On Friday 22 January 2010 18:11:48 Manu Abraham wrote: > On Fri, Jan 22, 2010 at 8:42 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > On Friday 22 January 2010 04:00:53 Andy Walls wrote: > >> On Fri, 2010-01-22 at 10:42 +0800, Michael Qiu wrote: > >> > Hi all, > >> > > >> > How can I export my MPEG decoder control interface to user space? > >> > Or in other words, which device file(/dev/xxx) should a proper > >> > driver for mpeg decoder provide? > >> > >> The MPEG decoder on a PVR-350 PCI card provides a /dev/video interface > >> (normally /dev/video16). > >> > >> The interface specification to userspace is the V4L2 API: > >> > >> http://www.linuxtv.org/downloads/video4linux/API/V4L2_API/spec-single/v4l2.html > > > > Not really. The v4l2 API specifies the MPEG encoder part, but not the decode > > part. > > > > The decoder part is (unfortunately) part of the DVB API. > > > > Some ioctls are documented here: > > > > http://www.linuxtv.org/downloads/v4l-dvb-apis/ch11s02.html > > > > However, that documentation is very out of date and you are better off looking > > in the include/linux/dvb/video.h header. > > > > In particular the new struct video_command and associated ioctls provides > > you with more control than the older VIDEO_CMD_ ioctls. > > > > Note that the V4L2 API will get a new event API soon that should supercede the > > event implementation in this video.h. The video.h implementation is pretty > > crappy (most of what is in there is crappy: poorly designed without much thought > > for extendability). > > > >> > And, in linux dvb documents, all the frontend interface looks like > >> > /dev/dvb/adapter/xxx, it looks just for PCI based tv card. > >> > If it's not a TV card, but a frontend for a embedded system without > >> > PCI, which interface should I use? > > > > V4L2, but with the ioctls defined in dvb/video.h. See for example the ivtv > > driver (ivtv-ioctl.c). > > > For a DVB STB, you don't need to use V4L2 in anyway.. It doesn't make > sense either... Depends on the hardware. If there are no V4L2 features that need to be supported, then you are correct. But if the hardware functions more as a video output device which can also do MPEG decoding, then the MPEG decoder ioctls should be implemented by the V4L2 device. To be honest, MPEG decoding should have been a V4L2 feature from the beginning. It really has nothing to do with DVB as such. > The presentation/scaler used with V4L2 is pretty much > legacy code. Huh? Not sure what you mean here. > For STB's generally DirectFB is used to give full > control. There are usually two parts: one is a framebuffer device for the OSD, and one is a (possibly V4L2) device node to do the MPEG decoding that support the video.h API. Regards, Hans > > Regards, > Manu > > -- Hans Verkuil - video4linux developer - sponsored by TANDBERG -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
