[linux-dvb] [PATCH] DMX_OUT_TSDEMUX_TAP: record two streams from same mux, resend

Peter Hartley pdh at utter.chaos.org.uk
Thu Feb 28 12:52:26 CET 2008

[Resending patch with proper signed-off-by and updated description, but
otherwise unchanged]

Hi there,

Currently (in linux-2.6.24, but linux-dvb hg looks similar), the
dmx_output_t in the dmx_pes_filter_params decides two things: whether
output is sent to demux0 or dvr0 (in dmxdev.c:dvb_dmxdev_ts_callback),
*and* whether to depacketise TS (in dmxdev.c:dvb_dmxdev_filter_start).
As it stands, those two things can't be set independently: output
destined for demux0 is depacketised, output for dvr0 isn't.

This is what you want for capturing multiple audio streams from the same
multiplex simultaneously: open demux0 several times and send
depacketised output there. And capturing a single video stream is fine
too: open dvr0. But for capturing multiple video streams, it's surely
not what you want: you want multi-open (so demux0, not dvr0), but you
want the TS nature preserved (because that's what you want on output, as
you're going to re-multiplex it with the audio).

At least one existing solution -- GStreamer -- sends all its streams
simultaneously via dvr0 and demuxes again in userland, but it seems a
bit of a shame to pick out all the PIDs in kernel, stick them back
together in kernel, and send them to userland only to get unpicked
again, when the alternative is such a small API addition.

The attached patch adds a new value for dmx_output_t:
DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. With this
patch and a dvb-usb-dib0700 (and UK Freeview from Sandy Heath), I can
successfully capture an audio/video PID pair into a TS file that mplayer
can play back.


Signed-off-by: Peter Hartley <pdh at utter.chaos.org.uk>
Acked-by: Andreas Oberritter <obi at linuxtv.org>

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