I have a tool that creates a series of 1 sec webm files (with Alpha information in the BlockAdditional element of each packet). Is it possible to create a Dash playlist, using MP4Box or gpac as follows?

- the segments are played in a sequence
- the video is not transcoded
- the alpha channel is preserved

I tried a variety of commands like:
```
MP4Box -dash 10000  /alpha/video_0000.webm:Period=0 /alpha/video_0001.webm:period=1 --muxtype=webm
```
This gets close, but it transcode to MP4. I also get an error saying:
```
Arg muxtype set but not used
```

I'm on Ubuntu 20. I installed gpac and mp4box with
```

 apt-get update && apt-get install -y --no-install-recommends libjpeg62 gpac 
 wget https://download.tsi.telecom-paristech.fr/gpac/release/2.2.1/gpac_2.2.1-rev0-gb34e3851-release-2.2_amd64.deb
 dpkg -i gpac_2.2.1-rev0-gb34e3851-release-2.2_amd64.deb 

```

Thanks for helping.
Is it possible to combine a series of WebM files into a Dash MPD playlist?
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Is it possible to combine a series of WebM files into a Dash MPD playlist?
Issue date:

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I have a tool that creates a series of 1 sec webm files (with Alpha information in the BlockAdditional element of each packet). Is it possible to create a Dash playlist, using MP4Box or gpac as follows?

- the segments are played in a sequence
- the video is not transcoded
- the alpha channel is preserved

I tried a variety of commands like:
```
MP4Box -dash 10000  /alpha/video_0000.webm:Period=0 /alpha/video_0001.webm:period=1 --muxtype=webm
```
This gets close, but it transcode to MP4. I also get an error saying:
```
Arg muxtype set but not used
```

I'm on Ubuntu 20. I installed gpac and mp4box with
```

 apt-get update && apt-get install -y --no-install-recommends libjpeg62 gpac 
 wget https://download.tsi.telecom-paristech.fr/gpac/release/2.2.1/gpac_2.2.1-rev0-gb34e3851-release-2.2_amd64.deb
 dpkg -i gpac_2.2.1-rev0-gb34e3851-release-2.2_amd64.deb 

```

Thanks for helping.
--- end body ---
