add harvesting tips

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+[[!meta title="Harvesting Q&A]]
+[[!meta copyright="Copyright © 2021, 2022 Sacha Chua"]]
+
+During the harvesting phase of the conference, we work on collecting
+the ideas that people shared in the Q&A sessions as well as any talks
+that were not available as pre-recorded videos. It's a great way to
+help speakers get stuff out of their heads and into a form we can all
+learn from. Here's a process for doing so.
+
+# Skim the transcript and the videos to see if anything needs to be removed, and which video to use
+
+BigBlueButton gives us the webcams and audio as one video
+(`--bbb-webcams.webm`) and the screenshare (if any) as another video
+(`--bbb-deskshare.webm`). If the speaker shared their screen, we can
+focus on that instead of their webcam. The following ffmpeg command
+combines the audio from the webcams (which has been previously
+extracted into a separate file, `--bbb-webcams.opus`) with the video
+from the screenshare.
+
+    ffmpeg -i example--bbb-webcams.opus -i example--bbb-deskshare.webm -c copy example--answers.webm
+
+We also want to check if people accidentally shared sensitive
+information on their screen, or if anyone said something that they
+might not have said if they remembered that thethe Q&A videos will be
+shared after the talk. Sometimes there's some time before we get
+around to closing the meeting at the end of the Q&A. Usually, a quick
+read of the transcript will show anything that needs to be trimmed.
+Here's how to stop the recording at a specified time:
+
+    ffmpeg -i input.webm -to hh:mm:ss -c copy output.webm
+
+Cutting out stuff from the middle of a recording is slightly more
+complicated. It might be easier to use a nonlinear video editor such
+as kdenlive to edit the video. If you want to use ffmpeg, using
+filters to select the frames and reencode the video will probably work
+out better than splitting the file into multiple parts and then
+concatenating them without reencoding, as the latter tends to need to
+be split on keyframes. Here's a sample command based on this
+[StackOverflow](https://stackoverflow.com/questions/64866231/remove-a-section-from-the-middle-of-a-video-without-concat) answer that removes the section between 15 seconds and
+45 seconds:
+
+    ffmpeg -i input.webm \
+      -vf  "select='not(between(t,15,45))',  setpts=N/FRAME_RATE/TB" \
+      -af "aselect='not(between(t,15,45))', asetpts=N/SR/TB" \
+      output.webm
+
+Alternatively, you can let us know what parts needs to be trimmed, and
+we can figure that part out.
+
+
+# Add chapter markers
+
+Chapter markers make it easier for people to jump to the part of the
+Q&A that they're interested in. You can see an example in the [Q&A for
+asmblox](https://emacsconf.org/2022/talks/asmblox/). You can make a text file with the hh:mm:ss or mm:ss
+timestamps and the chapter headings.
+
+    00:00 Introduction
+    01:12 Why did you choose an internal state versus many 'state buffers'?
+    02:10 Do you have plans to port shenzhen.io to Emacs?
+    02:29 Did this use WASM?
+    02:59 Why wasm rather than a more traditional Assembly dialect? It wouldn't be harder to implement, right?
+    05:08 Any next projects on your mind?
+    05:52 Does this work with any other paren-based editing packages?
+    06:46 What kind of tool could use this idea?
+    07:56 How did you go about designing the puzzles?
+    08:39 What are your favorite changes in the upcoming Emacs 29?
+    09:07 Are there tools to add more puzzles?
+
+Alternatively, you can edit the VTT file (`--bbb-webcams.vtt`) and add
+NOTE comments with the chapter headings before the subtitles that are
+part of that chapter. If you're using [subed](https://github.com/sachac/subed) to edit subtitles within
+Emacs, you can split the subtitle as needed with `M-.`
+(`subed-split-subtitle`) so that the subtitle starts with the
+question. You don't have to worry about getting the timestamps exact,
+as we can re-align them with `M-x subed-align`. Here's what that NOTE
+comment can look like:
+
+    NOTE Why did you choose an internal state versus many 'state buffers'?
+    
+    00:01:12.600 --> 00:01:16.039
+    Okay. So, the first question is why did you choose an internal state
+
+These can then be extracted with
+`emacsconf-subed-make-chapter-file-based-on-comments` from
+and included in our publishing workflow.
+
+
+# Edit the transcript
+
+If you want to make it even easier for people to learn from the Q&A,
+you can edit the transcript so that it can also be published on the
+wiki page. See [[Captioning tips|captioning]].