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Cpu for a... cpu-based HTPC

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August 31, 2011 10:39:10 PM

hi everyone

seems that a certain niche of encodings is moving en-masse to hi10p h.264 (n1) without looking back; this throws out of the window my dxva/vdpau/purevideo/whatever atom+ion HTPC (n2).

I'd like to not find myself again struck with an outdated hardware decoder, thus I'm looking for a software-decoding solution.



roughly, it seems (reading from user forums) that the cpu load increase in software decoding should be around 30-40%, a certain number of people report good performance on their 5-years old desktop/laptop cpu - usually, they don't mention the bitrate.

this unfortunately contrast with other user reports, and with my checks on test clips, in which the usage on a 3GHz, dual core E8400 is quite high, with the cpu essentially "overwhelmed" (n3) at high bitrate - e.g. 20Kbit/s (1080p); with 10Kbit/s segments - anyway - the two cores float sligtly above 60% with peaks to 80%.


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enough of the introduction; now: which cpu could fit an HTPC and play high-bitrate hi10 with sufficient guarantees that some other small tuning of the encoding/decoding won't choke again the system?


my impression is that an i3 2100 is not "far enough" from the current processor to put me in a safe position.

since the core i5s almost cost the same price (approximately they cover a 30 € wide range....), the i5 2500k looks pricey but the most interesting.

the i7 2600/k also would benefit from the hyperthreading, but the prices are quite higher and I fear that the heat would be too high for an HTPC.

there are "t/s" versions of the sandy bridges but the i3 2100t seems quite slower and the i5 2400s seems close to the 2400 but the 2400 bear well with small undervoltings... so it's not "extremely different" in terms of dissipated heat but costs more and is slower. the standard versions seem a better deal.

is my line of reasoning correct?

what would you suggest? any other interesting option?


thanks a lot in advance


ps: possible "rest of the system": a "cube" case, shuriken or big shuriken, enermax erpro 80+ 400w, no discrete video card, 4 gb of ddr3 or more; hd and bd-r; must run as quiet as possible.



n1: to my understanding, it's your usual h.264, but with two bits more in colour arithmetics

n2: since at the time of writing no support is present for the new encoding, nor I can find any statement by Nvidia about their schedule about it; at the time of writing, even the other "usual companies" seem in the same boat as Nvidia wrt hardware decoding support

n3: ffdshow and similar software ranges from 70% to 100% of occupation, madvr is struck to 100%, etc. when I hit 90-100%, several frames are dropped (of course)

More about : cpu cpu based htpc

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August 31, 2011 11:57:44 PM

This would be a good time to suggest a visit and post to AVS forums but as I (thought ) i understand it the Hi10p isnt new, its part of the h.264 spec. Its just one of the upper end profiles with BluRay being HiP. As for bitrate, iirc, 10bit needs about 1/2 of what 8bit needs.

I dont know anyone who has all 10bit capable hardware so everyone I know just used 10p as an intermediate step and finalizes to 8bit. This helps remove banding.
September 1, 2011 5:17:11 AM

still, several material has high bitrate - beats me why (I know of several sources that employ that kind of parameter - 20Mb/s - for regular jobs) - and I was looking for a cpu that can support that kind of workload and somewhat fits HTPC needs.

I might think "okay, they will settle down to 10Mbit/s" but it's risky to calibrate the cpu on that, i'd like to not find myself again after spending some 500€ and again not being able to play them without stutters.

for example, I'm not considering AMDs because the higher power versions have 125W TDP, and I guess it might become even harder to cool them off given the relatively tight headroom above the cpu (*), even if I'm tempted by the higher number of cores (usually the decoders are relatively good at employ them well).

Do you see any fault in the kind of choice I'm making? is the i5 2500k overkill (and the i3 2100 much better than my c2d e8400)? is it worth to jump to the i7 ? (would seem strange to me to actually need a top of range cpu just to play media files, no matter how crazy high might be the bitrate...)

thanks again ;) 

(*) meaning: If I have to cool them /silently/, a big fan is usually advisable (low revving, more airflow). If the 125TDP AMDs require a tower style 120mm cooler, they won't fit in a htpc case that in most of the cases have 120mm as /total/ height.
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