Avoid using gst video frames, and simply copy buffer instead. Use gst memory map to access pointer to RGBA data. unreferencing the buffer frees the memory (apparently). Also free OpenGL objects on close to free memory.
Overall, memory consumption seems to be reduced.
Async ending of gst pipeline in stream and media player sources caused a crash at termination as source was still not closed when process was ended. Fix is to ask for an immediate termination of gst pipeline upon delete of stream, and to wait for mixer manager to end current session when clearing.
Fading color (to black) is not useful for media with transparency; there fading of alpha is necessary; the fading mode allows to select fade color or fade alpha. Also the source control window had to be adapted, with a checkerboard to show the alpha effect. The cropping of the image in control window was also fixed.
Allows looking for audio streams in media files (settings) and enabling / disabling audio for each MediaPlayer individually. Control of volume per media, saving in session file.
Enable playing and seeking into a timeline on a media player that loaded an image. Timeline sets a duration (end) and is saved/loaded. Add a gstreamer imagefreeze element in the pipeline to simulate a playable stream. Distinction must be made between 'isImage' (what was loaded) and 'singleFrame' (what is in the pipeline). GUI is added and customized with menu and dialog.
Change implementation of gst pipeline in MediaPlayer to use gstreamer playbin. This makes everything works more smoothly (including instant rate change). This also opens the possibility to allow audio mixing. Other bugfixes include set play speed rate at start, add video effects on reopen media player.
2 new callbacks (PlayFastForward, PlaySpeed), modified Seek callback to take target time in seconds (instead of ratio of duration). Integrating this in Input Mapping GUI and Session saving.
All Stream report failure with logs, read in InfoVisitor for Sources. ImGuiVisitor for Sources also detect failure of source and its stream.
Cleanup of unused includes and functions.
