[mythtv-users] Performance from a different perspective
rpooser at gmail.com
Thu Jan 26 16:13:42 UTC 2006
Justin The Cynical wrote:
> On Tue, January 24, 2006 10:14, Raphael Pooser wrote:
>> In reality, encoding/decoding is computationally intensive, and at the
>> same time you need bandwidth as these actions involve streaming. since
>> Celeron is piss poor at floating point and has no bandwidth to access
>> the RAM, it must suck for HD on HTPCs. However, if anyone is using one
>> successfully I'd like to know.
> I've got one in the current Myth machine.
> 2 gig socket 478, machine is a FE/BE, SD broadcast, Avermedia M179.
> Playback takes about 50% of the CPU.
> My first build was a software encoding card on a much earlier verison of
> Myth, and the machine could /just/ play and record at the same time.
> IMO, for a remote FE, a "fast" Celeron will work fine for SD broadcast.
> mythtv-users mailing list
> mythtv-users at mythtv.org
It seems most people are talking about SD broadcasts, which I definitely
thing Celerons are up for. I think the original poster was asking with
a little more interest in HD though, which is basically why I said
celerons are no good, and I do think it's probably not the ideal
solution. That said, you can get by with quite low requirements for
playing back SD as well as software recording it. It seems people here
have quite a few problems stemming from their processor's pouvoir when
it comes to HD.
>Actually I have to completely disagree. For encoding and decoding
>applications caching is not very important. A cache only helps when
>you have spacial or temporal locality, video and audio encoding do not
>have temporal locality and the spacial locality is small, small enough
>for a small cache. In this sort of application you are streaming data
>in, performing some operations on it and streaming it back out never
>to be seen again (at the time scale a processor runs at).
>Also this is the sort of application that intel's highly pipelined
>architecture excels at, heavy on the math and very predictable
True cache isn't as important in encoding, but it is important plenty of other things mythtv is going to be doing. Start doing those things (ie commflagging) at the same time as trying to watch and record HD, and perhaps we have a different story. Now, I have to mention that your statement about intel being better than AMD at encoding is somewhat outdated. Yes this is historically true. But check the most up to date benchmarks on the most recent processors, the athlon X2 versus the dual core pentium D. Intel still wins a few but there are quite a few benchmarks now ending favorably for AMD. Basically the benchmarks are all over the map now, but athlons do very well with Lame right now for one thing. I'm not endorsing anybody but you know the usual review websites to check for these, the toms hardware review http://www.tomshardware.com/2006/01/10/amd_athlon_fx_60_dual_core_assault/page11.html on the FX60 for example includes the 3800+X2 and most of the pentium dual cores. There's another review on anandtech as well http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2668&p=7 etc. I'm not saying these sites are particularly good but in many cases the benchmarks are probably trustworthy.
The source you pointed out at anandtech http://www.anandtech.com/printarticle.aspx?i=2093 does show the celerons getting swept by athlon xps... although they are putting up good numbers. The only encoding tests they show are divx 5.1, in which the celerons mostly barely keep up with athlon xps. The fact that my three year old athlon 1700+ is able to keep up with these 1 year old celeron D's is pretty bad in fact. Now, I would not even say use an athlon XP for HD, so I certainly wouldn't use a celeron - as, sticking with my original point which those anandtech benches seem to confirm, a 2.8GHz celeron is more like a 2.0GHz anything else (like a 2GHz XP in the anandtech article).
However, I would say a pentium is fine for SD even with software encoding, certainly; but these certainly are not your best bang for the buck.
More information about the mythtv-users