"...because the geometry of the abyss demands it"
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README.org
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60
README.org
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* time, space, stacking, slicing, scanning, etc
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"Slitscan imaging techniques are used to create static images of time-based phenomena. In traditional film photography, slit scan images are created by exposing film as it slides past a slit-shaped aperture. In the digital realm, thin slices are extracted from a sequence of video frames, and concatenated into a new image."
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[[http://www.flong.com/texts/lists/slit_scan/][An Informal Catalogue of Slit-Scan Video Artworks and Research]] Compiled by Golan Levin.
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#+ATTR_HTML: :style margin-left: auto; margin-right: auto;
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#+name: unfolding
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#+caption: Egbert Mittelstaedt. Unfolding (2002)
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[[http://www.flong.com/storage/images/texts/slit_scan/34_egbert_mittelstaedt_665px.jpg]]
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This particular slitscan provides some slightly configurable scaffolding around ffmpeg (based on a blogpost from [[http://oioiiooixiii.blogspot.com/2017/11/ffmpeg-temporal-slice-stacking-effect.html][oioiiooixiii]]) and is intended for non-realtime rendering at various resolutions. it's neither first, nor last. it's not especially interesting, educational or efficient. just another cloudform in the endless space of possible implementation...
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* installation, configuration, operation, etc
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install (mac)...
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#+BEGIN_SRC shell
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brew install ffmpeg drracket
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git clone https://github.com/zzkt/slitscan.git
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#+END_SRC
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install (debian/ubuntu)...
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#+BEGIN_SRC shell
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sudo apt install ffmpeg racket
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git clone https://github.com/zzkt/slitscan.git
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#+END_SRC
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simple transform...
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#+BEGIN_SRC shell
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racket slitscan.rkt -v -i <input.mp4>
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#+END_SRC
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transform at 1080p and delete working files, with minimal command line noise...
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#+BEGIN_SRC shell
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racket slitscan.rkt --width 1920 --height 1080 --loglevel quiet --cleanup -i <input.mp4>
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#+END_SRC
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options...
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#+BEGIN_SRC shell
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slitscan [ <option> ... ]
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where <option> is one of
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-v, --verbose : various verbose messages
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-l <level>, --loglevel <level> : loglevel for ffmpeg e.g. quiet, error, warning, info, debug
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-c, --cleanup : Clean up temporary/working files
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--horizontal : output a horizontal video only (default: both)
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--vertical : output a vertical video only (default: both)
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--width <pixels> : width of output output video
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--height <pixels> : height of output output video
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-i <video>, --input <video> : input file
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-f <folder>, --folder <folder> : input folder
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--help, -h : Show this help
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#+END_SRC
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* further reading
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- The Fourth Dimension and How to Get There by Rudy Rucker
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- Muybridge's Complete Human and Animal Locomotion, Vol. I
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- Baroness Elsa, by Irene Gammel
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243
slitscan.rkt
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243
slitscan.rkt
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#! /usr/bin/env racket
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#lang racket
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;;; Temporal slice-stacking with FFmpeg (aka slitscan, etc+)
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;;;
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;;; Copyright (C) 2019 FoAM
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;;;
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation, either version 3 of the License, or
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;;; (at your option) any later version.
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;;;
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;;; This program is distributed in the hope that it will be useful,
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;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <https://www.gnu.org/licenses/>.
