… for Visual Effects

Tip #654: What is a B-spline curve?

Larry Jordan – LarryJordan.com

The key benefit of B-spline curves is their smoothness.

A simple B-spline curve, emphasizing it’s smoothness. (That corner isn’t a corner, it’s where two lines cross.)

Topic $TipTopic

A B-spline function is a combination of flexible bands that passes through the number of points that are called control points and creates smooth curves. These functions enable the creation and management of complex shapes and surfaces using a number of points. (That’s what it says here, not that I fully understand it.)

The term “B-spline” was coined by Isaac Jacob Schoenberg and is short for basis spline. B-splines are more general curves than Bezier curves. More simply, a Bezier is a special case of a B-spline.

The big difference between B-splnes and Bezier curves is smoothness. B-splines are made out several curve segments that are joined “smoothly.” Bezier’s on the other hand, can have corners.

A B-Spline curve can be a Bezier curve whenever the programmer so desires. Further B-Spline curves offer more control and flexibility than a Bezier curve. It is possible to use lower degree curves and still maintain a large number of control points. B-Spline, despite being more useful, are still polynomial curves and cannot represent simple curves like circles and ellipses. For these shapes, a further generalization of B-Spline curves, known as NURBS, is used.

EXTRA CREDIT

I’d share the math of B-splines with you, but, frankly, I don’t understand it. A Google search will turn up lots of university references.


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… for Codecs & Media

Tip #647: What is ffMPEG

Larry Jordan – LarryJordan.com

FFmpeg cannot be sold, it can only be given away.

Topic $TipTopic

FFmpeg is a free and open-source project consisting of a vast software suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the FFmpeg program itself, designed for command-line-based processing of video and audio files, and widely used for format transcoding, basic editing (trimming and concatenation), video scaling, video post-production effects, and standards compliance.

FFmpeg is able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge. It runs on Linux, Mac OS X, Microsoft Windows, the BSDs, Solaris, etc. under a wide variety of build environments, machine architectures, and configurations.

The FFmpeg project tries to provide the best technically possible solution for developers of applications and end users alike. Wherever the question of “best” cannot be answered we support both options so the end user can
choose.

FFmpeg is used by software such as VLC media player, xine, Cinelerra-GG video editor, Plex, Kodi, Blender, HandBrake, YouTube, and MPC-HC; it handles video and audio playback in Google Chrome, and Linux version of Firefox.

FFmpeg is free for personal use, however, it does not have a user interface. Graphical user interface front-ends for FFmpeg have been developed, including XMedia Recode and ffWorks.


… for Codecs & Media

Tip #650: What is a Raw file format

Larry Jordan – LarryJordan.com

Raw is not an acronym, it simply means “unprocessed.”

Topic $TipTopic

Raw is an image and video file format used by many high-end and professional digital cameras. RAW files are considered to be the best form of image file, since it does not process the picture, leaving total control of the editing to the user.

A camera raw image file contains minimally processed data from the image sensor of either a digital camera, a motion picture film scanner, or other image scanner. Raw files are named so because they are not yet processed and therefore are not ready to be printed or edited.

Raw image files are sometimes incorrectly described as “digital negatives”, but neither are they negatives nor do the unprocessed files constitute visible images. Rather, the Raw datasets are more like exposed but undeveloped film.

Like undeveloped photographic film, a raw digital image may have a wider dynamic range or color gamut than the developed film or print. Unlike physical film after development, the Raw file preserves the information captured at the time of exposure. The purpose of raw image formats is to save, with minimum loss of information, data obtained from the sensor.

There are dozens of raw formats in use by different manufacturers of digital image capture equipment.

EXTRA CREDIT

Here’s an Apple White Paper to learn more.


… for Apple Final Cut Pro X

Tip #639: All vs. any

Larry Jordan – LarryJordan.com

Any is inclusive, All is exclusive.

The Search Filter dialog, showing options for keyword searches.

Topic $TipTopic

When searching for files using keyword search you have two main options: “Any” and “All.” Here’s what they mean.

When using keyword search – which is a great way to organize and find clips and ranges within a clip – there are four key search options. Here’s what they mean.

