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

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

[Peter Hartley]

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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).

The attached patch adds a new value for dmx_output_t:
DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. The main
question I have, is, seeing as this was such a simple change, why didn't
it already work like that? Does everyone else who wants to capture
multiple video streams, take the whole multiplex into userspace and
demux it themselves? Or do they take PES from each demux0 device and
re-multiplex that into PS, not TS?

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.

	Peter


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--- include/linux/dvb/dmx.h~	2008-01-24 22:58:37.000000000 +0000
+++ include/linux/dvb/dmx.h	2008-02-25 23:01:45.000000000 +0000
@@ -39,9 +39,10 @@ typedef enum
 	DMX_OUT_DECODER, /* Streaming directly to decoder. */
 	DMX_OUT_TAP,     /* Output going to a memory buffer */
 			 /* (to be retrieved via the read command).*/
-	DMX_OUT_TS_TAP   /* Output multiplexed into a new TS  */
+	DMX_OUT_TS_TAP,  /* Output multiplexed into a new TS  */
 			 /* (to be retrieved by reading from the */
 			 /* logical DVR device).                 */
+	DMX_OUT_TSDEMUX_TAP /* Like TS_TAP but retrieved from the DMX device */
 } dmx_output_t;
 
 
--- drivers/media/dvb/dvb-core/dmxdev.c~	2008-01-24 22:58:37.000000000 +0000
+++ drivers/media/dvb/dvb-core/dmxdev.c	2008-02-25 23:02:29.000000000 +0000
@@ -374,7 +374,8 @@ static int dvb_dmxdev_ts_callback(const 
 		return 0;
 	}
 
-	if (dmxdevfilter->params.pes.output == DMX_OUT_TAP)
+	if (dmxdevfilter->params.pes.output == DMX_OUT_TAP
+	    || dmxdevfilter->params.pes.output == DMX_OUT_TSDEMUX_TAP)
 		buffer = &dmxdevfilter->buffer;
 	else
 		buffer = &dmxdevfilter->dev->dvr_buffer;
@@ -618,7 +619,7 @@ static int dvb_dmxdev_filter_start(struc
 		else
 			ts_type = 0;
 
-		if (otype == DMX_OUT_TS_TAP)
+		if (otype == DMX_OUT_TS_TAP || otype == DMX_OUT_TSDEMUX_TAP)
 			ts_type |= TS_PACKET;
 
 		if (otype == DMX_OUT_TAP)

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

[Andreas Oberritter]

Peter Hartley wrote:
> The attached patch adds a new value for dmx_output_t:
> DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. The main
> question I have, is, seeing as this was such a simple change, why didn't
> it already work like that? Does everyone else who wants to capture
> multiple video streams, take the whole multiplex into userspace and
> demux it themselves? Or do they take PES from each demux0 device and
> re-multiplex that into PS, not TS?

I like your patch and would like to ask Mauro to integrate it if no one
objects, mainly because it serves as a basis for a DMX_ADD_PID ioctl
suggested by Felix Domke some months ago.

Regards,
Andreas

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

[Zaheer Merali]

2008/2/26 Peter Hartley <pdh@utter.chaos.org.uk>:
> 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).
>
>  The attached patch adds a new value for dmx_output_t:
>  DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. The main
>  question I have, is, seeing as this was such a simple change, why didn't
>  it already work like that? Does everyone else who wants to capture
>  multiple video streams, take the whole multiplex into userspace and
>  demux it themselves? Or do they take PES from each demux0 device and
>  re-multiplex that into PS, not TS?
>

With GStreamer, what we do is userspace demuxing and only on dvr and
not the demux device and start by only filtering the PAT pid, then
when the first PAT comes and has been parsed, add to the filter the
PMT pids for the programs that we want and then as each PMT comes add
to the filter the es pids. We provide different ts's for each of the
programs on different src (output) pads in the mpegtsparse element.
Programs can be selected, added, removed on the fly. We have a
compound gstreamer element that basically encompasses the dvbsrc which
reads from the device and the mpegtsparse that does the ts parsing
called dvbbasebin. And an example that would record multiple  programs
is as follows:

gst-launch-0.10  dvbbasebin adapter=0 frequency=10773000 polarity=h
symbol-rate=22000 program-numbers=6301:6302:6304 name=d .program_6301
! queue ! filesink location=bbc1lon.ts d.program_6302 ! queue !
filesink location=bbc2eng.ts d.program_6304 ! queue ! filesink
location=bbcnews24.ts

So we don't take the whole multiplex into userspace, just the pids we
need on an as needed basis.

