Subtitle validation with mediainfo is problematic

[philstopford]

From what I can see in the code, subtitles that are not recognized as such by mediainfo are rejected. This affects 'ass' subtitle files, which mediainfo doesn't seem to return text count for. Using the command line mediainfo against 'srt' files, the text is reported. For valid 'ass' files, there is no usable return from mediainfo.

In cine-encoder, this means that while the file requester allows for 'ass' files to be selected, they are rejected as invalid by the tool.

[philstopford]

As an addition to this, it's not possible to query picture subtitles for their dimensions using mediainfo; this makes it difficult to detect situations where picture subtitle streams are differently dimensions to the video stream. Ideally, it would be possible to get the subtitle dimensions and then request upsizing/downsizing as needed to fit the output target dimensions.

I'm going to take a look and see if there's a way to manage this generically.