Some source formats are easier to index than others, especially when they already contain a keyframe index which can be read separately (e.g. AVI, MKV); for more broadcast oriented containers without such index chunks (especially TS), an indexer application has to follow the whole file, trying to demultiplex the streams and looking for starts of decodable blocks in each stream, which is a lot more elaborate.
Indexers supporting only a small range of input formats (few containers, one video stream only) may be faster (ignoring unsupported streams) than more generic indexers supporting a wider range (more containers, several audio streams too, maybe even subtitles).
|