Re: [mythtv-users] HDTV digital static with DVB

[ffrr]

Chris Trown wrote:

 




 This thread has me wondering, now.  I just got MythTV going and 
have done some test records.


 The Simpsons Halloween special recorded just fine, but it was in 
SD format(Recorded from the HD channel).  That same night, I tried to 
record Law & Order:CI.  That recording had a lot of breakups and qudio 
dropouts.


 The system is a 3.06GHz P4 with a HD3000 and a Rosewill Nvidia 
5200FX.


 My understanding is that recording DVB streams is not CPU 
intensive.  The card just grabs the digital data off the air and the 
system writes it to disk for later manipulation/transcoding.  Am I 
correct?  



That is my understanding of it as well, and what I see in practice.  
Recording a show hardly loads the CPU at all.



If that is true, then I am casting a suspicious eye to problems with 
reception.  I know that there is one channel that MythTV's scan didn't 
pick up.


 So I guess my question, is how can I tell if the problem I'm 
seeing is trouble with recption vs. a possible system throughput issue?



It is hard.  I would expect that true reception problems would be less 
frequent and VERY random. I have yet to see a true reception problem on 
mine - I am lucky that I have very good reception.  Also, reception 
problems would not correlate at system load and especially disk I/O. 

Try starting a large file copy on the SATA drive while watching live TV 
under Myth.



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Re: [mythtv-users] HDTV digital static with DVB

[Chris Trown]

Preston Crow wrote:

On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:

I chased video glitches from my DVB setup for ages, and with a lot of 
help from the list, I finally nailed it.  It was the Si 3112  SATA 
controller chip doing nasties on the PCI bus and corrupting the mpeg 
stream from the DVB card.


This would correlate with your observation that it is worse with system 
load, in particular disk access.



I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
file on the SATA drive, I get some glitches.  If I do the same to a file
on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
get a perfect recording.

So it doesn't look like it's the SATA chipset doing something nasty.  In
fact, the SATA drive, being on a faster bus, gives me a better recording
than the PATA drive.  This makes it look more like my original theory of
being an issue that can be solved in the DVB driver.  Of course, it
could be the SATA chipset or anything else on the PCI bus, but if
something were corrupting the DVB traffic, wouldn't it also corrupt
other traffic, like disk I/O?

Instead of it being a kernel buffer that is too small, perhaps it is too
slow to pull the data off of the card?




 This thread has me wondering, now.  I just got MythTV going and 
have done some test records.


 The Simpsons Halloween special recorded just fine, but it was in 
SD format(Recorded from the HD channel).  That same night, I tried to 
record Law & Order:CI.  That recording had a lot of breakups and qudio 
dropouts.


 The system is a 3.06GHz P4 with a HD3000 and a Rosewill Nvidia 5200FX.

 My understanding is that recording DVB streams is not CPU 
intensive.  The card just grabs the digital data off the air and the 
system writes it to disk for later manipulation/transcoding.  Am I 
correct?  If that is true, then I am casting a suspicious eye to 
problems with reception.  I know that there is one channel that MythTV's 
scan didn't pick up.


 So I guess my question, is how can I tell if the problem I'm 
seeing is trouble with recption vs. a possible system throughput issue?


Chris...

--
"Those who would give up essential liberty to purchase a little
temporary safety deserve neither liberty nor safety" -- Benjamin
Franklin
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Re: [mythtv-users] HDTV digital static with DVB

[ffrr]

Preston Crow wrote:


On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
 

I chased video glitches from my DVB setup for ages, and with a lot of 
help from the list, I finally nailed it.  It was the Si 3112  SATA 
controller chip doing nasties on the PCI bus and corrupting the mpeg 
stream from the DVB card.


This would correlate with your observation that it is worse with system 
load, in particular disk access.
   



I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
file on the SATA drive, I get some glitches.  If I do the same to a file
on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
get a perfect recording.
 



But is your linux system running from the SATA drive?  If so, it is 
still being used - maybe by all sorts of background processes at the 
same time. Booting from SATA drives, and putting the DVB data on an IDE 
drive did not cure the glitches for me.  Your ram disk experience is 
interesting, but I think it may have worked because it was so very fast.




So it doesn't look like it's the SATA chipset doing something nasty.  In
fact, the SATA drive, being on a faster bus, gives me a better recording
than the PATA drive.  This makes it look more like my original theory of
being an issue that can be solved in the DVB driver.  Of course, it
could be the SATA chipset or anything else on the PCI bus, but if
something were corrupting the DVB traffic, wouldn't it also corrupt
other traffic, like disk I/O?
 



