From MythTV Official Wiki
Note: These are an overview of the changes between 0.23 and the current 0.23.1 release of MythTV.
The 0.23.1 packaged release encompasses revisions from the 0.23-fixes branch of SVN numbered  to . If you need changes newer than that (notably , which introduces a retry workaround for problems with newer kernel V4L/IVTV interfaces), you'll need to check out SVN and build from that.
- Fix segfault when there is a change in the video stream e.g. resolution or aspect ratio. 
- Fix NEXTSOURCE/PREVSOURCE key bindings to prevent a deadlock when changing sources in Live TV (i.e. when hitting the "Y" key). 
- Fix potential crashes on video startup. , 
- Fix fullscreen display. 
- Fix calling external applications with myth_system(). 
- Compilation fixes. 
- Fix QtDBus check. 
- Fix linking on certain combinations of configure options and distributions when building from source.     
- Fix compilation of libswscale and libavcodec on x86_32 builds with GCC 4.2 and higher. 
- Handle AMD Athlon(tm) II processors in --enable-proc-opt. 
- Fix GUI hang (all white or brown screen, possibly with tiny fonts on top) when specified and fallback themes are missing. 
- Fix DB schema version checks and eliminate redundant pre-upgrade backups when multiple schemas are updated. , 
- Fix check for valid MythTV configuration directory. 
- Fix handling "Delete, but allow re-record" when used during recording. 
- Fix image stretching on non-square pixel displays. 
- Add yr.no and Weather Underground scripts and remove weather.com maps. 
- Add Weather Underground static radar maps. 
- Miscellaneous theme and other changes. , 
- Added `mythpython` utility for quick interpreter access and version output. 
- Fix a crash on exit when run with certain command-line arguments (such as --clearcutlist).