On 25 Jun 2010, at 13:43, James Courtier-Dutton wrote:
2010/6/25 Andre vdr@dinkum.org.uk:
On 19 Jun 2010, at 09:00, Goga777 wrote:
which problems do you have with hvr4000 ???
I get semi random glitches in the recordings that the Satix doesn't get also my Nova S+ (before it packed up last week) doesn't get the glitches. It's significantly better since the upgrade to Ubuntu 10.04, even though I was running 2.6.33 kernel on 9.04 and latest v4l drivers.
My next debugging step will be to ditch my Nova T500 for a while, after some reading on the linux-media list it seems this driver doesn't play nicely with busy interrupts and with three tuner cards and six disks this machine is busy.
I would be surprised if one DVB card had more or less glitches than another.
Well it seems to be the case, the feed I have is from an oversized dish on a communal system, no dropouts even in heavy rainstorms, I specced it that way :-) Also I checked that the dish alignment was central to the constellation (figure 8 paths) rather than lined up on only one bird as seems to be consumer industry norm! I work in Satellite TV in case you hadn't guessed, although more uplinks and fiber feeds than downlinks.
I have 4 feeds, there seems to be no variation is signal strength between them, if I record from DVBS2 on the Satix card I get the odd glitch at the start of the recording, in the first 30 seconds and maybe one glitch in every other 1 hour programme. If I record with the HD S2 or HVR4000 I get 5 or 6 glitches in a 30 minute programme, actually the HVR 4000 seemed worse than the HD S2 but it's ok now I moved it to a different PC, different feed for a different satellite so can't really compare them now. If I record a DVBS transmission BBCHD or ITVHD on my Nova S+ it's fine, rarely ever a glitch, if I use the Satix, the same, the HD S2 gives me 5 or 6 a hour again.
I've seen the same problem with very little variation across VDR, MythTV and TV Headend on the same hardware. If I have only a HVR 4000 or HD S2 in the PC it seems to work with almost no glitches.
Oh and I'm only talking about HDTV, I record very very little SDTV, the system records about 6 or 7 hours of HDTV a night, three simultaneous recordings is common, of course I only watch a small amount of this :but this is what PVR software is all about :-)
Glitches on DVB are more likely cause by bad reception so receiver sensitivity and worse S/N ratio would be the most likely causes. DVB satellites move around the sky in a figure of 8 shape, so depending on where your dish is pointing, the signal signal strength might vary over time. Was the S/N ratio the same on both cards?
Haven't checked S/N but I'm not convinced there is any comparability in the S/N stats across different cards, the figures look very untrustworthy and reading the linux-media list suggests the stats across drivers are not to be trusted.
The glitches are fairly significant, several frames are missing, a gop or two is affected, in between glitches not a single error, symptoms the same on FTA or encrypted. There doesn't appear to be any corresponding dmesg at the time of the glitches.
It might be that the hard disks are causing the problem or the filesystem.
Quite likely, I have 6 sata disks in the main machine, ICH6 & SIL24, Hitachi & Samsung 1TB & 1.5TB drives, I have had significant problems with sata disconnects under Ubuntu 9.04 but no problems at all since going to 10.04.
Which file system are you using?
EXT3 on md raid 1 for /boot XFS on LVM on md raid1 for /, /home & /var XFS on separate LVMs for 4 video storage mounts.
I know rieserfs is particularly bad for low latency application.
Any other suggestions gratefully received :-) I'm considering a motherboard swap in the main machine.
Andre
James
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