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Anyone getting compressor GPU benefits? Not me.

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Tangier Clarke
Anyone getting compressor GPU benefits? Not me.
on Jun 10, 2015 at 8:23:45 pm

Just wondering if anyone is seeing benefits form the GPU acceleration out of Compressor by using the "send to compressor" feature out of FCP X. I have the appropriate Compressor feature turned on in it's preferences.

I keep getting faster results just giving compressor a Quicktime exported from FCP X first.

Using ProRes 422/ 23.98/ 720p on the same edit and applying Compressor HD 720p web sharing setting:

Quicktime to Compressor: 19:44
FCP X to Send to Compressor: 25:17
FCP X export using Compressor setting: 20 min.

I realize i did not factor in the time it takes to make the initial Quicktime movie in the first test. However I assumed that GPU acceleration would speed things up. Perhaps it's only for certain codecs.

Mac Pro (Late 2013)
3.5 GHz 6-Core Intel Xeon E5
32 GB 1866 MHz DDR3 ECC
AMD FirePro D700 6144 MB
FCP X 10.2.1
Compressor 4.2

Tangier


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Oliver Peters
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 10, 2015 at 10:42:37 pm

What GPU acceleration do you expect? It's only going to accelerate scaling and some effects, not general encoding. That's CPU-based. The Xeon also has no special acceleration for H264 encoding, like the i5 and i7 CPUs.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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Tangier Clarke
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 10, 2015 at 11:30:51 pm

Just realizing it only applies to certain computers and certain compression scenarios.

Tangier


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Joe Marler
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 1:30:41 am

The GPU can greatly accelerate certain *effects*. E.g, applying color correction to every pixel of a frame is parallelizable, so the many parallel elements in a GPU can help.

Parallelizing transcoding when using an interframe codec like H.264 is extremely difficult. In a recent interview with editor Scott Simmons and Andrew Page (nVidia Product Manager for Professional Video Technologies), they explained:

"there are a lot of tasks that can't be broken down to be parallel: encoding is one, decoding some of the camera compressed formats is another one...what happens in frame 2 depends on frame 1, we do something to frame 1 then feed the results into frame 2....that's pretty much an encoding problem...everything is interrelated, so we can't break it up into lots of different simultaneous things." (That Studio Show podcast, 5/20/14: https://itunes.apple.com/us/podcast/that-studio-show/id293692362?mt=2)

Maybe eventually some clever developer will figure out how to more effectively harness the GPU for encoding but as of today it hasn't happened to a great degree.

This is why Intel's Quick Sync feature works so well: it is essentially an on-chip ASIC (Application Specific Integrated Circuit) designed for transcoding. It only works for a narrow range of codecs (MPEG-2, H.264 single-pass) but for those it is really fast. The upcoming Intel Skylake CPU will have an improved Quick Sync that supports more codecs. Unfortunately Xeon CPUs (which means Mac Pro) do not have Quick Sync. This was probably because Quick Sync -- while not implemented totally in the GPU -- requires some on-chip GPU resources, so Intel would have to put the entire GPU on Xeon to get that function. That would have cost millions of transistors, when the design priority for Xeon was server and workstation performance, and those use discrete GPUs or don't need one.

Much academic research is still being done in this area and there are many papers about possible future ways to accelerate video encoding/decoding with a GPU. So maybe someday a future FCP X update will more fully harness the Mac Pro GPUs for video encoding. However as of today it's not generally done, at least for interframe codecs like H.264.


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Bret Williams
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 3:21:06 pm

Wow. Chock another one up for the iMac. I'm not sure how long Tangier's origins timeline is, but I haven't seen a 20 min export in years. I export using a custom compressor setting from FCP X to h264 and my 3-10 min show exports are measured in minutes or even seconds. And if Inunderstand right that tech is also working on the decompression, which is likely why it seems unnecessary to optimize DSLR and other h264 codecs.

But the guys at Ripple were hyping up the newest release of compressor, saying that send to compressor is now optimized in the same way as exporting directly from X with a compressor setting is or the same as exporting in compressor is. And that previously using send to compressor was slower than a direct compressor setting export from x. But Tangier's tests don't seem to confirm this.


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Tangier Clarke
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 4:45:36 pm
Last Edited By Tangier Clarke on Jun 11, 2015 at 4:47:35 pm

More details about the project:

Duration: 8min 31sec
Format: 720p60
Project Codec: Apple ProRes 422
Media source: Content reading from and writing to external drive connected via FW800 through thunderbolt adapter.

