Re: V4L2_PIX_FMT_RAW

["H. Willstrand" <h.willstrand@gmail.com>]

On Wed, Feb 20, 2008 at 10:11 PM, Thomas Kaiser
<linux-dvb@kaiser-linux.li> wrote:
>
> H. Willstrand wrote:
>  > On Wed, Feb 20, 2008 at 9:42 PM, Thomas Kaiser
>  > <linux-dvb@kaiser-linux.li> wrote:
>  >> H. Willstrand wrote:
>  >>  > On Wed, Feb 20, 2008 at 9:22 PM, Thomas Kaiser
>  >>  > <linux-dvb@kaiser-linux.li> wrote:
>  >>  >> H. Willstrand wrote:
>  >>  >>  > On Wed, Feb 20, 2008 at 8:25 PM, Thomas Kaiser
>  >>  >>  > <linux-dvb@kaiser-linux.li> wrote:
>  >>  >>  >> Why is V4L2_PIX_FMT_RAW not included as a pixel format in V4l2?
>  >>  >>  >>
>  >>  >>  >>  I would like to just forward the stream from my webcam "as it is" to user space .
>  >>  >>  >>
>  >>  >>  >>  V4L2_PIX_FMT_RAW looks as it is the right thing I need.
>  >>  >>  >>
>  >>  >>  >
>  >>  >>  > V4L2 drivers should not perform any video transformations, the driver
>  >>  >>  > provides user space with hardware supported formats.
>  >>  >>
>  >>  >>  Ok, so, I need a entry for Pixart chips.
>  >>  >>  PAC207: a line based coding algo.
>  >>  >>  PAC7311: the interpretation of JPEG from Pixart
>  >>  >>  PAC7302: the _new_  interpretation of JPEG from Pixart
>  >>  >>
>  >>  >>  V4L2_PIX_FMT_RAW would make my live easier.
>  >>  >>
>  >>  >>  The option to forward the stream "as it is" would be really nice. When the
>  >>  >>  manufacture of some video streaming devices (like webcams) do their own thing,
>  >>  >>  you can forward the raw stream and the user application can take care of the
>  >>  >>  decoding of the stream.
>  >>  >>
>  >>  >>  For me it looks not like such a bad idea!!!???
>  >>  >>
>  >>  >
>  >>  > Yes, it might be a good idea to add something like V4L2_PIX_FMT_PAC207, etc.
>  >>  > This is anyhow the case with the PWC family.
>  >>
>  >>  I think the better is to just forward the stream to userspace.
>  >>  Then we have to make a lib which can be called from all these video application
>  >>  around to decode the stream.
>  >>
>  >>  Somebody talked already about this on the list.
>  >>
>  >>  When the cam is able to send a stream in a good known format it is no problem to
>  >>  handle this with the right V4L2_PIX_FMT_..., but if not, we need a "official"
>  >>  way to get this "devil" stream to user space!
>  >>
>  >
>  > Well, it can go ugly if one piece of hardware supports several "raw"
>  > formats, they need to be distinct. And in the end of the day the V4L2
>  > drivers might consist of several identical "raw" formats which then
>  > aren't consolidated.
>  >
>  > Harri
>
>  I don't really understand what you try to say here.
>  I want to have the stream forwarded "as it is" to user space. Then the v4l2
>  driver even have not to know what kind of stream this is!
>  We just forward the stream (again) "as it is" to user space.
>  Now, the user space application (viewer app, skype or what ever) has to decide
>  if they can handle the stream.
>
Ok, if a driver exposes a RAW format, how can a application know if it
can handle the format? By looking at the driver name? What if the
driver have several RAW formats? (they might have)

Next, standardization is a good thing, and hopefully chip set vendors
tries to keep down the number of formats, so it's a good idea to try
define distinct V4L2_PIX_FMT for each distinct format.

Cheers,
Harri


>  PS: Why do you answer OFF-LIST? I think it is a nice topic to discussed with
>  everyone on the list.
I thought I did, sorry for that.

//Harri

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