Video_Terms

https://proxyman.io/posts/2019-11-15-Can-we-bypass-ssl-pinning# Video Terms

Intro

So while being in high level architecture meetings around working in video streaming space, I quickly realize the exorbitant amount of acronyms used daily in those conversations. So I decided to expand upon my learnings and categorized them so that its easier for me to refer or forward my learnings to someone in need.

Text

Subtitles

The term "subtitles" is used for transcriptions of spoken text providing translations in different languages for viewers.

Subtitles are a form of captioning used to translate the audio dialogue from one language into another. Simply put, subtitles translate a video’s language into another. You’ll see subtitles used in many foreign films and programs.

Closed Captions

Closed captions are created to allow people who are deaf or hard of hearing to experience the video, so they also include background sounds and speaker changes. On the other hand, subtitles assume that the viewer can hear the audio and as a result do not contain the background sounds or notifications for speaker changes.

What is 608 and 708 Closed Captioning?

Media

Info copied from whatwg.org

Media Resource

A media resource has an associated origin, which is either "none", "multiple", "rewritten", or an origin. It is initially set to "none".

A media resource can have multiple audio and video tracks. For the purposes of a media element, the video data of the media resource is only that of the currently selected track (if any) as given by the element's [videoTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-videotracks) attribute when the event loop last reached step 1, and the audio data of the media resource is the result of mixing all the currently enabled tracks (if any) given by the element's [audioTracks](https://html.spec.whatwg.org/multipage/media.html#dom-media-audiotracks) attribute when the event loop last reached step 1.

Media Element

Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete set of media data, e.g. the complete video file, or complete audio file.

Video

Main Video

SDR

Standard Dynamic Range

HDR

High Dynamic Range

HDR 10

Dolby Vision

HDR - Extended

BitRate

The content being encoded with given bits for every scene / every second.

eg. 200 MB file of resolution 1080p (full HD) (16:9 aspect ratio) of 10 mins with x265 (HEVC) encoding has a suggested average of 3728.75 kbps according to this calculator. Of course it depends on what content is being played and the scenes in the video.

check out video bitrate calculator in tools section

Resolution

HD

High Definition

720p - HD
1080p - FullHD
2160p - UItraHD

SD

Standard Definition

360p
480p
560p

Aspect Ratio

16:9 - common Widescreen ( HDTV ) (720p, 1080p , 2160p)
16:10 - Laptop Widescreen sometimes.
21:9 - Ultra wide
4:3 - CRT TV (Old TVs) Old Nintendo / console games

2.39:1 - widescreen cinema

Letterboxing

letterboxing (‘black bars’) in the video

Audio

Normal Audio

Commentary

Dub

Stereo

Left and Right channels in the audio stream. Hence Stereo

Mono

Only one directional sound pumped in or recorded.

Surround

Has L + R, Back L + R, Subwoofer and Center.
5.1
5 Channels and .1 is the subwoofer

7.1
7 channels and 1 subwoofer

7.2.4
7 channels, 2 subwoofer and 4 height ceiling speakers

Spatial Audio

Doesn't only have L + R channels but it has more channels to support Height information as well.
Apple has its own variant of Dolby Atmos kind of implementation.
Windows has Spatial audio surround.
Apple Airpods support spatial audio with extra meta data of input source file and use headphones accelerators hardware sensors to map it to surround sound.

Pre Roll | Mid Roll | Post Roll

Pre roll just means ads that are played before content playback begins.
Mid Roll would be an ad being played in middle.
Post Roll ad at the end.

Ad Break

An ad content which has duration of time to be played with resolution and links.

Ad Schedule

Collection | Array of Ad Breaks in a video stream file.

DAI - Dynamic Ad Insertion

Freewheel

Ad server which you can plug in - whose sole responsibility is to give us an array of ads "personalized" ads depending on the user being fingerprinted at the current instance.

Server Side Ads

HLS

Apple's implementation of delivering video content via internet HTTP Live Streaming format specification.
Android / Roku and other platforms use DASH instead of HLS.
This HLS file is also sometimes referred as manifest file.

.m3u8 file format in Text readable format.

HLS Format Examples

VOD

Video on demand

Ads aren't valuable for first few days
C3 for VOD is not that valuable like Linear Live TV.

C3
C4 - Day four

IVOD

IVOD Impulse Video on Demand
IVOD Internet Video on Demand
IVOD Interactive Video On Demand
IVOD Instant Video On Demand

Linear

Also referred as TVE Linear

what is linear tv

Live Asset

T6 Title 6

Basically just rules from USA govt. to make sure they comply with certain rules

what-title-6-video

T6 VOD Server Side Ads

A special fallback protocol exists for T6 VOD assets which inserts ads from server side. It kinda manipulates manifest. Internally its codenamed as VEX.

Time

Wall Clock

Actual UTZ time with full format - Date and Time.

Offset Time

TimeMSec - Milli Secs
Or an offset of Secs from the initial playback stream head.

Unix Epoch

Its a unix date time variant to describe a constant way of time format.

