Video: AAC Demystified: How the AAC audio codec works and how to make sense of all its crazy profiles.

The title says it all! Alex Converse speaks here at the San Fancisco Video Tech meet up while he was working at Google discussing the ins and outs of AAC – and since he implemented an AAC decoder himself, he should know a thing or two about it.

Sure enough, Alex delivers by talking about the different version of AAA that have been around since MPEG 2 AAC through to the high efficiency AACs we have seen more recently.

Walking through the AAC Encoder block diagram we look at each of the different sections from sampling, MDCT (a type of Fourier transform) to psychoacoustic processing, stereo processing and more.

We then start to look at the syntax for the way the streams are structured which brings us in to understanding the AAC channel modes, and the enhanced mechanisms for encoding and processing used by the later versions of AAC including HE-AAC V2.

Alex finished with quick look at low delay codecs and a Q&A.

A great, detailed, overview of AAC. Ideal for developers and those who need to fully understand audio.

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Speaker

Alex Converse Alex Converse
Senior Software Engineer,
Twitch

Video: VP9 Transcoding for Live eSports Broadcast

VP9 is a well-known codec, but it hasn’t seen many high-profile, live deployments which makes Twitch’s move to deliver their platform using VP9 in preference over AVC all the more interesting.

Here, Yueshi Shen from Twitch, explains the rationale for VP9 by explaining the scale of Twitch and looking at their AVC bitrate demands. He explains the patent issues with HEVC and VP9 then looks at decoder support across devices and platforms. Importantly, encoder implementation is examined leading to Twitch’s choice of FPGA to provide live encoding.

Yueshi then looks at the potential of AV1 to Switch_Frame to provide low-latency broadcast at scale.

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Speaker

Yueshi Shen Yueshi Shen
Principal (Level 7) Research Engineer & Engineering Manager,
Twitch

Video – Live Streaming with VP9 at Twitch TV

Tarek Amara from Twitch explains their move from a single codec (H.264) to multiple codecs in order to provide viewers an optimal viewing experience.

In this session, Tarek shares findings on VP9’s suitability for live streaming and the technical and industrial challenges such move involves. Covering:

  • VP9 encoding performance,
  • Device and player support,
  • Bandwidth savings,
  • The role of FPGAs
  • plus an overview of how the transcoding platform need to change to enable VP9 encoding and delivery at scale.

This presentation is from the Video Engineering Summit at Streaming Media West 2018.

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Speaker

Tarek Amara Tarek Amara
Senior Video Specialist,
Twitch TV/Amazon