One of my main work drives is a thunderbolt connected 8TB RAID10 Rocstor Arcticroc Hybrid 7T. So I imagine if my content source read/write from that volume, the numbers would change, however they should all change respectively to the drive speed and throughput of thunderbolt and the ultimate picture would look the same.

Tangier


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Joe Marler
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 5:56:38 pm

[Bret Williams] "But the guys at Ripple were hyping up the newest release of compressor, saying that send to compressor is now optimized in the same way as exporting directly from X with a compressor setting is or the same as exporting in compressor is. And that previously using send to compressor was slower than a direct compressor setting export from x. But Tangier's tests don't seem to confirm this.
"


The Ripple guys are correct -- before the latest version, Compressor was slower than FCP X if exporting single-pass H.264 material. On my limited tests it was about 50%-100% slower. This probably wasn't purely lack of Quick Sync, since that usually makes a 4x or 5x difference.

Re-testing on Compressor 4.2 and FCP X 10.2.1 shows Compressor is much faster. Whether single-pass H.264 (which uses Quick Sync) vs multi-pass H.264 (which does not), Compressor is now modestly faster than FCP X, whereas before it was slower on both.

Whatever they did Compressor is now a lot faster. It must be using Quick Sync because otherwise it would be impossible to beat FCP X on single-pass H.264. There may be other GPU refinements or optimizations besides this.

If someone did back-to-back testing on a Mac Pro with prior versions of Compressor and FCP X, they might find it's relatively improved. However it will never be as fast as an iMac on single-pass H.264 because of the lack of Quick Sync.

This doesn't mean an 8-core or above nMP isn't a good machine -- it's better than an iMac for most heavy duty tasks.
These are very brief tests on a 2013 iMac 27, 32GB, 8TB Pegasus R4, GTX-780m.

On my iMac it takes about 53 sec for FCP X to export a 07:30 720p video to single-pass H.264; Compressor 4.2 takes about 47 sec.

So I am not convinced Tangier's slow export is due to lack of Quick Sync. It shouldn't take 20 minutes. I suggest he try exporting with these parameters as a test from FCP X:

- Master File
- Format: Computer
- Video codec: H.264 Faster Encode
- Resolution: 1280 x 780

If that is a lot faster then create a Compressor pre-set with similar settings and export to that.


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Tangier Clarke
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 6:54:14 pm

I ran your test and the results were 9min 43 sec. straight from FCP X.

Tangier


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Bret Williams
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 8:42:03 pm

Might be just about right. Pretty much real time. The iMac h264 acceleration (QuickSync?) is only good on the single pass CBR stuff. You switched to single pass and it cut your render in half, but you still don't have the acceleration.


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Joe Marler
Re: Anyone getting compressor GPU benefits? Not me.
on Jun 11, 2015 at 10:53:10 pm

There's something funny going on. My previous test was 47 sec for Compressor export an 07:30 H.264 storyline to single-pass H.264 at 720p. However when I switch to a slightly longer 09:30 timeline -- using the same Compressor preset, it takes 12:30. That same storyline takes about 03:20 to export using FCP X to single-pass H.264 at 720p.

The first storyline is a 720p/30 H.264 video which was previously exported from Premiere Pro CS6. The 2nd (slow) storyline is a 09:30 multicam project I did in FCP X. The source material is a mix of 1080p/30 AVCHD, MP4 from Canon camcorders, 1080p/30 H.264 from a GoPro and H.264 from a Canon 5D3.

I then exported the 2nd 09:30 MC storyline, re-imported it, then exported that to single-pass H.264 using both FCP X and Compressor.
FCP X: 01:36
Compressor: 01:26

I then loaded another library with a 07:30 single-cam project composed of various material from Canon camcorders, Nikon and Canon DSLRs, and exported that to single-pass H.264 using both FCP X and Compressor:
FCP X: 01:21
Compressor: 01:20

All of the above is using unoptimized material.

So there is something about the MC storyline I have which makes export about 4x slower with Compressor than with FCP X. It's suspicious that is roughly the same difference as Quick Sync makes, but I am definitely using a single-pass H.264 preset. I tested with and without CBR and it made not difference.

I'll do more testing if I have time, but I am concerned about the wide variation in export performance.


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