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;;;
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;;;
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;;; Authors
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;;;
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;;; nik gaffney <nik@fo.am>
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;;;
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;;; Requirements
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;;;
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;;; Racket, ffmpeg and zsh or bash (probably)
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;;;
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;;; Commentary
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;;;
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;;; Mostly scaffolding around ffmpeg, based on a shell script from oioiiooixiii
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;;; http://oioiiooixiii.blogspot.com/2017/11/ffmpeg-temporal-slice-stacking-effect.html
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;;;
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;;; Further details, instructions and digression can be found at
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;;; https://github.com/zzkt/slitscan/
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;;;
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;;; Revision history
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;;;
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;;; - 2017-10-01 - shell script from oioiiooixiii
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;;; - 2019-08-08 - cmprzs, convert, reconstruct
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;;; - 2019-08-10 - racket translation, info
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;; cli options
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(define verbose? (make-parameter #f))
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(define cleanup? (make-parameter #f))
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(define filename (make-parameter "untitled"))
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(define input-folder (make-parameter ""))
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(define loglevel (make-parameter "")) ;; leave unset by default
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;; output options horiz/vert/both
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(define hout-only? (make-parameter #f))
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(define vout-only? (make-parameter #f))
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(define output-width (make-parameter 640))
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(define output-height (make-parameter 360))
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;; parse command line
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(define getopt
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(command-line
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#:program "slitscan"
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#:once-each
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(("-v" "--verbose") "various verbose messages" (verbose? #t))
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(("-l" "--loglevel") level "loglevel for ffmpeg e.g. quiet, error, warning, info, debug" (loglevel level))
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(("-c" "--cleanup") "Clean up temporary/working files" (cleanup? #t))
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(("--horizontal") "output a horizontal video only (default: both)" (hout-only? #t))
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(("--vertical") "output a vertical video only (default: both)" (vout-only? #t))
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(("--width") pixels "width of transform video" (output-width pixels))
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(("--height") pixels "height of tansform video" (output-height pixels))
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(("-i" "--input") video "input file" (filename video))
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(("-f" "--folder") folder "input folder" (input-folder folder))
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#:args () ; rest of the args?
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(printf "slitscanning: ~a\n" (filename))))
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;; emulation of $(...) shell syntax
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(define-syntax zout
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(syntax-rules ()
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((_ cmd) (string-trim (with-output-to-string (lambda () (system cmd)))))))
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;; echoing verbosity
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(define-syntax vecho
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(syntax-rules ()
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((_ str ...) (when (verbose?) (printf str ...)))))
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(cond ((and (verbose?) (string=? "" (loglevel))) (loglevel "info"))
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((and (not (verbose?)) (string=? "" (loglevel))) (loglevel "error")))
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;; variables/various
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(define folder (if (not (string=? "" (input-folder)))
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(input-folder)
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(zout "mktemp -d")))
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(vecho "using folder: ~a\n" folder)
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;(define fffeature "ffprobe -v quiet -select_streams v -of default=noprint_wrappers=1:nokey=1 -show_entries stream=")
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(define fffeature "ffprobe -v error -of default=noprint_wrappers=1:nokey=1 -show_entries format=")
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;; assume most/all codecs/formats/streams have a duration
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(define duration (let ((f (string->number
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(zout (format
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"~aduration \"~a\""
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fffeature (filename))))))
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(if f f 0)))
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(vecho "duration: ~a seconds\n" duration)
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;; determine fps from input file or default to 24
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(define fps (let ((f (string->number
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(zout (format
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"~ar_frame_rate \"~a\""
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fffeature (filename))))))
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(if f f 24)))
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(vecho "fps: ~a\n" fps)
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;; number of frames. estimate for codecs/formats/streams without nb_frames
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(define frames (let ((f (string->number
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(zout (format
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"~anb_frames \"~a\""
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fffeature (filename))))))
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(if f f (ceiling (* duration fps)))))
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(vecho "frames: ~a\n" frames)
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;; output dimensions. change if/as required via opts...
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(define w (output-width))
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(define h (output-height))
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(vecho "transform dimensions: ~ax~a\n" w h)
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;; FFmpeg Filterchains
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(define stemStart "select=gte(n\\,")
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(define stemEnd "),format=yuv444p,split[horz][vert]")
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(define horz (format "[horz]crop=in_w:1:0:n,tile=1x~a[horz]" h))
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(define vert (format "[vert]crop=1:in_h:n:0,tile=~aX1[vert]" w))
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(define merge "[0:v]null[horz];[1:v]null[vert]")
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(define scale (format "scale=~a:~a" w h))
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;; check resume?
