What characteristics of a CPU are important for fast x264 encoding and avisynth?

[moviefan]

Hi guys,

I have planned to build a HTPC in near future to play my DVDs and hopefully soon Blu-rays. I also want to use it for video processing and encoding using avisynth and x264. What is most important about a CPU for these purposes? Is it clock rate, cache...? For the HTPC, I would like to have power efficient CPU, so I thought about I mobile one, like the Intel Core 2 Duo SU9400 (Ultra Low Voltage) or maybe (when it gets affordable) the Intel Core 2 Quad X9300 (mobile quad core)... But how do you think they compare to standard quad core CPUs with TDP around 95W? Most likely it will be a trade-off between power and efficiency, right?

Regards

[Audionut]

http://www.techarp.com/x264_Benchmark/sd/results-trends.htm

http://www.techarp.com/x264_Benchmark/sd/results-stock.htm


Data illustrates that more L2 Cache doesn't mean more performance. If anything, it's showing the opposite trend for dual chips.

Not a totally fair comparison (minor differences in the memory), but the extra cores in the Yorkfield more then doubled the encoding performance.

In general, x264 performance scales in a linear fashion, in other words, if you overclock the machine by 20 %, the performance increases by 20 %.

[gigah72]

if you look here:
http://www.techarp.com/x264_Benchmark/hd//results-1.htm

see the results for same cpu, faster ram seems also to make a difference.

[check]

buy 2gb of cheap and slow DDR2 RAM (so you waste less money on it), then maximise x, where x = (number of physical cores * speed in MHz).

[Blue_MiSfit]

Yep. It's all CPU, unless you're feeding something massive, like uncompressed 1080p :D

Also, DGDecode can be the bottleneck if you're decoding high bitrate MPEG-2 (only in extreme caes).

~MiSfit

[Shinigami-Sama]

if you're using avisynth + x264
as fast as a CPU as you can afford
then as much ram as you can afford

thats about it

[Sagekilla]

Memory shouldn't as big of an issue. Go for 2 GB at least, and 4 GB if you feel like it. You won't really want or need more than 2, unless you plan on going for 64-bit and staying with that.

As they said however, your best bet is going for a very good CPU. Any of the "low end" quad cores would perform great, since threading with encoding and decoding (If you use CoreAVC Pro) is excellent.

[Shinigami-Sama]

Memory shouldn't as big of an issue. Go for 2 GB at least, and 4 GB if you feel like it. You won't really want or need more than 2, unless you plan on going for 64-bit and staying with that.

As they said however, your best bet is going for a very good CPU. Any of the "low end" quad cores would perform great, since threading with encoding and decoding (If you use CoreAVC Pro) is excellent.

you seen how much memory some of those avisynth plugins use?

[Yoshiyuki Blade]

AVISynth can only utilize so much memory before crashing. I have 8 GB, but I have to use setmemorymax(1024) to prevent crashes. To make use of the ram, I usually have 3-4 instances of x264 running while playing a game :P.

[Comatose]

buy 2gb of cheap and slow DDR2 RAM (so you waste less money on it), then maximise x, where x = (number of physical cores * speed in MHz).
Well, to maximize MHz, you'll usually need the better quality RAM as very cheap RAM usually stops POSTing once you go over the stock speed.

[Avenger007]

In the big picture, increasing MHz offers only a small advantage. The real breakthrough comes with a new architecture, vis-à-vis Intel Core i7 (good renaming move since I can't pronounce Nehalem :D).

[Shinigami-Sama]

In the big picture, increasing MHz offers only a small advantage. The real breakthrough comes with a new architecture, vis-à-vis Intel Core i7 (good renaming move since I can't pronounce Nehalem :D).

neh-hay-lem(ming)

[Avenger007]

OK, I pronounced it like nehh-haa-lem. Thanks.

[moviefan]

So to conclude: important are clock speed, number of cores and RAM (amount and timing). So would there be a difference between let's say an Intel Core2Quad Q9450 (2.66 Ghz, 95W) and an Intel Xeon L5420 (2.5 GHz, 40W) except for the little clock speed difference... Obviously, the Xeon only needs less than half the power for very similar technical data.

[Shinigami-Sama]

xeons use slower server memory
and they scale together well

but with the huge price difference between them I'd say it isnt' worth it

[Audionut]

In the big picture, increasing MHz offers only a small advantage. The real breakthrough comes with a new architecture, vis-à-vis Intel Core i7 (good renaming move since I can't pronounce Nehalem :D).

Not really.

http://audionut.homeip.net/uploads/65v45.png
http://audionut.homeip.net/uploads/scability.png

Although to be fair, Kentsfield and Yorkfield aren't different architecture's, and Nehalem is bringing some big changes to the architecture of Intel cpu's.

[squid_80]

AVISynth can only utilize so much memory before crashing. I have 8 GB, but I have to use setmemorymax(1024) to prevent crashes. To make use of the ram, I usually have 3-4 instances of x264 running while playing a game :P.
Any 32-bit program can only utilize up to 2Gb (3Gb in some circumstances) in windows. Avisynth is fixed in the latest RC builds.

[TL0]

Nehalem was tested to offer 44% performance increase :eek: over Penryn in Anandtech preview using AutoMKV 2_Pass_Insane_Quality profile

http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3326&p=6

[Yoshiyuki Blade]

So to conclude: important are clock speed, number of cores and RAM (amount and timing). So would there be a difference between let's say an Intel Core2Quad Q9450 (2.66 Ghz, 95W) and an Intel Xeon L5420 (2.5 GHz, 40W) except for the little clock speed difference... Obviously, the Xeon only needs less than half the power for very similar technical data.

Around 2GB of RAM would be good enough for XP. 4 GB is supposedly the sweet spot for Vista64. You probably won't notice any real-world improvemets by having faster ram with tighter timings. As long as you lock the divider to 1:1, that's usually good enough (where the memory speed is equal to the FSB speed).

For example, the most of the latest Core 2s have a FSB speed of 333 MHz (1333 MHz quad pumped), so DDR2 667 (aka 333 Mhz at DOUBLE data rate) is easily suitable. If you plan on overclocking and can bet on achieving high FSB values with your mobo and CPU (such as 400-500 MHz), you'll need anywhere from DDR2 800 to 1000 to be safe. I wouldn't count on getting those kinds of OCs on a quad though.

Of course, if youre feeling risky (or cheap :p), you can overclock DDR2 667 to 800+ speeds.

Any 32-bit program can only utilize up to 2Gb (3Gb in some circumstances) in windows. Avisynth is fixed in the latest RC builds.

Oh, thats certainly good news! I'll check that out once I get my rig up and running again (intermittent hard drive failure x_X).

[Sagekilla]

you seen how much memory some of those avisynth plugins use?

Yes, I have. I've never had an issue with avisynth scripts under 2 GB of RAM, and I have used extremely complex scripts before.

[saint-francis]

For the money just get a Q6600 and overclock it a bit. They all seem to overclock 25% without needing to raise the voltage. You spend a lot less than you would on something like a Q9450 and get comparable performance.

[lexor]

Except that Intel just announced that q9xxx are going go down in price to replace the 6xxx series completely and a higher frequency version will be introduced for higher end segment. So to buy q6xxx right now is not a good idea.