Provide pure Dart support in case of a platform is not supported

[bdlukaa]

Imagine we try to run this project in the web, iOS or macOS. Likely, a Not Supported error will be thrown.

With a pure dart implementation of this, we could make this work for every platform. I am not saying to remove the native implementation, since they're faster than Dart, I'm saying to support all the platforms, regardless of how fast it is.

This could be done through ffi and add a pure dart implementation for the web, or just don't provide web support (I don't see how web apps would be manipulating media files, and if they do, that'd be uneffectively).

great project btw :)

[alexmercerind]

There are actually reasons for this to be not supported:

• On Android, we're using MediaMetadataRetriever, since its an Android API we cannot use it in just Dart.
• One of the goals of this library is to not run on UI thread, its impossible with FFI unless one wants to hack around with NativePorts (and I'm tired with that).
• libmediainfo as used on Windows or Linux will require compilation of additional shared library regardless & Dart packages don't offer some "setup script" like Python for example. (Please see most packages which use FFI just lookup for functions inside core O.S. shared libararies (which have a defined path in every OS installation), and not a custom compiled shared library like this project e.g. win32, desktop_notifications etc.)
• For supporting, iOS & macOS, I will have to compile different shared library (for different OS & even architecture) thus, we cannot "we could make this work for every platform".
• With that being said, Windows itself offers an internal API for extracting metadata, but its not as powerful as this.

[alexmercerind]

For web, few people have ported libmediainfo to WASM, but I don't see a reason why would one force users to download 6 MB shared library, when they can just send metadata as JSON without having to parse the file.

[bdlukaa]

As I said, ffi is not the only way around this, only a possibility.

We could have a pure dart implementation, regardless of how fast it is, to support all the platforms.

Me, as a developer, get really frustrated when a plugin doesn't support the platform I'm targeting

[alexmercerind]

As I said, ffi is not the only way around this, only a possibility.

That's what I'd assume from a "pure Dart" title, and if you want to write entire parsing & reading in Dart, it will be really really slow (atleast 10 times). It will take years to come up with something comparable to existing MediaMetadataRetriever or LibMediaInfo. It will require extensive studying & implementation for supporting each codec/container and their tag specifications. It's no easy task. You'll end up creating your own TagLib in Dart, but a lot lot slower. I initially used an id3 reading project from pub.dev & my app used to parse music in ~20 seconds, but after this barely 4 seconds.

Supporting just particular tagging system e.g. ID3V2 etc. is not goal since I want to deal with all kind of formats.