[linux-dvb] Re: V4 Denc API Proposal

[Johannes Stezenbach <js@linuxtv.org>]

On Mon, Oct 11, 2004 at 07:59:00PM +0100, Rob.McConnell@Zarlink.Com wrote:
> Please find attached a revised version of the V4 DENC API that now includes
> the ability to set the teletext source to be from a demux or rec-656 device
> or memory.  I have also added the ability for the closed-caption source to
> be set to a rec-656 device or memory.  REC-656 can contain ancillary data
> in the blanking period.  The ancillary data can be teletext, closed
> caption, or many other data types (e.g. audio).

What is the use case for this? Just that some DENCs on the market
have this capability doesn't mean it makes sense to have it
in the API.


  /*! Used to set the input source */
  struct dvb_denc_source {
  	enum dvb_denc_source_type   type;  /*!< input source type */
  	int                         fd;    /*!< file descriptor of the device (video/video scaler, OSD or REC-656) */
  };

We would have difficulties in the implementation to use a non-DVB
file descriptor here (OSD), and we have not yet decided on the
scaler device. I would simply enumerate the inputs 0..N. It is
totally hw dependent what they mean (e.g. 0 == mixture of various
scalers and OSD layers, 1 == only one scaler (for VCR)).

  enum dvb_denc_ttx_source_type {
  	DVB_DENC_TTX_SOURCE_DEMUX,  /*!< pass through the demux decoder feed */
  	DVB_DENC_TTX_SOURCE_REC656, /*!< REC-656 ancillary data (VANC) */
  	DVB_DENC_TTX_SOURCE_MEMORY, /*!< directly into the decoder via the DVB_DENC_SET_TTX ioctl */
  };

We don't need DVB_DENC_TTX_SOURCE_MEMORY, we have DVB_DENC_SET_TTX.
(If we connect to the demux DVB_DENC_SET_TTX must fail.)

And I would like to drop that rec565 stuff. Keep it simple and stupid.

Regards,
Johannes