[mythtv-users] Performance, TV, Network, Video Cards, Identifying bottlenecks (long)

bdh at bos.nl bdh at bos.nl
Mon Apr 14 13:21:56 EDT 2003


The one thing I can think of is that its network performance related. The fact 
that live tv works better than recorded indicates that. 

I think that the problem with your setup is that you save the recorded shows 
via nfs on another server. This presents a performace problem for your backend 
server, it has to load the video via nfs and stream it across the same network 
link to the frontend clients.

This is what I can think of regarding network performance :)

My 2 cents....

Dennis

> Greetings.  First off I want to thank Isaac and all the Myth developers,
> this application really rocks and certainly rivals (and surpasses in
> many areas) the functionality of my TiVo.
> 
> I have been setting up a MythTV system for video distribution around my
> house.  I have been having problems with numerous different elements.  I
> am hoping that documenting my system with this post will help me get it
> in order.  Hopefully people will spot my weak areas and help me fortify
> the system.  I am currently in the setup and testing phase of the MythTV
> experience.  Here is how I am currently set up:
> 
> Master Backend:
> Debian Stable (2.4.20)
> Athlon 1 GHz processor (unstable at 1 GHz [7.5 X 133Mhz], running at 7.5
> x 125Mhz [937MHz])
> Asus A7v133 Motherboard
> 256 MB PC133 SDRAM
> Mounted storage via NFS
> Disk: Maxtor 91080D5 10GB
> #hdparm /dev/hda
> /dev/hda:
>  multcount    = 16 (on)
>  I/O support  =  1 (32-bit)
>  unmaskirq    =  1 (on)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  nowerr       =  0 (off)
>  readonly     =  0 (off)
>  readahead    =  8 (on)
>  geometry     = 1313/255/63, sectors = 21095424, start = 0
>  busstate     =  1 (on)
> #hdparm -tT /dev/hda
> /dev/hda:
>  Timing buffer-cache reads:   128 MB in  0.75 seconds =170.67 MB/sec
>  Timing buffered disk reads:  64 MB in  4.32 seconds = 14.81 MB/sec
> 
> Audio: es1371 based
> Video: Savage 2000 64MB composite out
> Tuner: Hauppauge WinTV-Go (mono)
> 
> 
> File/Database Server
> RedHat 7.3 (2.4.18-3)
> Athlon 1.2 GHz processor
> Asus A7v Motherboard
> 512 MB PC133 SDRAM
> Storage Disks:
> /dev/md0: 136 GB RAID5 (4 x 45GB ATA 100/133)
> /dev/md1: 194 GB RAID5 (8 x 27GB ATA 100/133)
> #hdparm -tT /dev/md[0-1]
> /dev/md0:
>  Timing buffer-cache reads:   128 MB in  0.63 seconds =203.17 MB/sec
>  Timing buffered disk reads:  64 MB in  1.43 seconds = 44.76 MB/sec
> /dev/md1:
>  Timing buffer-cache reads:   128 MB in  0.62 seconds =206.45 MB/sec
>  Timing buffered disk reads:  64 MB in  0.90 seconds = 71.11 MB/sec
> 
> 
> Frontend Candidate 1:
> AMD k6-2 @ 375 MHz
> 
> Frontend Candidate 2:
> Pentium II @ 275 MHz
> 
> Frontend Candidate 3:
> Celeron A @ 300 MHz
> 
> Frontend/Backend Candidate 4:
> Pentium II @ 333 MHz X 2
> 
> Misc Frontend Parts:
> Remote: Creative CIMR 100 IR reciever x 3
> Video: S3 Savage 2000 64MB Composite out x 2
> Video: ATI Radeon 7500 Svid + Composite
> Video: ATI Rage 128 SVid + Comp out, Comp in
> Video: ATI Rage II+DVD Svid + Composite
> Tuner: AI Tech WaveWatcher NeTV-PCI (Zoran zr36120 + Phillips 7110A)
> Capture: Generic BT848 Capture with SVid+Composite in
> Audio: ymfpci, es1370, es1371, oplSAx, opti
> Various Hard Drives, Memory, etc.
> 
> Issues:
> 
> I am having issues in quite a few areas (and have worked through more
> problems than I can count to get where I am already) so I will try to
> categorize the issues:
> 
> 1. System Performance: The main issue is performance problems with video
> playback.  I am unsure whether the issue is with the frontend or backend
> machines, but I suspect the problem is on the frontend.  The only
> configuration where I was able to get any acceptable playback was using
> frontend #2 with the radeon video card.  Also, I am only able to get
> acceptable playback for live TV, if I am trying to record the show and
> watch it on the frontend, the playback stalls every .5-1.5 seconds and
> the audio stutters and cuts out.  The backend is set up to use it's
> local disk for live TV buffering, but to use the file server via NFS for
> recordings.  The load on the file server while these operations are
> happening is negligible.  The processor on the backend machine is
> usually 50-80% utilization if it is recording and a frontend is
> playing.  The processor on the frontend machines ranges by machine, but
> none of them seem to use full utilization during playback.  However, on
> machines 1 and 3 the playback freezes every second or so, with
> corresponding audio dropout.  Frontend system 4 has not yet been tested
> with myth.  Frontend #1 was used as a freevo system in the past, with
> acceptable performance playing back MPEG2 files exported from a TiVo.
> One of the drives has MythVideo on it, but it has not yet been tested
> with the TiVo files.  I am using the default settings for recording live
> TV and scheduled recordings.
> 
> So I guess my question in this area is what are the minimum system
> requirements for a frontend system?  Are any of the candidates listed
> above going to be able to cut it in the performance arena?  Do I just
> need to optimize the way things are set up on the systems that can't
> play video well (or the backend system) or are they simply too
> underpowered and no amount of optimization will suffice?
> 
> 2.  Network Performance.  As I stated above, I am attempting to use a
> remote NFS server for storing recordings.  When I am trying to record
> something and watch it on frontend 2 (which can watch live TV with
> almost acceptable performance) the video stutters as described above.  I
> am wondering if these problems are related to network performace.  The
> NFS server and the backend server are connected via a 24 port netgear
> 100 Mb rackmount hub.  During the testing phase the frontends have been
> connected to a 8 port 100 Mb D-link switch.  Is it possible that my
