Comments to "Requirements for Adaptive Bit Rate Streaming"

Hi Clarke, All,

A few (minor) comments/questions to the "Requirements for Adaptive Bit Rate Streaming":

1.       The terms "programme (program)", "Media Track", "Source ID", "Source Buffer", "Track Buffer", "Initialisation Segment", "Media Segment", and "Random Access Point" are not used in the Requirements or Use cases.

Do we need these definitions in this document ?



2.       In particular, should we remove the last sentence in the "Track Buffer" as that is leading to nowhere ?

"Track Buffer

A hypothetical buffer that represents initialization and media data for a single AudioTrack or VideoTrack that has been queued for playback. This buffer may not exist in actual implementations, but it is intended to represent media data that will be decoded no matter what media segments are appended to update the source buffer. This distinction is important when considering appends that happen close to the current playback position. Details about transfers between the source buffer and track buffers are given here."


3.      "Adaptive Bit Rate Streaming" vs "Adaptive Bit Rate Content" vs "Adaptive Bit Rate Media": Is the term "Adaptive Bit Rate" expected to cover the definition for all these terms used throughout the document ?
"Adaptive Bit Rate
Adaptive bit rate media is characterized by short independent parallel media stream segments that can be individually selected and rendered according to some selective criteria. Typically, the parallel segments are differentiated by a feature such as required bandwidth, image resolution, etc."


4.      Observation: "Adaptive Bit Rate Method" and "Adaptive Bit Rate System" are used in the document almost equivalently to mean the same thing. If there is a true difference intended that is not obvious in the Requirements and Use cases.
Adaptive Bit Rate Method
An adaptive bit rate method refers to an algorithmically distict approach to implementing adaptive bit rate streaming.
Adaptive Bit Rate System
An adaptive bit rate system refers to a comprehensive implementation of adaptive bit rate streaming. HLS and Smooth Streaming, for example, would be considered adaptive bit rate streaming systems.


5.       To clarify the meaning of a couple of requirements the following changes are proposed (to relax the potential confusion in the equivalent use of "ABR method" and "ABR system"):
No ABR Method Preference
The standard interface to support adaptive bit rate streaming ABR media system must not advantage one specific ABR method over another.
HTML aspires to be a level playing field. This philosophy enables innovation to flourish and allows superior solutions to become quickly implemnted and adopted. ABR media systems are and should continue to be innovative solutions within this spirit of openness. Support for different ABR systems should not require any proprietary modification of the user agent
Open Source Browsers
The standard interface to support adaptive bit rate streaming ABR methods must work with "open source" browsers.
The ability for a browser vendor to implement playback of ABR media in accordance with the requirements in this document must be supported.

Br,
Juhani