[linux-dvb] Re: V4 API Versioning

[Johannes Stezenbach <js@convergence.de>]

Rob.McConnell@Zarlink.Com wrote:
> 
> Is there any chance that the current version of the V4 API can be included
> in the version.h file either explicitely or implicitely using CVS?
> 
> Example: Version 4.0.1 or Version 4 revision 1

How about this:

#define DVB_API_VERSION 4
#define DVB_API_MINOR_VERSION 1

> I can see much discussion in the near future occuring on the other areas of
> interest, namely the audio/video and front-end devices.  For example, we
> would definitely like to see the video device separated into 2 distinct
> areas such as video decoding and video scaling.  This would more closely
> map our h/w.

The video API does not really take care of scaling, that's left for
either video4linux (for PCI cards) or DirectFB, or a proprietary API.

Normally the application would listen for
DVB_VIDEO_SEQUENCE_HEADER_CHANGED events and set the scaler
approriately.

However, it might be possible that the application does not react
fast enough to the event, and then one or two frames might be displayed
with the wrong scaler settings.
Also for pan&scan, one would need one event per displayed picture
to adjust the scaler.

That's why the DVB_VIDEO_SET_SCREEN_ASPECT_RATIO and
DVB_VIDEO_SET_PRESENTATION_FORMAT ioctls are part of the video API.
Scaler adjustments for pan&scan and format changes would then
be handled inside the driver, but the mapping to the screen is
controlled via DirectFB or v4l.

(The ioctls are also needed for the av7110 based PCI cards, where two
scalers exist: One in the av7110 which takes care of scaling
to PAL/NTSC format for TV-out, and one in the saa7146 which
scales the TV format for display on-screen. Historically, there
is no API for direct control of the av7110 scaler, the firmware
takes care of that automatically.)


I would be interested to know what you have in mind for the scaler
API, and how you plan to implement reliable pan&scan.


Regards,
Johannes


-- 
Info:
To unsubscribe send a mail to ecartis@linuxtv.org with "unsubscribe linux-dvb" as subject.