Support multi track video playback

[patrickwasp]

Description:
support for multi-track video playback. This feature is essential for users who work with video files containing multiple video tracks, such as different camera angles, commentary tracks, or alternate scenes.

Use Case:
Multi-track video playback is beneficial for a variety of users, including:

1. Video Editors and Filmmakers: To preview and compare different takes or angles within a single video file.
2. Educators and Trainers: To provide multiple perspectives or explanations in one video file.
3. Media Enthusiasts: To enjoy movies or shows with alternate scenes or director's commentary without needing separate files.

Proposed Implementation:

• UI Integration: Add a menu item under the "Video" menu to switch between available video tracks.
• Hotkeys: Provide customizable hotkeys for quick switching between video tracks.
• Track Information Display: Display the current video track information (such as track name or language) in the playback controls area.
• Playlist Support: Allow seamless switching between video tracks without interrupting playback or requiring the user to reload the video file.

Benefits:

• Enhanced User Experience: Users can easily switch between video tracks without needing to open multiple files or use external software.
• Increased Versatility: Makes IINA a more powerful tool for professionals and enthusiasts working with complex video files.

[low-batt]

Similar to many open source projects IINA is layered on top of other projects. For audio/video playback and subtitle rendering support IINA is using a library from the mpv project. For IINA to be able to support such a feature it would have to be possible to accomplish this using mpv.

Something similar was requested in mpv issue mpv-player/mpv#3854. That issue was closed because mpv can do this, it just requires a good bit of complex configuration.

This came up in IINA issue #3964. That issue contains a screenshot of two videos being played side-by-side in IINA.

Of course what is being requested in this issue is direct convenient support for multi-track playback. Today that would require IINA "hiding" the complex mpv configuration required to achieve this. For example, mpv will not play more than one track in a video file at a time. IINA would have to hide that it is actually opening the file more than once.

[hooke007]

I think OP is talking about cycle vid instead. (It's also Cycle through the available video tracks. in mpv https://mpv.io/manual/master/#keyboard-control)
https://mpv.io/manual/master/#options-vid

[low-batt]

@hooke007 I think you might be right. In that case some of this is already available. Under the Video menu there is a Cycle Video Tracks menu item. With the default IINA key bindings that menu item is bound to ⌃⌘V. So at least two of the requested features are already present.