[mythtv-users] Pixelation/Bad Recordings HDHR Prime -- I am at my wits end

[Captain Hook]

On Friday, September 13, 2013, Frank Feuerbacher wrote:

>  On 13-09-12 02:41 PM, Captain Hook wrote:
>
> <Snip>
>
>   I know you can use RDM devices, but it doesn't seem to easily allow me
> to do this with onboard storage.  There are options for iSCSI/SAN
> devices, but I see in the link it may be possible, although it seems
> unclear if they've actually added an add-in controller card or not.
>
> I am using virtual disks, yes.  They are added through vSphere which
> then carves up the physical disk and creates VMDKs presented to my
> VMs.
>
> I've run a few benchmarks against these disks in the VMs and I don't
> really see much in the way of poor performance.  It is my
> understanding that recordings really don't take much in the way of
> performance and you can easily use even 5400 RPM drives with multiple
> simultaneous recordings.  My recordings thus far have almost
> exclusively been one at a time.
>
> I am using ESXi because I am very familiar with it and like to run
> multiple OSes and use it's capabilities (snapshots, migrating data,
> etc.).  I built a fairly decent performing server hoping to be able to
> utilize one box for everything.  I am using Windows Server because I
> run an MS shop in the day time and wanted a domain at home.
>
> I will consider running Ubuntu on the box and then using another
> virtualization method, but I'd really like to avoid that if possible.
> _______________________________________________
>
>  I have a 4 CPU 2.6Ghz HD4000 Ubuntu box with 16G ram. It has 3 spindles
> and I thought I was in good shape cpu, gpu and disk throughput wise.
> However, I was a little sloppy about some of my processes and got
> pixelation problems at times. The core problem was i/o. The machine mostly
> runs mythtv to record 1 or 2 HD content shows (Ceton infinTV card). It also
> encodes shows using Handbrake to .mkv.
>
> One spindle is my root and home filesystems (also where handbrakes writes
> encoded movies)
> One spindle is for mythtv and the scratch area for editing/trimming movies
> One spindle is my movie repository for XBMC
>
> One of the mistakes that I made was having mythtv perform commercial
> detection after a show was recorded instead of during the recording. This
> triples the I/O on the same spindle. I also copied the recording to a
> scratch area (on the same spindle) for manual trimming and Handbraking
> instead of creating a symlink (which meant each recording had another
> read/write pass). I also ran avidemux to build an index on each recording
> to save me time later. Finally, I had all of these operations running at
> the "normal" I/O and cpu priority.
>
> To fix, I changed commercial detection to run during recording. I changed
> to use symlinks and I modified my job script to run avidemux with lower I/O
> and cpu priority using:*
> *
>
> *ionice -c idle -t /usr/bin/nice -n10* <command>
>
> Similarly, I lowered the priority of my handbrake scripts. I also have
> mythbackend running with a nice value of -5. After these changes I have not
> encountered any problems. If I did have trouble, the next thing I would do
> is move my scratch copies of shows to another drive. This would mean that
> the mythtv drive would have two passes over each recording one to write and
> one to read it for copying to another drive. I don't think I have tried
> increasing any buffer caches. It might help.
>
> Finally, I also had problems with the cable signal strength. I proved this
> using the signal strength reading from my InfiniTV card. The cable company
> concurred and added an amplifier, but the signal strength varied
> significantly over the bandwidth so they had to add an attenuator for some
> frequency ranges. Anyway, you do have to pay close attention to the use of
> splitters, and you seem to have quite a few. Your cable modem probably
> needs special handling, but all of your video devices should receive the
> same signal strength. If you have 5 video receivers, then you are much
> better off with a 5-way splitter (ignoring the cable modem) than to have a
> tree of splitters. Make sure they are good splitters and not Home Depot
> specials.
>
> Good luck.
>
>
Great info, thanks!  I will certainly look into all of these things. I was
just about to rebuild everything using KVM on top of Ubuntu. I may
reconsider that. Thanks again.
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