diff options
Diffstat (limited to '2020')
| -rw-r--r-- | 2020/organizers-notebook.org | 166 |
1 files changed, 125 insertions, 41 deletions
diff --git a/2020/organizers-notebook.org b/2020/organizers-notebook.org index 84ff7f36..cfbbf357 100644 --- a/2020/organizers-notebook.org +++ b/2020/organizers-notebook.org @@ -59,9 +59,13 @@ O1 - main organizer, O2 - secondary organizer or volunteer **** Tech issues - If can't be easily resolved, play pre-recorded talk early and try again later (or follow up) - Stream a technical issues slide to the end point -* Timing -| 00 | Opening remarks | 13:09 | 20:01 | +* Splitting up the stream recording into individual files + +** Timing + +** Day 1 +| 00 | Opening remarks | 13:04 | 20:08 | | 02 | An Emacs Developer Story: From User to Package Maintainer | 27:24 | 51:39 | | 03 | Q&A Idea to Novel Superstructure: Emacs for Writing | 1:00:10 | 1:09:21 | | 05 | Q&A Bard Bivou(m)acs - Building a bandcamp-like page for an album of music | 1:41:30 | 1:55:12 | @@ -69,7 +73,7 @@ O1 - main organizer, O2 - secondary organizer or volunteer | 07 | Q&A Beyond Vim and Emacs: A Scalable UI Paradigm | 2:32:02 | 2:36:34 | | 08 | Building reproducible Emacs | 2:38:03 | 2:55:21 | | 09 | Q&A Orgmode - your life in plain text | 4:22:00 | 4:27:48 | -| 12 | One Big-ass Org File or multiple tiny ones? Finally, the End of the debate! | 4:55:23 | 5:11:37 | +| 12 | One Big-ass Org File or multiple tiny ones? Finally, the End of the debate! | 4:55:23 | 5:11:38 | | 13 | Experience Report: Steps to "Emacs Hyper Notebooks" | 5:13:07 | 5:25:11 | | 15 | Moving from Jekyll to OrgMode, an experience report | 5:47:45 | 6:04:16 | | 16 | Org-roam: Presentation, Demonstration, and What's on the Horizon | 6:06:05 | 6:27:55 | @@ -79,41 +83,121 @@ O1 - main organizer, O2 - secondary organizer or volunteer | 20 | OMG Macros | 7:28:00 | 7:50:36 | | 40 | Closing remarks part 2 | 7:51:48 | 8:04:25 | -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 13:09 -to 20:08 -c:a copy -c:v copy emacsconf-2020--00-opening-remarks.webm -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 27:24 -to 51:39 -c:a copy -c:v copy emacsconf-2020--02-an-emacs-developer-story-from-user-to-package-maintainer--leo-vivier.webm -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 1:00:10 -to 1:09:22 -c:a copy -c:v copy emacsconf-2020--03-questions-idea-to-novel-superstructure-emacs-for-writing--bala-ramadurai.webm -ffmpeg -y -i 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emacsconf-2020--18-org-roam-technical-presentation--leo-vivier.webm -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 7:24:01 -to 7:27:24 -c:a copy -c:v copy emacsconf-2020--40-closing-remarks-part-1.webm -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 7:28:00 -to 7:50:37 -c:a copy -c:v copy emacsconf-2020--20-omg-macros--corwin-brust.webm -ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 7:51:48 -to 8:04:26 -c:a copy -c:v copy emacsconf-2020--40-closing-remarks-part-2.webm - - -** Low res - -ffmpeg -y -i emacsconf-2020--00-opening-remarks.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--00-opening-remarks--480p.webm -ffmpeg -y -i emacsconf-2020--02-an-emacs-developer-story-from-user-to-package-maintainer--leo-vivier.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--02-an-emacs-developer-story-from-user-to-package-maintainer--leo-vivier--480p.webm -ffmpeg -y -i 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-max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--17-org-mode-and-org-roam-for-scholars-and-researchers--noorah-alhasan--480p.webm -ffmpeg -y -i emacsconf-2020--18-org-roam-technical-presentation--leo-vivier.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--18-org-roam-technical-presentation--leo-vivier--480p.webm -ffmpeg -y -i emacsconf-2020--40-closing-remarks-part-1.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--40-closing-remarks-part-1--480p.webm -ffmpeg -y -i emacsconf-2020--20-omg-macros--corwin-brust.