As per my other message (just sent) it did indeed cause disk problems 
initially.  That chipset is just rubbish!  It sounds like your BIOS 
already copes with the timing problem, as my BIOS update did, but with 
the same unfortunate result for the DVB data stream.



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Re: [mythtv-users] HDTV digital static with DVB

[ffrr]

Preston Crow wrote:


On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
 

I chased video glitches from my DVB setup for ages, and with a lot of 
help from the list, I finally nailed it.  It was the Si 3112  SATA 
controller chip doing nasties on the PCI bus and corrupting the mpeg 
stream from the DVB card.


This would correlate with your observation that it is worse with
system load, in particular disk access.
   



Not only that, but I bought a new SATA drive at about the same time as I
switched to the DVB drivers.

Did you ever get a good resolution?
 

Yep, swore long and loud at the manufacturers of such shoddy hardware 
:-) , then built a whole new dedicated Knoppmyth system on an old 850MHz 
box, using a 250GB IDE drive I went out and purchased.


Absolutely perfect recordings every time now !




I have an ASUS A7N8X Deluxe motherboard, which includes on-board a
Silicon Image Sil 3112A controller; the same one you found to be your
problem.
 



Yep, many people have since told me horror stories about them.


I suppose that if I can't fix some setting somewhere, then my best hope
is to buy a separate PCI SATA card with a different controller chip;
that would at least be cheaper than buying a new 400GB hard drive.
 





Well, what initially happened was, I was getting corrupt file systems 
frequently.  When I realised it was the controller, I found a BIOS 
update that included/added a parameter to extend some obscure timing.  
This had 4 setting from memory, something like 10us, 20us, 30us, and 
1ms.  That rang alarm bells as the doco said to try the first 3 and if 
corruption still occurred, set it to 1ms.  This is s much larger, 
but guess what.  I needed it set to 1ms to get reliable hard disks.  

I am 99% sure that this new setting made my DVB glitches much worse.  I 
hadn't really noticed them before, as I think they were so infrequent, I 
just put it down to signal noise.  But now, they were intolerable. (This 
was all using Mythtv under a Mandriva 2005le install)


I built a quick Knoppmyth install on an old 15GB IDE drive I had around, 
and with the Sata drives disconnected, and obviously all other hardware 
still the same, I had perfect pictures.  This is the point that I built 
the separate, non-SATA machine.


I still use the SATA machine as my daily desktop, and it is now 
reliable.   Just no good for DVB cards.

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Re: [mythtv-users] HDTV digital static with DVB

[Patrick Wagstrom]

> On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
> > I chased video glitches from my DVB setup for ages, and with a lot of 
> > help from the list, I finally nailed it.  It was the Si 3112  SATA 
> > controller chip doing nasties on the PCI bus and corrupting the mpeg 
> > stream from the DVB card.
> > 
> > This would correlate with your observation that it is worse with system 
> > load, in particular disk access.
> 
> I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
> file on the SATA drive, I get some glitches.  If I do the same to a file
> on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
> get a perfect recording.
> 
> So it doesn't look like it's the SATA chipset doing something nasty.  In
> fact, the SATA drive, being on a faster bus, gives me a better recording
> than the PATA drive.  This makes it look more like my original theory of
> being an issue that can be solved in the DVB driver.  Of course, it
> could be the SATA chipset or anything else on the PCI bus, but if
> something were corrupting the DVB traffic, wouldn't it also corrupt
> other traffic, like disk I/O?
> 
> Instead of it being a kernel buffer that is too small, perhaps it is too
> slow to pull the data off of the card?
> 
> --PC

I'm also experiencing the same behavior after a system upgrade from a
low end athlon to a nice new Athlon64.  I just had a chance to do a
little debugging and I found that disabling the SiI chip and all of my
SATA ports did nothing.  Furthermore, for me dumping it to a ram disk
did NOT produce a perfect recording or anything even close to it.  It
was pretty sad indeed.

I also observed the signal levels on the card while I was getting the
stream and I noticed that signal levels dropped noticeable (from f8c4 -
near perfect) to cXXX and bXXX (where XXX varied), causing the signal to
lose out.  This is very interesting and it suggests that the cards are
susceptible to some form of interference related to the bus.  When I
leave the system idle it happily reports a perfect signal all the time.

