CODEWITHSUNDEEP
mpeg-dash
Andrei
Andrei

Reputation: 21

MPEG-DASH trick modes

Does anyone know how to do trick modes (rewind/forward at different speeds) with MPEG-DASH ? DASH-IF Interoperability Points V3.0 states that it is possible.

Upvotes: 2

Views: 2890

Answers (2)

dede
dede

Reputation: 1

You can try an indication on ISO/IEC 23009-1:2014(E) => Annex A

The client may pause or stop a Media Presentation. In this case client simply stops requesting Media Segments or parts thereof. To resume, the client sends requests to Media Segments, starting with the next Subsegment after the last requested Subsegment.

If a specific Representation or SubRepresentation element includes the @maxPlayoutRate attribute, then the corresponding Representation or Sub-Representation may be used for the fast-forward trick mode. The client may play the Representation or Sub-Representation with any speed up to the regular speed times the specified @maxPlayoutRate attribute with the same decoder profile and level requirements as the normal playout rate. If a specific Representation or SubRepresentation element includes the @codingDependency attribute with value set to 'false', then the corresponding Representation or Sub-Representation may be used for both fast-forward and fast-rewind trick modes.

Sub-Representations in combination with Index Segments and Subsegment Index boxes may be used for efficient trick mode implementation. Given a Sub-Representation with the desired @maxPlayoutRate, ranges corresponding to SubRepresentation@level all level values from SubRepresentation@dependencyLevel may be extracted via byte ranges constructed from the information in Subsegment Index Box. These ranges can be used to construct more compact HTTP GET request.

Upvotes: -2

Sebastian Annies
Sebastian Annies

Reputation: 2468

the general idea is laid out in the document but the details are not specified.

A DASH segmenter should add tracks with a frame rate lower than normal to a specially marked AdaptationSet. Roughly you could say (even though in theory you should look at the exact profile/level thresholds) half frame rate is double playoutrate. A quarter frame rate is quadruple playoutrate.

All this is only an offer to the DASH client to facilitate ffwd. The client can use it but doesn't have to. If the DASH client doesn't understand the AdaptationSet at all it will disregard it due the EssentialProperty that marking it as track play AdaptationSet.

I can't see that fast rewind can be supported in any spec conforming way. You'd need to implement it according to your needs but with no expectation of interoperability.

Upvotes: 1

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