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

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

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!

ISDB not only does hierarchical split. It also splits the OFDM carriers
into 3 layers, each layer with its own modulation, guard interval, inner
FEC, etc. Each of those layers behave as an independent channel,
providing different bit rates.


Cheers,
Mauro