On Monday, September 13, 2010 12:50:31 Matti J. Aaltonen wrote:
> On Sat, 2010-09-11 at 14:10 +0200, ext Hans Verkuil wrote:
> > There are also up to three ways the RDS data can be received/sent: either as
> > RDS blocks, or using controls, or as a completely raw bitstream. The latter
> > is
> > unlikely to be used for RDS output, but a cheap RDS receiver might just do
> > this
> > (and I believe these devices actually exist).
>
> I thought that the "raw" mode meant reading and writing (uninterpreted)
> RDS blocks. At least that's what the wl1273 chip does and that was what
> I meant. Is there already a way to deal with this case?
I had to dig into the linux-media archives, but I found one chip (the cx2388x)
that produces a 38 kHz 16 bit RDS data stream that needs to be demodulated in
software. That's really raw :-) But I'm not aware of any board based on this
chipset that actually uses this.
> Anyway the difference between the "completely raw bits" and the "raw"
> blocks is small. And I doubt the usefulness of supporting the
> "completely raw" format.
I don't intend to support it now. But we need to realize that it exists and
we have to plan for it.
Regards,
Hans
>
> B.R.
> Matti
>
> > So I propose to add the following tuner capability flags:
> >
> > V4L2_TUNER_CAP_RDS_READWRITE 0x0100 Use read()/write()
> > V4L2_TUNER_CAP_RDS_CONTROLS 0x0200 Use RDS controls
> >
> > And this allows us to add a RDS_RAW_READWRITE in the future should we need
> > it.
> >
> > We do need to add these capability flags to the existing RDS drivers (there
> > are only a few, so that's no problem) and we need to document that for RDS
> > capture the READWRITE is the default if neither READWRITE or CONTROLS is
> > set,
> > and that for RDS output the CONTROLS is the default in that case.
> >
> > Comments?
> >
> > Hans
> >
>
>
>
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG, part of Cisco
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