Editing with Apple's new iMacs

Posted By Larry Jordan on January 14, 2013 11:30 am | Permalink
By Larry Jordan

OK. I'm impressed!
Last November, the day they went on sale, I ordered a new 27-inch iMac to replace my main editing system.

The new unit arrived the end of December and, as these things tend to work out, as soon as I unpacked it, I needed to give it to our talented production assistant to do some Web database work for the last two weeks. (First, it's a tribute to the admiration I hold her in that she was even able to TOUCH this system and, second, I felt like she was using a Ferrari to ferry kids to and from school.)

Finally, she went back to school. Now it was my turn. While I haven't done a ton of work with it - yet - I want to share what I've learned.

This thing is fast! It loads fast. It runs smoothly. It renders quickly. Export is faster than realtime. The screen is clear and easy to read. And it has speed to burn.


I purchased a 27-inch iMac with:
* 34GHz Quad-Core Intel Core i7
* 16GB RAM
* 1TB Fusion Drieve
* NVidia GeForce CTX 675MX  graphics processor
* 1GB video RAM
* Wired Apple Mouse
* Wired Apple Keyboard

I was especially intrigued with how the Apple Fusion drive would work. The Fusion drive combines the speed of a Solid State Drive (SSD) with the storage capacity of a standard hard disk (often called "spinning media"). I knew that I would be getting external storage, so I didn't get the largest Fusion drive, as I didn't see the benefit of the extra storage on the internal drive.

Also, I am not a fan of wireless keyboards or mice, especially for desktop systems. If something goes wrong with the system, you often need a wired keyboard or mouse to fix it. I found the wired keyboard and mouse worked great.

I began my tests by editing a one-hour ProRes 422 project using Final Cut Pro X. Single-stream video, dual-channel audio running at about 15 MB/sec. (This is about five times the data transfer of a single AVCHD video stream.)

NOTE:  Adobe does not currently support the GPU in the new iMacs. However, there is a workaround that allows you to turn on the GPU in a non-supported manner. I'll be writing about that, and providing a look at Adobe Premiere Pro CS6 running on this new system shortly.

To get started, I did a quick comparison. Launching Final Cut Pro X on my 2010 MacBook Pro 4,1 took 24 seconds. Launching FCP X on my new iMac took four seconds. SIX TIMES faster!

According to Apple, "The Fusion drive combines the high storage capacity of a traditional hard drive with the high performance of flash storage. With a Fusion Drive in your iMac, disk-intensive tasks in Final Cut Pro X, such as importing and optimizing media, are faster and more efficient."
A Fusion drive "learns" what files are used most often and moves them from the spinning hard drive to the SSD. This means that it delivers the best performance to the files you use the most often. (As a sidelight, with today's technology, SSDs are significantly faster than spinning media, in fact, SSDs are slightly faster at reading (playing back) data than writing (recording).)

So what does this mean? Last week, I was at the Storage Visions conference in Las Vegas talking with a variety of storage and system developers trying to better understand SSDs.

NOTE: There is an inverse relationship between performance and speed. The faster a storage device is, the less data it holds for the same amount of money. 7200 RPM drives deliver data more slowly than a 15,000 RPM drive, but the 7200 RPM drive holds more data. SSDs are faster than spinning hard drives but, for the same amount of money, spinning hard drives hold more data.

The Fusion drive does not cache files; that is, make a copy of the file from the hard drive and store it on the SSD. Instead, the file is stored either on the hard disk or on the SSD, but not both. Files you use the most are stored on the SSD to provide the fastest performance.

According to the Blackmagic Design Disk Speed Test, which is available in the Mac App Store, the speed of the Fusion drive measures 323.1MB writing, and 411.3 reading. Whew! Truly fast!!

However, even though the Fusion drive is amazingly speedy, I don't recommend it for storing your media. This is because you'll get the best performance from this drive when you are accessing the same files over and over - such as the operating system and applications. Media files are generally played once, and they are done. Constantly playing different files, or rendering different portions of the timeline does not benefit from the speed an SSD can provide to the same extent.

SSD drives work the best when accessing the same files - like databases, or applications - or when working with lots of smaller files.

When editing video, a better option is to attach a Thunderbolt RAID as your media drive, which is what I did. I'm using the G-Technology G-RAID, which is a two-drive RAID-0.

When I measured the speed of the G-RAID using the Blackmagic Disk Speed Test, it was slower than the Fusion drive, measuring 250.2MB/second writing and 260.2MB/second reading. But the G-Technology RAID provided far more storage: 4TB vs. 1TB in the Fusion drive. (As a side-note, the G-RAID has a maximum capacity of 8TB, while the Fusion drive tops out at 4GB.)

NOTE: RAID-0 drives don't provide any data redundancy. If you lose either drive, you lose all your data. For editors needing more storage or even faster performance, I recommend using one of the Promise Pegasus RAIDs, which provide RAID 5-level data redundancy and speeds more than double that of the G-Technology RAID.

To verify the findings of the Blackmagic test, I also measured the speed of the G-RAID using the AJA System Test utility, available from the AJA website (http://www.aja.com/en/products/software), illustrating that regardless of the files sizes involved, the speed of the G-RAID is pretty consistent at 260MB/second for both reads and writes.

