Forced Subtitles Track duplication bug?

[Steven Mancera]

Hi there,

Recently I’ve been muxing SRT subtitles on my MP4 content, and stumbled upon an annoying and confusing bug.

Problem

Where I have 2 English subtitles : English & English SDH. On TV app on macOS it just shows that 2 subtitles.
But on QuickLook, QuickTime and Home Sharing on tvOS, it shows 3 subtitles : English, English SDH Forced and English SDH.

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Steps

See what I want to do is :

• put 2 SRTs on a MP4, one that is non SDH, one that is SDH
• set them in appropriate languages.
• Name the subtitle files as their own language. Rename Subtitle Track to English with English set as Language.
• And the Subtitles Auto-select and subtitles turned on the default language when you open the video file.

Here’s what I am doing so far…

• Name the subtitle files as their own language. Rename Subtitle Track to English with English set as Language.
• Check Auxiliary Content, Transcribe… and Describe…, uncheck Main Program Content for SDH English subtitles.
• Meanwhile the non-SDH English subtitles just stays as Main Program.
• For the subtitles to auto selected once upon I open the video file, I select the default Sound Track > Sound Settings > Subtitles > I pick the non-SDH English subtitles. That’s what I assume that settings is for.

Bug Descriptions

• Opening the video file strangely doesn’t even auto-select the English SDH Forced subtitles anyways. It’s not forced.
• It still selects the English one by default.
• macOS’s TV app doesn’t show the English SDH Forced duplicated track.
• But strangely on Home Sharing app on tvOS, it shows it and selecting the English SDH Forced crashes the app.
• On macOS’s QuickTime and QuickLook, selecting it doesn’t show or render any subtitles at all.
• Undoing the options picked Subtitles on Sound Settings, saving the new metadata, and reopening the file on QuickTime or Home Sharing app doesn’t remove the third Forced subtitle either.
• Exporting the subtitles, deleting the Subtitle tracks, saving the metadata again, re-opening the video file to check if the embedded subtitles is now gone, re-adding the two subtitles again, re-doing the metadata and saving, opening it again on QuickTime still shows the same 3 subtitles.

• It’s the same for multi-language subtitles files too, it duplicates too. Interestingly, it only shows on SDH subtitles. As I’ve said, I didn’t set any SDH subtitles as “Forced” as I like non-SDH as the default instead.

  * Removing the SDH options (the Transcribe… and Describe… checkbox) and saving it strangely just now shows :

  • English
  • English
  • English Forced

Did Subler failed to remove the Forced Subtitle metadata or what? For some reasons, is it possible that Subler leaving some leftover metadata for Forced Subtitles that it can’t or forgot to remove, that makes this behavior appear?

Notes

I click these options for subtitles metadata, based on what I assume is right and appropriate. As still right now, there’s no detailed Help article or documentation for what Main Program, Auxiliary Content and other options is on the Subtitles wiki. It would be cool if we’ll have documentations explaining and clarifying what all of these options does, explaining it in detail. Or maybe a crowdsourced, open source Wiki.

So what am I doing wrong here? Is this a bug on metadata writing on Subler, Apple TV or my fault on choosing wrong options based on wrong assumptions on Subtitles metadata options?

Am I right assuming picking Subtitles on the Sound Track, is for the subtitles to automatically show up on that Sound Track or upon file opening?

Sorry for a lengthy posts, but thanks for all the work you put into this.