Regards

Zaheer

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

[Florian Lohoff]

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On Tue, Feb 26, 2008 at 05:25:24PM +0000, Peter Hartley wrote:
> The attached patch adds a new value for dmx_output_t:
> DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. The main
> question I have, is, seeing as this was such a simple change, why didn't
> it already work like that? Does everyone else who wants to capture
> multiple video streams, take the whole multiplex into userspace and
> demux it themselves? Or do they take PES from each demux0 device and
> re-multiplex that into PS, not TS?

With getstream a little toy project of mine i basically just fetch the
whole stream with pid 0x2000 for budget cards, or join individual pids
on non-budget cards and do the whole remuxing stuff in userspace.

It is okay to have a MpegTS demux in kernel space as its a "unify the
interface" thingy for all different cards, but the section reassembly
is just a little featured moved to the kernel where it IMHO does not
belong to.

RFC1925 - The twelve networking thruths:

   (12) In protocol design, perfection has been reached not when there
           is nothing left to add, but when there is nothing left to
	   take away.

Flo
-- 
Florian Lohoff                  flo@rfc822.org             +49-171-2280134
	Those who would give up a little freedom to get a little 
          security shall soon have neither - Benjamin Franklin

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

[Andreas Oberritter]

Hello Peter,

one thing I forgot to mention is that your patch misses a
"Signed-off-by" line.

Please take a look at
http://www.linuxtv.org/v4lwiki/index.php/SubmittingPatches#Sign_your_work
and resend your patch accordingly.

You should also send a copy of it to v4l-dvb-maintainer@linuxtv.org and
include the following line:

Acked-by: Andreas Oberritter <obi@linuxtv.org>

Thanks,
Andreas

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

[Trent Piepho]

On Wed, 27 Feb 2008, Andreas Oberritter wrote:
> Peter Hartley wrote:
> > The attached patch adds a new value for dmx_output_t:
> > DMX_OUT_TSDEMUX_TAP, which sends TS to the demux0 device. The main
> > question I have, is, seeing as this was such a simple change, why didn't
> > it already work like that? Does everyone else who wants to capture
> > multiple video streams, take the whole multiplex into userspace and
> > demux it themselves? Or do they take PES from each demux0 device and

Yes, they all demux in userspace themselves.  If you search the archives,
I've pointed out this same problem.

One thing you do lose with the kernel demuxing system is the relationship
between the different streams.  For instance, a PMT change takes effect for
all packets that follow it, but with the demuxed streams, you don't know
where that is.

Of course if you want to work with existing systems, you have to demux in
userspace since no one will have this new feature yet.  And if you're doing
that anyway, it's more work to add additional support for demuxed TS
streams to your software.  That probably why no one has bothered to add
this feature.

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

[Manu Abraham]

Zaheer Merali wrote:

> So we don't take the whole multiplex into userspace, just the pids we
> need on an as needed basis.

Though this will work for FTA streams, it won't work for scrambled streams.

Regards,
Manu

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

[Zaheer Merali]

On Wed, Feb 27, 2008 at 10:56 PM, Manu Abraham <abraham.manu@gmail.com> wrote:
> Zaheer Merali wrote:
>
>  > So we don't take the whole multiplex into userspace, just the pids we
>  > need on an as needed basis.
>
>  Though this will work for FTA streams, it won't work for scrambled streams.
>
>  Regards,
>  Manu
>

Maybe I gave a simplistic description fo what we do, but I can confirm
we have encrypted streams decrypted also with dvbbasebin in gstreamer
talking to the cam. It was done in last year's Summer of Code by
Alessandro Decina.

Zaheer

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