linux-kernel - Re: [PATCH] [resend] usbvision: disable scaling for Nogatech MicroCam

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Date:	Fri, 22 Jul 2011 23:22:02 +0200
From:	Ondrej Zary <linux@...nbow-software.org>
To:	Devin Heitmueller <dheitmueller@...nellabs.com>
Cc:	Joerg Heckenbach <joerg@...kenbach-aw.de>,
	Dwaine Garden <dwainegarden@...ers.com>,
	linux-media@...r.kernel.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Hans Verkuil <hverkuil@...all.nl>
Subject: Re: [PATCH] [resend] usbvision: disable scaling for Nogatech MicroCam

On Friday 22 July 2011 22:06:59 Devin Heitmueller wrote:
> On Fri, Jul 22, 2011 at 4:00 PM, Ondrej Zary <linux@...nbow-software.org> wrote:
> > Scaling causes bad artifacts (horizontal lines) with compression at least
> > with Nogatech MicroCam so disable it (for this HW).
> >
> > This also fixes messed up image with some programs (Cheese with 160x120,
> > Adobe Flash). HW seems to support only image widths that are multiple of 64
> > but the driver does not account that in vidioc_try_fmt_vid_cap(). Cheese
> > calls try_fmt with 160x120, succeeds and then assumes that it really gets
> > data in that resolution - but it gets 128x120 instead. Don't know if this
> > affects other usbvision devices, it would be great if someone could test it.
> >
> > Signed-off-by: Ondrej Zary <linux@...nbow-software.org>
> >
> > diff -urp linux-2.6.39-rc2-/drivers/media/video/usbvision//usbvision-video.c linux-2.6.39-rc2/drivers/media/video/usbvision/usbvision-video.c
> > --- linux-2.6.39-rc2-/drivers/media/video/usbvision//usbvision-video.c  2011-07-16 16:42:35.000000000 +0200
> > +++ linux-2.6.39-rc2/drivers/media/video/usbvision/usbvision-video.c    2011-07-16 16:36:43.000000000 +0200
> > @@ -924,6 +924,11 @@ static int vidioc_try_fmt_vid_cap(struct
> >        RESTRICT_TO_RANGE(vf->fmt.pix.width, MIN_FRAME_WIDTH, MAX_FRAME_WIDTH);
> >        RESTRICT_TO_RANGE(vf->fmt.pix.height, MIN_FRAME_HEIGHT, MAX_FRAME_HEIGHT);
> >
> > +       if (usbvision_device_data[usbvision->dev_model].codec == CODEC_WEBCAM) {
> > +               vf->fmt.pix.width = MAX_FRAME_WIDTH;
> > +               vf->fmt.pix.height = MAX_FRAME_HEIGHT;
> > +       }
> > +
> >        vf->fmt.pix.bytesperline = vf->fmt.pix.width*
> >                usbvision->palette.bytes_per_pixel;
> >        vf->fmt.pix.sizeimage = vf->fmt.pix.bytesperline*vf->fmt.pix.height;
> > @@ -952,6 +957,11 @@ static int vidioc_s_fmt_vid_cap(struct f
> >
> >        usbvision->cur_frame = NULL;
> >
> > +       if (usbvision_device_data[usbvision->dev_model].codec == CODEC_WEBCAM) {
> > +               vf->fmt.pix.width = MAX_FRAME_WIDTH;
> > +               vf->fmt.pix.height = MAX_FRAME_HEIGHT;
> > +       }
> > +
> >        /* by now we are committed to the new data... */
> >        usbvision_set_output(usbvision, vf->fmt.pix.width, vf->fmt.pix.height);
> >
> >
> > --
> > Ondrej Zary
> 
> Hello Ondrej,
> 
> Drivers are permitted to return a different resolution than what the
> application provided in the S_FMT call.  It is the responsibility of
> the application to look at the struct after the ioctl() call and if
> the values are not what it expects to then accommodate the change.
> 
> In other words, this sounds like a bug in Cheese.

Seems that this bug is widespread - the same problem appears also in guvcview
and adobe flash. I think that the driver is broken too - it should return
corrected resolution in TRY_FMT.

> Devin
> 



-- 
Ondrej Zary
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