Time Scale

90k or 100k
30fps
24 fps it all divides evenly in 90k
60fps

PTS

Presentation timestamp
The presentation timestamp (PTS) is a timestamp metadata field in an MPEG transport stream or MPEG program stream that is used to achieve synchronization of programs' separate elementary streams (for example Video, Audio, Subtitles) when presented to the viewer.
PTS Wiki

Formats

MPEG

AAC

HEVC

It has both hvc1 and hev1 formats

hvc1 parameter sets are stored out-of-band in the sample entry (i.e. below the Sample Description Box ( stsd ) box)

hev1 parameter sets are stored out-of-band in the sample entry and/or in-band in the samples (i.e. SPS/PPS/VPS NAL units in the bitstream/ mdat box)

comment source

AV1

Encoders

video encoding tips

Packager

Super 8 - Internal tool to package streams via Just in time to deliver right encoded assets from different tools.

Decoders

Broadcasting

EAS

Emergency Alert System - this is being used for broadcasting emergency video over television or network to provide shelter / tornado / war anything which takes precedence since it could be life threatening. I don't have any examples since I haven't had the chance to watch live tv too much in north america. But I'm guessing this would have been placed by broadcasting FCC or governing agency after world war II or cold war to quickly mitigate broadcast messages or sirens like the ole' days of radio broadcast interrupt as depicted in "Tom & Jerry" show.

FCC | fema - EAS

Unique Tags

SCTE

Scete tag to find the information around HLS / stream.
Convey information

#EXT-X-SCTE35:TYPE=0x41,CUE=/DB7AAAAAAAAAP/wBQb+sPKHTfsn+XAABBAACRCZCg///////

Time Shifting

Wiki - time shifting

In broadcasting, time shifting is the recording of programming to a storage medium to be viewed or listened to after the live broadcasting.

DVR

Digital Video Recorder - Wiki

VCR

wiki - video cassette recorder

CDVR

cloud DVR

CDVR FAQs by Spectrum

TSB

Time shift buffer

CTSB

Cloud time shift buffer

time shift tv explained

FOG

FOG - Fetches live linear manifest and fragment from TSB as if it is from cloud.

Internal tooling to host a local web server using mongoose to serve video/audio content from its local or cloud recorded state. It is a proxy implementation to make sure that the SDK interface remains similar like its interacting with an actual network URL. Instead of using DASH | HLS manifest file url endpoints it proactively proxies them to redirect towards cloud | local recording assets.
Pretty neat, I think we do this in-order to avoid some restrictions on certain DRM streams etc. Not fully known why this workaround is being put in place by certain video streaming libraries or products.

Recording

Hot Recording

The timeline keeps playing while recording?
When the recording is happening in work in progress and still Live playlist.
The playlist "Event" style playlist (Hybrid of Linear and VOD).
It just starts with n number of fragments and it keeps adding more fragments on apple HLS.

Cold Recording

When the recording is completed and then it becomes cold recording.
The playlist will become VOD playlist.

Guides

EPG

electronic program guide (EPG)

Interactive programming guides (IPGs)
Or TV Listings | TV guides

Session

Heartbeat

As described by my architect.
It's generally a periodic request sent as a 'keep alive' / I'm still here / periodic update mechanism. Like the player sending a heartbeat analytics message every 60s with info about the stream. The app also sends a periodic request to monitor that the user is still watching a stream and count towards their max concurrent streams limit.

Could be also extended towards the Analytics heartbeats.

CDN

Client Steering

HLS Content Steering | apple specific
apple wwdc | Deliver reliable streams with HLS Content Steering

Tech Papers: Implementing HLS/DASH Content Steering at Scale

URL Reform

This is where the new URL's are generated according to different CDN and replace the regex accordingly.

URL

We kinda follow a RFC for decoding the URL asset resource to hit the asset resource n times depending on the retry strategy or different CDNs.

URL Resolver

URL Parser

See brand specific Sky implementation product name Conviva

Upscaling

Soap Opera effect

Frame insertion / intermission / adding
Interpolating
24 fps -> 60 fps

DSP (Digital Signal Processing)

Analytics

Nielson

The company to catch analytics by actual hardware in live tv.

VPA

Internal Platform Analytics which plugs in the data depending on the object file defined for us.

Previews

Thumbnail generation

You can do it via i-frame or something in the HLS manifest file

Playback

Trick Play

When you disable the fast forward or rewind on the player controller in the video. When you disable / enable the trick play - it gives the user an option to get full control of the scrubbing or jumping on the timeline ++ / -- .
Seeking operations on the timeline.

Timeline

Its the progress bar on the video player.
Showcasing how much progress it has made eg. 2 mins video
35 secs have passed

// - for the video playback
// = for time passed
= = = = - - - - - - - - - - - - - - - - - - - - - - - - - -

// * for ads
* * = = = - - - - - - - - * * * - - - - - - - - - - - * * * -

but its not purely for ads as you think of them, they could have a bumper for another program before or after the content with this API like for live tv programming.

Retune

When the player needs to be deallocated and then retuned or restarted from scratch in order to initiate the state properly. Reset basically.

DRM

Digital Rights Management

Hardware

Software

Widewine

Fairplay

Apple's variant of DRM on audio / video. HLS and AV Foundation | AVKit libraries.

Brands

Sky

Sky is an european video giant for publishing video

Sky Go
Sky EPG

Tata Sky - joint venture with Tata (India) & Sky

Coniviva | Conviva

I believe this is just a product name for Sky (Europe) which does the URL parsing and resolving.
CDN steering and analytics module for Video streaming.