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adjusting height (576>480) when changing video standard?

 

 

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martin.dauskardt at gmx

Feb 27, 2010, 1:55 AM

Post #1 of 3 (1682 views)
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adjusting height (576>480) when changing video standard?

Let's say width and height was initially set to 720x576
(V4L2_BUF_TYPE_VIDEO_CAPTURE/ VIDIOC_S_FMT) by the application.

What happens, when we set a different standard (using VIDIOC_S_STD) which has
525 lines per frame (NTSC, PAL_M):

Wil the driver automatically set 720x480?
will it also automatically switch to 720x576 when the standard is changed
again to 625 lines?

Or should/must the application also set the appropriate width/height each time
the standard changes?

Greets,
Martin

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martin.dauskardt at gmx

Feb 28, 2010, 2:32 PM

Post #2 of 3 (1540 views)
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Re: adjusting height (576>480) when changing video standard? [In reply to]

answering my own question:
The ivtv drivers does change the size from 720x576 to 720x480 automatically
when I change the video standard to PAL-60

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awalls at radix

Feb 28, 2010, 3:51 PM

Post #3 of 3 (1540 views)
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Re: adjusting height (576>480) when changing video standard? [In reply to]

On Sun, 2010-02-28 at 23:32 +0100, Martin Dauskardt wrote:
> answering my own question:
> The ivtv drivers does change the size from 720x576 to 720x480 automatically
> when I change the video standard to PAL-60

Just fuirther confirming that is correct; here's a short snippet of code
from ivtv-ioctl.c:ivtv_s_std():

itv->std = *std;
itv->is_60hz = (*std & V4L2_STD_525_60) ? 1 : 0;
itv->params.is_50hz = itv->is_50hz = !itv->is_60hz;
itv->params.width = 720;
itv->params.height = itv->is_50hz ? 576 : 480;

itv->params are the MPEG encoder parameters.

The function then goes on to call the subdevices:

ivtv_call_all(itv, core, s_std, itv->std);

which should call the s_std method in the saa7115 or cx25840 (or
whatever) module.

Both the saa7115 and cx25840 module change the number of lines in
response to a video standard change.

Regards,
Andy



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