  • Any. This displays every clip that contains even one of the search criteria. For example, the screen shot displays clips that contain either “People Video” or “Dancing.”
  • All. This displays every clip that contains all the search criterial. For example, this displays only clips that contain both “People Video” and “Dancing.”
  • Does Not Include Any. This displays every clip that does not contain even one of the search terms. For example, this displays all clips that do not contain either “People Video” or “Dancing.”
  • Does Not Include All. This only displays clips that do not contain all search criteria. For example, this would not show clips that contain both “People Video” and “Dancing,” but would show clips that contain one of these.

EXTRA CREDIT

Search results are displayed instantly, as soon as you select them. Experiment with these on your own media and discover how they can help you find the clip you need when you need them.


… for Visual Effects

Tip #632: Crop vs. Trim: What’s the Difference?

Larry Jordan – LarryJordan.com

The difference is what happens to the original frame size.

The Crop vs. Trim options in Apple Final Cut Pro X.

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It’s a simple thing that confuses a lot of people: What’s the difference between crop and trim?

Well, first, they have a lot in common:

  • Both remove portions of the image.
  • Both use rectangles to work their magic
  • Both allow us to concentrate the viewer’s eye on a certain part of the image.

The big difference is that crop always reduces the image size to match the cropped area, while trim does not alter the image size.

EXTRA CREDIT

If you trim an image on the lowest layer, you’ll create black areas for the removed portions of the original image.

Generally, trimming is used for elements on higher layers/tracks, while cropping is used for the lowest layer/track/background.


… for Codecs & Media

Tip #636: Compressor: What is a Job Action?

Larry Jordan – LarryJordan.com

This only applies when one setting is applied to a video.

The Job Action menu at the bottom of the Job panel in Compressor.

Topic $TipTopic

A Job Action in Apple Compressor is an automated activity that occurs when a compression task is complete. It is assigned to the job, not to a compression setting. Here’s how it works.

  • Select a movie (called a “job” in Compressor), not the compression setting.
  • At the bottom of the Job panel is the Action section. This describes what can be done with a compressed file when compression is complete.
  • There are ten options, as illustrated in this screen shot. Save only means the file will be saved and nothing else done to it.

For example, choosing Publish to YouTube, asks for your log-in credentials, project title, description and tags. When compression is complete, the compressed file will be automatically transferred to YouTube with the tags you specify.


… for Visual Effects

Tip #614: What is the Alpha Channel

Larry Jordan – LarryJordan.com

Alpha channels allow us to combine multiple images into a new single image.

Topic $TipTopic

An alpha channel is essentially any channel other than the channels that define color values for pixels in an image. In graphics, the alpha channel is the part of the data for each pixel that is reserved for transparency information. 32-bit graphics systems contain four channels — three 8-bit channels for red, green, and blue (RGB) and one 8-bit alpha channel.

NOTE: 8-bit color channels means that each channel can display up to 256 shades of that color.

The alpha channel is really a mask. It specifies how the pixel’s colors should be merged with another pixel when the two are overlaid, one on top of the other. In a 2D pixel which stores a color for each pixel, additional data is stored in the alpha channel with a value ranging from 0 to 1. A value of 0 means that the pixel is transparent while a value of 1 means the pixel is fully opaque.

Typically, alpha channels are defined per object. Different parts of the object would have different levels of transparency depending on how much you wanted the background to show through. This allows you to create rectangular objects that appear as if they are irregular in shape — you define the rectangular edges as transparent so that the background shows through. This is especially important for animation, where the background changes from one frame to the next.

Rendering overlapping objects that include an alpha value is called alpha blending. Blend modes provide a variety of ways to do this alpha blending.

EXTRA CREDIT

The concept of an alpha channel was introduced by Alvy Ray Smith in the late 1970s and fully developed in a 1984 paper by Thomas Porter and Tom Duff.


… for Codecs & Media

Tip #613: Blu-ray Disc File Formats

Larry Jordan – LarryJordan.com

The most popular distribution format for Blu-ray Disc is H.264/AAC.

The Blu-ray Disc logo.

Topic $TipTopic

Continuing our look at Blu-ray Discs that we started in Tip #612, here’s a list of supported codecs for Blu-ray Discs.

NOTE: You can use any media format for mastering, but files for distribution must use one of these formats.


According to this Sony website, the following audio and video codecs are supported on Blu-ray Disc® media.

Video Codecs

  • MPEG-2: Enhanced for HD, also used for playback of DVDs and HDTV recordings.
  • MPEG-4 AVC: Part of the MPEG-4 standard also known as H.264 (High Profile and Main Profile).
  • SMPTE VC-1: A standard based on Microsoft® Windows Media® Video (WMV) technology.

