Encoding

alt

Finding the Just Noticeable Difference with Netflix VMAF

VMAF stands for Video Multimethod Assessment Fusion, but all you really need to know is that it’s the video quality metric co-invented by Netflix to replace the Peak Signal to Noise Ratio (PSNR) that used to fuel the company’s per-title encoding function. In the image above, which is courtesy of Netflix, you see how VMAF scores on the left more closely match …

Read More »

Apple’s Bitrate Control Strategy: Do as I Do, Not as I Say

Apple’s HLS Authoring Specifications for Apple Devices approves up to 200% constrained VBR but Apple’s actual encodes are more like 110-120% constrained. What Apple Says As you probably know, Apple recently made sweeping changes to their HLS recommendations, including changing from 110% constrained VBR for VOD in TN2224, to 200% constrained VBR in the HLS Authoring Specifications for Apple Devices …

Read More »

How PSNR Compares to VMAF and SSIMplus

As quality metrics go, PSNR is considered a blunt tool obsoleted by higher end metrics like Netflix’s VMAF or SSIMwave’s SSIMplus. That said, it’s accessible and understood, and has been used for years. Of course, none of that matters if it delivers misleading results. So that’s what I decided to test in a round of two tests. This is the first, …

Read More »

Choosing the Data Rate for your Mezzanine Files

(Note: This article was amended to show the comparative results at 6 mbps) Summary (The MPD) As more and more producers move their encoding to the cloud, or distributing via OVPs or other service providers, the data rate for the mezzanine files is significant factor for upload time and bandwidth and storage costs. The big question is, how much extra …

Read More »

Cloud Pricing Survey Shows Hybrik Least Expensive Option By Far

I recently finished a white paper comparing the pricing for a new cloud encoding service named Hybrik with multiple cloud providers, including Amazon Elastic Transcoder, Microsoft Azure, Bitmovin, encoding.com, Telestream Cloud, and Zencoder. The white-paper was sponsored by Hybrik, and you can download it below. By way of background, I ran all calculations by the respective services (except Amazon) to verify my …

Read More »

Choosing the Segment Duration for DASH or HLS

Summary This research-based article details the factors to consider when choosing the segment duration for DASH or HLS. By way of background, when choosing an HLS or DASH segment duration for VOD video, the nature of the server/player connection is critical. For persistent connections, a segment size of two-three seconds produces good quality and optimal system throughput. For non-persistent connections, …

Read More »

Book Excerpt: VBV Buffer Explained

This article is kind of a prequel to my book, Encoding by the Numbers, which I published in 2016. That is, I published this article to get commentary from folks who read it, which I factored back into my book. Unfortunately, I changed content management systems in 2018 and lost the comments.  One of the topics I’m addressing in my …

Read More »

The Four Pillars of Video Encoding

Figure 1. The four critical aspects to consider before video encoding. Executive Summary: While video quality is always top of mind, consider deliverability, compatibility, and playability before finalizing your video encoding presets. Too often we look at video encoding with a single point of focus; achieving the best possible quality for the lowest possible data rate. However, as I was …

Read More »

How Netflix Pioneered Per-Title Video Encoding Optimization

The Netflix blog post entitled Per-Title Encode Optimization boldly declares that “to deliver the best quality video to our members, each title should receive a unique bitrate ladder, tailored to its specific complexity characteristics.”

Read More »

Beamr Technology Assessment

I recently finished evaluating Beamr Video. The evaluation included analyzing the quality of the resulting clips using objective measures such as PSNR, SSIM and VQM, and conducting extensive viewing of the optimized clips, assessing their subjective quality compared to the original clips. Following this evaluation, I concluded that “for 99.99% of the expert and average viewers, the Beamr-processed clips would …

Read More »