
delivering frames late.
--
Tim Roberts,
Providenza & Boekelheide, Inc.

Hi, Tim Roberts:

Thanks very much for your soon reply.

First, I have reported the actually timestamps(25fps) in the video frame
header, even though uncompressed YUY2 frame type decriptor defined the each
frame interval is 30fps.
Second, we also develop ourself device driver, and report the 5 frame
drop count per second in the reqeust KSPROPERTY_DROPPEDFRAMES_CURRENT, then
the same problem is not produced.
But for MS Windows inbox UVC driver, I can't see any dropped frame
counts, and the problem happened.
Does it mean that there are some bugs ?

in other way, we have do the following experiment:
if our device output the fixed frame rate 15fps, and also report the actuall
timestamps(15fps) in the header, MS Windows inbox uvc driver will report the
correct dropped frame counts(15 frame per second), and of course, the problem
is also not happned.

Thanks;

BR
Hardys

"Tim Roberts" wrote:

> Mini UVC UAC <> wrote:
> >
> > our device is an USB Video Device compliant with USB Video Class V1.0.
> >After loaded the Microsoft InBox UVC driver, the video preview function is OK.
> >But when capture video, then playback it, the capture duration is
> >inconsisten with video duaration.
> > for the UVC descriptor, he uncompressed YUY2 frame type decriptor
> >report the each frame interval is 30fps, and our device acturally output
> >25fps.
>
> That's a problem, don't you think? Do you report actual timestamps in your
> headers?
>
> > But When capture the video using AMCAP or Ulead, there are no any
> >dropped counts reported by the software/uvc driver. I think it is the main
> >reason which lead to inconsistence.
> > So whether there are some bugs about MS Inbox UVC 1.0 Driver? Who can
> >give me some suggestion about how to compute the dropped counts?
>
> Why do you think there are bugs? No frames were dropped. You are just
> delivering frames late.
> --
> Tim Roberts,
> Providenza & Boekelheide, Inc.
> .
>

Mini UVC UAC <> wrote:
>
> First, I have reported the actually timestamps(25fps) in the video frame
>header, even though uncompressed YUY2 frame type decriptor defined the each
>frame interval is 30fps.

Why is the actual frame rate different than what you reported in the
descriptor? When do you know the actual frame rate? Maybe you need to
report a frame range in the descriptor, then report the actual rate during
the probe and commit process.

> Second, we also develop ourself device driver, and report the 5 frame
>drop count per second in the reqeust KSPROPERTY_DROPPEDFRAMES_CURRENT, then
>the same problem is not produced.
> But for MS Windows inbox UVC driver, I can't see any dropped frame
>counts, and the problem happened.
> Does it mean that there are some bugs ?

I doubt it. Technically speaking, no frames are being dropped. The driver
has delivered every frame that was sent. You hardware is lying: it is
delivering frames at a rate different from the rate you promised.
--
Tim Roberts,
Providenza & Boekelheide, Inc.

Hi, Tim:
The case which actually frame rate is different with the rate reported
in the descritor table is very polular. and most parts of other usb cameras
vary the frame rate according to the light exposure, in order to get better
image quality.
For describe the question simply and clearly, I just select the fixed
rate 25fps as the example.

"Tim Roberts" wrote:

> Mini UVC UAC <> wrote:
> >
> > First, I have reported the actually timestamps(25fps) in the video frame
> >header, even though uncompressed YUY2 frame type decriptor defined the each
> >frame interval is 30fps.
>
> Why is the actual frame rate different than what you reported in the
> descriptor? When do you know the actual frame rate? Maybe you need to
> report a frame range in the descriptor, then report the actual rate during
> the probe and commit process.
>
> > Second, we also develop ourself device driver, and report the 5 frame
> >drop count per second in the reqeust KSPROPERTY_DROPPEDFRAMES_CURRENT, then
> >the same problem is not produced.
> > But for MS Windows inbox UVC driver, I can't see any dropped frame
> >counts, and the problem happened.
> > Does it mean that there are some bugs ?
>
> I doubt it. Technically speaking, no frames are being dropped. The driver
> has delivered every frame that was sent. You hardware is lying: it is
> delivering frames at a rate different from the rate you promised.
> --
> Tim Roberts,
> Providenza & Boekelheide, Inc.
> .
>