V4L2-library June 2007

v4l2-library@linuxtv.org

1 participants
2 discussions

Re: [V4l2-library] V4L: stk11xx, add a new webcam driver
by Thierry Merle 30 Jun '07

30 Jun '07

Hi Jiri, I CC-ed the answer on the ML since there are some information for comment and action. Jiri Slaby a écrit : > Hi. > > Wow. I was out for only two days, and so many things had changed. We have ML, > pages on linuxtv... Good work! > > Yes, Mauro had the good idea to create a separate list in order to discuss between interested people as it concerns only a specific problem. > I have been thinking about your idea of preserving the old base driver > /dev/videoX and yes, it's a better solution, it still lets space for user to > choose which one he wants to use (more output formats, but slower vs. only > limited formats but no overhead). > > Well, we will see if my solution is possible. The first difficulty is to implement the base driver 'lock' operation. A device is locked when it is opened so we have to call the 'open' operator of the base driver with the /dev/video0 inode. I don't know how to do this yet from another driver using the video_device structure. The initial code in the repository may be wrong. I just initiated the files to start with something concrete to patch. There are many other points to implement: the helper daemon interface, the helper daemon itself, and the decompression library. If you look at all the SDs, you will find all messages exchanged with the helper daemon. I don't know what is the best implementation for exchanging messages with the helper daemon: read/write or ioctl? I know that the data exchange must be mmapped between the driver and the daemon for performance. The library shall be put in the v4l-dvb/v4l2-apps/ directory. There is already a lib that can be used to interface with the v4l2 extended driver. The helper daemon itself shall be put in v4l-dvb/v4l2-apps/ too. We can create a daemon/ directory to put the helper daemon code. >> I am contacting some webcam developers to join and help us to share the >> ideas and code. >> > > Great. When we have consensus, could I get write access to your repo or do you > want me to post patchsets or? > In fact some developers have already joined by themselves, welcome :) Patches should be posted on the ML for comment, then I will put them in my repository as soon as they are approved. Of course each patch will be signed-off-by the author and put in the repository as is. You will find the procedure that details all that in the wiki: http://www.linuxtv.org/v4lwiki/index.php/How_to_submit_patches > thanks, > Cheers, Thierry

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v4l2 library initiated
by Thierry Merle 28 Jun '07

28 Jun '07

v4l2-library initiated. A new v4l2 library is initiated to implement userspace decompression algorithms that cannot fit in kernelspace. Some multimedia peripherals cannot provide video pictures in a well known format (like YUV, RGB, ...). They provide compressed video pictures and the algorithm to uncompress them may be complex or may have a proprietary license. Complex algorithm are forbidden in kernelspace so we need to implement them in userspace. In a first step, this v4l2 library will provide a way to uncompress video pictures in userspace to ease the applications' labour. A first solution is specified here: http://www.linuxtv.org/v4lwiki/index.php/V4L2UserspaceLibrary A first implementation is started here: http://linuxtv.org/hg/~tmerle/v4l2_extension We invite any concerned driver developer or application developer to suscribe to the specific v4l2-library mailing-list in order to participate to this project. To suscribe to this ML, go to the v4l2-library mailing-list http://www.linuxtv.org/cgi-bin/mailman/listinfo/v4l2-library Future evolutions of this library could provide other features beyond video decompression, that would require userspace processings. Let's have fun! Cheers, Thierry.

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V4L2-library June 2007