QoE Metrics Reporting - Support for samplingPeriod

[dsilhavy]

Feature description

TS 26.512 Section 11.4.3 defines the metrics reporting format to be used for 5G Media Streaming referencing the scheme urn:3GPP:ns:PSS:DASH:QM10 and TS26.247 clause 10.6.1 and 10.6.2.

Some metrics defined in TS26.247 and ISO/IEC 23009-1 are typically not event driven. Consequently, they shall be derived at a certain interval rather than being updated every few milliseconds. For that reason, a new property named samplingPeriod was added to 26.512, see also 5G-MAG/Standards#78 for details.

Note: As our current implementation of QoE metrics reporting does not implement all the specified QoE metrics the samplingPeriod is currenly only relevant for BufferLevel. In the future other QoE Metrics such as AverageThroughput will be added and shall also take the samplingPeriod into account.

[dsilhavy]

Added support for samplingPeriod to request BufferLevel periodically. In addition, I think it is useful to derive the current buffer level in the following situations as well:

• When a new media segment has been appended to the buffer
• When the player transitions to the BUFFERING state, meaning the buffer is empty

I don't think this is explicitly mentioned in the specification though.

[dsilhavy]

Implemented in #67