To reduce the size of a Blu-ray movie, you can make a copy in MKV format, after removing all unnecessary audio tracks, subtitles, etc. This will require special programs.
Blu-ray and MKV formats
The standard container for blu-ray video is M2TS (Mpeg2 Transport Stream). This media container is located on a blu-ray disc in the Stream folder and includes HD video, HD audio and other information.
The MKV (or Matroska) format is a free and open standard format. It is possible to have multiple video / audio streams, pictures or subtitles in one MKV file.
In order to make a copy of a blu-ray movie in MKV format without loss of quality, you need to remux the streams. Remuxing is a change from one format to another without re-coding. You just need to "take" audio and video streams from the original file and reformat them without any changes to another format. Simply put, you need to get two cubes (audio and video) out of one box and put them in another box. As a result, the quality remains the same, and the user receives the desired format (in this case, MKV).
The process of getting MKV format from blu-ray
To make a copy of a blu-ray movie in MKV format, you need two programs. With tsMuxer, you need to "split" a blu-ray file into its components and get separate audio and video tracks. Then use the mkvmerge program to glue them together in MKV format.
First you need to look at the detailed parameters of the source file. For example, in KMPlayer this can be done by selecting the "Recording Information" item from the context menu (or by using the Alt + J combination). You need to remember the format used (for example, AVC), the frame rate (frame rate) and the average bit rate (bit rate). These parameters should remain the same. Then you need to look at the sound parameters: audio codec, bit rate and sound at the sampling rate. These parameters also need to be saved.
After that, you need to run the tsMuxer program. You can add a file through the "Input" item in the menu bar. Next, in the "Browse" field, you must specify the folder in which the extracted tracks will be saved, and then select the "Start Demux" item. Thus, a separate video track and a separate audio track will be obtained.
Next, you need to run the mkvmerge program. With its help, you can collect several audio and video tracks into one MKV file, delete unnecessary information (English track or subtitles) or split the video into parts (so that the files fit on discs). After starting the program, you need to add a video stream through the "Input" tab. Then, in the "Tracks, chapters and tags" field, you need to select the video stream and switch to the "Format and specific options" tab. In the line "FPS" you must specify the frame rate - 30.
Then you need to add an audio track, specify the folder to save the finished file and click the "Start processing" button. After completing the assembly process, you will get an MKV file with the same parameters as the original blu-ray movie.
