JavaScript API for DASH client adaptation algorithm. More...

Collaboration diagram for JS DASH Adaptation API:

Data Structures
interface	JSDASHClient
	JSDASHClient API. More...

interface	JSDASHGroup
	JSDASHGroup API. More...

interface	JSDASHQuality
	JSDASHQuality Object. More...

interface	JSDASHStats
	JSDASHStats API. More...

interface	JSDASHDownloadStats
	JSDASHDownloadStats API. More...

interface	JSDASHSRD
	JSDASHSRD. More...

Detailed Description

This section documents the JavaScript API available for implementing your own adaptation logic in GPAC DASH client.

The algorithm is chosen using the option algo of the dashin filter :

gpac -i source.mpd:algo=myalgo.js vout
//or
gpac -i source.mpd --algo=myalgo.js vout

The loaded JavaScript context has all JS modules available in GPAC, except WebGL.

It is also possible to bind the custom agorithm from a JSFilterSession using JSFSFilter.bind

Data Structure Documentation

interface JSDASHGroup

The JSDASHGroup object provides a description of a group (AdaptationSet in DASH), and its available qualities.

Collaboration diagram for JSDASHGroup:

Data Fields
attribute readonly unsigned long	idx	group index, as used in rate_adaptation callback
attribute readonly unsigned long long	duration	group duration in milliseconds, 0 if unknown (live)
attribute readonly JSDASHSRD	SRD	Spatial Relationship Description, or null if none
attribute readonly Array	qualities	list of available qualites, array of JSDASHQuality objects

interface JSDASHQuality

The JSDASHQuality object provides a description of a quality (Representation in DASH).

Collaboration diagram for JSDASHQuality:

Data Fields
attribute readonly DOMString	ID	ID (Representation ID)
attribute readonly DOMString	mime	MIME type
attribute readonly DOMString	codec	codec parameter
attribute readonly unsigned long	bitrate	average bitrate in bits per second
attribute readonly boolean	disabled	if true, the quality is disabled (cannot be played)
attribute readonly unsigned long	width	video width in pixels
attribute readonly unsigned long	height	video height in pixels
attribute readonly Fraction	fps	video frame rate
attribute readonly Fraction	sar	video sample aspect ratio
attribute readonly unsigned long	samplerate	audio samplerate
attribute readonly unsigned long	channels	audio number of channels
attribute readonly double	ast_offset	DASH AST offset for low-latency, 0 otherwise
attribute readonly Array	sizes	size of all segments in this quality for onDemand profiles. If unknown, set to null

interface JSDASHStats

The JSDASHStats object provides a description of current group state before adaptation logic

Data Fields
attribute readonly unsigned long	rate	last segment download rate in bits per second
attribute readonly unsigned long	filesize	last segment size in bytes
attribute readonly float	speed	current playback speed
attribute readonly float	max_speed	max supported playback speed computed from associated decoder runtime statistics, 0 if unknown
attribute readonly unsigned long	display_width	display width of the object in pixels, 0 if no video in object
attribute readonly unsigned long	display_height	display height of the object in pixels, 0 if no video in object
attribute readonly unsigned long	active_quality	index of active quality at the time the algo is run, or of last downloaded quality if previous segment was skipped
attribute readonly unsigned long	buffer_min	minimum buffer level in milliseconds below witch rebuffer will happen
attribute readonly unsigned long	buffer_max	maximum buffer level allowed in milliseconds. Packets won't get dropped if overflow, but the algorithm should try not to overflow this buffer
attribute readonly unsigned long	buffer	current buffer level in milliseconds
attribute readonly unsigned long	degradation_hint	degradation hint, 0 means no degradation, 100 means tile completely hidden
attribute readonly unsigned long	total_rate	cumulated download rate of all active groups in bytes per seconds - 0 means all files are local

interface JSDASHDownloadStats

The JSDASHDownloadStats object provides a description of current segment download statistics for a group

Data Fields
attribute readonly unsigned long	bits_per_second	current estimated download speed in bits per second
attribute readonly unsigned long long	total_bytes	total bytes to download
attribute readonly unsigned long long	bytes_done	bytes downloaded
attribute readonly unsigned long long	us_since_start	time in microsecond since segment was scheduled for download
attribute readonly unsigned long	buffer_duration	buffer duration in milliseconds
attribute readonly unsigned long	current_segment_duration	duration of segment being downloaded, 0 if unknown

interface JSDASHSRD

The JSDASHSRD object provides the SRD description of a group.

Data Fields
attribute readonly unsigned long	ID	ID of SRD source - all SRD with same source describe the same video composition, possibly with different grid sizes
attribute readonly long	x	X coordinate of SRD for this tile
attribute readonly long	y	Y coordinate of SRD for this tile
attribute readonly long	w	width of SRD for this tile - 0 for tile base track
attribute readonly long	h	height of SRD for this tile - 0 for tile base track
attribute readonly long	fw	total width of SRD descriptor for this tile
attribute readonly long	fh	total height of SRD descriptor for this tile

attribute JSDASHClient dashin

global context property representing the one and only JSDASHClient object attached to the loaded script