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--20-omg-macros--corwin-brust--480p.webm -ffmpeg -y -i emacsconf-2020--40-closing-remarks-part-2.webm -max_muxing_queue_size 1024 -vf scale=854:480 -c:v libvpx -c:a copy emacsconf-2020--40-closing-remarks-part-2--480p.webm +** Commands used for splitting + +#+begin_src sh :eval no 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emacsconf-2020--12-one-big-ass-org-file-or-multiple-tiny-ones-finally-the-end-of-the-debate--leo-vivier.webm +ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 5:47:44 -to 6:04:17 -c:a copy -c:v copy emacsconf-2020--15-moving-from-jekyll-to-orgmode-an-experience-report--adolfo-villafiorita.webm +ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 6:06:00 -to 6:27:56 -c:a copy -c:v copy emacsconf-2020--16-org-roam-presentation-demonstration-and-whats-on-the-horizon--leo-vivier.webm +ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 7:24:00 -to 7:27:09.50 -c:a copy -c:v copy emacsconf-2020--40-closing-remarks-part-1.webm +ffmpeg -y -i main.webm-2020-11-28--08-48.webm -ss 7:28:00 -to 7:50:50 -c:a copy -c:v copy emacsconf-2020--20-omg-macros--corwin-brust.webm + +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 15:40 -to 27:27 -c:a copy -c:v copy emacsconf-2020--41-opening-remarks.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 34:48 -to 1:03:54.75 -c:a copy -c:v copy emacsconf-2020--22-powering-up-special-blocks--musa-al-hassy.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 1:30:40 -to 1:49:18 -c:a copy -c:v copy emacsconf-2020--23-incremental-parsing-with-emacs-tree-sitter--questions--tuan-anh-nguyen.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 4:33:04 -to 4:37:30 -c:a copy -c:v copy emacsconf-2020--26-emacs-as-a-highschooler-how-it-changed-my-life--questions--pierce-wang.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 4:50:00 -to 5:59:30 -c:a copy -c:v copy emacsconf-2020--28-welcome-to-the-dungeon--erik-elmshauser-corwin-brust.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 6:08:20 -to 6:12:42.40 -c:a copy -c:v copy emacsconf-2020--30-a-tour-of-vterm--questions--gabriele-bozzola-sbozzolo.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 6:25:18 -to 6:31:04.90 -c:a copy -c:v copy emacsconf-2020--31-lakota-language-and-emacs--questions--grant-shangreaux.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 6:58:20 -to 7:20:38 -c:a copy -c:v copy emacsconf-2020--33-maxima-a-computer-algebra-system-in-emacs--fermin.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 6:58:20 -to 7:20:38 -c:a copy -c:v copy emacsconf-2020--33-maxima-a-computer-algebra-system-in-emacs--fermin.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 7:55:44 -to 8:02:02 -c:a copy -c:v copy emacsconf-2020--35-waveing-at-repetitive-repetitive-repetitive-music-zmusic--questions--zachary-kanfer.webm +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 8:03:32 -to 8:40:01.10 -c:a copy -c:v copy emacsconf-2020--42-closing-remarks.webm +#+end_src + +Run this code before a copy of the ffmpeg scripts (adjusting the value of adjust as needed) and it will show only the lines that need tweaking. + +#+begin_src emacs-lisp :eval no + (save-excursion + (while (re-search-forward "^ffmpeg.*?-ss +\\([^ ]++?\\) +.*$" nil t) + (let* ((adjust 4) + (from (save-match-data + (let ((s (match-string 1)) num) + (if (string-match "\\(\\([0-9]+\\):\\)?\\([0-9]+\\):\\([0-9]+\\)\\(.