Add ability to save cover image with options.coverPath

[xidb]

No description provided.

[parshap]

Thanks for the contribution! I'm confused what this is doing exactly though. Is this saving a cover image from e.g., a .mp3 file to a separate file? Could you add some usage documentation to the readme?

[xidb]

Yeah, it's doing exactly what you described =)
I updated readme.
And also i fixed and issue i had, when multiline data like lyrics are not properly saved to output.
parseLine function assumes that line has key in format "key=data", but those lyrics lines do not have it.
So i edited it, so if line does not have key, than data should be appended to last line that has key.

That's how multi-line field looks in ffmpeg output in console:

With issue, object key created for each line of lyrics:

Issue fixed, all lyrics lines are stored in lyrics key:

[xidb]

Forgot to set -codec -copy parameter for output cover image, so it can be saved without re-encoding. I will make commit later.

[parshap]

This looks great! Thanks for the docs and the multi-line fix. I'm happy to merge this once you're done.

[xidb]

Hey!
Sorry for a long delay. I couldn't found a way to get -codec copy working with images properly... you need to know output format to provide a correct extension, and ffmpeg does not have things like mimetype.
So i think i'm done there, i hope it's ok in that state =)

By the way, You probably have also done ffmetadata for some project where you need it and maybe you will find interesting, i have some thoughts on music metadata libs for node.

I needed a lib, which could read all meta tags from audio files, even custom, and images and write certain tags like lyrics. I found your lib first and started with it. And i started this pull request, because reading images was not supported, and because reading other fields is fine.
Then i found out, that ffmetadata removes uncommon metadata and images from files on writing lyrics. I couldn't fix it, and it was not acceptable to me. Also when you reading tags for thousands of audio files in cycle it starts leaking, a lot of orphan ffmpeg processes start to appear, and then my app just crashes. It's fine for 1000 files, and maybe 10000, but 50000 is too much.
You surely did a great job on your lib, don't think i'm just criticizing, i just have an idea for my app, that need something else.
So i started digging deeper...

I found https://github.com/vankasteelj/mediainfo-wrapper. It reads all the same tags as ffmetadata, but also reads images in base64, and also size of static binary for Mediainfo is a lot smaller, around 7Mb, because it don't need all these crazy video converting features. So i think for reading tags mediainfo-wrapper is superior. But it cannot write anything.

Finally i found node-taglib2 (https://github.com/voltraco/node-taglib2). It's a node native binding to C++ library taglib2. Unfortunately, in it's master state it cannot read or write any custom tags (like lyrics). Reading and writing was done implicitly for each field in a code, and only common tags like artist were supported. On the other hand it works fine with reading-writing images.
So i also came up with pull request... I made node-taglib2's implicit custom tags property reading into dynamic, and now it can read anything like ffmetadata or mediainfo-wrapper. I also added support for writing lyrics, which i needed the most in the first place. It could be done with other custom tags, it can be even done dynamically based on input data, but i stopped on lyrics =) ...and probably my C++ code is far from perfect, because i haven't written a line in C++ before, haha. But i plan to do dynamic tags writing later, for now it's working flawlessly for my needs.
It has one downside - you need to build it, but it kinda easier for my cross-platform app than managing 3 separate static bin files of ffmpeg.
So i think now node-taglib2 on my latest branch (i haven't got any feedback on PR) is an ultimate metadata library for node. =)

If something of it helps, i'd be glad, maybe some of my findings can spare some time for anyone.

[parshap]

Thanks @xidb!

Your comments make a lot of sense. Yes, I created node-ffmetadata for a music organizer app. I remember coming across node-taglib and finding it promising, but incomplete. Eventually I too ended up on a taglib-based solution, going through the Python bindings via a child process call instead. Pretty roundabout, but it worked at the time.

I would be happy to add your findings to the readme so users can find the best tool for their needs. Edit: Done.