Andy, Thanks - I'm looking over the source code for the V4L2 sample capture application (http://v4l2spec.bytesex.org/v4l2spec/capture.c) for inspiration. I'm still more than a little unclear how I go about transforming my captured frame into an image file. Can you point me in the direction of a utility/methodology that I can use to transform RGB/BGR/YCbCr/greyscale into JPEG/PNG/GIF or similar? Cheers, Mike > -----Original Message----- > From: Andy Walls [mailto:awalls@xxxxxxxxxxxxxxxx] > Sent: 09 November 2010 12:29 > To: Michael PARKER > Cc: Daniel GlÃckner; linux-media@xxxxxxxxxxxxxxx > Subject: RE: Format of /dev/video0 data for HVR-4000 frame grabber > > On Tue, 2010-11-09 at 10:34 +0100, Michael PARKER wrote: > > Daniel, > > > > Many thanks for your mail. Please excuse the naivety of my questions - > > I'm a h/w guy and a nube to the s/w world. > > > > Do you know which of these is the default format or how to determine > > the format I'm seeing coming out of /dev/video0? > > $ v4l2-ctl -d /dev/video0 --list-formats > $ v4l2-ctl -d /dev/video0 --get-fmt-video > $ v4l2-ctl --help > > > Do you have a suggestion for how data captured from /dev/video0 can be > > converted into a recognisable image format (JPEG, GIF, PNG etc.)? > > > > I'm keen, if possible, to grab the single frame image using just > > command line tools and without recourse to ioctls, compiled code etc. > > v4l2-ctl can set up the device. As you and Daniel mentioned, dd can > read off a frame given the proper parameters. > > > > Also, how do I synchronise dd to the beginning of a new frame (and > > thus avoid capturing sections of two frames)? > > When dd open()s the device and does a read() it should start a capture. > When dd close()s the device and exits, it should stop the capture. I'm > fairly certain stopping and restarting a capture should resynchronize > things, but I'm not sure. The overhead of stopping and starting a > capture may cause you some noticeable delays, but again, I'm not sure. > > I think the answer is to write some code and use the Streaming I/O > ioctl()s interface to get frame based data. I know you were hoping to > avoid that. > > Regards, > Andy > > > Thanks again, > > > > Mike > ÿô.nlj·Ÿ®‰†+%ŠË±é¥Šwÿº{.nlj·¥Š{±þg‰¯â^n‡r¡öë¨è&£ûz¹Þúzf£¢·hšˆ§~††Ûÿÿïÿ‘ê_èæ+v‰¨þ)ßø
