micheal..you are telling that read() function will do the same as the mmap() does..but the read() will read the data from the memory i think....is this ,,ap() is also doing the same one?if yes....how its actually the data (when capturing the video) was stored in memory....?
--- On Fri, 23/1/09, Michael Williamson <michael_h_williamson@xxxxxxxxx> wrote:
From: Michael Williamson <michael_h_williamson@xxxxxxxxx>
Subject: Re: mmap()
To: shariefbe@xxxxxxxxxxx
Date: Friday, 23 January, 2009, 10:28 PM
--- On Fri, 1/23/09, niamathullah sharief <shariefbe@xxxxxxxxxxx> wrote:
> From: niamathullah sharief <shariefbe@xxxxxxxxxxx>
> Subject: mmap()
> To: "video4linux list" <video4linux-list@xxxxxxxxxx>,
"Kernel newbies" <kernelnewbies@xxxxxxxxxxxx>, "micheal
williams" <michael_h_williamson@xxxxxxxxx>
> Date: Friday, January 23, 2009, 7:14 AM
> Hello, Actually what is mmap()?why it used?shall we
> write the program without that function?
The mmap() function makes the memory containing
the picture pixel data available to the program.
The alternative is to use the read() function,
to get the picture pixel data. I do not have
a program that does it that way.
It is possible to get picture pixel data from a
camera from the shell prompt like this:
# head -c 304128 /dev/video0 > pict.raw
That does the same things as open() and
read() functions do using a 'C' program.
-Mike
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