Missing a decoder for a newly developed gstreamer media type

[Eslam Ahmed]

For reference, I managed to get the `uridecodebin` autoplugger to work by
telling it when to stop decoding and force-expose the caps by setting the
caps property of the `uridecodebin` as follows:
`gst-launch-1.0 uridecodebin uri=rtsp://localhost:8553/test
caps=video/x-mytype ! mytypedemux ! h264parse ! avdec_h264 ! videoconvert !
autovideosink`

Then I thought about changing the src caps of `mytypedemux` to:
```
Pad Templates:
  SRC template: 'src'
    Availability: Always
    Capabilities:
      video/x-h264
          stream-format: byte-stream
              alignment: au

  SINK template: 'sink'
    Availability: Always
    Capabilities:
      video/x-mytype
```

and ran the following pipeline but it still did not work, still showing the
same error as mentioned earlier:
`gst-launch-1.0  uridecodebin uri=rtsp://localhost:8553/test
caps=video/x-h264 ! h264parse ! avdec_h264 ! videoconvert ! autovideosink`

This is the perfect pipeline since I pointed out earlier that
`video/x-mytype` is nothing more than `video/x-h264` but with some metadata
prepended to every key-frame.

I have no idea what else to do other than making `mytypedemux` having a
primary rank.


Best Regards,
Eslam Ahmed


On Sun, Sep 12, 2021 at 10:35 AM Eslam Ahmed <eslam.ahmed at avidbeam.com>
wrote:

> The current caps look like this:
> ```
> Pad Templates:
>   SINK template: 'sink'
>     Availability: Always
>     Capabilities:
>       video/x-mytype
>
>   SRC template: 'src'
>     Availability: Always
>     Capabilities:
>       ANY
> ```
>
> I have also changed it to the following but it didn't work (although it
> might wrong, I just wanna see the decodebin plugs it int)
>
> ```
> Pad Templates:
>   SINK template: 'sink'
>     Availability: Always
>     Capabilities:
>       video/x-mytype
>
>   SRC template: 'src'
>     Availability: Always
>     Capabilities:
>       video/x-raw
> ```
>
> also when introspect other elements such as this one
> `gst-inspect-1.0 --print-plugin-auto-install-info
> /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstisomp4.so` you get results as
> follows:
> ```
> decoder-video/quicktime;
> decoder-video/mj2;
> decoder-audio/x-m4a;
> element-mp4mux;
> encoder-video/quicktime, variant=(string)3gpp;
> etc.
> ```
> but my element produces `element-mytypedemux`
>
> I think this is the reason why it's not working.
> How do I make sure of  my plugin/caps properly is being registered through
> all plugins/caps tree, and available during automatic caps
> selection/testing?
>
> Best Regards,
> Eslam Ahmed
>
>
> On Fri, Sep 10, 2021 at 6:06 PM Anton Pryima <zingfrid at gmail.com> wrote:
>
>> Hello Eslam.
>>
>> I'm sorry, I was not able to quickly find appropriate links, but overall
>> idea is: you should check, does your plugin/caps properly registered
>> through all plugins/caps tree, and available during automatic caps
>> selection/testing.
>>
>> Best regards,
>> Anton.
>>
>> On Thu, Sep 9, 2021 at 6:25 PM Eslam Ahmed via gstreamer-devel <
>> gstreamer-devel at lists.freedesktop.org> wrote:
>>
>>> Hello,
>>>
>>> I have recently developed a new media type called `video/x-mytype` which
>>> is basically an encoded video stream, say H264, that has some encoded
>>> metadata prepended on it. To that end, I have written 2 elements mytypemux
>>> and mytypedemux namely.
>>>
>>> Consequently, mytypemux takes 'video/x-h264' and produces
>>> `video/x-mytype` and mytypedemux takes `video/x-mytype` and produces
>>> whatever was tagged by mytypemux which is in this case none other than the
>>> 'video/x-h264'.
>>>
>>> I wanted to send `video/x-mytype` over the network, so I used
>>> `rtpgstpay` to payload what was coming out of mytypemux  into
>>> `GstRTSPMediaFactory`, mounted it and served as an rtsp stream.
>>>
>>> In the receiving pipeline, the following happens which works perfectly:
>>> `gst-launch-1.0 rtspsrc location=rtsp://localhost:8884/test !
>>> rtpgstdepay ! mytypedemux ! h264parse ! avdec_h264 ! videoconvert !
>>> autovideosink`
>>>
>>> Now, I am trying to make it work via a `uridecodebin` but I keep getting
>>> the following error from the `decodebin`:
>>> `Missing decoder: video/x-mytype (video/x-mytype)`
>>>
>>> So the pipeline knows about the type of the media type so there's no
>>> need for typefinding, it just needs a decoder. I had hoped that it would
>>> auto-plug `mytypedemux` but it didn't.
>>>
>>> So, What do I need to do to make the uridecodebin pick my demuxer?
>>>
>>> FYI:
>>>
>>>    - `gst-inspect-1.0 --print-plugin-auto-install-info
>>>    /usr/local/lib/gstreamer-1.0/libmytypedemux.so` produces
>>>    `element-mytypedemux` so it's an element but not a decoder?
>>>    - mytypedemux has a primary Rank
>>>
>>>
>>> Best Regards,
>>> Eslam Ahmed
>>>
>>
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