MPEG DASH TILED STREAMING 指定tile的位置

SRD

SRD ： Spatial Relation Description

SRD is an approach for streaming only spatial sub-parts of a video to display devices, in combination
with the form of adaptive multi-rate streaming that is intrinsically supported by MPEG DASH.
The SRD feature extends the Media Presentation Description (MPD) of MPEG DASH by describing
spatial relationships between associated pieces of video content.
This enables the DASH client to select and retrieve only those video streams at those resolutions that are relevant to the user experience.

SRD Syntax

SRD Syntax

Syntax and semantics of SRD information

source_id

The MPD author can signal SRD descriptors for each of the different content items in the same MPD.
Identical values of source_id in different SRD descriptors indicate that these SRD descriptors belong to the same reference space.
Conversely, SRD descriptors with different source_id have no spatial relationship with each other.

如果source_id相同，說明SRD descriptors屬於同一參考空間。
如果source_id不同，說明SRD descriptors沒有空間關係。

舉例

(1) 例1

<AdaptationSet>
<SupplementalProperty schemeIdUri="urn:mpeg:dash:srd:2014" value="0,3840,2160,3840,2160,7680,2160"/>
...
</AdaptationSet>

(2) 例2

<SupplementalProperty schemeIdUri="urn:mpeg:dash:srd:2014" value="0,2,0,2,2"/>

(3) 例3

<SupplementalProperty schemeIdUri="urn:mpeg:dash:srd:2014" value="0,0,0,1,1,2,2"/>

source_id ： 0
object_x ： 0
object_y : 0
object_width : 1
object_height : 1
total_width : 2
total_height : 2

表明源視訊按照2*2進行切割， 當前tile位置為(0, 0), 寬和高的大小均為源視訊寬高的2分之一。

MP4Box中如何指定SRD

MP4Box -dash 1000 [other dash params]  source.mp4:desc_as=<SupplementalProperty schemeIdUri=\"urn:mpeg:dash:srd:2014\" value=\"0,0,1,1,1,2,2\"/>

indicates that source.mp4 is placed at X=0, Y=1 with width 1 and height 1 on a tiling grid of size 2×2.

References:

https://pdfs.semanticscholar.org/73bb/96a1d8415f675857704ce77739a4fd46f992.pdf
https://gpac.wp.imt.fr/2016/05/25/srdtuto/