Great, thanks for your help Devin. -Trevor On Wed, Jul 31, 2013 at 12:00 PM, Devin Heitmueller <dheitmueller@xxxxxxxxxxxxxx> wrote: > On Wed, Jul 31, 2013 at 11:55 AM, Trevor Anonymous > <trevor.forums@xxxxxxxxx> wrote: >> Hi all, new to the list, hope this is an appropriate place to ask this. >> >> Quick question: >> I can extract NTSC analog closed captions with the Hauppauge 950Q as follows: >> 1. Run v4l2-ctl -i 1 ## Set input to composite >> 2. In a test application, open file /dev/video0 >> 3. Read 1 byte from the file >> ** Note: This seems to be sufficient to "start" the device >> ** Calling VIDIOC_STREAMON ioctl is *not* sufficient >> 4. Run: zvbi-ntsc-cc -c -d /dev/vbi0 ## Prints the closed captions >> 5. Close file handle to /dev/video0 when finished. Device "stops". >> My question: Is opening the device and reading 1 byte a good/ok way to >> start the device? I'm only interested in closed captions, and want >> this to be as small a footprint as possible. I'm worried that this >> method may break in future driver versions. > > Hi Trevor, > > The fact that you need video streaming in order to access CC is a bug > in the driver (brought to my attention only a couple of weeks ago). I > didn't properly setup the referencing counting for when to start/stop > the isoc FIFO, so the arrival of data is implicitly tied to the use of > /dev/video. > > The hack you've described should work as long as you keep the > filehandle open (in fact it's pretty much what the other user hacked > in userland to workaround the bug). That said, I would like to fix > the underlying bug so that the driver behaves like it's supposed to > (which means you should be able to access /dev/vbi for CC capture > without having to muck with streaming from /dev/video). I suspect > that the fix won't cause the workaround you're proposing to stop > working. > > Devin > > -- > Devin J. Heitmueller - Kernel Labs > http://www.kernellabs.com -- 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
