How Much Video Processing Performance Boost Do the Latest PC Processors Deliver?
Now that Intel has launched Ivy Bridge-based CPUs that triple the core count of early Nehalem-based workstations from four to 12, can video editors expect significant performance gains? In this article we'll assess the performance gain from the 12-core HP Z800 to the 24-core HP Z820 with respect to both editing and streaming encoding.
Editing and Rendering Tests
To test editing and rendering, I created 29 test sequences in Adobe Premiere Pro (version 7.0.1-105) from different camera formats, from DV to 4K RED, which I rendered into multiple formats, including MPEG-2 for DVD and Blu-ray, and H.264 for Blu-ray and for uploading to services like YouTube. In terms of workflow, I created the sequences in Premiere Pro and rendered them in the Adobe Media Encoder (AME), which is the typical editing and output workflow.
The tests include a range of real-world projects that I produced and synthetic tests that I pulled together from footage shot in formats that I don’t typically produce with. I also liberally used projects and content provided by Adobe with their Creative Suite product launch materials, since they typically use more advanced formats than I do, with a more indie movie-type feel than the event-type of productions that I typically produce. Though a couple of the Adobe projects are effects and layer-laden, for the most part the projects are relatively straightforward, real world-type projects, not strewn with extra effects and layers to maximize the potential impact of the new hardware capabilities.
My analysis involved two series of tests. I ran the first series of tests in dedicated mode, with no other operations running on the computer. Then I ran a second series of tests with Adobe Encore producing an H.264-encoded Blu-ray Disc in the background during the entire rendering cycle. Within these two test scenarios, I ran every test twice—once with hyperthreading (HTT) enabled, once with HTT disabled—and used the faster of the two results in my comparisons. In general, the Z820 performed faster with HTT disabled, while the Z800 performed faster with HTT enabled.
Table 1 (below) presents the results by format. The first column, No Blu-ray, represents the results of the comparison tests performed in dedicated mode; If you edit and render in dedicated mode, the first column is for you. The second column shows the results when a Blu-ray Disc project was rendering in the background; if you frequently edit with CPU-intensive tasks running in the background, the results in the second column will be more relevant.
Table 1. Results by format, with and without Blu-ray rendering in the background.
Using Excel’s conditional formatting feature, I color-coded the results to show a red background when the Z820 was slower than the Z800, yellow when the Z820 was less than 30% faster than the Z800 and green when the Z820 was 30% faster than the Z800 or higher. These numbers are obviously arbitrary, but the colors do tend to separate the winners from the losers.
Time and space don’t allow for a comprehensive discussion of the projects and project types, but let me touch on the outliers. The MPEG-2 project is a real-world project with source video created by a TriCaster that I used to mix the live production. While this probably isn’t a significant use case for many producers, it’s interesting that MPEG-2-based XDCAM EX codec was also a lackluster performer comparatively on the Z820. That said, HDV-based projects, which included three real-world projects, did seem to benefit from the extra capabilities of the Z820, as did XDCAM HD.
The DVCPRO test sequence came straight out of an Adobe Creative Suite sample project, and is of the indie film genre (short snippets of multiple cameras), rather than event (a simple multicamera mix). While there probably aren’t a lot of DVCPRO HD producers out there any longer, this format didn’t seem particularly efficient from a multicore perspective.
The DSLR projects comprised a ballet audition I produced while reviewing the Canon 7D, plus two synthetic projects created from Canon 5D videos included in Adobe’s Creative Suite demo projects. I would have expected to see more benefit with these projects, but when I ran Windows Task Manager to test CPU utilization on the Z820, it hovered around 40%, perhaps indicating that the decoder used by these formats was not that efficient.
The RED and other 4K formats not only benefited from the extra CPU cores (see Figure 3), but also from the enhanced capability for data I/O, particularly with other CPU-intensive tasks running in the background. As you move into 4K production, it appears that multiple cores could deliver some significant benefit.
Beyond these musings, what should you take from this diverse data set from disparate projects built using different source formats? First, don’t assume that extra cores on a new computer will deliver a by the numbers proportional benefit. With some formats and projects it may, with others it might not.
Before buying a new computer to speed rendering and performance, run Windows Task Manager while rendering on your current computer and see how efficiently your primary applications are using your existing cores. If it looks like Figure 2, throwing more cores at the problem could actually slow things down. If it looks like Figure 3 (below), which reflects Adobe Media Encoder rendering a RED project, there’s a good chance that your investment in additional cores will be rewarded by significant performance improvement.
Figure 3. This view of Windows Task Manager makes Intel engineers jump for joy.