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;; rezise video
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(define resized-video (string-append folder "/resized.mkv"))
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(define (resize)
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(define ffmpeg-r1
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(format "ffmpeg -loglevel ~a -i \"~a\" -vf ~a -crf 10 \"~a\" 2>&1 | grep 'frame=' | tr \\n \\r; echo"
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(loglevel) (filename) scale resized-video))
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(vecho "resizing video: ~a\n" resized-video)
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(system ffmpeg-r1))
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;; slice/crop/loop
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(define (slice)
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(for ((i (range frames)))
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(vecho "Frame: ~a of ~a\r" i frames)
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(define ffmpeg-s1
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(format
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"ffmpeg -loglevel ~a -i \"~a\" \
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-filter_complex \"~a~a~a;~a;~a\" \
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-map '[horz]' \
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-vframes 1 ~a/horz_frame~a.png \
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-map '[vert]' \
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-vframes 1 ~a/vert_frame~a.png"
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(loglevel) resized-video
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stemStart i stemEnd horz vert
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folder i
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folder i))
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(system ffmpeg-s1))
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(vecho "\n"))
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;; Join images (optional sharpening, upscale, etc. via 'merge' variable)
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(define (assemble)
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(vecho "Creating output videos\n")
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(define ffmpeg-a0 ;; horizontal & vertical videos (from .sh)
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(format
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"ffmpeg -loglevel ~a \
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-r ~a -i ~a/horz_frame%d.png \
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-r ~a -i ~a/vert_frame%d.png \
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-filter_complex \"~a\" \
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-map '[horz]' \
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-r ~a \
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-crf 10 \
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\"~a_horizontal-smear.mkv\" \
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-map '[vert]' \
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-r ~a \
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-crf 10 \
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\"~a_vertical-smear.mkv\""
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(loglevel)
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fps folder
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fps folder
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merge
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fps (filename)
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fps (filename)))
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(define ffmpeg-a1 ;; horizontal frame stack
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(format
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"ffmpeg -loglevel ~a -r ~a -i ~a/horz_frame%d.png \"~a_horizontal-smear.mkv\""
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(loglevel) fps folder (filename)))
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(define ffmpeg-a2 ;; vertical frame stack
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(format
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"ffmpeg -loglevel ~a -r ~a -i ~a/vert_frame%d.png \"~a_vertical-smear.mkv\""
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(loglevel) fps folder (filename)))
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;; assemble
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(cond ((hout-only?) (system ffmpeg-a1))
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((vout-only?) (system ffmpeg-a2))
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(else (system ffmpeg-a1)
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(system ffmpeg-a2))))
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;; spatial extents (frames -> image) summary
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(define (framecat start offset)
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(define montage-h1
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(format "montage ~a/horz_frame~a.png ~a/horz_frame~a.png ~a/horz_frame~a.png ~a/horz_frame~a.png ~a/horz_frame~a.png -tile x1 -mode concatenate ~a-slitscan-s~a.o~a.jpg"
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folder start
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folder (+ start offset)
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folder (+ start (* offset 2))
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folder (+ start (* offset 3))
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folder (+ start (* offset 4))
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(filename) start offset))
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(system montage-h1))
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(define (image) (framecat 1 (/ frames 5)))
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;; delete working files (or not)
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(define (cleanup)
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(if (cleanup?)
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(begin (system (format "rm -rf ~a" folder))
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(printf "Removed temp files at ~a\n" folder))
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(vecho "leaving working files at ~a\n" folder)))
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;; output in 3 (or 4 (or 5)) steps
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(when (resize) (printf "resized\n"))
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(when (slice) (printf "slicwd\n"))
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(when (assemble) (printf "assembled\n"))
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(when (cleanup) (printf "done\n"))
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;;; FIN
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