Audio Codecs

  • Linear PCM (LPCM): Offers up to 8 channels of uncompressed audio.
  • Dolby Digital® (DD): Format used for DVDs also known as AC3, offers 5.1-channel surround sound.
  • Dolby Digital® Plus (DD+): Extension of DD, offers increased bitrates and 7.1-channel surround sound.
  • Dolby® TrueHD: Extension of MLP Lossless, offers lossless encoding of up to 8 channels of audio.
  • DTS Digital Surround®: Format used for DVDs, offers 5.1-channel surround sound.
  • DTS-HD®: Extension of DTS, offers increased bitrates and up to 8 channels of audio.

… for Codecs & Media

Tip #588: What is ProRes?

Larry Jordan – LarryJordan.com

ProRes is a good choice for capture, editing and master files.

The Apple ProRes logo.

Topic $TipTopic

Apple ProRes codecs provide a combination of multistream, real-time editing performance, impressive image quality, and reduced storage rates. ProRes codecs take full advantage of multicore processing and feature fast, reduced-resolution decoding modes. All ProRes codecs support any frame size (including SD, HD, 2K, 4K, 5K, and larger) at full resolution. The data rates vary based on codec type, image content, frame size, and frame rate.

As a variable bit rate (VBR) codec technology, ProRes uses fewer bits on simple frames that would not benefit from encoding at a higher data rate. All ProRes codecs are frame-independent (or “intra-frame”) codecs, meaning that each frame is encoded and decoded independently of any other frame. This technique provides the greatest editing performance and flexibility.

A variety of cameras can now capture and record a wider gamut of
color values when working in log or raw formats. You can preserve a wider color gamut by recording with the ProRes LOG setting on certain cameras such as the ARRI ALEXA or transcoding from the RED® camera’s REDCODE® RAW format. This results in deeper colors and more detail, with richer red and green areas of the image.

EXTRA CREDIT

Here’s an Apple White Paper that explains ProRes in more detail.

The table of file sizes, at the end, are invaluable in planning storage requirements.


… for Codecs & Media

Tip #589: Pick the Right Version of ProRes

 Larry Jordan – LarryJordan.com

I recommend ProRes 422 for camera media and ProRes 4444 for computer media.

The Apple ProRes logo.

Topic $TipTopic

Apple provides this description of the six different versions of ProRes:

Apple ProRes 4444 XQ: The highest-quality version of ProRes for 4:4:4:4 image sources (including alpha channels), with a very high data rate to preserve the detail in high-dynamic-range imagery generated by today’s highest-quality digital image sensors.

Apple ProRes 4444: An extremely high-quality version of ProRes for 4:4:4:4 image sources (including alpha channels). This codec features full-resolution, mastering-quality 4:4:4:4 RGBA color and visual fidelity that is perceptually indistinguishable from the original material. Apple ProRes 4444 is a high-quality solution for storing and exchanging motion graphics and composites, with excellent multi-generation performance and a mathematically lossless alpha channel up to 16 bits.

NOTE: Apple ProRes 4444 XQ and Apple ProRes 4444 are ideal for the exchange of motion graphics media because they are virtually lossless, and are the only ProRes codecs that support alpha channels.

Apple ProRes 422 HQ: A higher-data-rate version of Apple ProRes 422 that preserves visual quality at the same high level as Apple ProRes 4444, but for 4:2:2 image sources.

Apple ProRes 422: A high-quality compressed codec offering nearly all the benefits of Apple ProRes 422 HQ, but at 66 percent of the data rate for even better multistream, real-time editing performance.

Apple ProRes 422 LT: A more highly compressed codec than Apple ProRes 422, with roughly 70 percent of the data rate and 30 percent smaller file sizes. This codec is perfect for environments where storage capacity and data rate are at a premium.

Apple ProRes 422 Proxy: An even more highly compressed codec than Apple ProRes 422 LT, intended for use in offline workflows that require low data rates but full-resolution video.

My general recommendation is to use ProRes 422 for all images shot on a camera (except RAW formats), and ProRes 4444 for all media converted from RAW or Log or media generated on a computer.

EXTRA CREDIT

Here’s an Apple White Paper that explains ProRes in more detail.