[0-9]+\\)?" s) + (progn + (setq num + (+ (* 3600 (string-to-number (or (match-string 2 s) "0"))) + (* 60 (string-to-number (or (match-string 3 s) "0"))) + (string-to-number (or (match-string 4 s) "0")) + (string-to-number (concat "0" (or (match-string 5 s) ""))))) + (if (> (% num adjust) 0) + (number-to-string (- num (% num adjust))) + nil)) + s))))) + (if from + (replace-match from nil nil nil 1) + (replace-match ""))))) +#+end_src + +ffmpeg -y -i main.webm-2020-11-29--08-44.webm -ss 23116 -to 6:31:04.90 -c:a copy -c:v copy emacsconf-2020--31-lakota-language-and-emacs--questions--grant-shangreaux.webm + +Thanks to SirVolta and bandali for figuring out keyframe issue! +*** Additional notes +I've decided to use a etherpad document for this to make it possible for everyone to contribute and fix mistakes. Hope that's ok for everybody interested. +And hopefully I won't destroy too much by accidentally hitting Emacs keys :') + +Feel free to edit at will. The goal of this document is to learn as much as possible about video manipulation +using ffmpeg. + + +**** video compression: keyframes and deltaframes + https://blog.video.ibm.com/streaming-video-tips/keyframes-interframe-video-compression/#keyframe + The problem is actually really simple. Most video contains a lot of non changing background images. It would be wasteful to re-encode all that every single frame. This is solved by only sometimes encoding the entire frame (keyframe, also called interframe or i-frame) and use the difference between the video in that frame and the current frame most of the time (deltaframe). The exact ratio between keyframes and deltaframes is a configuration option of the encoder. But this means that if you grab just a single frame, chances are high that it is a deltaframe and you would need at least one more keyframe or, depending on the codec, even all of the frames before, after or in between to restore the original frame content. This is also why going frame by frame backwards in MPV is so slow, and VLC doesn't even support it. It has to go all the way backwards to the last keyframe and reconstruct from there. + + This means that when copying data, you can only start and stop on keyframes as deltaframes need the data before and possibly after it to work. + + The VP8 codec used appears to only look backwards to a previous keyframe. + This explains why all endings were perfect. + + To be reliable with all codecs, I consider the data after keyframes as important as the data before. + +**** Possible solution + I'm thinking about splitting the rendering process in three pieces: + 1. cut the time before the first keyframe and after the last keyframe using re-encoding + 2. from that point (so between the first and last keyframe) cut using copy codec + 3. merge the three + This way there is the least possible amount of re-encoding done while still having frame perfect timing. + It would mean figuring out a way to coax ffmpeg into splitting exactly on iframes and knowing where this is. + + I think it's okay to cut to the keyframe boundary before the start timestamp. Up to three extra seconds of content never hurt anyone. =) + + I'm currently testing a proof-of-concept script to do exactly this. + + Command to extract all keyframe times: + AV_LOG_FORCE_NOCOLOR=1 ffmpeg -i input -vf select='eq(pict_type\,PICT_TYPE_I)' -f null NUL -loglevel debug 2>&1 | grep -F 'select_out:0' | awk '{print $4 " " $6}' + It should be a lot more efficient (or more like less inefficient) using start and end times. + + Using this data, it should be possible to glue everything together in a script. Although it is going to be annoying dealing with time in seconds and HH:MM:SS.ms format. time<->string conversions. Yaay... + Or just go with seconds everywhere. Human readable formats are nice but kinda pointless now you can't edit them without causing keyframe issues. + +**** resources + (all links work with LibreJS enabled) + https://blog.video.ibm.com/streaming-video-tips/keyframes-interframe-video-compression/ + https://blog.streamspot.com/blog/compression-codecs-keyframes-and-the-basics-of-stream-quality + https://blog.superuser.com/2012/02/24/ffmpeg-the-ultimate-video-and-audio-manipulation-tool/ + https://superuser.com/questions/138331/using-ffmpeg-to-cut-up-video + http://blog.webmproject.org/2010/05/inside-webm-technology-vp8-alternate.html + + + + + + |