Re: [PATCH RFCv3] dvb: Add DVBv5 properties for quality parameters

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em Fri, 4 Jan 2013 01:02:02 +0530
Manu Abraham <abraham.manu@gmail.com> escreveu:

> On Fri, Jan 4, 2013 at 12:57 AM, Mauro Carvalho Chehab
> <mchehab@redhat.com> wrote:
> > Em Fri, 4 Jan 2013 00:39:25 +0530
> > Manu Abraham <abraham.manu@gmail.com> escreveu:
> >
> >> Hi Antti,
> >>
> >> On Thu, Jan 3, 2013 at 9:04 PM, Antti Palosaari <crope@iki.fi> wrote:
> >> > On 01/01/2013 06:48 PM, Manu Abraham wrote:
> >> >>
> >> >> On Tue, Jan 1, 2013 at 8:30 PM, Mauro Carvalho Chehab
> >> >> <mchehab@redhat.com> wrote:
> >> >>
> >> >>> [RFCv4] dvb: Add DVBv5 properties for quality parameters
> >> >>>
> >> >>> The DVBv3 quality parameters are limited on several ways:
> >> >>>          - Doesn't provide any way to indicate the used measure;
> >> >>>          - Userspace need to guess how to calculate the measure;
> >> >>>          - Only a limited set of stats are supported;
> >> >>>          - Doesn't provide QoS measure for the OFDM TPS/TMCC
> >> >>>            carriers, used to detect the network parameters for
> >> >>>            DVB-T/ISDB-T;
> >> >>>          - Can't be called in a way to require them to be filled
> >> >>>            all at once (atomic reads from the hardware), with may
> >> >>>            cause troubles on interpreting them on userspace;
> >> >>>          - On some OFDM delivery systems, the carriers can be
> >> >>>            independently modulated, having different properties.
> >> >>>            Currently, there's no way to report per-layer stats;
> >> >>
> >> >>
> >> >> per layer stats is a mythical bird, nothing of that sort does exist. If
> >> >> some
> >> >> driver states that it is simply due to lack of knowledge at the coding
> >> >> side.
> >> >>
> >> >> ISDB-T uses hierarchial modulation, just like DVB-S2 or DVB-T2
> >> >
> >> >
> >> > Manu, you confused now two concept (which are aimed to resolve same real
> >> > life problem) - hierarchical coding and multiple transport stream. Both are
> >> > quite similar on lower level of radio channel, but differs on upper levels.
> >> >
> >> > Hierarchical is a little bit weird baby as it remuxes those lower lever
> >> > radio channels (called layers in case of ISDB-T) to one single mux!
> >>
> >> That is not really correct. There is one single OFDM channel, the layers
> >> are processed via hierarchial separation. Stuffing exists, to maintain
> >> constant rate.
> >>
> >> http://farm9.staticflickr.com/8077/8343296328_e1e375b519_b_d.jpg
> >>
> >> When rate is constant within the same channel..
> >> (The only case what I can think parameters could be different with a
> >> constant rate,
> >> is that stuffing frames are unaccounted for. Most likely a bug ?)
> >
> > What did you smoke? That picture has nothing to do with ISDB!
> >
> 
> ARIB STD – B31
> Version 1.6-E2
> －17－
> Fig. 3-2 shows the basic configuration of the channel coding.
> 
> It just shows, you understand crap.

That is the picture you need to look, not the random one you picked.
It clearly shows there that, after the hierarchical coding done by
the "Division of TS into hierarchical levels", the TS packets are
split into 3 independent channels, each with its own convolutional
coding, carrier modulation, etc.

This picture shows how each program is split at the FDM sub-carriers:
	http://en.wikipedia.org/wiki/File:ISDB-T_CH_Seg_Prog_allocation.jpg.svg

There, LD programs are at segment 0 (S0). HD programs use 12 segments
and SD programs use 4 segments.

As each segment group has a different spectrum (as they're using FDM),
and are modulated with different encoding schemas (modulation type, FEC,
etc), they have different QoS measures.

Segment 0 (the one at the center of the spectrum) is less sensitive to
inter-channel interference. That's why it is used for LD programs.


Cheers,
Mauro