On 11-Jun-01 Gerd Knorr wrote:
>> If V4L/V4L2 is going to include the Phillips packed 4:2:0 format, then
>> it'd probably be best to call it PHILLIPS_420 or something like that,
>> since there are obviously very many possible 4:2:0 packed format
>> component orderings.
>
> Exactly that's why I'd like to know whenever the format used by the
> phillips webcam is a standard format or some dirty hack by phillips
> to make the hardware cheap: 420 instead of 422 to get more frames/sec
> over usb and packed instead of planar because it's easier to handle.
Well, since I am the author of this Philips driver[1], I can probably shed
some light on this... The format produced _now_ by the driver is this:
even lines: YYYY UU YYYY UU YYYY ...
odd lines: YYYY VV YYYY VV YYYY ...
(NB: this was clearly documented in the convertor routines). If this is
standard or not, I don´t know.
This is what comes out of the camera over the USB bus when in non-compressed
mode. Since there was no definition given of YUV420, I choose that as the
format for this palette. This is also the output of the decompressor
routines (though it can also deliver YUV420P without penalty). Since there
was also a definition of YUV420P, I added that with a simple convertor
routine (it´s not really a convertor, just shuffling around bytes to the
correct place).
> I don't like the idea of adding non-standard formats to v4l/v4l2 ...
That´s why I added a bunch of convertors, and this is exactly why I got so
pissed off when Alan ripped out that code. The driver is now appearantly
even less than brain-dead, since not a single tool, apart from my own
camstream, can now use this driver. It delivers a format nobody understands,
and the format it could use isn´t allowed.
But, if nobody else uses this format, we might as well promote it to
´YUV420´ or ditch it all together. But in that case I must include code to
go from internal format to YUV420P.
Oh yes, something else: it seems YUYV == YUV422 as well.
- Nemosoft
[1] One ´l´ only!
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