Apple ProRes 422 codec vs. Uncompressed HD

UPDATE — October, 2011: ProRes is no longer just an editing codec – it’s also used in portable field recording devices to bypass in-camera compression, capturing directly to ProRes with 10-bit 4:2:2 quality, ready to edit! Learn more about this exciting new hardware here or see our review of the Atomos Ninja for a detailed look at just one of the solutions that we provide.

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Apple introduced the ProRes 422 video codec for Final Cut Studio 2 users in 2007. The codec is said to offer uncompressed quality in a compressed codec, but many editors are nervous about using anything less than full uncompressed video to retain broadcast quality. So what is ProRes 422, and how does it measure up against uncompressed HD video?

ProRes 422 is a full-raster codec, meaning the video is not scaled down. The full 1920x1080 image is used, unlike DVCPRO-HD or XDCAM, which scale HD 1080 video down to 1280x1080 and 1440x1080 respectively, effectively tossing out a large amount of picture data to save space.

Next, ProRes 422 uses a full 10-bit 4:2:2 color space, which provides much better color fidelity than 8-bit color. This makes a real difference when color grading and compositing images. There is simply more color data to work with, and that can eliminate color banding issues by providing more steps in color gradients.

ProRes 422 uses a variable bit-rate compression scheme in which complex scenes are less compressed than basic or static scenes, so the quality is distributed as needed to maximize the efficiency of the codec for the best possible image. For 1080i, the ProRes 422 data rate is 145Mbps, and there’s also an HQ setting with a 220Mbps rate.

Compared to uncompressed HD video, ProRes files are about five times smaller, using about 20% as much hard drive space per hour. This means smaller, less expensive storage systems can be utilized, making broadcast-quality HD video production more affordable to smaller production houses and independent video producers. ProRes 422 HD video files are so efficient they can be captured and edited on a Mac Book Pro, something you wouldn’t try with uncompressed HD!

There are other HD codecs with lower data rates available, but because they are more highly compressed, they take more processing power to encode and decode (play back). The ProRes 422 codec provides a good middle-ground by providing a smaller file size than uncompressed, while providing easy capture and playback on even marginal machines.

But what about quality? Review after review by video professionals have consistently rated ProRes 422 quality as "visually equivalent" and "undistinguishable" from uncompressed footage, even after multiple encode/decode cycles. This can’t be said about many other compressed codecs available today.

Another important benefit of ProRes 422 is that it allows more layers of Dynamic RT playback. 4 layers of 1080i can be expected, and 720p 24 editors can expect up to 14 layers of HQ footage playback in real time. For reference, a powerful 8-core machine with a video RAID might only play a single stream of uncompressed HD.

Even if you don’t normally work with uncompressed video, ProRes 422 can help editors who shoot with compressed formats such as HDV, which is an 8-bit 4:2:0 format using MPEG-2 Long-GOP compression. HDV does not hold up well to editing, so by capturing to the ProRes 422 codec right away, quality will be maintained from that point on, and it’s easier for the system to work with as well.

The ProRes 422 codec is supported in the AJA IoHD product, which is a portable capture and playback interface for use with Mac computers. SD and HD video with audio can be captured via a comprehensive set of professional inputs, with the incoming video being converted to ProRes 422 in the AJA hardware and sent to the Mac via Firewire. When playing back ProRes 422 clips from the Final Cut Pro 2 timeline, video is sent over the Firewire back to the IoHD to be sent out any of the unit’s many outputs to various recorders and displays at full quality.

Another i/o device for the Mac is the Matrox MXO2, which has similar connectivity to the IoHD, but lacks a hardware ProRes 422 encoder – it is up to the host computer to encode to ProRes on the fly using its processor, so older Mac Books may not be up to the task to capture HD footage. As always, it’s a good idea to not only compare tech specs, but check video forums online to see how devices like these are performing for actual users to help determine which would suit your needs and budget.

One last tip – while the ProRes HQ codec is great for video from high-end sources, it may be overkill for formats like HDV. It’s been reported that users are better off to use the standard ProRes 422 codec at 145Mbps with the lower-end HD formats, as there is no advantage to using the HQ codec when starting with a highly-compressed and scaled HD source format.

If you’re a Final Cut Pro 2 user and have not tried working with ProRes 422, you owe it to yourself to try it today and see the benefits for yourself.

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