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Tip #815: Download the Safari Technology Preview

… for Codecs & Media

Tip #815: Download the Safari Technology Preview

Larry Jordan – LarryJordan.com

Safari Technology Preview provides an early look at “what’s coming.”

The Safari Technology Preview logo.

Topic $TipTopic

Apple’s Safari Technology Preview provides an early look at upcoming web technologies in macOS and iOS. It showcases the latest layout technologies, visual effects, developer tools, and more, so users can provide input on how they are implemented.

Designed more for web developers than end users, this free software:

  • Previews the latest web technologies. Get a preview of the latest advances in Safari web technologies, including HTML, JavaScript, and CSS.
  • Easy to update. You can update Safari Technology Preview right from the Mac App Store. Updates occur every few weeks.
  • Access powerful developer tools. Use the latest version of the powerful Web Inspector and Responsive Design Mode to modify, debug, and optimize your websites.
  • Provide feedback. Use Feedback Assistant to send feedback directly to Apple about issues and enhancement requests. Simply select Report an Issue from the Help menu in Safari Technology Preview.
  • Run side-by-side with Safari. Safari Technology Preview is a standalone app that works side-by-side with the current version of Safari, so you can continue to use and reference the current release.
  • Surf seamlessly with iCloud. Safari Technology Preview works with iCloud, so you can access your latest Safari Favorites, bookmarks, and Reading List.

Here’s the link to learn more and download the latest version, or beta copies of upcoming versions.

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Tip #780: What’s a Proxy File?

… for Codecs & Media

Tip #780: What’s a Proxy File?

Larry Jordan – LarryJordan.com

Proxy files are a tradeoff: faster performance with lower image quality.

The proxy file (green) has 1/4 the pixels of the source media, but with the same geometry. The pixels aren’t bigger, just fewer.

Topic $TipTopic

At its simplest, a proxy file is a “stand-in,” a proxy, for another file. However, when it comes to media, a proxy file is a smaller version of the original file.

This reduced size provides several benefits:

  • Smaller storage requirements
  • Slower bandwidth requirements
  • Ability to run on older or slower systems

However, while smaller files are a good thing, the real challenge is to create proxy files that provide a similar geometry to the source file, otherwise, any effects you create with them will need to be altered when you switch back to the source media.

For this reason, proxy files, by intent, are 1/4 the size of the source image but with the same aspect ratio as the source file. This decreases file size and bandwidth by 75%, but matches the geometry of the source.

The easiest way to create this is to divide each frame into a series of 4-pixel grids, then remove 3 of the 4 pixels in each grid. This means that a 4K (3840 x 2160) becomes 960 x 540. Often, many proxy files use 1280 x 720 because this is already a common video format.

While not providing the same image quality as the source media, the image is good enough to use for editing, until the time comes for final effects, color grading and output.

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Tip #781: What is Debayering?

… for Codecs & Media

Tip #781: What is Debayering?

Larry Jordan – LarryJordan.com

Virtually all cameras only record partial images. Debayering is required to make them whole.

A camera sensor Bayer pattern (Image by en:User:Cburnett – Own work, CC BY-SA 3.0)

Topic $TipTopic

Debayering, or demosaicing, is a digital image process that reconstructs a complete image from the incomplete color samples recorded by virtually every video camera.

In this screen shot, notice that the camera records twice as many green pixels as either red or blue.

Wikipedia writes: Most modern digital cameras acquire images using a single image sensor overlaid with a color filter array (CFA). This has alternating red (R) and green (G) filters for odd rows and alternating green (G) and blue (B) filters for even rows. There are twice as many green filters as red or blue ones, catering to the human eye’s higher sensitivity to green light.

Since each pixel of the sensor is behind a color filter, the output is an array of pixel values, each indicating a raw intensity of one of the three filter colors. (The camera sensor itself only captures luminance data.) Thus, an algorithm is needed to estimate for each pixel the color levels for all color components, rather than a single component. Demosaicing is part of the processing required to render these grayscale images into a viewable image.

EXTRA CREDIT

Many modern digital cameras can also save images in a raw format allowing the user to demosaic them using software, rather than using the camera’s built-in firmware.

Here’s a Wikipedia article to learn more.

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Tip #782: Compare Proxy Files to Source Media

… for Codecs & Media

Tip #782: Compare Proxy Files to Source Media

Larry Jordan – LarryJordan.com

Proxy files are optimized for editing and small file size.

