add support for inputOptions and videoFilters in transcode plugin

[TheoLeCalvar]

Description

This PR adds support for inputOptions and videoFilters in transcode plugins.
Transcode plugins can be used to add support for new encoders.
However, some require inputOptions and thus cannot be used with current transcode plugin API.

For instance, vaapi hardware accelerated encoders require these input options -hwaccel vaapi -hwaccel_output_format vaapi -vaapi_device /dev/dri/renderD128

Related issues

Closes #3846

Has this been tested?

• 👍 yes, I added tests to the test suite
• 👍 yes, light tests as follows are enough
• 💭 no, because this PR is a draft and still needs work
• 🙅 no, because they aren't needed
• 🙋 no, because I need help

[Chocobozzz]

Please could you add tests in https://github.com/Chocobozzz/PeerTube/blob/develop/server/tests/plugins/plugin-transcoding.ts using https://github.com/Chocobozzz/PeerTube/blob/develop/server/tests/fixtures/peertube-plugin-test-transcoding-one/main.js?

See https://docs.joinpeertube.org/contribute-getting-started?id=unit-tests for the documentation

[TheoLeCalvar]

I'm wondering if this PR should also include a mechanism to mitigate #3919 .
Plugins could provide the name of the filter to use for scaling, with scale as default value.

With this info we could use the correct filter name here

PeerTube/server/helpers/ffmpeg-utils.ts

Line 239 in b70025b

filter: 'scale',

And we could replace the call to size() here

PeerTube/server/helpers/ffmpeg-utils.ts

Line 400 in b70025b

command = command.size(size)

by a manually written scale filter that would use the filter name provided by the transcode-plugin.

[Chocobozzz]

Okay thanks, so to summarize if we do the following things, does it fix all the issues?

• Add ability for plugins to register a custom scale function that should return { filterName: string, value: string }. The default in PeerTube would be something like { filterName: 'scale', value: 'w=trunc(oh*a/2)*2:h=360' } or { filterName: 'scale', value: 'w=-2:h=360' } (not sure what is the best)
• Don't use .size() but a custom .outputOption in PeerTube core but the registered scale function (both for VOD and Live videos)
• Don't provide .videoFilters param for plugins

[TheoLeCalvar]

That looks good for me, it enough for my use case (adding hardware transcode).

Add ability for plugins to register a custom scale function that should return { filterName: string, value: string }. The default in PeerTube would be something like { filterName: 'scale', value: 'w=trunc(oh*a/2)*2:h=360' } or { filterName: 'scale', value: 'w=-2:h=360' } (not sure what is the best)

I did a quick search in ffmpeg documentation and it looks like all scale filters support the w=-2:h=XX syntax.
I'm not sure why fluent-ffmpeg uses trunc because -2 does the same.
The ffmpeg documentation explains it here https://trac.ffmpeg.org/wiki/Scaling

So I think it is not strictly necessary for plugins to provide the arguments to the filter since they are always the same in our use case.

Don't provide .videoFilters param for plugins

👍

[Chocobozzz]

Okay thanks for the feedback. I'll update this PR.

[TheoLeCalvar]

Ok, thanks.

[Chocobozzz]

I updated the PR accordingly. @TheoLeCalvar Could you review & test please?

[TheoLeCalvar]

Except these small problems it looks good to me.
Tests look good.
I also ported my plugin to this version and it works great.

[Chocobozzz]

Thanks!