> problems viewing programs that are recording are related to network
> performance?  What are the bandwidth requirements for recording (and
> playing back) programs?  Are there other people who are using NFS mounts
> to record programs?  With so many variables (backend performance,
> frontend performance, network performance, file server performance,
> etc.) it is hard to narrow down where the problems are.  Is it possible
> that I need to upgrade to a switched network for the backend servers (or
> even gigabit??).  Or are my problems related to system performance and
> not network performance?
> 
> 3.  Video Out.  As you can see from the array of video cards listed
> above, I have tried quite a few things trying to get the video signal to
> my television.  I need either s-vid or composite output that works in X,
> but so far, none of the listed video cards can give me that.  Has anyone
> used any of the cards listed above for output to a television?  When I
> was using system #1 for freevo, I used one of the savage 2000 cards
> listed above.  I was enthusiastic about this card, because it gave
> acceptable video playback under freevo and the composite output worked
> automatically under X, as opposed to all the ATI cards listed above,
> which seem to have problems displaying X on the alternate outputs.  So
> enthusiastic in fact, that I bought another one for use in my envisioned
> video network.  Unfortunately, once I tried to use this card with MythTV
> I discovered that it did not support XV accelerated output and on
> further investigation, I don't know if they ever will have XV support.
> Does anyone else have this card, and are there any workarounds for using
> MythTV with cards that don't have XV support?  The card really does a
> good job of outputting X to the TV, and I would love to be able to use
> the two cards that I have in some capacity.  The ATI cards all have
> tv-out support under windows, but so far I have been unable to get them
> to work at all under Linux.  Are there alternate drivers available that
> might help me out on the ATI front?  I have looked at the Gatos drivers,
> but the documentation is unclear on what cards are supported and what
> features are supported with each card.  Is there anyone that is using
> one of the above ATI cards that successfully uses the TV-out under
> Linux?  Or does everyone use scan converters?  All the scan converters I
> have seen are quite expensive and I am reluctant to purchase one (or
> many) when I have all these video cards that have the hardware to output
> a composite signal.  None of the frontends are going to be used for
> fancy displays, they just need to be able to output a decent composite
> or s-video signal to a normal television.  I would certainly prefer to
> use the many cards I have listed, but if I am unable to, can someone
> recommend a card that will work flawlessly for tv-out under Linux?  I
> would like to spend as little money as possible, as I have already sunk
> a ton of money into this and I am likely to end up with a bunch of
> hardware that I cannot use.  I have seen many posts about the NVidia
> cards, will something like the 440 mx (or similar) give me the TV output
> that I need?
> 
> 4.  Audio.  When I am watching video on the system that nominally works
> (frontend 2) the audio is out of sync.  When I start watching the video,
> the terminal gives an error to the effect of "Can't query audio buffers
> on this card, audio will be out of sync".  I believe the card was the
> Yamaha using the ymfpci module.  Is there something I can do to fix
> this, or am I just out of luck with this sound card?  Would it suffice
> for the backend machine (which is currently using an es1371 card)?
> 
> Also, I was wondering about the btaudio module.  Has anyone used the
> WinTV-go with btaudio successfully?  I have loaded the module, and it
> sets up /dev/dsp2 and 3 (digital and analog), but piping the output from
> those dsps to the sound card only gives popping or nothing.  Currently,
> I am using the analog output into the sound card line in, but I would
> love to dump the sound card on the backend to make room for additional
> tuners.
> 
> I also have an alternate video feed that has a single channel that I
> would like to distribute with Myth.  I was thinking of purchasing an old
> secondhand VCR (or cable box) and piping the channel onto the composite
> input of the generic bt848 card that I have.  How should this be set
> up?  I obviously need to set this up as a second video input, but how do
> I set up the listings side of it.  I pull the XMLTV listings manually
> for another application, and have been using mythfilldatabase --file to
> load the file (which also contains the channel on the second cable
> feed).  Do I need to do a second xmltv pull that gets just this channel
> and create a input entry for it?  How will it appear in the EPG?  Will
> it be on the very end since it is a different input source or will the
> channel number sort itself in with the existing channels?
> 
> Concerning the AI Tech WaveWatcher NeTV-PCI (Zoran zr36120 + Phillips
> 7110A), has anyone used this thing?  There are drivers in the kernel
> source, but they are seriously broken and set up to use the old i2c
> interface.  Does anyone know if there has been any effort to port the
> drivers to the new i2c interface?  Or are these drivers going to fall by
> the wayside and I will have another useless piece of hardware.
> I know this is a hugely rambling post, and I apologise.  I am just
> hoping by posting it I would able to get input on my setup from people
> who have more experience with Myth than I, and also to rudimentarily
> document my setup.  I appreciate any and all input on my setup, from
> "you're an idiot" to "this is exactly what you need to do to make this
> work effectively".
> 
> TIA for any advice.
> 
> 
> 
> 
> 
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