Subtitle formats

[winscripter]

I'd like to add subtitle reading/writing support to SharpMP4.

I've began by creating a blank library named SharpSubtitles, to align with naming conventions of other projects. Let me know if this needs to be renamed.

In order to begin adding subtitle formats, I'd need to ask a few questions.

• Which subtitle formats would you like me to implement? I've heard MP4s typically reference SRT, VTT or SSA formats, but if you'd like a broader subtitle support, e.g. TTML, I can implement those too.
• Would you like async support? For instance, await subtitle.WriteAsync()
• Should I group formats into namespaces? For instance, SRT subtitles live under the SharpSubtitles.Srt namespace.

I would like to note that I'm not really experienced with MP4 boxes so I'm not really sure how would I add the subtitle track, but I will implement the formats themselves which acts as a nice infrastructure.

I've made sure to start with subtitles first since these are generally easier to implement and debug for me.

[jimm98y]

The idea was to implement the same feature set as in https://github.com/jimm98y/SharpMp4Parser/blob/8321ff89b9fa246962afb80289b8c8213c0ea31a/src/SharpMp4Parser/Muxer/Tracks/TextTrackImpl.cs#L84, https://github.com/jimm98y/SharpMp4Parser/blob/8321ff89b9fa246962afb80289b8c8213c0ea31a/src/SharpMp4Parser/IsoParser/Boxes/ISO14496/Part30/WebVTTSampleEntry.cs#L8 and https://github.com/jimm98y/SharpMp4Parser/blob/8321ff89b9fa246962afb80289b8c8213c0ea31a/src/SharpMp4Parser/IsoParser/Boxes/ISO14496/Part30/XMLSubtitleSampleEntry.cs#L8 in order to close the gaps in between SharpMp4 and SharpMp4Parser.

[winscripter]

@jimm98y Apologies for the delayed response, should I implement the specified tracks/sample entries or should I also write implementations for parsing these subtitles? The names WebVTTSampleEntry and XMLSubtitleSampleEntry and TextTrackImpl suggest WebVTT and TTML functionality.