MacPro 8-core benchmarks

[nimno]

I've been using an iMac Core Duo 1.83 GHz with 512 MB of ram to rip DVDs recently. Typical movie would rip at about 2 hours, using H.264 and 1 Mbps bitrate. A lot of DVDs that I've done would slow down to sometimes 8fps and seem to take forever; typically the best I would see would be about 20 fps.

The new 8 core Xeon was much faster, but not nearly as fast as I was hoping. Perhaps that performance will improve with Leopard, but for now, a movie that took 2 hours the other day on the slower iMac took about 27 minutes to rip with the MacPro. Considering it has a clock speed approaching twice that of my iMac (and 4 times the cores) a 4X speed-up is less that one might otherwise suspect, I think.

Regardless, it's nice to exerience faster-than-real-time ripping. This way, when I screw something up, I get to find out about it 4 times faster than before.

[rhester]

There are diminishing returns on higher numbers of cores due to the limitations of threading an inherently linear process. Do not expect performance to scale linearly with the number of processors (or the clock speed, though the latter makes far more of a difference).

Rodney

[baggss]

What you can do is run multiple instances of Handbrake without taking a significant hit in FPS on any of them. I can run 2 on my Quad and still pull 50-60FPS on each, with all 4 CPUs running at 85-95% and the system not bogged down at all. With an 8 core I suspect you could pull maybe 4 at a time.

[DaveGee]

Going by the accepted definitions (wrt DVDs) isn't it:

RIP = Copy VIDEO_TS from DVD --> HD
ENCODE = Transcode VIDEO_TS (MPEG2) to h.264 (or whatever)

If so then....

RIP speed would be limited to the DVD drive and IIRC the FASTEST drives read (pressed-movie-dvds) at apx 12x (perhaps a little more) and most tend to rip at 8x speed. Also some drives are 'riplocked' by the mfg so it will only read 'pressed dvd movies' at 2x.

ENCODE speed is where the 8 cores would / should really kick in since h.264 is clearly a 'CPU INTENSIVE' task and an 8 core machine SHOULD encode faster than some older (slower) machine provided HandBrake has access to the data files it's trying to encode.

It might be wiser to get the movie off the DVD first (and perhaps a few of them) and then queue them all up in HB and letter-rip with one (or more) instances of HB pinning all those cores to the limit!

Dave

[baggss]

I've tested copying DVDs directly off the DVD or from an MTR produced Video_TS Folder. On my Quad there is not real noticeable increase in rip speed, maybe 4 or 5 FPS, but that varies from DVD to DVD.

Doing so would save wear and tear on the DVD drives themselves, but they are fairly cheap to replace at this point anyhow, so I don't see it as a big deal.

[tubbyman]

Another thing that you can try (if you are comfortable with the command line) is to start up your encodes in terminal and force the number of cpus that mediafork thinks are available to something higher by setting the "--cpu/-C" switch.

[DaveGee]

Another thing that you can try (if you are comfortable with the command line) is to start up your encodes in terminal and force the number of cpus that mediafork thinks are available to something higher by setting the "--cpu/-C" switch.

This would be a great vX.y feature (hint hint)

Dave

[tubbyman]

I have found the results of setting this switch highly dependent on architecture. Linux/Mactel on core duo and amd64 seem to do best with the defaults. My G5 handles up to 3x the actual number of cpus with ease.