Implemented additional template variables for ffmpeg video splitter

[wjs018]

Implemented the suggested template variables per #231. These new template variables are only possible for ffmpeg as mkvmerge does not support changing file output names in the same way and it is not planned for the future either (per this issue).

One quirk I found while testing this out is that a template variable cannot have an underscore after it. For example, using split-video -f '$VIDEO_NAME_$SCENE_NUMBER' will only replace the $SCENE_NUMBER variable and will not substitute the $VIDEO_NAME variable. However, if you run split-video -f '$VIDEO_NAME-$SCENE_NUMBER' then they both substitute just fine. I am not sure if this is a bug with python's safe_substitute function, but thought it was worth mentioning.

One final issue I ran into is that if the output filename has a : (colon) character in it, then ffmpeg crashes and will not proceed (relevant stack exchange). So, for the timecodes in filenames I replace the colons with semicolons.

I have not touched documentation for this yet, but can do so if this is to be merged.

For completeness sake, here are the new variables that are implemented:

• $START_TIME
• $END_TIME
• $START_FRAME
• $END_FRAME

The discussion in #231 also mentioned $FRAME_NUMBER for the save-images command, but it seems that one has been done already (back in February)

[Breakthrough]

Looks good to me. Here's a quick checklist I think we should use going forwards:

• Target for next release branch (v0.6.1 in this case, please rebase the PR)
• Ensure code has unit tests (I think this is clear enough to not need them or can be added in future)
• Update the documentation if required

I was hoping anyone could retarget it but I think the author has to. I'll see if there's any kind of Git hooks that can automate this. I'm hoping to keep main/master always at the latest stable release is why, but in the long term maybe we should instead use a branch named "stable" for that purpose.

I also noticed a few of the workflows aren't running on PRs (Windows builds + code formatting checks) so I have some TODOs there as well.

Edit: I also want to see if you're able to merge this once it's approved now that you should have the correct permissions.

[Breakthrough]

Forgot to mention, re:

One quirk I found while testing this out is that a template variable cannot have an underscore after it. For example, using split-video -f '$VIDEO_NAME_$SCENE_NUMBER' will only replace the $SCENE_NUMBER variable and will not substitute the $VIDEO_NAME variable. However, if you run split-video -f '$VIDEO_NAME-$SCENE_NUMBER' then they both substitute just fine. I am not sure if this is a bug with python's safe_substitute function, but thought it was worth mentioning.

Nice find, that's very interesting indeed. I wonder if that could be addressed in the future with #239 if we use a style that includes a suffix as well as a prefix.

[lgtm-com]

This pull request introduces 1 alert when merging e48fc24 into de30d9b - view on LGTM.com

new alerts:

• 1 for Unused import

[wjs018]

Merged v0.6.1 branch from upstream and rebased the PR to compare against the v0.6.1 branch.

Still remaining is to update docs. Happy to take care of it in the next couple days.

[Breakthrough]

Approved once lint issues fixed.

[camjac251]

Would it be possible to add this to the custom ffmpeg settings -a option as well? I have been trying to figure out how to write the starting timecode for files with ffmpeg without -timecode after the encoder but haven't been able to. It would be perfect if it could grab the -ss and set that as the starting timecode but I don't think ffmpeg has such a function, even with -copytb 0

[Breakthrough]

@camjac251 absolutely, that's a very good idea. Can you file a feature request for that so we can track the work? Thanks.