On Sunday 04 June 2006 23:36, Chris Bagwell wrote:
> Hi All,
>
> About 3 months ago I sent an email to the v4l mailing list asking
> some questions about implementing CROP support to the saa7115 driver.
> By that I mean the ability to crop off the edges of your input video
> while still on the card instead of doing it in software (I use it to
> crop off some black bars that my external sat reciever adds).
>
> Hans was nice enough to give me some pointers and I half way
> implemented this before getting distracted by other projects and
> shelving it. I thought I'd dust off what I have and send it to the
> list to see if I can get some help finishing it up. Probably, I
> should send the saa7115.c portions to the v4l list to get some
> feedback as well?
Yes, please do. That is the best place to mail it to.
>
> The attached patches are based on kernel 2.6.16 and ivtv-0.6.2. I've
> had no luck in getting SNV ivtv or mercurial v4l-dvb to compile on
> my Fedora Core 5 system.
What fails to compile?
> What the attached patches do are add the
> V4L2 CROP ioctl() to the saa7115 driver and ivtv driver. I've also
> added two new options to ivtvctl that map to the V4L2 API:
> --get-crop and --set-crop.
>
> What doesn't work right now:
>
> 1) Specifying crop height values that are close to the FMT capture
> height doesn't work. When the video scale ratio (output/input)
> approaches 1 then the captured video only gets a few lines towards
> the top. For example, if your input video is cropped to 720x470 and
> your capturing FMT is set to 720x480 then only about 10 lines of
> picture get updated every frame. If you crop your input window to
> 720x480 and capture a video of 720x600 then it works fine (480/470 is
> to close to one, 600/480 isn't so bad).
>
> 2) I've noticed a few combinations of widths that cause the color to
> switch to shades of blue. Theres probably some limitation I don't
> understand yet (for instance, maybe scale widths have to be divisible
> by 4).
>
> 3) Setting the cropping to very low values causes the driver to lock
> up or stall. For example, if I set the input crop size to a width of
> 100 (out of 720 possible width) then the call to ivtvctl locks up and
> I can't read data from /dev/video0. The saa7715 docs mention some
> limits on scaling but I haven't calculated those yet to see what is
> to low. Sometimes this even locks up the whole computer.
>
> Thanks for any help,
> Chris
Thanks for your efforts!
Hans
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