Littera Nova

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A brief post-mortem of technical issues at Solstice - Part 1, Livestream

Word count: 1292 (~8 minutes), Last modified: Tue, 14 Dec 2021 07:42:51 GMT

The setup this year aimed to provide both audience talkback and main output from the mixer (i.e. the sound that was going through the auditorium speakers) to the livestream. The purpose of this was to provide ambiance and a more immersive experience of being in the room to those following along at home or in the childcare room inside the center. To accomplish this, there were two channels provided into the stream - one from an audience mic which sat on the video mixing table, and one from a submixer that received the output of the main mixer that also sat on the video mixing table. Both of these channels fed into an audio interface (one as the L channel and one as the R channel) that then connected to laptop running OBS (the broadcasting software). The purpose of the submixer was to allow the person running the livestream to also adjust the mix to be better for headphones, since I was mixing for the room rather than headphones (differences include balance and how much bass to include). I was not aware that there would be a significant contingent of people listening along at home, as the last solstice that I provided tech for (in 2019) did not have a large number of people listening, and I did not anticipate virus + weather causing a number of people to stay home when they otherwise may have been in-person. I apologize for the sub-par audio experience and I'm taking a number of steps to avoid this next year.

One major echo source at the beginning was due to the audience mic being out of phase with the main mix. Because the audience mic was physically some distance back from the singers, and the planetarium main speakers had some additional response delay, the main mix required some delay to be added to match the audience mic. This was not done to my understanding. The original plan at tech rehearsal was to use a laptop provided by Celestia which I set up some configuration on in OBS for doing phase correction, but there was a last-minute swap to another person and laptop which did not have this correction. At the beginning of the show I was notified by one of the choir members that someone listening along at home in (a platform that I don't have experience with and will investigate options for next year) noticed this echo, so I moved from the audio desk to the video desk, manually turned the audience mic to 0, and ran back to the audio desk before the show started.

This was not sufficient, apparently - I hypothesize but do not have confirmation that the laptop's mic was also being mixed into the OBS stream as well. Some time mid-show I believe that this was turned off which allowed the audio quality to be better (but with no audience ambient noises).

I don't believe that the video desk utilized the submixer, so I imagine that the bass levels on the stream were much lower than they ought to be - the speaker system in the planetarium is extremely boomy for reasons unknown to me.

Some amount of the distortion was due to the piano gain either being turned up during the show on the device, or being played significantly louder than I expected or was done during rehearsal. A similar issue was on Taylor's wireless headset mic with singing being louder than anticipated during soundcheck.

I intended to push captions to the livestream and indeed wrote a program for doing this. This program was on the laptop that was not used for OBS, however, and so captions were unavailable.

I planned to save all 16 audio channels available for remixing later, but a USB-Ethernet adapter broke right before the show so we couldn't connect the laptop for saving channels to the board.

Some amount of the audio may be recoverable - thanks to gwillen's foresight, a mono recording off the board should exist and I'll hopefully be using the livestream video with this audio as a basis for an edited video (with captions). I'll also fiddle with the L-R recording from OBS, if the livestream runner did not downmix to mono then I might be able to simply offset one channel and fix the echo.

Plans/recommendations for next year

Livestream is available at the YouTube channel.