Pixelation When Recording HD

#1
Ive had a few issues of pixelation/stuttering when recording in the HD channels.

it doesn't always happen, but its quite annoying when it does. Basically like stutters, then jumps forward. Only seems to happen with the HD Channels.

My aerial positing is fine, Was done professionally.

It doesn't stutter when watching it live, just a few times when recording.

Any ideas?
 

Black Hole

May contain traces of nut
#5
I don't believe this is a custom software issue; as far as I know rendering a recorded file (StDef or HiDef) is a hardware operation (except possibly for disk access) with very little competition for resources.
 

af123

Administrator
Staff member
#6
If you exercise the disk when recording/playing back HD content, then it's fairly easy to cause it to stutter, even with the original firmware - just try deleting a folder with a few recordings in it while watching HD.
 

Black Hole

May contain traces of nut
#8
I've had a play, useful data for general consumption.

Simultaneous recording of two HiDef programmes, playback of a HiDef recording, and DLNA streaming of another HiDef recording - no problem. Ditto while performing a couple of gigabytes copy to USB - no problem. I then deleted a couple of gigabytes, and got stutters in the recordings. (I can't imagine what's so hard about deleting - all it needs to do is mark the disk sectors as free in the allocation tables.)

Then I ran simultaneous recording of two HiDefs, one streamed playback of HiDef, live timeshifted play of a third HiDef channel, and 5GB copy from USB to internal disk. Again, no problem until I queued up a delete.

So that's 3 write and 2 read operations at HiDef data rate, plus a copy write from USB at (what I guess was) about 4 or 5 times HiDef data rate.

In summary, there seems to be plenty of bandwidth for normal operations, just avoid deleting while recording (and possibly copies to virtual drive).
 
OP
OP
J
#9
I've had a play, useful data for general consumption.

Simultaneous recording of two HiDef programmes, playback of a HiDef recording, and DLNA streaming of another HiDef recording - no problem. Ditto while performing a couple of gigabytes copy to USB - no problem. I then deleted a couple of gigabytes, and got stutters in the recordings. (I can't imagine what's so hard about deleting - all it needs to do is mark the disk sectors as free in the allocation tables.)

Then I ran simultaneous recording of two HiDefs, one streamed playback of HiDef, live timeshifted play of a third HiDef channel, and 5GB copy from USB to internal disk. Again, no problem until I queued up a delete.

So that's 3 write and 2 read operations at HiDef data rate, plus a copy write from USB at (what I guess was) about 4 or 5 times HiDef data rate.

In summary, there seems to be plenty of bandwidth for normal operations, just avoid deleting while recording (and possibly copies to virtual drive).
Thing is i havent deleted or copied?

I have no recorded programs, i go to record a program. Say for example other night.

Recorded Eastenders and then Corrie, while i was out. Nothing else recorded, no videos on the drive.

Playback was a bit dodgy through both of them. Not sure why!
 
#12
It might be worth checking what HD Mux your Humax is tuned to. I live between 2 transmitters and one of them upped the power recently on the HD Mux and for some unknown reason my HDR decided to lock on to the worse signal - the quality would have been pretty good if the aerial was above the roofline, but the signal quality through the house and via the back of the aerial was marginal, to say the least.

The channel information link at the bottom of the webif screen can be very helpful when diagnosing that sort of problem, although the information about channel power levels is sometimes a bit variable in quality. If you do do a manual scan to tune for your HD Mux, make sure that you set the channel scan type to DVB-T2 and not DVB or the Mux won't be found.
 

Black Hole

May contain traces of nut
#13
Brand New Toshiba 1TB USB3.0 Drive.
This seems to imply you are talking HD-FOX - different ball game. For one thing, the Humax port isn't USB3. I was experimenting with loading on the internal drive of an HDR-FOX. There ought to be enough bandwidth even so.

That said, like I mentioned before I have had stutters in HiDef recordings despite there being nothing else that should have been going on at the same time, even on an HDR-FOX.
 
OP
OP
J
#14
It might be worth checking what HD Mux your Humax is tuned to. I live between 2 transmitters and one of them upped the power recently on the HD Mux and for some unknown reason my HDR decided to lock on to the worse signal - the quality would have been pretty good if the aerial was above the roofline, but the signal quality through the house and via the back of the aerial was marginal, to say the least.

The channel information link at the bottom of the webif screen can be very helpful when diagnosing that sort of problem, although the information about channel power levels is sometimes a bit variable in quality. If you do do a manual scan to tune for your HD Mux, make sure that you set the channel scan type to DVB-T2 and not DVB or the Mux won't be found.
How can i check or change etc?
 
#18
It sounds like you haven't got the same issues as I do, but you're going to have to do the research - I live in Suffolk and there's no way for me to find out for you. Plug your postcode into the ukfree location checker and see if there are any other transmitters nearby (they should be listed top right, give them a go). If they are listed, check out both the sources I gave you and the frequencies listed on the webif channels page to see if you might be receiving the wrong HD Mux- if the HD Mux is different to what your research suggests, try a manual retune and see if it helps.
 

xyz321

Well-Known Member
#19
One thing you could try is to align the disk's partitions on 4k boundaries. However, I'm not sure if it will make a significant difference so it's probably a long shot. The newer drives use 4k sectors internally so it is best to have everything aligned on 4k boundaries. The Humax UI format does not seem to do this - check this by typing 'fdisk -lu' at the telnet command prompt. If the start numbers are not exactly divisible by 8 then it could be potentially speeded up by repartitioning and reformatting.

See this post for how to reformat with aligned partitions on the box - obviously all the data will be lost if you go down this route.
 

Black Hole

May contain traces of nut
#20
I had a slight burst of pixellation in a StDef programme recorded last night (Sky At Night), when the only other thing my box was doing was streaming StDef to the HD-FOX. I know it's something we would prefer not to happen, but I don't think it's something to get worked up about - in my view it is simply a bit of interference in the reception at the time, which naturally causes a disturbance in the recorded data. It is possible that it has a greater effect on playback than it would when viewed live.
 
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