[Sumover-dev] RE: Possibility of merging vic features / multithreadedness

[Douglas Kosovic]

Hi Andrew,

[resending email from work after receiving a bounce indicating my ISP's SMPTP server was black listed when I sent it from home]

I'm CC'ing Leon the author of UQ Vislab vic, but no longer works at UQ Vislab.

> I'd like to know if there are any licensing or other obstacles in 
> merging features from the UQ vic to the mpeg4 vic branch. I know there 
> are a lot to do, but primarily I'm concerned with the Linux DV1394 
> grabber, as it seems there's no way currently to take a DV input and 
> transcode it to mpeg4 on linux (in the context of AG/vic) as far as I 
> know. I saw mention of a 1394 grabber in the configure script for the 
> mpeg4 branch - I haven't tried it yet, but how does it compare to the UQ version?

The grabber-linux1394.cpp code in the VIC mpeg4 SVN branch is for IIDC webcams (e.g. like the firewire based Apple iSight that is no longer sold). Other issue with this grabber is that it is using the older libdc1394 1.x API, while new linux distributions come with libdc1394 2.0.x which is a substantially different API.

Currently the only way to transcode is to use one of the V4L firewire utilities :
   http://www.linuxtv.org/wiki/index.php/V4L_IEEE1394_devices
which are less than ideal in terms of reliability and usability.

I've been thinking of writing linux DV and IIDC grabbers for mpeg-4 vic, but haven't gotten around to it, except for a bit of code I started writing for a new IIDC grabber.

> The other major feature would be the multithreading. I'm curious about 
> the effects - the underlying ffmpeg encoding for mpeg4 should be able 
> to be multithreaded, correct? Would it be possible for mpeg4 encoding 
> to be multithreaded in vic? From testing on Windows with the Intensity 
> card, it seems like 1080i encoding is almost impossible if it's 
> confined to a single core.

I think adding multi-threading would be the way to go for encoding anything above 720p.

You might have seen my email last week or the week before to AG-tech about the Blackmagic linux drivers being released in June. It'll be interesting to see how 1080i HDMI capture performs with UQ Vislab VIC compared to UCL VIC for mpeg4 encoding. Modifications will need to be performed to both versions of VIC to be able to do the actual comparison.

> Also, were there plans to merge the mpeg4 branch back into the "main"
> branch? What benefits would this have?

I think it's on the TODO list, but I'm more interested in seeing new source tarballs being released for libuclmmbase, vic and rat as I want to prod the package maintainers of Debian, Ubuntu, FreeBSD and NetBSD to updated their UCL packages. Recently some licensing issues have been resolved and I want to submit the packages to the Fedora Project repository.

As for merging UQ Vislab VIC changes back into the UCL SVN repository, that's going to be a major project.


Cheers,
Doug