Ichthyostega
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Some sections of the Lumiera website document meeting minutes, discussion protocols and design proposals from the early days of the project; these pages were initially authored in the »Moin Moin Wiki« operated by Cehteh on pipapo.org at that time; this wiki backed the first publications of the »Cinelerra-3« initiative, which turned into the Lumiera project eventually. Some years later, those pages were transliterated into Asciidoc semi-automatically, resulting in a lot of broken markup and links. This is a long standing maintenance problem problem plaguing the Lumiera website, since those breakages cause a lot of warnings and flood the logs of any linkchecker run.
124 lines
5.5 KiB
Text
124 lines
5.5 KiB
Text
2023-09-13 Lumiera Developers Meeting
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=====================================
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:Author: Ichthyo, Benny
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:Date: 2023-09-14
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Sep 13, 2023 on #lumiera 20:00 - 22:30 UTC +
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__Participants__
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* ichthyo
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* benny
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* cehteh
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_Summary written by Ichthyo and reviewed by Benny_
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''''
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Focus Topics
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------------
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_Ichthyo_ started to define a collection of *FocusTopics*.
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These are topics towards which we focus our attention for further development *after* the
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current Engine integration is completed. Some tickets currently of interest were enhanced
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and extended, and new tickets created, which were all marked with the `FocusTopic` Tag.
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-> See https://issues.lumiera.org/report/17[Report-17] in the Lumiera Issue Tracker
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_Ichthyo_ identified some difficult issues concerning session modifications and change logging,
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especially in connection with rules based configuration.
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We discussed in some detail event sourcing, session modification, session configuration
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and representation of a configuration possibly as a context in the session. Of particular
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interest is the portability of a session from one machine to another and, consequently,
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the problems that can arise when a change in configuration occurs: these should be
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recorded as an event in the Event-Log. However, this requires the representation of the
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entire configuration in a consolidated form as part of The Model. A change in the
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configuration could then be detected and recorded as an event.
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Another task of concern is how the actual Diff Messages will be generated. We could first
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manipulate the data model and then _detect_ a diff. Yet the favourable solution would be
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to interpret the commands and directly derive the events associated with the commands,
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with an attached diff, which can then be applied against the data model as a _projection._
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A discussion followed to sort out which topics should be addressed first.
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It seems the topics regarding Event Log and Session persistence
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https://issues.lumiera.org/ticket/1234[#1234]
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https://issues.lumiera.org/ticket/540[#540] and
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https://issues.lumiera.org/ticket/569[#569]
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should be addressed first, since these may lead to decisions relevant to many other parts
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of the system. Possibly also
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https://issues.lumiera.org/ticket/332[#332] regarding a full definition of placement capabilities.
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The topic of Placement interpretation will be addressed in the *next* vertical slice,
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where we intend to add a clip to the timeline. To do this, we'll require at least a
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_simple_ resolution capability of Placements, because we'll attempt do the groundwork for
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The Builder.
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_Benny_ proposes to add »interface« and »mock« tickets for Event-Log and Placements,
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blocking the full implementation follow-up tickets. Then these preliminary parts can be
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addressed first and integrated as part of the »Add Clip« Vertical Slice. For Context:
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currently the »Playback« Vertical Slice is being worked on, aiming towards a first
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integration of the Render Engine.
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Playback Vertical Slice
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-----------------------
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_Ichthyo_ reports on the progress of the »Playback Vertical Slice« effort.
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- Memory Manager is implemented and tested
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- Activity Language is also completed and tested
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- a passive worker pool has been implemented, based on the C++17 concurrency framework
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Next steps:
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- retrofit our existing thread wrapper (which was based on POSIX) to use C\+\+17 thread support;
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this should be a drop-in replacement, since our own old design almost completely matches the
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design and feature set standardised with C++17
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- complete implementation of the Scheduler Layer-2, integrating Activity-Language and worker pool
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- integration test of The Scheduler
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Documentation Index and Glossary
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--------------------------------
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_Benny_ reworked and extended the documentation overview in the Lumiera website.
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This can be published now.
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Moreover, _Benny_ investigated Glossary and Index generation. It turns out that
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ASCIIDOC already provides an index generation feature, which could be configured and used
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to build an index. But there is no support to generate a glossary which we'll build soon.
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The next goal would be to build a prototype for testing and to see how this can be
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integrated into the website infrastructure.
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Library solutions for Video Display
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-----------------------------------
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_Benny_ conducted some research regarding library solutions for *video display*, notably
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ffmpeg, GStreamer and libVLC. It was rather easy to code up an ``hello world'' example based on
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GStreamer, while it was difficult to find suitable documentation regarding the ffmpeg based
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solution. Moreover, GStreamer seems to have a much more active and helpful community.
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Next steps would be to look in more depth into libVLC, and especially to compare the
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feature sets of these solutions. _Cehteh_ points out that MPV (formerly MPlayer) would also
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be an interesting point of reference. _Benny_ mentions that GTK4 offers an integrated
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video display capability. We'll investigate these frameworks further.
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Extended discussion ensued regarding video frameworks and the difficulties regarding the plethora
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of interfaces, especially when it comes to hardware acceleration support. Ideally, the Lumiera
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project should follow the solutions provided by a sufficiently active community, capable of following
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the constant evolution of interfaces and frameworks.
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It was agreed upon that the »Playback Vertical Slice« just needs a very simple solution to output
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raw video (RGB888 or YUV), and offers a good opportunity for experimentation to find a suitable
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support framework.
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''''
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Next meeting
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------------
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The next meeting will be Wednesday **Oct 11, 20:00 UTC**.
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You are welcome to join.
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''''
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