[linux-dvb] ves1820 FEC off? EN 300 468 -> cable:has inner fec, on implementing

thomas schorpp t.schorpp at gmx.de
Mon Jul 25 12:23:07 CEST 2005


Johannes Stezenbach wrote:
> Robert Schlabbach wrote:
> 
>>From: "thomas schorpp" <t.schorpp at gmx.de>
>>
>>>why this:
>>>p->u.qam.fec_inner = FEC_NONE;
>>
>>DVB-Cable has no _inner_ FEC. The outer FEC is Reed-Solomon 204/188.
> 
> 
> Hm, yes, EN 300 468 disagrees with EN 300 429 here, which I guess
> is the origin of the fec_inner parameter, carried over from the
> Nokia API...
> 
> Johannes
> 

in 429 the framing shows only outer r-s fec.

the latest 468 standard says we HAVE inner fec(!)

(c) ETSI
6.2.13.1 Cable delivery system descriptor
See table 32.
Table 32:
Cable delivery system descriptor

Syntax Number of bits Identifier

cable_delivery_system_descriptor(){
descriptor_tag 8 uimsbf
descriptor_length 8 uimsbf
frequency 32 bslbf
reserved_future_use 12 bslbf
FEC_outer 4 bslbf
modulation 8 bslbf
symbol_rate 28 bslbf
FEC_inner 4 bslbf <------ XXX
}

...

Semantics for cable delivery system descriptor

ETSI EN 300 468 V1.6.1 (2004-40 11)
FEC_outer: The FEC_outer is a 4-bit field specifying the outer Forward
Error Correction (FEC) scheme used
according to table 33.

Table 33: Outer FEC scheme
FEC_outer bit 3210 Description
0000 not defined
0001 no outer FEC coding
0010 RS(204/188)
0011 to 1111 reserved for future use

...

FEC_inner: The FEC_inner is a 4-bit field specifying the inner FEC
scheme used according to table 35.

Table 35: Inner FEC scheme
FEC_inner bit 3210 Description
0000 not defined
0001 1/2 conv. code rate
0010 2/3 conv. code rate
0011 3/4 conv. code rate
0100 5/6 conv. code rate
0101 7/8 conv. code rate
0110 8/9 conv. code rate
1111 no conv. coding
0111 to 1110 reserved for future use
NOTE: Not all convolutional code rates apply for all modulation
schemes.

6.2.13.2 Satellite delivery system descriptor
-end-

i'll implement this in the driver until weekend -if- someone gets me
programming registers and values or a full datasheet, theres no on the
web, or i try using the ves1x93 data...

i really need this here, its a catastrophy:

status 1f | signal ffff | snr dfdf | ber 00044c96 | unc 0000003c |
FE_HAS_LOCK
status 1f | signal ffff | snr dede | ber 0004885a | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr e0e0 | ber 0004885a | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr dddd | ber 00042f40 | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr dcdc | ber 00042f40 | unc 00000044 |
FE_HAS_LOCK
status 1f | signal ffff | snr dddd | ber 00042f40 | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr dada | ber 0004effc | unc 00000000 |
FE_HAS_LOCK
status 1f | signal ffff | snr d9d9 | ber 0004effc | unc 00000000 |
FE_HAS_LOCK

y
tom





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