remove packages with error on apt-get update

I am very new to linux. I tried to install sopcast on it but it failed and then I installed it on wine. But now every time i run the sudo apt-get update it is taking very long trying to install(?) the sopcast package and fails every time. How can i completely stop ubuntu from trying to install this package?

Here is whats going on in the terminal when i run sudo apt-get update.
A lot of Ign: lines, like

Ign:24 http://ppa.launchpad.net/ferramroberto/sopcast/ubuntu xenial/main i386 Packages

and it ends with

W: The repository 'http//ppa.launchpad.net/ferramroberto/sopcast/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: http//ppa.launchpad.net/lyc256/sopcast-player/ubuntu/dists/vivid/Release.gpg: Signature by key 732241F9E505AA9CBC15CC719A2E47237733638E uses weak digest algorithm (SHA1)
E: Failed to fetch http//ppa.launchpad.net/ferramroberto/sopcast/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.

I am not having any big issues with this, its just that every time i run the update command i need to wait for 4-5 minutes. Is there any file I need to edit to stop it from trying to install the sopcast package?
I tried sudo apt-get --purge remove sopcast* but this did not change anything

Don't confuse update with upgrade in Ubuntu... they sound the same but they're very different. sudo apt-get update does not "install" anything, ever. It simply updates your computer with the source information so that when you sudo apt-get install you will upgrade or install the latest version (assuming you do sudo apt-get install right after doing sudo apt-get update).

You might want the PPA again later on (for example if you want to update packages related to sopcast), so just comment out the line rather than removing it in your /etc/apt/sources.list file. It should be near the bottom of the file. You'll need sudo privileges to modify it, so open it in whichever text editor you're most comfortable in.

sudo gedit /etc/apt/sources.list or
sudo nano /etc/apt/sources.list or
sudo vi /etc/apt/sources.list

Edit: I just checked and looks like that site doesn't even have code for xenial (16.04). http://ppa.launchpad.net/ferramroberto/sopcast/ubuntu/dists/ The latest is for quantal (12.10). Given this, it's probably best to remove the line entirely rather than commenting out.