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From: Jean-Francois Moine <moinejf@free.fr>
To: Hans de Goede <j.w.r.degoede@hhs.nl>
Cc: Video 4 Linux <video4linux-list@redhat.com>
Subject: v4l library - decoding of Pixart JPEG frames
Date: Thu, 14 Aug 2008 19:14:05 +0200	[thread overview]
Message-ID: <1218734045.1696.39.camel@localhost> (raw)

Hello Hans,

I found that the webcams containing a Pixart JPEG chip (PAC 73xx)
generate strange JPEG frames: they contains 'ff ff ff xx' markers every
1024 or 512 bytes and there are eight unused bits at the end of each
JPEG block (I saw also a 90 degrees rotation with the PAC 7302).

So, I added a new pixel format V4L2_PIX_FMT_PJPG for this encoding. It
is generated by the pac7311 subdriver of gspca. May you add the code for
decoding this format in the V4L library?

I could have done a patch by myself, but the tiny jpeg decoder is rather
complex, and I could not find the right place to do the job. If it may
help, I wrote a simple image viewer (http://moinejf.free.fr/siv.c) which
takes a raw webcam image and displays it via gtk+. It contains the
Pixart JPEG decoder and the two differences from normal JPEG are
identified by 'pac7311'.

Cheers.

-- 
Ken ar c'hentañ |             ** Breizh ha Linux atav! **
Jef             |               http://moinejf.free.fr/


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             reply	other threads:[~2008-08-14 17:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-08-14 17:14 Jean-Francois Moine [this message]
2008-08-14 18:51 ` v4l library - decoding of Pixart JPEG frames Thomas Kaiser
2008-08-17 11:47 ` Hans de Goede
2008-08-18  7:34   ` Jean-Francois Moine

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