Hi Bhupesh, On Wednesday 01 August 2012 14:26:33 Bhupesh SHARMA wrote: > Hi Laurent, > > I have a query for you regarding the support and testing of MJPEG frame type > in the UVC webcam gadget. > > I see that in the webcam.c gadget, the 720p and VGA MJPEG uvc formats are > supported. I was trying the same out and got confused because the data > arriving from a real video capture video supporting JPEG will have no fixed > size. We will have the JPEG defined Start-of-Frame and End-of-Frame markers > defining the boundary of the JPEG frame. > > But for almost all JPEG video capture devices even if we have kept a frame > size of VGA initially, the final frame size will be a compressed version > (with the compression depending on the nature of the scene, so a flat scene > will have high compression and hence less frame size) of VGA and will not > be equal to 640 * 480. > > So I couldn't exactly get why the dwMaxVideoFrameBufferSize is kept as > 614400 in webcam.c (see [1]). The dwMaxVideoFrameBufferSize value must be larger than or equal to the largest MJPEG frame size. As I have no idea what that value is, I've kept the same size as for uncompressed frames, which should be big enough (and most probably too big). > Can you please let me know your opinions and how you tested the UVC gadget's > MJPEG frame format. > > [1] http://lxr.linux.no/linux+v3.5/drivers/usb/gadget/webcam.c#L232 -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