NOTE: By way of comparison, a FireWire 800 RAID tops out between 85-90MB/second.

The Fusion drive automatically transfers files between the hard disk and the SSD. You don't need to do anything, the operating system decides what to put where.

When working with very large files that exceed the free space on the SSD, you may experience stuttering playback with high-resolution video. (This is one of the main reasons I recommend using an external Thunderbolt drive for media storage.)
Thunderbolt RAIDs, depending upon how they are configured, can provide faster throughput and greater storage capacity than a Fusion drive. This is especially important for multicam work.

In addition to the Fusion drive, the other big speed boost in the iMac comes from an improved graphics card.

The CPU processes instructions one after the other - serially. The GPU processes multiple instructions at once - parallel. Parallel is always faster and ideally suited to a variety of video tasks.
All effects in Final Cut Pro X are Motion projects, so using effects in FCP X or Motion benefit from using the GPU. Exporting that requires transcoding (like converting ProRes into H.264 for Web viewing) will be faster. Other operations such as color grading, Ken Burns Effects, and speed changes also benefit because they use the GPU for realtime playback and background rendering.

For my system, I only got 1GB of video RAM (VRAM). I learned from Apple that more VRAM means faster rendering, exporting and better realtime performance.

The CPU and RAM can't be ignored, but we already know how these work. My system has a Quad-core 3.4GHz Intel i7 CPU and 16GB of RAM.

During normal editing operations, I was cruising along using 12-15 percent of total CPU cycles. This allows plenty of overhead when the editing gets more challenging - say with multicam work.
RAM usage, when running Final Cut Pro X, hovered around 2GB.

NOTE: Apple tells me that ProRes (which uses I-frame compression) uses less RAM than long-GOP video codecs like HDV, AVCHD or XDCAM EX.

This proves a point I've been making in my classes and webinars recently: virtually every Mac shipping today is fast enough to edit video; even 2K or 4K images. The real test is the graphics processing unit (GPU) and the speed of your storage system.

I got the 27-inch iMac because I wanted the larger monitor size. It truly makes a difference when watching images. I can see a 720p image at 100 percent size and still have plenty of room for the Event Browser and Timeline.

I had a spare 24-inch Apple monitor sitting around doing nothing, so I plugged it in. Works great. Now I can edit projects using one or two monitors. This isn't necessary, but it sure impresses clients!

NOTE: A two-monitor set-up would be especially helpful if you are editing 1080p material, or larger, as you could display the Viewer to your largest monitor and view your image at 100 percent size. All my current work is shot for the web at 720p, so the extra monitor is nice, but not necessary. I principally use it to display the Event Browser.

Apple makes a point of highlighting the reduced reflections of the screen. I didn't notice a big difference between the new monitor and my older 24-inch monitor. Video looked great, text was totally readable and the reflections in the glass didn't bother me because I made a point to position the screen to minimize reflections.

I did two quick Multicam tests. The first was a six-camera XDCAM-EX shoot and edited using the XDCAM EX video format natively. (You need to install the XDCAM drivers by downloading Sony's XDCAM Transfer software - a 30MB download.)

When editing multicam, be sure to set Final Cut Pro X > Preferences > Playback to Better Performance to avoid dropped frames. Also, I recommend checking all three dropped frame indicators in that preference window to make sure you aren't experiencing hard drive problems.

Six streams of XDCAM EX video took 12 percent of my CPU and 38 MB/second of data during playback. However, XDCAM EX uses MPEG-2 as its compression codec, and can become taxing on your system as the stream count rises. For example, when editing the XDCAM EX footage natively, I could easily edit six streams of video. However, I got a few dropped frame warnings when I quickly jumped around in the Timeline, or cut too quickly. The dropped frame warnings were not serious, but I wanted to see if I could eliminate them.

So, I did a second test by converting all six video streams to ProRes 422.This required FCP X to pull about 105 MB/sec from the G-RAID during the edit.

However, the CPU load was well less than 20 percent and FCP X used less than 3GB of RAM.
When using ProRes 422, no matter how fast I cut, or how much I jumped around inside the Timeline, I did not get a single dropped frame error.

NOTE: Using this many streams of ProRes requires a Thunderbolt drive. FireWire speeds top out at 85MB/second, which is not fast enough to edit more than four streams of ProRes 422 video. There is a serious performance benefit to optimizing media when editing multicam projects.

The performance of this iMac system makes me want to shoot a project with 10-12 cameras just to watch FCP X edit it.

Frankly, this 27-inch iMac blows the doors off my MacPro. It edits single camera projects easily. Its ability to edit multicam projects is limited only by the speed of your storage - with the caveat that optimizing media into ProRes is strongly encouraged.

If you are looking for a system that can handle whatever video format you throw at it, I am VERY impressed with this new iMac.

Larry Jordan is a producer, director, editor, author, and Apple Certified Trainer with more than 35 year's experience. Based in Los Angeles, he's a member of the Directors Guild of America and the Producers Guild of America. Visit his website at www.larryjordan.biz.