When building certain mlt files with melt 7.1.0, they run just fine, but when building them with melt 6.24.0, the error message
[producer_xml] Property without service 'property'?
[producer_xml] Property without service 'property'??
appears any number of times. A minimal working example showing this warning precisely twice is the following:
<?xml version="1.0"?>
<mlt>
<profile width="1920" height="1080"/>
<chain id="chain0">
<property name="resource">mwe-in.mp4</property>
</chain>
<playlist id="playlist0">
<entry producer="chain0"/>
</playlist>
</mlt>
What is the origin of this error? How can it be fixed?
The documentation is rather sparse on properties and in particular does not seem to mention what it would even mean for a property to have a service. The check for properties without services however is still in the current code (though I have not checked whether the code is dead by now).
Chain services were added in 7.0.0 - they were not supported in 6.24.0 yet.
The XML will not work in 2.24.0 because it uses a chain. You can change "chain" to "producer" to make it work if you do not need to use chain/link features.