MKVToolnix is a set of tools to create, alter and inspect Matroska files under Windows.

With these tools one can get information about (mkvinfo) Matroska files, extract tracks/data from (mkvextract) Matroska files and create (mkvmerge) Matroska files from other media files. Matroska is a new multimedia file format aiming to become THE new container format for the future.

Changes in MKVToolnix 4.3.0 :

- mkvmerge: bug fix: Appending tracks which would normally be compressed (e.g. with header removal compression) and turning off compression for those tracks with "--compression TID:none" (or the corresponsing option in mmg) was resulting in the second and all following appended tracks to be compressed all the same.
- mkvextract: bug fix: Errors such as 'file does not exist' did not cause mkvextract to quit. Instead it continued and exited with the result code 0.
- mkvmerge: bug fix: Certain frames in certain h.264/AVC raw tracks were handled wrong, e.g. files created by x264 versions starting with revision 1665. The situation occured if an IDR slice comes immedtiately after a non-IDR slice and the IDR slice has its frame_num and pic_order_count_lsb fields set to 0.
- mkvmerge: enhancement: Attachments will be rendered at the beginning of the file again. Fix for bug 516.
- mkvpropedit, mmg's header editor: Fixed a crash corrupting files in certain situations. If the updated header fields required filling exactly one byte with an EbmlVoid element and if the next Matroska element's "size" was already written with its maximum length (8 bytes) then the crash would occur. Such files are written by e.g. lavf. Fix for bug 536.
- All: bug fix: Fixed a couple of format strings in translations which could cause the programs to crash.
- mkvinfo: new feature: mkvinfo will show the h.264 profile and level for AVC/h.264 tracks along with the CodecPrivate element.