Re: cx18, s5h1409: chronic bit errors, only under Linux

[Steven Toth <stoth@kernellabs.com>]

David Ward wrote:
> On 06/08/2009 10:17 AM, Devin Heitmueller wrote:
>> On Mon, Jun 8, 2009 at 10:14 AM, Steven Toth<stoth@kernellabs.com>  
>> wrote:
>>   
>>>> Please let me know how I should proceed in solving this.  I would be 
>>>> happy
>>>> to provide samples of captured video, results from new tests, etc.
>>>>        
>>> When you tune using azap, and you can see UNC and BER values, what is 
>>> the
>>> SNR value and does it move over the course of 30 seconds?
>>>
>>> -- 
>>> Steven Toth - Kernel Labs
>>> http://www.kernellabs.com
>>>      
>> Also, I believe UNC and BER display garbage when signal lock is lost,
>> so do you see the "status" field change when the BER/UNC fields show
>> data?
>>
>> Devin
>>
>>    
> Steven, Devin,
> 
> Thanks for your replies.  The signal and SNR are usually in the range 
> 0x0128 - 0x0140.  They may increment or decrement on a per-second basis 
> but otherwise remain steady.  The status field does not change most of 
> the time when bit errors occur, but it does lose the lock from time to 
> time for a second.  Here is a representative sample:
> 
> david@delldimension:~$ azap -r RTN
> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> tuning to 555000000 Hz
> video pid 0x0051, audio pid 0x0052
> status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 |
> status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 |
> status 1f | signal 012e | snr 012e | ber 00001b04 | unc 00001b04 | 
> FE_HAS_LOCK
> status 1f | signal 012c | snr 012e | ber 00000000 | unc 00000000 | 
> FE_HAS_LOCK

Your SNR is very low, 0x12c is 30db. I assume you're using digital cable this is 
borderline.

I like my cable system at home to be atleast 32db (0x140) bare minimum, it's 
typically 0x160 (36db) for comfort.

It's possible that the tuner and 1409 driver are a little more optimized under 
windows.

How much attenuation can you add under windows with signal loss? It's probably 
reasonably close to the edge also.

-- 
Steven Toth - Kernel Labs
http://www.kernellabs.com