Here's the hardware that I've got right now that may be relevant:
Athlon 64 3200+, MSI K8N-Neo4 Platinum, pcHDTV HD3000, wintv PVR250, a
bunch of IDE disk drives.

Before when the tuner was in an Athlon 700 with an Epox k7-kxa
motherboard the recordings were crisp and clean.  Maybe it should just
back in there and I need to stream recordings over the network or
something.

I also started a thread on the pchdtv message board about this issue.
You can find it at: http://pchdtv.com/forum/viewtopic.php?p=6378

Unfortunately, I don't think that I'm skilled enough to do this sort of
debugging.  Should we file this bug with pcHDTV or the DVB folks?

--Patrick


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Re: [mythtv-users] HDTV digital static with DVB

[Preston Crow]

On Tue, 2005-11-08 at 20:35 -0500, Preston Crow wrote:
> I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
> file on the SATA drive, I get some glitches.  If I do the same to a file
> on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
> get a perfect recording.

And one more update:  I've found the solution for the PATA drive is to
set the multisector I/O count to 16 (it was 0)
# hdparm -m16 /dev/hdc

Unfortunately, I don't seem to be able to set any useful parameters on
my SATA drive:
/dev/sda:
 IO_support   =  0 (default 16-bit)
 readonly =  0 (off)
 readahead= 16 (on)

Trying to change IO_support gives an error:
 setting 32-bit IO_support flag to 1
 HDIO_SET_32BIT failed: Invalid argument
It also doesn't seem to have a multisector I/O option.

So it does look like some performance improvements on the SATA drive are
what I need, but the tuning options aren't exposed.

--PC

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Re: [mythtv-users] HDTV digital static with DVB

[Preston Crow]

On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
> I chased video glitches from my DVB setup for ages, and with a lot of 
> help from the list, I finally nailed it.  It was the Si 3112  SATA 
> controller chip doing nasties on the PCI bus and corrupting the mpeg 
> stream from the DVB card.
> 
> This would correlate with your observation that it is worse with system 
> load, in particular disk access.

I have two hard drives.  If I simply cat /dev/dvb/adapter0/dvr0 to a
file on the SATA drive, I get some glitches.  If I do the same to a file
on the PATA drive, I get tons of glitches.  If I do it to a ram disk, I
get a perfect recording.

So it doesn't look like it's the SATA chipset doing something nasty.  In
fact, the SATA drive, being on a faster bus, gives me a better recording
than the PATA drive.  This makes it look more like my original theory of
being an issue that can be solved in the DVB driver.  Of course, it
could be the SATA chipset or anything else on the PCI bus, but if
something were corrupting the DVB traffic, wouldn't it also corrupt
other traffic, like disk I/O?

Instead of it being a kernel buffer that is too small, perhaps it is too
slow to pull the data off of the card?

--PC

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Re: [mythtv-users] HDTV digital static with DVB

[Preston Crow]

On Tue, 2005-11-08 at 17:14 +1000, ffrr wrote:
> I chased video glitches from my DVB setup for ages, and with a lot of 
> help from the list, I finally nailed it.  It was the Si 3112  SATA 
> controller chip doing nasties on the PCI bus and corrupting the mpeg 
> stream from the DVB card.
> 
> This would correlate with your observation that it is worse with
> system load, in particular disk access.

Not only that, but I bought a new SATA drive at about the same time as I
switched to the DVB drivers.

Did you ever get a good resolution?

I have an ASUS A7N8X Deluxe motherboard, which includes on-board a
Silicon Image Sil 3112A controller; the same one you found to be your
problem.

I suppose that if I can't fix some setting somewhere, then my best hope
is to buy a separate PCI SATA card with a different controller chip;
that would at least be cheaper than buying a new 400GB hard drive.

--PC

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Re: [mythtv-users] HDTV digital static with DVB

[ffrr]

Preston Crow wrote:


I'm having trouble with digital static-like artifacts on my HDTV
recordings using the DVB drivers.  This seems to be unrelated to signal
strength, but noticeably impacted by system load.  If I'm watching a
recording or recording another channel on another tuner, the problem
gets worse.

I know that my system has the throughput to handle the bandwidth, so it
seems that there's some buffer that's too small, but I haven't been able
to find it.

This has been an issue with my HD-2000 card for several months, so it's
not a recent driver change.

