Modernize the tool

[vibhoothi]

This is small refactoring and improvement work I did a few months back, I guess it will be useful for R&D,

Things changed

• Use sha1sum instead of shasum
• Using master instead of old hashed version
• Introduce AV1 encoder and decoder
  • rav1e
  • dav1d

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[pbos]

Hi, added some feedback re using master directly. Could you split this into three or four pull requests as they seem independent to me?

• Updating the current revision (and removing the expired flag), but to a specific recent hash and not "master"?

• Optional separate: Add a --revision flag to setup.sh to pull down a different version than the pinned hash.

• Using sha1sum instead of shasum
• Adding the AV1 encoder/decoder pair.

[pbos]

Hi, the previous tagged commit is intentional, that way two checkouts get the same version of the library they're comparing. Unfortunately that hash is ancient since I stopped working on this.

If you want to you can update the hash to the current master (so that you can remove the spatial-svc flag below). You can also add a --revision command-line flag so that you could run ./setup.sh --revision=master.