Re: [GnomeMeeting-devel-list] Firewire AVC support: looks broken to me

[Georgi Georgiev <chutz gg3 net>]

On 04/07/2003 at 09:21:04(+0200), PUYDT Julien used 1.7K just to say:
> Great news: I just unloaded raw1394 and video1394, and loaded them in
> that order: raw1394 then video1394. I then asked gm to open
> /dev/video1394/0: it worked!

Yep. However, next time you restart, even if you load the modules in the order
you think is correct, it may not work. I think I had to do some magic like

modprobe video1394
modprobe raw1394
modprobe -r video1394
modprobe video1394

So if you have problems next time - have this in mind.

> I made the following observations:
> * kino opens /dev/raw1394, and is happy without video1394: it doesn't
> seem to care about the order;
> * gnomemeeting can't open /dev/raw1394 (isn't dma available only on that
> device?);

I have no idea how the part with accessing the *1394 devices works. The code
currently looks like:

handle = raw1394_new_handle();
num_cards = raw1394_get_port_info(handle, g_pinf, 16);
raw1394_set_iso_handler(handle, 63, & RawISOHandler);

As you can see, the device name is not mentioned anywhere. I have no idea how
the raw1394 library works, but I wouldn't be surprised if it can do fine *with*
the {raw,video}1394 modules loaded and *without* the /dev entries existing. At
a point of time I was even thinking about making the avc1394 class report
device names like avc1394:0:1 which could mean for example avc1394 device, host
0, camera 1. The code would almost not change at all. It can even be done right
away by doing a simple search/replace in the video4avc1394.cxx code).

> * the image looks much better in kino than in gm; notice that it may be
> due to the fact that a lesser quality is set for the device, as the
> video stream is supposed to go out on the net, while kino probably asks
> the best quality, as the video stream is supposed to be stored&used
> locally.

In the gnomemeeting case, the same image that kino uses is first rescaled to a
CIF or QCIF resolution, then compressed with a pretty low bitrate codec
(compared to the original 3600000B/s DV stream). Not to mention the interlaced
effect. Of course it will look worse.

-- 
 /   Georgi Georgiev    / Computers are unreliable, but humans are      /
\     chutz gg3 net    \  even more unreliable. Any system which       \
 /  +81(90)6266-1163    / depends on human reliability is unreliable.   /
\  ------------------- \  -- Gilb                                      \