Topic $TipTopic

Here’s a table that compares proxy file storage and bandwidth requirements to source media.

Keep in mind that unlike H.264, proxy files are optimized for editing. H.264 is often difficult to edit on older or slower systems.

Data Rates and Storage Needs for UHD Media
4K Media Frame rate Bandwidth Store 1 Hour
H.264 30 fps 18.75 MB/sec 67.5 GB
ProRes Proxy 30 fps 22.75 MB/sec 82 GB
ProRes 422 30 fps 73.6 MB/sec 265 GB
BMD RAW 3:1 30 fps ~175 MB/sec 630 GB
R3D Redcode 4K 4:1 30 fps 215 MB/sec 774 GB

Notes:

  • H.264 specs based on JVC specs
  • ProRes specs from Apple ProRes White Paper
  • Blackmagic specs interpolated from Blackmagic Design website
  • Red redcode specs from Red website

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Tip #756: AME: New Adobe Stock Encoding Presets

… for Codecs & Media

Tip #756: AME: New Adobe Stock Encoding Presets

Larry Jordan – LarryJordan.com

Six new ProRes presets for Adobe Stock media.

The new Adobe Stock encoding presets for Adobe Media Encoder.

Topic $TipTopic

Adobe Media Encoder has six new Adobe Stock encoding presets in the May, 2020 update. These six presets include video-only, as well as audio and video settings for three frame sizes:

  • HD (1920 x 1080 pixels)
  • UHD (3840 x 2160 pixels)
  • 4K (4096×2160 pixels)

All three use ProRes 422 HQ, and encode into a Rec. 709 color space QuickTime movie using frame rates that match the source media.

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Tip #758: AME: New ProRes Encode Presets

… for Codecs & Media

Tip #758: AME: New ProRes Encode Presets

Larry Jordan – LarryJordan.com

The new ProRes encoding settings in AME for QuickTime and MXF OP1a.

Topic $TipTopic

The May, 2020, update to Adobe Media Encoder now includes twelve new ProRes compression presets for both Windows and Mac versions. Presets are located in the Broadcast category and include:

  • Apple ProRes Proxy
  • Apple ProRes LT
  • Apple ProRes 422
  • Apple ProRes 422 HQ
  • Apple ProRes 4444 (with and without an alpha channel)

The only format missing is ProRes 4444 XQ, which is a high-end origination format, so it isn’t surprising that AME doesn’t include it.

NOTE: ProRes RAW can only be recorded by a camera, it isn’t a delivery format.

The settings support two wrapper formats:

  • QuickTime
  • MXF OP1a

By default, each setting matches the frame size and frame rate of the source media, though this can be modified when the preset is applied.

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Tip #759: AME: New HEVC Encoding Presets

… for Codecs & Media

Tip #759: AME: New HEVC Encoding Presets

Larry Jordan – LarryJordan.com

All HEVC presets are set at 8-bit, which is faster, but not suitable for HDR media.

The HEVC encoding presets in Adobe Media Encoder.

Topic $TipTopic

The May, 2020, update to Adobe Media Encoder now includes seven new HEVC (H.265) compression presets for both Windows and Mac versions. Presets are located in the HEVC category and include:

  • SD 4:3
  • SD 16:9
  • 720p HD
  • 1080p HD
  • 4K UHD
  • 8K UHD

There’s also an option to match the source media frame size, for example, for vertical media.

Each preset defaults to 8-bit encoding to take advantage of the speed of hardware acceleration. However, HDR clips require 10-bit encoding, which is available, but compresses at a MUCH slower rate.

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Tip #744: What is Interlacing?

… for Codecs & Media

Tip #744: What is Interlacing?

Larry Jordan – LarryJordan.com

Interlacing was needed due to limited bandwidth.

Interlace artifact – thin, dark, horizontal lines radiating off moving objects.

Topic $TipTopic

Even in today’s world of 4K and HDR, many HD productions still need to distribute interlaced footage. So, what is interlacing?

Interlacing is the process of time-shifting every other line of video so that the total bandwidth requirements for a video stream are, effectively, cut in half.

For example, in HD, first all the even numbered lines are displayed, then 1/2 the frame rate later, all the odd numbered lines are displayed. Each of these is called a “field.” The field rate is double the frame rate.

NOTE: HD is upper field first, DV (PAL or NTSC) is lower field first.

In the old days of NTSC and PAL this was done because the broadcast infrastructure couldn’t handle complete frames.

