[linux-dvb] RFC: Multiple TS recordings

Johannes Stezenbach js at linuxtv.org
Tue Apr 11 17:14:10 CEST 2006


On Tue, Apr 11, 2006, Andreas Oberritter wrote:
> Johannes Stezenbach wrote:
> > That is not entirely true. If you want teletext packets for
> > decoding *and* send them out via VBI within the driver at
> > the same time, you'd use DMX_OUT_TAP with DMX_PES_TELETEXT0.
> > At least that's how interpreted the API, but maybe it was
> > just a hack...
> 
> My understanding is that your case would require the application to set
> up two separate filters on different file descriptors, i.e. one with
> DMX_OUT_DECODER+DMX_PES_TELETEXT0 and one with
> DMX_PES_OTHER+DMX_OUT_TAP. Otherwise you can't stop your recording
> without stopping VBI.

It's not about recording, but software-decoding teletext while
at the same time outputting it as VBI (so people can choose,
and the VCR can use it to set its clock etc.).
The clean way to implement would have been to route VBI
data from userspace back to VBI driver for output, but
using DMX_OUT_TAP+DMX_PES_TELETEXT0 saves a few CPU cycles.

AC3 output via spdif on the DVB card vs. on
the sound card, or software-decoding AC3 for PCM
output might be another application of this hack.
But I guess VDR works different and doesn't rely on that.

> But I know that what you describe is how the av7110 driver behaves. In
> my opinion it is a bug.

It's not a bug, it's a feature :-)

Anyway, using DMX_OUT_TAP + DMX_PES_OTHER_TS wouldn't conflict
with it, would it?


Johannes



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