Many people think that Matroska is a codec for creating high-quality compressed video files, but nothing can be farther from the truth. Actually Matroska is just a multimedia container for video, audio and subtitles – it packs them together to produce the single media file while the individual audio or video streams could be encoded by Matroska supported codec such as H264 or AAC. Matroska encapsulated files are commonly available in the MKV format. And now you can extract various elements from the MKV files using a free tool called Inviska MKV Extract. Well, you can extract them using FFmpeg, but Inviska MKV Extract makes everything easy through its simple-to-follow interface.
This tool requires another software, also freeware, called MKV Toolnix. In fact when you launch MKV Extract tool, it asks for the location where your MKV Toolnix files are residing, in case it is unable to automatically locate by itself. You can also change MKV Toolnix path later on from the MKV Extract settings. For this, pull down the File menu and select Preferences. Then you can type in the full path of MKV Toolnix under the MKVExtract category and click on the OK button.
Once this is done, you can simple start adding the MKV files to the Inviska MKV Extract window by pulling File Add Files or by dragging-n-dropping them onto the window. You can choose which of the video, audio, subtitles or other elements you want to extract for each of the individual MKV files. Or you can choose to batch-extract video, audio etc. for all the added MKV files. Clicking on the Begin button will start the extraction process.
The process is really fast. For my 35 MB MKV file having very high quality audio, it finished the extraction in less than 2 seconds. This is very impressive. But all the audio or video streams are extracted in the same format as they were encoded. For me, all the audio files were extracted in the OGG Vorbis audio format. If you want to convert them into something more acceptable like MP3, then you can use FFmpeg.
You can download Inviska MKV Extract from https://www.inviska.com/mkvextract/.