As broadcasters converted to HD at the end of the last century, they needed to make a choice; again due to limited bandwidth: They could either choose to broadcast a single 720 progressive frame, or an interlaced 1080 frame.

Some networks chose 720p because they were heavily into sports, which looks best in a progressive frame. Others chose interlaced, because their shows principally originated on film, which minimized interlaced artifact, which is illustrated in the screen shot.

As we move past HD into 4K, the bandwidth limitations fade away, which means that all frames are progressive.

EXTRA CREDIT

It is easy to shoot progressive and convert it to interlaced, with no significant loss in image quality. It is far harder to convert interlaced footage to progressive; and quality always suffers. Also, the web requires progressive media because interlacing looks terrible.

For this reason, it is best to shoot progressive, then convert to interlacing as needed for distribution.

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Tip #745: What is HDR Rec. 2020 HLG

… for Codecs & Media

Tip #745: What is HDR Rec. 2020 HLG

Larry Jordan – LarryJordan.com

HLG is compatible with both HDR and SDR broadcast and television sets.

Chart showing a conventional SDR gamma curve and Hybrid Log-Gamma (HLG). HLG uses a logarithmic curve for the upper half of the signal values which allows for a larger dynamic range.

Topic $TipTopic

High-dynamic-range video (HDR video) describes video having a dynamic range greater than that of standard-dynamic-range video (SDR video). HDR capture and displays are capable of brighter whites and deeper blacks. To accommodate this, HDR encoding standards allow for a higher maximum luminance and use at least a 10-bit dynamic range in order to maintain precision across this extended range.

While technically “HDR” refers strictly to the ratio between the maximum and minimum luminance, the term “HDR video” is commonly understood to imply wide color gamut as well.

There are two ways we can display HDR material: HLG and PQ. (Tip #746 discusses PQ).

HLG (Hybrid Log Gamma) is a royalty-free HDR standard jointly developed by the BBC and NHK. HLG is designed to be better-suited for television broadcasting, where the metadata required for other HDR formats is not backward compatible with non-HDR displays, consumes additional bandwidth, and may also become out-of-sync or damaged in transmission.

HLG defines a non-linear optical-electro transfer function, in which the lower half of the signal values use a gamma curve and the upper half of the signal values use a logarithmic curve. In practice, the signal is interpreted as normal by standard-dynamic-range displays (albeit capable of displaying more detail in highlights), but HLG-compatible displays can correctly interpret the logarithmic portion of the signal curve to provide a wider dynamic range.

HLG is defined in ATSC 3.0, among others, and is supported by video services such as the BBC iPlayer, DirecTV, Freeview Play, and YouTube. HLG is supported by HDMI 2.0b, HEVC, VP9, and H.264/MPEG-4 AVC.

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Tip #746: What is HDR Rec. 2020 PQ?

… for Codecs & Media

Tip #746: What is HDR Rec. 2020 PQ?

Larry Jordan – LarryJordan.com

PQ provides for the brightest images, even though technology today can’t fully support it.

The PQ inverse EOTF (electro-optical transfer function). I thought you’d like to see the math.

Topic $TipTopic

High-dynamic-range video (HDR video) describes video having a dynamic range greater than that of standard-dynamic-range video (SDR video). HDR capture and displays are capable of brighter whites and deeper blacks. To accommodate this, HDR encoding standards allow for a higher maximum luminance and use at least a 10-bit dynamic range in order to maintain precision across this extended range.

While technically “HDR” refers strictly to the ratio between the maximum and minimum luminance, the term “HDR video” is commonly understood to imply wide color gamut as well.

There are two ways we can display HDR material: HLG and PQ. (Tip #745 discusses HLG).

Perceptual Quantizer (PQ), published by SMPTE as SMPTE ST 2084, is a transfer function that allows for the display of high dynamic range (HDR) video with a luminance level of up to 10,000 cd/m2 and can be used with the Rec. 2020 color space.

NOTE: cd/m2 refers to “candela per meter squared.” One cd/m2 equals one IRE.

PQ is a non-linear electro-optical transfer function (EOTF). On April 18, 2016, the Ultra HD Forum announced industry guidelines for UHD Phase A, which uses Hybrid Log-Gamma (HLG) and PQ transfer functions with a bit depth of 10-bits and the Rec. 2020 color space. On July 6, 2016, the ITU announced Rec. 2100, which uses HLG or PQ as transfer functions with a Rec. 2020 color space.

The key takeaway here is that PQ supports extremely bright images, but in a format that is not compatible with anything else.

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