Feature request: faster extraction of subtitle/audio tracks without video remux

[remuxer_ger]

It would be very useful if MakeMKV could extract selected audio and/or PGS subtitle tracks from a Blu-ray/UHD title without requiring the primary video stream to be included in the MKV output.

My main use case is speed, not storage. For example, when I only want to inspect three German PGS subtitle tracks on an UHD, MakeMKV currently forces me to remux the full 70–80 GB video stream as well.
Ideally, MakeMKV could offer a mode that demuxes only the selected stream PIDs from the chosen playlist/title and skips unnecessary video remuxing wherever technically possible.

This would be very helpful for:
- checking forced subtitle tracks
- subtitle correction workflows
- extracting replacement audio tracks
- preparing custom remuxes

Even if the disc still has to be read sequentially in some cases, avoiding the full video remux/write path should? make these workflows significantly faster.

Have a nice day

[dcoke22]

The data on a DVD or blu-ray is multiplexed together. This means that for any given title on a disc multiple separate data streams are interleaved together into a single stream. On a DVD or blu-ray this means the video, every audio track, and every subtitle track are all interleaved together. That stream of bits is put on an optical disc in a big spiral (similar to a vinyl record) so the laser pickup of an optical drive can read it from the spinning disc. Multiple titles are put into the big data spiral on a disc in a linear fashion, one after the other, with their beginning and ending spots indexed so the optical drive can skip to a specific title or a specific chapter in the current title.

The laser pickup in an optical drive only reads a single stream of bits off the optical disc. All the audio, video, and subtitles have to able to be read at the same time or near enough to the same time so the player can show all of that stuff synchronized together as the output. If those things were not multiplexed together, the laser pickup would have to read from different parts of the disc simultaneously, which it can not do.

Since the data is multiplexed together, the only way to access any part of the data is for the optical drive to read the whole multiplexed stream and for MakeMKV demultiplex the stream and save the parts you're interested in into a file. There's no software change that can overcome the limitations of reading a multiplexed stream of data from an optical disc.

[flojo]

... the laser pickup would have to read from different parts of the disc simultaneously, which it can not do.

Buffering. It's up to the player.

Subtitles can be a "sidecar" even on CD and this has been done since the DivX.avi days and there was ways to "pad" a image to force multiple subtitles to the outer disc area for faster reading. In 2026 I don't think a player would have a problem buffering _ALL_ subtitles.