Re: [DRAFT 1] Linux Media Summit report - March, 26 2015 - San Jose - CA - USA

[Mauro Carvalho Chehab <mchehab@osg.samsung.com>]

Hi Patrick,

Em Thu, 23 Apr 2015 09:06:35 +0200
Patrick Boettcher <patrick.boettcher@posteo.de> escreveu:

> Hi Mauro,
> 
> I could not participate at your Summit, but may have an input to the
> media-controller in DVB - see below.
> 
> 
> On Wed, 22 Apr 2015 15:31:46 -0300 Mauro Carvalho Chehab
> <mchehab@osg.samsung.com> wrote:
> 
> > This is the first draft for the Linux Media Summit Report.
> > 
> > Please note that the items 3 to 5 are not in good shape. In special,
> > nobody took Etherpad notes on item 4.
> > 
> > Please review. I'll publish a second (final?) draft after having some
> > feedback.
> > 
> > Regards,
> > Mauro
> > 
> > -
> > 
> > Linux Media Summit - March, 26 2015 - San Jose - CA - USA
> >  
> >  
> > Attendees:
> > 
> > 
> >     Angelos Manousaridis <amanous@gmail.com>
> >     Bob Moragues <bob.moragues@lge.com>
> >     Chris Kohn
> >     Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> >     Hans Verkuil <hverkuil@xs4all.nl>
> >     Hyun Kwon
> >     Karthik Poduval <karthik.poduval@gmail.com>
> >     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >     Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> >     Michal Lebik
> >     Mohammed CHERIFI mcherifi@cisco.com
> >     Rafael Chehab <chehabrafael@gmail.com>
> >     Ron Birkett
> >     Schuyler Patton
> >     Shuah Khan <shuahkh@osg.samsung.com>
> > 
> > 1) Media Controller support for DVB
> > Mauro presented a set of slides (add link) showing how the DVB
> > pipelines look like and underlined that several topics needs to be
> > addressed by the Media controller:
> > 
> > a) dynamic creation/removal of pipelines
> > b) change media_entity_pipeline_start to also define the final entity
> > c) how to setup pipelines that also envolve audio and DRM?
> > d) how to lock the media controller pipeline between enabling a
> > pipeline and starting it, in 
> > 
> > How to do complex pipelines in DVB?
> >  
> > - The DVB demux can filter MPEG-TS traffic (either in hardware or in
> > software) and can send multiplexed TS to the dvr node, elementary
> > streams to the demux node and can create network interfaces for
> > elementary streams (ES) via the net node.
> > - a given set of elementary streams can go to one of those three
> > options only, or it can be sent directly to a GPU and/or an ALSA
> > pipeline.
> > - there is support for hardware PID filtering at the Kernel, but no
> > support (yet) for a real hw demuxer that splits the MPEG TS into
> > separate DMA MPEG-TS and/or ES streams.
> > - frontend device node is to be attached to the demod entity and it
> > will control the demod, the tuner and a possible LNA via the active
> > Media Controller links.
> > - dvr/net/demux device nodes are attached to the demux entity.
> > - the net interfaces are not (yet) represented via MC: we need the
> > ability to remove entities dynamically for that, and we are not
> > really sure if we want this at all. So, it as agreed to wait for
> > support for removing entities to arrive, then this need can be
> > discussed again.
> > - For now we can safely assume that there is only one Satellite
> > Equipment Control (SEC) in each active data path that goes through a
> > tuner/demod. So each frontend will control just one SEC. Should we
> > encounter really complex scenarios, then we should consider having
> > device nodes for SEC entities.
> 
> What about demod-diversity: demods of some manufacturers can be used to
> combine their demodulated symbols and, due to their different antennas
> and RF-paths, improve the overall reception quality.
> 
> If we ever have someone contributing in this area with hardware-drivers,
> it would be nice to have the user-space possible to select
> demod-combinations. It should be possible to add and remove a demod
> to a diversity-chain when and when not being tuned to a channel.

It makes sense to map demod diversity via the media controller.

Not sure what would be the best way to map it though, as I don't have
a clear understanding about how the hardware pipelines are set for
demod diversity.

The way the media controller currently is is that it maps only the
data flow. There are discussions about how the control flow should
happen.

The data flow for a normal demod is:

	IF (or baseband) ---> [demod] ---> MPEG-TS


>From dib0700 demod drivers, I remember that several of the demods have
a concept of a "slave demod". Are those full demods that can get an
IF/baseband input and produce a MPEG-TS output, or are those just
IP blocks that have the IF/baseband input but doesn't produce an
MPEG-TS output, but, instead, sends some sort of data into the "master
demod"?

In other words, would the dataflow be something like

                 IF                   TS
	[tuner] ---> [master demod] ----->[          ]
	  | IF                       TS   [ combiner ] ---> [demux]
	  |--------> [slave demod]  ----->[          ]

or:
                 IF                          TS
	[tuner] -----------> [master demod] ---> [demux]
  	  | IF                     ^
          |                        | (what sort of data?)
	  |----> [slave demod] ----|

Or is it something else?

Regards,
Mauro