My system:
HD-2000 with rooftop antenna for ATSC (works fine with video4linux drivers)
Air2PC HD-5000 with digital cable QAM (works perfectly with non-HD channels)
Kernel: 2.6.14 with CVS DVB drivers (for HD-5000 support).
All DVB drivers built into the kernel (not modules).

Probably irrelevant:
ivtv-0.4.0 for PVR-250
AMD 2500+
SATA drive
nVidia FX5200 with xvmc
 





I chased video glitches from my DVB setup for ages, and with a lot of 
help from the list, I finally nailed it.  It was the Si 3112  SATA 
controller chip doing nasties on the PCI bus and corrupting the mpeg 
stream from the DVB card.


This would correlate with your observation that it is worse with system 
load, in particular disk access.


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RE: [mythtv-users] HDTV digital static with DVB

[C. R. Oldham]

Greetings,

Thanks all for your replies--antennaweb.org is definitely what I needed.

--cro

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RE: [mythtv-users] HDTV digital static with DVB

[James C. Dastrup]

>Sorry, I don't know the answer to your question, but I was wondering where
>you are located physically and how you can tell that there are digital OTA
>broadcasts in your area?  I live in the Phoenix metro area (Chandler) and
>can't seem to find any information on whether or not any of the local TV
>stations are broadcasting digital (other than the local PBS affiliate KAET).

http://www.antennaweb.org/  
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RE: [mythtv-users] HDTV digital static with DVB

[Preston Crow]

On Mon, 2005-11-07 at 13:08 -0700, C. R. Oldham wrote:
> I was wondering where
> you are located physically and how you can tell that there are digital OTA
> broadcasts in your area?

Near Boston, MA.

> I live in the Phoenix metro area (Chandler) and
> can't seem to find any information on whether or not any of the local TV
> stations are broadcasting digital (other than the local PBS affiliate KAET).

http://antennaweb.org/
Put in your address, and it will tell you what stations you can hope to
pick up, what type of antenna you will need, and what direction to point
it in.  I was lucky in that all my stations are within five degrees of
each other, so a good directional antenna gets them all.

> In addition, you mention a rooftop antenna for your digital ATSC setup--it
> seems from reading I have done on the web that digital TV still broadcasts
> in the VHF bands, so a "standard" VHF antenna should work fine?

Nope, they're all UHF.  For example, Fox KSAZ-DT is channel 10.1, but it
broadcasts on the frequency for UHF channel 31.

> Related to your original question, it sounds like you can't pinpoint when
> this problem started.  Has it always been the case that you get static with
> the HD2000?

Always with the DVB drivers, but never with the video4linux drivers.
That's why I think it's a buffer size issue.  With the DVB drivers, I
generally get perfect sound, and just a few squares or rectangles of odd
colors popping up every few seconds.  Occasionally, it gets worse, and
may even skip over a fraction of a second on playback.

> Not being a "real" Myth user as of yet, it "feels" to me that your cards are
> not getting enough PCI bus bandwidth.  You might try swapping the cards in
> the slots (as sometimes preference is given to a card based on its slot), or
> flashing the BIOS on your motherboard in case a recent BIOS update might
> tinker with PCI timing.  Those are just guesses on my part.

Possible, but I don't know if that would explain the video4linux driver
working.  That makes me suspect it's a driver issue, not a bus issue.

--PC

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RE: [mythtv-users] HDTV digital static with DVB

[C. R. Oldham]

Preston,

Sorry, I don't know the answer to your question, but I was wondering where
you are located physically and how you can tell that there are digital OTA
broadcasts in your area?  I live in the Phoenix metro area (Chandler) and
can't seem to find any information on whether or not any of the local TV
stations are broadcasting digital (other than the local PBS affiliate KAET).


In addition, you mention a rooftop antenna for your digital ATSC setup--it
seems from reading I have done on the web that digital TV still broadcasts
in the VHF bands, so a "standard" VHF antenna should work fine?

Related to your original question, it sounds like you can't pinpoint when
this problem started.  Has it always been the case that you get static with
the HD2000?

Not being a "real" Myth user as of yet, it "feels" to me that your cards are
not getting enough PCI bus bandwidth.  You might try swapping the cards in
the slots (as sometimes preference is given to a card based on its slot), or
flashing the BIOS on your motherboard in case a recent BIOS update might
tinker with PCI timing.  Those are just guesses on my part.

--cro

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