How to Develop a Viable 4K Production Workflow
If you take one thing away from this section, remember that 1MB = 8Mb and to be careful not to confuse the two. I see producers confusing megabytes and megabits far too often around the web, and it makes figuring out your recording, throughput, and storage requirements especially difficult.
To illustrate the difference between HD and 4K codec bitrates, the Sony 1920x1080 60P AVCHD implementation has a maximum bitrate of 28Mbps, while the Sony 4096x2160 60P XAVC implementation has a maximum bitrate of 600Mbps. Recording at 600Mbps requires 20 times more data throughput for a single stream, but you may still be able to play back this 4K 60P video from a single hard drive as they typically can read and write around 120MB/sec (megabytes per second) or 960Mbps (megabits per second), but if you’re trying to edit in a multicam environment, or with a higher-bitrate codec, a single video editing hard drive will not suffice. You can edit 4K video from an SSD but SSD cost-per-GB is magnitudes higher than that of HDDs, and reduced storage capacity and increased cost may sway you towards a RAID array of HDDs.
Once you move to the Sony FS700 or the identical 4K output from the F5 or F55 recorded on the AXS-R5 + HXR-IFR5 Sony RAW recorder you have to move beyond a single drive at 24P, as the bitrate on these recordings is 960Mbps. There is no additional compression with higher frame rates as with AVCHD, so moving to 60P 4K is going to command 2.5x the data rate: 2.4Gbps or 300MB/sec. Figuring out the bitrate of other cameras might take a lot of reading and cross referencing, but in general most manufacturers list their 24P bitrates, so keep in mind that the 60P rate will have a 2.5x higher bitrate.
My own video editing system has a four-disk internal hardware RAID 0 using 2TB WD RED drives and it can sustain a 390MB/sec read/370MB/sec write speed. This means I could edit a single 4K 60P Sony RAW video file if I wanted to. RAID 0 (also known as striping), offers improved performance through parallel read and write operations across multiple drives, but it lacks data redundancy and fault tolerance, which means you have a much higher chance of losing all your data because one drive error will cause your array to degrade. To balance out this higher risk I back up my internal video editing RAID nightly to a Sans Digital 5-bay hardware RAID tower configured in a RAID5 with 2TB HGST drives. RAID5 adds one level of redundancy at the expense of some read and write speed. Although I don’t use this backup enclosure for video editing, I could; it has a respectable 200MB/sec read/230MB/sec write speed.
One side benefit of having such a fast internal RAID is that I can edit HD video over my network, accessing this RAID from a second workstation, while my editor is editing on the workstation that houses the internal RAID. This is very useful when we need simultaneous access to projects that were originally edited on the main workstation and to leverage my investment in a proper video editing RAID solution and backup.
4K NLE
It goes without saying that selecting your 4K nonlinear video editing software is an important workflow decision -- as important as the type of camera, its internal or the paired external codec you will record to, and ensuring adequate read/write speed on your video editing drive or RAID array. Just keep in mind that if your camera is a new model using a new codec and your NLE is from a previous generation, you might need to upgrade your software as many new codecs will not be supported.
I found this out myself while researching this article and working with Sony XAVC 4K footage from the Sony PXW-Z100. I couldn’t import the 4K video on my backup laptop, which still runs Adobe Premiere Pro CS6. You’ll experience similar results with the Cinema DNG codec that only recently became supported by Premiere Pro CC and was supported earlier by Final Cut Pro X and DaVinci Resolve.
The 4K-capable Sony PKW-Z100
I also struggled to connect the recording media to my laptop as it lacked a PCIe slot that eliminates the need for a dedicated card reader. My solution to transfer the footage was to use the camera as a card reader and connect my laptop to it via its USB port. Unfortunately this was a painfully slow process over USB 2.0, which took 3.75x longer than real time to transfer.
XQD recording slots for 4K capture on the Sony PXW-Z100.
With all these new recording media options and larger file sizes you have to seriously consider the workflow required to capture the footage you just filmed and how to do this as quickly as possible. Don’t assume your all-in-one card reader will support the new recording media your camera uses and that even if a card is reverse compatible that you will want to create a bottleneck in capturing by capturing through Parallel ATA or USB2.0 type connections instead of faster Serial ATA, PCIe, USB3.0, or Thunderbolt connections.
Delivery Codec
4K delivery is much simpler than the wide range of HD and SD delivery options, but there are some caveats. Video tape, DVDs, and Blu-ray Discs are not 4K-compatible, so the most viable 4K delivery options include online delivery and on a hard drive or memory stick for local playback. For online 4K playback, there are fewer options than with HD, and YouTube can be a good place to start. Initially I didn’t think that YouTube 4K support, such as YouTube Live (YouTube’s webcasting service) was available to all users, but both were enabled on a new YouTube account I created that is linked to my Gmail account.
Initially, I ran into problems because I was trying to upload a 4096x2160 4K video. YouTube supports only 3840x2160 UHD video and I had to crop, re-encode, and re-upload a new MP4 video file. YouTube recommends 2160P high-profile MP4 video with a 35-45Mbps video bitrate. I also had to drop my frame rate from 2160 60P to 2160 30P in Adobe Premiere Pro CC because it doesn’t support the MP4 codec at level 5.2 that is required for this frame rate and tops out at level 5.1. This would be the same workflow regardless of whether the playback was online or local via hard drive, as 4K options are limited, at least within Adobe Premiere Pro CC as of this late-April writing.
Premiere Pro CC MP4 encoding tops out at level 5.1.
Of course, in order for viewers to be able to see 4K video, they have to have a 4K monitor, a sufficient and sustained data rate, and the ability to decode your video file. YouTube cloud-encodes HD and SD versions automatically to expand payback compatibility.
The other 4K export option that I discovered within Premiere CC is the SMPTE standard DPX file, which is more useful if you are sending your video for color grading or archiving than as a delivery codec. Other delivery codecs to consider are HEVC/H.265, which Netflix is using to stream its 4K content, but this will require additional plug-ins such as Cinemartin Cinec and a playback device that supports this codec. Early 4K TV adopters are finding that they need to add additional 4K streaming devices to support HEVC streaming in their UHD TVs.
Final Thoughts
4K content is here today and here to stay. Content acquisition is much easier than the rest of the workflow, led by consumer devices such as the millions of 4K cell phones, 4K POV cameras, and soon 4K Interchangeable Lens cameras that will lead the way for wider professional 4K adoption. 4K screen adoption is increasing rapidly too, and this just leaves some workflow issues for editing and distribution to be solved and adopted before 4K will be viable across a wide range of video production markets.
This article appears in the June 2014 issue of Streaming Media magazine.
4K image via Shutterstock
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