Video: Things Developers Believe About Video Files (Proven Wrong by User Uploads)

For many transcoding workflows, efficiency or quality are the primary factors defining how they are created. But when ingesting user-generated videos like those uploaded to the online video platform, Vimeo, life gets difficult. Dealing with the wide variety of formats uploaded and the many edge cases in the way that otherwise normal AVC videos are delivered means throwing out any assumptions you ever had and analysing every aspect of the file.

Senior video encoding engineer, Derek Buitenhuis takes us through the many lessons he and his colleagues have learnt over the years. Don’t, he says, assume that properties don’t change between frames – sometimes they change in every single frame. Assuming that you have a single frame rate throughout the video is another ‘no no’ as there are many variable-frame rate videos.

Derek also looks at dealing with samples stamped with negative timestamps, the need for sample durations, the myriad of issues seeking through a file, the fun of having some frames that aren’t displayed and multiple-track videos.

Colour spaces, no surprise to anyone, cause handling difficulties for example if the bitstream colour properties are different to those in the container. As the talk finishes, we’re left considering old MPEG2 files that can have unavoidable banding, replicating looping MOV files, and dealing with QuickTime special effects channels that animate a fire on the screen.

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Derek Buitenhuis Derek Buitenhuis
Senior Video Encoding Engineer,

Video: How Libre Can you Go?

Many companies would love to be using free codecs, unencumbered by patents, rather than paying for HEVC or AVC. Phil Cluff shows that, contrary to popular belief, it is possible stream with free codecs and get good coverage on mobile and desktop.

Phil starts off by looking at the codecs available and whether they’re patent encumbered with an eye to how much of the market can actually decode them. Free codecs and containers like WebM, VP8 etc. are not supported by Safari which reduces mobile penetration by half. To prove the point, Phil presents the results of his trials in using HEVC, AVC and VP8 on all major browsers.

Whilst this initially leaves a disappointing result for streaming with libre codecs on mobile, there is a solution! Phil explains how an idea from several years ago is being reworked to provide a free streaming protocol MPAG-SASH which avoids using DASH which is itself based on ISO BMFF which is patent encumbered. He then explains how open video players like video.js can be modified to decode libre codecs.

With these two enhancements, we finally see that coverage of up to 80% on mobile is, in principle, possible.

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Phil Cuff Phil Cluff
Streaming Specialist,