Fix issue where download video is without sound.

[weyhan]

This year, Apple has split the audio track into a separate stream, so the audio track has to be downloaded separately.

Unfortunately, with this change, I've not figured how to make avconvert to do the same merging of the audio and video track. So, that part is taken out from the script until the time I've found how to get avconvert to work the same as ffmpeg.

[ohoachuck]

Thanks !

[weyhan]

You're welcome.

[ohoachuck]

Have you seen there is a crash when using latest swift version (I believe). It's seems to crash when xcode-select --version give 2363.
The weird part is that this work on Playground but not on terminal. I haven'y yet figured out why.

O.

[weyhan]

I've just tested on the latest Xcode and it looks like the swift compiler crash. Xcode 10.1 I was working on has no issue though. Because the swift compiler crashed, I can't figure out what is the root cause. :|

[weyhan]

As far as I can tell, it crashes when calling the download functions in DownloadSessionManager. It may be due to code not compatible with the latest Swift but it's also a bug in the compiler that causes it to crash. I think the best way to deal with it is to make a note in the readme that Xcode 10.2.1 is currently not supported?

[ohoachuck]

Hum... I'm not sure.
I have the latest Xcode - Version 10.2.1 (10E1001) and it's works for me.
And for some unknown reason, my version of xcode-select doesn't seems to be the same as others.
Mine is 2354. Some others have 2363 (for the same Xcode version - Version 10.2.1).

[weyhan]

That is really strange. I’m not at my Mac now so I can’t verify my version. Will check later to confirm.

_{Sent with GitHawk}

[ohoachuck]

Better to move the discussion to the related issue here: #87
I found out that while I had the latest Xcode version my mac os wasn't the latest and I'm confuses about who bring update to swift ...
Since I have made the updated on mac os this afternoon: I have now the issue.
/usr/bin/swift probably used by the script is updated. So it's more probably a swift 5 issue.
I wonder if Xcode the /usr/bin/swift ...