# Inquiry: AV2 Multistream Support in GStreamer

**URL:** https://discourse.gstreamer.org/t/inquiry-av2-multistream-support-in-gstreamer/5871
**Category:** Plugin and library development
**Tags:** android
**Created:** [August 5, 2026, 6:39am UTC](https://discourse.gstreamer.org/t/inquiry-av2-multistream-support-in-gstreamer/5871 "2026-08-05T06:39:02Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![dengfei660](https://discourse.gstreamer.org/user_avatar/discourse.gstreamer.org/dengfei660/32/1718_2.png) [@dengfei660](https://discourse.gstreamer.org/u/dengfei660)
#### Post date: [August 5, 2026, 6:39am UTC](https://discourse.gstreamer.org/t/inquiry-av2-multistream-support-in-gstreamer/5871/1 "2026-08-05T06:39:02Z")

</div>

Hi all,

I’m looking into the technical roadmap for supporting AV2’s **multistream** feature in GStreamer and would appreciate your insights on the implementation details.

### **1. Parser & Demuxer**

AV2 multistream introduces a new layer structure where a single temporal unit can contain multiple coded extended layer units. This implies the need for a new parser/demuxer element that can:

- Identify and split the different streams within the AV2 bitstream

- Expose multiple source pads (1-to-N), similar to how existing demuxers work

- Handle the multistream\_decoder\_mode flag and the associated MSDO OBU

Would this be implemented as a dedicated `av2parse` element, or could it be integrated into a broader `av2demux`? How should the stream headers and OBU parsing be structured to expose each layer as a separate stream?

### **2. Decoder**

With `dav2d` already available as an AV2 software decoder, integrating it seems straightforward for single-stream decoding. However, for multistream:

- Does `dav2d` currently support multistream decoding mode, or would this require extension?

- How should the decoder handle multiple layers – as separate decoder instances, or a single instance producing multiple output pads?

- Would we need a new element like `av2multidec` that explicitly handles multistream, or can the existing `av2dec` be extended?

### **3. Display & Rendering**

For displaying multiple streams (e.g., multi-angle, VR/AR layers, or PiP), what’s the recommended approach?

- **Option A:** Use separate sink branches (e.g., multiple `autovideosink` elements) for each stream

- **Option B:** Composite streams into a single output using elements like `compositor` or `videomixer` for tiled display

- **Option C:** Leverage `GstStreamCollection` and `GST_EVENT_SELECT_STREAMS` for application-level stream selection and switching

### **4. Pipeline Construction**

What would a typical pipeline look like? My initial thought:

text

```auto
filesrc location=file.av2 ! av2parse ! av2multidec ! ...

```

But how would the branching work? With a 1-to-N demuxer/parser, the pipeline would need to dynamically link pads as they are created:

text

```auto
filesrc ! av2parse name=p
p.src_0 ! queue ! av2dec ! videoconvert ! autovideosink
p.src_1 ! queue ! av2dec ! videoconvert ! autovideosink

```

Would `decodebin3`/`playbin3` be able to autoplug such a multistream AV2 source, or would custom bin/pipeline construction be required?

### **Summary of Questions**

| **Area** | **Key Questions** |
| --- | --- |
| **Parser** | How to parse OBUs and expose multiple streams? New element or extend existing? |
| **Decoder** | Does `dav2d` support multistream? Single or multiple decoder instances? |
| **Display** | Separate sinks vs. compositor vs. stream selection API? |
| **Pipeline** | How to dynamically link pads? Autoplugging with decodebin3? |

I’d appreciate any thoughts, references to similar implementations (e.g., how HEVC MVC or VP9 spatial layers are handled), or pointers to ongoing work.

Thanks