23 nov. 2010

Picking the Right Version of ProRes

This article was first published in the May, 2010, issue of
Larry's Monthly Final Cut Studio Newsletter. Click here to subscribe.

With the release of Final Cut Pro 7, Apple increased the number of ProRes versions from two to five:

  • ProRes 422 Proxy
  • ProRes 422 LT
  • ProRes 422
  • ProRes 422 HQ
  • ProRes 4444

So, that begs the question: which version should you use for your project.

First, four of the five flavors of ProRes are identical in every respect, except one. They all support:

  • Intra-frame encoding, meaning each frame is individually compressed as a stand-alone picture, unlike GOP-based encoding like XDCAM EX or HDV.
  • Variable bit-rate data encoding, creating smaller files than constant bit rate encoding.
  • 10-bit color depth, for very high color fidelity
  • 4:2:2 chroma sub-sampling, the maximum allowed for video formats
  • Fast render times, much faster than GOP-compressed video like XDCAM EX or HDV
  • Faster editing within Final Cut Pro
  • Matching the frame rate, frame size, and pixel aspect ratio of the source video
  • Optimized for multiple processor support

Unlike H.264, ProRes encoding and decoding are optimized for multiple processors.

ProRes 4444, the fifth version, builds on the first four ProRes versions, then adds support for the following:

  • RGB or YCbCr color space
  • Up to 12-bit color support
  • Inclusion of the transparency (alpha channel) information in a clip

If you need a clip to retain transparency information, which is called the "Alpha channel," you only have one choice: ProRes 4444. None of the other ProRes versions support clip transparency.

Well, since it's clear that ProRes 4444 is the absolute "best" in terms of quality, it seems like we should all just select ProRes 4444 and be done with it.

The problem with this approach is that your file sizes can be quite large, not as large as fully uncompressed HD, but still pretty darn big. And, unless you have a specific need for this format, you probably won't be able to see the difference between ProRes 4444 and other ProRes versions. Also, using ProRes 4444 in your project probably means you'd need to render every shot.

Think of ProRes 4444 as the replacement for the Animation codec. We use the Animation codec when we want to move files between one application and another; for example, between After Effects and Final Cut. Then, once it's in Final Cut, you render it into the final version you need for your project.

As a transfer format, ProRes 4444 is great. As a video editing format, it's way past overkill. Most of the time, you will be fully happy with one of the four other versions. And your file sizes will be much smaller.

The four other versions of ProRes differ in only one area: data rate. Changing the data rate directly affects file size and image quality. The slower the data rate, the smaller the resulting file and, potentially, the lower the image quality.

For example, here's a table that showcases the difference. This is just a guide, different formats create different file sizes, but the general proportions will be the same.

ProRes Version Store 1 Hour of 720p/60*

ProRes 422 Proxy

20 GB

ProRes 422 LT

46 GB

ProRes 422

66 GB

ProRes 422 HQ

99 GB

ProRes 4444 (no alpha)

148 GB

* Source: Apple Inc. ProRes White Paper, June, 2009.

However, the situation isn't as grim as you might think. Here are some suggestions you can reflect on as you are trying to decide what codec to use.

RECOMMENDATIONS

If you are shooting GOP-compressed media - HDV, XDCAM HD, XDCAM EX, AVCHD, AVCCAM - your editing and render times will greatly benefit from converting your footage from the source format into some version of ProRes.

At a minimum, when editing one of these formats, select the Timeline and go to Sequence > Settings > Render Control and change the codec from Same as Source to Apple ProRes 422. My tests have shown that there is about a 40% speed improvement in rendering when you switch to ProRes.

ProRes 422 HQ: This is the highest-quality video format, but unless you are shooting very carefully-lit, high-end video, such as RED, HDCAM, or HDCAM SR, the quality of your source image doesn't equal the format. Use this version only for high-end work.

ProRes 422: This is the format I recommend for anyone shooting DSLR, HDV, AVCHD, XDCAM EX, XDCAM HD, AVCAM, or P2. Great image quality, with file sizes 30-35% smaller than ProRes 422 HQ. Since the DSLR images start as H.264, which is already quite compressed, ProRes 422 most closely matches the original image quality.

ProRes 422 LT: This is the format to use if you have tons of footage, need to edit using smaller (i.e. less storage space) hard drives, or are going to go thru an off-line to on-line process.

ProRes 422 Proxy: This format should only be used when file size is more important than image quality. Training files, library archive files, or other reference media are a good choice for this format.

NOTE: If you are on an older, non-Intel system, ProRes may not be a good choice for you. The math involved is very CPU-intensive and older systems may not be able to encode or play it fast enough.

ProRes is an excellent video codec and one that has achieved great popularity in the industry. However, that doesn't mean you always need to select the absolute highest quality -- many times our images weren't that good to start with.

By spending a few seconds thinking about which ProRes version best matches our video format, we can save a ton of time and storage space down the road.

 

Larry Jordan is a post-production consultant and an Apple-Certified Trainer in Digital Media with over 25 years experience as producer, director and editor with network, local and corporate credits. Based in Los Angeles, he's a member of both the Directors Guild of America and the Producers Guild of America.

The information in this article is believed to be accurate at the time of publication. However, the author assumes no liability in case things go wrong. Please use your best judgment in applying these suggestions.

The opinions expressed in this article are solely those of the author. This newsletter has not been reviewed or sanctioned by Apple or any other third party. All trademarks are the property of their respective owners and are mentioned here for editorial purposes only.

Links to my website home page or this article are welcome and don't require prior permission.

Very Interesting post from Larry Jordan on the use of the adequate ProRES Codec in FCP 7

Posted via email from Video Film & TV World