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Original commit message from CVS: * docs/design/draft-tagreading.txt: Added open issues/thoughts to draft.
64 lines
2.2 KiB
Plaintext
64 lines
2.2 KiB
Plaintext
Tagreading
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----------
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The tagreading (metadata reading) use case for mediacenter applications is not
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to well supported by the current GStreamer architecture. It uses demuxers on the
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files, which generelly said takes too long. what we wan't is secialized elements
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that just do the tag-reading.
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The idea is to have one plugin 'tagread' simmilar to 'typefind' that provides
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elements for the different formats. The advantage of having those in on plugin
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would be that when building a metadatabase one only loads this plugin.
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Then there would be a tagbin, that similar to decodebin does a typefind and then
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plugs the right tagread element. It might plug a demuxer as a fallback solution.
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Still it would be nice to reuse code from demuxers/tag-filters.
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Design
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------
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The plan is that applications can do the following:
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pipeline = "filesrc ! tagbin"
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for (file_path in list_of_files) {
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filesrc.location=file_path
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pipeline.set_state(PLAYING)
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// wait for TAGS & EOS
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pipeline.set_state(READY)
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}
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* it should have one sinkpad of type ANY
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* it should send EOS when all metadata has been read
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(and all tags have been sent)
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* it could have a generic element that uses taglib
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http://developer.kde.org/~wheeler/taglib.html
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* tagread-elements should have RANK_NONE to be not autoplugged by decodebin
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Open Issues
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-----------
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* would it make sense to have 2-phase tag-reading
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* 1st phase: get tag-data that are directly embedded in the data
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* 2nd phase: get tag-data that has to be generated fetched
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* e.g. album-art via web, video-thumbnails
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* what about caching backends
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* it would be good to allow applications to supply tagbin with a tagcache-
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object instance. whenever tagbin gets a uri to tagread, it consults the
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cache first. whenever there is a cache-miss it will tag-read and then store
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in the cache
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GstTagList *gst_tag_cache_load_tag_data (GstTagCache *self, const gchar *uri);
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gst_tag_cache_store_tag_data (GstTagCache *self, const gchar *uri, GstTagList *tags);
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Reuse
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-----
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ogg : gst-plugins-base/ext/ogg
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avi : gst-plugins-good/gst/avi
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mp3 : gst-plugins-good/gst/id3demux
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wav : gst-plugins-good/gst/wavparse
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qt : gst-plugins-bad/gst/qtdemux
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