Improvements to the handling of subtitles: we make additional efforts to extract STPP subtitles from a sequence of fMP4 segments, as a .ttml file. ffmpeg does not currently seem to be able to extract this in the more commonly supported SRT format. When saving to a Matroska container (.mkv or .webm output files), we attempt to embed subtitle tracks with mkvmerge instead of with MP4Box (which fails).
Fix off-by-one bug in the calculation of the number of media fragments to download when using SegmentTemplate addressing with $Number$. The initialiation segment was being counted towards the number of segments, but should not be. Bug reported by @vidasi.
When the audio and video tracks are unsynchronized due to a difference in their startTime attribute, we attempt to fix this desynchronization during muxing. This is a rare problem in the wild and has not been heavily tested. The fix is currently only implemented when using ffmpeg as a muxer application (uses the -itsoffset commandline option).