[AG-TECH] Any more H.264 news?

Piers O'Hanlon p.ohanlon at cs.ucl.ac.uk
Mon Apr 21 19:18:48 CDT 2008


Hi folks,

I thought I'd just clarify a couple of things relevant to the Firewire
camera discussion - There are two basic types of the firewire cameras:
- AVC - DV 'handycam' video camera - which provide DV compressed
video, usually with audio
- DCAM - simpler devices that just provide uncompressed video

(for more details see: http://en.wikipedia.org/wiki/FireWire_camera)

The support for these cams aries under windows, and Linux
- Under linux there's different respective support libraries (libdc,
libavc) to directly bring in the two different types of video - there
are also higher level apps that can convert DCAM (coriander) and AVC
(DV4Linux) video streams to video4linux - they seem to work but are a
bit flakey at times. As far as UCL-VIC goes there is an alpha driver
for DCAM video which currently doesn't really work, and there's no
support for AVC cameras. On the decode side there also alpha support
for DV decode which also doesn't quite work (anyone is welcome to
debug these - we only have limited time...). I understand that the VIC
from UQ DOES have support for AVC devices but I'm not sure if handles
DCAM devices.
- Under Windows I have tested a DCAM device successfully but that
doesn't mean they all work (though they should do). I have not tested
an AVC device as yet but I suspect there may be problems (as mentioned
on the list e.g by Andrew Rowley). In theory the Direct Show Windows
capture should be able to create a filter-graph that would need to
include a DV-to-YUV converter (DS filter) but I'm not clear if this is
actually happening (or that Windows ships such a DS filter...). I
don't know whether the UQ VIC supports DCAM/AVC under windows
separately?

Piers.


On Tue, Apr 22, 2008 at 12:12 AM, Nathan Gardiner
<nathan.gardiner at canterbury.ac.nz> wrote:
>
>
> Hi Andrew,
>
> I have come across this before. Are you using the extended video producer
> for windows? If you are then it doesn't work with PAL cameras (which UK,
> Australia and NZ etc use).
>
> In regards to the UQ vislab DV / HDV services, under my ubuntu box I had a
> similar problem until I installed a fairly up-to-date NVidia Graphics card
> and drivers. (I am currently using an 8800 card).
>
>
> Hope this helps.
>
>
> Regards,
> Nathan
>
>  ________________________________
>  From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov] On
> Behalf Of Andrew Rowley
> Sent: Monday, 21 April 2008 10:32 p.m.
> To: Andrew Ford; Douglas Kosovic
> Cc: ag-tech
> Subject: RE: [AG-TECH] Any more H.264 news?
>
>
>
>
>
>
> Hi,
>
>
>
> I have tried firewire capture on windows and get similar results – I just
> get a kind of set of lines (see attached image).
>
>
>
> I have a feeling that this is due to vic assuming that the camera source is
> a standard size (e.g. 352x288) when it isn't.  It looks like it is picking
> up an image from the camera (it changes when I move around in front of the
> camera) but it is only using some of that image (I think).
>
>
>
> This was using a Sony MiniDV camera.
>
>
>
> Andrew :)
>
>
> ---------------------------------------------------------
>
>   Andrew G D Rowley
>   Senior Development Officer
>
>   Research Computing Services
>   The University of Manchester
>   Kilburn Building, Oxford Road
>   Manchester, M13 9PL
>
>   t :  +44 (0) 161 275 0685
>   e :  Andrew.Rowley at manchester.ac.uk
>   w :  www.manchester.ac.uk/researchcomputing
>
> ---------------------------------------------------------
>
>  ________________________________
>
>
> From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov] On Behalf
> Of Andrew Ford
> Sent: 18 April 2008 21:21
> To: Douglas Kosovic
> Cc: ag-tech
> Subject: Re: [AG-TECH] Any more H.264 news?
>
>
>
> On Wed, Apr 16, 2008 at 8:54 PM, Douglas Kosovic <douglask at itee.uq.edu.au>
> wrote:
>
>
>
> UQ Vislab vic doesn't do any transcoding from DV (or HDV) firewire devices
> to other codecs, so if the codebase was merged as it stands now, it wouldn't
> do what you are trying to do anyway.
>
>
>
> Well, doing raw DV without transcoding would be fine (if it were on both
> platforms), since we can spare the bandwidth - that's what we're already
> doing via the ExtendedVideo services on Windows, but we'd like to be able to
> move on to something more cross-platform.
>
>
>
> Have you tried using DV4Linux so that your Camcorder can be seen as a V4L
> device? I haven't tried it myself.
>
>
>
> Interesting, I'll have to try that out. Would vic theoretically be able to
> transmit 640 (or 720)x480 video from a V4L device?
>
>
> As for the flashing verticle line artifacts on Windows, I don't seem them,
> but I was using a quad-core 2.6GHz Xeon.
>
>
>
> We've seen it here on a couple of different systems - a Dell w/ a dual-core
> + hyperthreading 3.46Ghz CPU, and Suns with 2x dual-core 2.2Ghz Opterons -
> so I doubt it's CPU-related. Can anyone else chime in if they've tried the
> firewire capture on Windows?
>
> --Andrew




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