MP4 support for HTTP push.

[j0sh]

What does this pull request do? Explain your changes. (required)

This implements most of #1418 . The exception is that it does not implement output configuration via webhook. The output can be set to MP4 via the HTTP push file extension. This can be quickly tested on the broadcaster via:

ffmpeg -re -i input -c:a copy -c:v copy -f hls -hls_segment_filename "http://localhost:8935/live/mp4/%d.mp4" -

and the results inspected via curl the resulting playlist(s) at http:localhost:8935/live/mp4.m3u8 . ffplay of individual segments will work as well.

Specific updates (required)

• server: Take MP4s as input for HTTP push …
  Most of the changes are in the following areas:

  • Adds a format -> extension lookup function
  • Adds a extension -> format inverse lookup function
  • Adds a format -> mime type lookup function
  • Protocol Buffers changes, and conversions to/from VideoProfile
  • Slotting in the lookups and error handling where appropriate
  • Lots and lots of tests.

The extensive testing and strict error handling is both to codify
intended behavior and to ensure misuse resistance to further changes. 949a063

• The file extension of temp files mostly doesn't matter for us anymore, so renamed the temp files we generate in order to avoid future confusion about the file type. MP4 support for HTTP push. #1429

• Added documentation 3959817

• Updated LPMS to Add MP4 format to VideoProfile. lpms#176 (needs to be merged prior to this ; any changes there will be updated here in go.mod)

How did you test each of these updates (required)

• Unit testing. Tests are the bulk of the additions here.
• Manual testing / playback with the following simple scenarios (B -> OT, local storage on both, played back via ffplay):
  • RTMP
  • ffmpeg HLS push (with mpegts)
  • ffmpeg HLS push (with mp4, as described above)
  • Standalone T with MP4 and mpegts
• Visual inspection of multipart hexdump (but did not attempt to parse + extract)
• Checked with GCS to verify file extension and content type

Does this pull request close any open issues?

Fixes #1418

Checklist:

• README and other documentation updated
• Node runs in OSX and devenv
• All tests in ./test.sh pass

[darkdarkdragon]

mp4 muxer/demuxer should be added to install_ffmpeg.sh

[j0sh]

@darkdarkdragon Ah yes.

Added a unit test that will iterate through all our formats, to catch this type of oversight in the future: 8abe8ab . That failed exactly as expected.

Added mp4 to the muxer/demuxer and tests pass now. 06b8783

[j0sh]

Rebased to fix up a merge conflict. Git SHAs have changed but commit structure is otherwise the same in case someone was in the middle of reviewing things (eg, still contains the pending fixups from #1429 (comment))

[j0sh]

2c075d9 Updated to incorporate latest LPMS, including the libavfilter performance fix and MP4 support among other things:

livepeer/lpms#176
livepeer/lpms#177
livepeer/lpms#178
livepeer/lpms#179

[darkdarkdragon]

LGTM 🚢

[yondonfu]

LGTM! Left one note about a comment about a possible bug in existing code. I'll leave it up to you whether to address it in this PR or separately (I noted that I'm fine with doing it separately).