OK,
Here are my test results:
VIDIOC_G_JPEGCOMP:
MJPEG compression:
quality: 100
APPn: 0
APP_len: 0
APP_data:
COM_len: 0
COM_data:
markers: 0x10
vid:046d
pid:0808
driver:uvcvideo
VIDIOC_S_JPEGCOMP: Device or Resource Busy
So I can't set the quality value, I'll try it later on other cameras, but I
don't expect this to change
Best regards,
Paulo
2009/6/2 Laurent Pinchart <[email protected]>
> Hi Paulo,
>
> On Tuesday 02 June 2009 17:35:17 Paulo Assis wrote:
> > Hi,
> > I think I can add this to guvcview and run some tests, but I would like
> > some info on the v4l2_jpegcompression struct, especially on the
> > **jpeg_markers flag, I believe for mjpeg I should set all flags, except
> > V4l2_JPEG_MARKER_DHT, since huffman tables are not included in the video
> > stream, is this correct, or it just doesn't make any difference?
>
> It won't make any difference with the uvcvideo driver. The driver ignores
> the
> flags on VIDIOC_S_JPEGCOMP and returns V4L2_JPEG_MARKER_DQT only on
> VIDIOC_G_JPEGCOMP. The DHT, DRI and COM segments are not included in the
> MJPEG
> stream, and the APP0 segment is not user-configurable.
>
> > Also is the correct aproach a call to VIDIOC_G_JPEGCOMP for filling the
> > struct and then just change the quality entry and call VIDIOC_S_JPEGCOMP?
>
> This is still unclear in the specification. I would assume that drivers
> will
> fix the flags if the requested value is unsupported. If you want to make
> sure
> you don't modify them, calling G_JPEGCOMP prior to S_JPEGCOMP sounds good.
>
> Best regards,
>
> Laurent Pinchart
>
>
_______________________________________________
Linux-uvc-devel mailing list
[email protected]
https://lists.berlios.de/mailman/listinfo/linux-uvc-devel
