New XML format questions

[amindfv at mailbox.org]

On Thu, Aug 19, 2021 at 10:34:51PM -0600, amindfv at mailbox.org wrote:
> With the new Kdenlive version I've got (20.12.3), there are a bunch of new things I'm trying to get my head around in the project XML. Here's a snippet with a few of them:
> 
>     <playlist id="playlist6">
>      <entry producer="1" in="00:00:00.000" out="00:00:22.042">
>       <property name="kdenlive:id">2</property>
>      </entry>
>      <blank length="00:00:01.042"/>
>      <entry producer="producer0" in="00:00:01.125" out="00:00:04.958">
>       <property name="kdenlive:id">3</property>
>      </entry>
>      <blank length="00:00:01.208"/>
>      <entry producer="1" in="00:00:00.000" out="00:00:04.958">
>       <property name="kdenlive:id">2</property>
>      </entry>
>      <entry producer="producer0" in="00:00:00.000" out="00:00:01.083">
>       <property name="kdenlive:id">3</property>
>      </entry>
>     </playlist>
>     <playlist id="playlist7"/>
>     <tractor id="tractor3" in="00:00:00.000" out="00:00:34.292">
>      <property name="kdenlive:track_name">Video 1</property>
>      <property name="kdenlive:trackheight">71</property>
>      <property name="kdenlive:timeline_active"/>
>      <property name="kdenlive:thumbs_format"/>
>      <property name="kdenlive:audio_rec"/>
>      <track producer="playlist6"/>
>      <track producer="playlist7"/>
>     </tractor>
> 
> The above makes a Kdenlive track ("Video 1"). In previous versions, this would have been represented as a single playlist. Now there seem to be two playlists - one empty - fed into a tractor.
> 
> Here's an example of the new grouping syntax as well:
> 
>     <property name="kdenlive:docproperties.groups">[
>       {
>           "children": [
>               {
>                   "data": "3:555",
>                   "leaf": "clip",
>                   "type": "Leaf"
>               },
>               {
>                   "data": "0:555",
>                   "leaf": "clip",
>                   "type": "Leaf"
>               }
>           ],
>           "type": "AVSplit"
>       }
>     ]
>     </property>
> 
> 
> I have many questions. Help with any of them is much appreciated:
> 
>   - Why are there two playlists for "Video 1"? What is the purpose of the empty "playlist7"?
>   - Entries now have a "kdenlive:id" property. What is this ID? Note in the above the IDs are doubled: there are two different Entries with ID 2, and two with ID 3.
>   - In the group syntax, what is the "data" property? As a guess, is it a kdenlive ID and a number of frames from the beginning of the track?
>   - What group types are there other than "AVSplit" and "Leaf"? Where can I find a list of the types and their meanings?

I can answer my own question for this one, at least:

https://invent.kde.org/multimedia/kdenlive/-/blob/master/src/definitions.h#L43-48 gives:

    enum class GroupType {
        Normal,
        Selection, // in that case, the group is used to emulate a selection
        AVSplit,   // in that case, the group links the audio and video of the same clip
        Leaf       // This is a leaf (clip or composition)
    };

I guess "Normal" means the thing that's created when you select 2 different clips and hit control-g or right-click and select "group clips"?

>   - What "leaf" types are there other than "clip"?
> 
> Thanks,
> Tom