Choosing an HD video format - based on CPU requirements?

[rohan]

I'm trying to choose an HD encoding format (for 720p in this case) that will play nice with system resources.

I've played with WMV9, h264, and XviD.

They all look pretty good (264 and WMV9 seem to look the best at HD 720p). XviD seems to be the least processor intensive (for playback), but it's also a little poorer on quality, and larger in file size. 264 tends to require a little more power than my HTPC system has.

What would you guys recommend for HD encoding? I realize that there is a lot of personal preference here.

And I'm poor, so getting a better HTPC isn't in the cards :(

[Awatef]

What are the specs of your HTPC? (CPU, Memory size, GPU & graphics memory size)

[zambelli]

Well, you've already kind of guessed most of it: in terms of decoding performance, XviD is easiest, followed by WMV9, and finally H.264. If you've got a video card made after 2005, you can probably get some WMV9/VC-1 decoding support from the GPU through DXVA. For H.264 DXVA support, you'll probably need an even newer card and a dedicated player (I don't think anybody has implemented H.264 DXVA decoding support in a system-wide DirectShow decoder).

So until I see your specs, I'd probably recommend XviD or WMV9.

[rohan]

Athlon XP 2800+
512mb DDR
Radeon 9200

(I know it's weak)

Is WMV9 better quality (typically) than XviD at high definition?
Or is that in my head?

[Inventive Software]

What about VP7?

[rohan]

Where do you think VP7 decoding requirements would fall? In between WMV9 and H264?

[Awatef]

Your system is everything but weak, 720p shouldn't be a problem.

WMV is not an option since it is a closed format (Put Windows Media Player 11 on your machine anyway, it should be the fastest for WMV-HD decoding).
Go for H.264 and use CoreAVC instead of ffdshow for decoding.
On my system, CoreAVC decoding is as fast as -if not faster than- XviD decoding!!

If you still can't get it to work right, it may be your graphics card. It should have at least 128MB RAM. If it doesn't, you may consider buying a new one w/ 256MB (That way you're in even for 1080p!). It shouldn't cost more than 55€/75US$ (and sell your old card on eBay :))

[Inventive Software]

Where do you think VP7 decoding requirements would fall? In between WMV9 and H264?

Well, according to http://www.on2.com/technology/vp7/, you're just about set in the playback zone for 1080p, most certainly for 720p, but there currently isn't any graphical hardware acceleration for VP7, which is where WMV9 and H.264 have the slight edge IMHO. You can however give it a shot and see whether it'll work.

XviD can reach WMV9 and H.264 quality, you just have to play with the settings. What's your intended medium or file-size for backing up?

[rohan]

I'm looking for a 2 hour movie to fall somewhere between 5gb and 10gb (the smaller the better). I suppose that would probably be around 5,000 kbps or up

I've tried XviD on 95% quality, encoded in ffdshow. It's good, really good, but not perfect.

I will try CoreAVC - if that can give me 264 at a better decoding speed, that might be a good choice.

I tried VP7, and boy, it takes a LONG time to encode. Much slower than even 264. I'm encoding from a dual core, 2gb system, and it was giving me around 2 fps. Where XviD was up around 9 or 10.

[rohan]

Let me ask a follow-up question about the video card comment -

Does the video card take care of a lot of the decoding work? IE, if my CPU is hitting 99% on a particular movie, can a better graphics card offload some of that work?

If so, will it do so for any format? (IE, XviD, 264, WMV, etc)

[Doobie]

AMD XP 2800+ is marginal for HD, but it works on WMV or Xvid at a reasonable compression level. Any codec more demanding is not going to play well.

I don't think the video card will make any difference (it's not the bottleneck).

[Inventive Software]

Your current video card won't take ANY of the decoding work, however the newer NVIDIA 8 series cards and probably ATI's new cards will off-load most (if not, all) of the decoding of H.264 and maybe WMV9 / VC-1. The "budget" 8 series card from NVIDIA would be a worth-while investment, if your system's not AGP... that said, if you go with CoreAVC, check out the entire thread (http://forum.doom9.org/showthread.php?t=104277) in the MPEG-4 / AVC sub-forum; you may find benchmarks for similar systems to yourself.

I wasn't aware of VP7 having that high an encoding requirement, but I've only ever used that in DVD resolution, not HD. But did you try decoding it in HD?

[Awatef]

@ rohan
I'm positive, CoreAVC will decode 720p on your HTPC without any problem. ffdshow is indeed much slower. Even PowerDVD with ATi hardware acceleration is slower than CoreAVC!
As for the graphics memory size, all codecs seem to require at least 128MB for HD videos (even though 64MB is supposedly enough for 720p WMV). I presume this is due to buffering in the graphics memory for the overlay.

For WMV-HD playback, make sure you have the latest drivers for your ATi card (would be 6.11 I think) as well as WMP11 and see if it helps (I'm not sure wether your card generation can take advantage of DXVA but it's worth a try).

[zambelli]

WMV is not an option since it is a closed format
Not true. WMV9 is Microsoft's brand of VC-1, and VC-1 is a SMPTE standard.

[Awatef]

@ zambelli
Indeed, I was talking about WMV as a container :p ;)

[Inventive Software]

But WMV isn't the container... it's ASF! WMV is ASF renamed :p ;)

[Awatef]

@ Inventive Soft
It's all cosmetics ;)

[zambelli]

@ Inventive Soft
It's all cosmetics ;)
But given that the rest of the discussion has been about codecs, I don't see how you got on the topic of containers. Plus, Rohan never said proprietary formats were out of the question.
If he wanted to keep clear of proprietary standards, he could still use VC-1 in MP4 or MPEG2-TS.