preset:
    name: Split video on black frames (ffmpeg)
    group: video
    plugin: executor
    props:
        set:
            scenes: { value:"{%uinput}.tmp", escape:true }
        script:
            analyze:
                info: Finding scenes
                exec: "ffmpeg -i {%input} -vf blackframe=amount=90:thresh=64 -f null -"
                parse: { from: 'stderr', regex: '/^frame=[\s]*([0-9]+)\s/', frame:1 }
                extract:
                    # Write everything matching '[Parsed_blackframe' to file
                    - { from: 'stderr', regex: '/^\[Parsed_blackframe/', write:'{%scenes}' }
            split:
                info: Splitting video
                call: scenesplitter
            cleanup:
                info: Cleaning up
                exec: "rm {%scenes}"
        helpers:
            scenesplitter: |
                /*
                * This is what the contents of %scenes look like:
                *
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1312 pblack:100 pts:1313312 t:43.777067 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1313 pblack:99 pts:1314313 t:43.810433 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1314 pblack:99 pts:1315314 t:43.843800 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1315 pblack:99 pts:1316315 t:43.877167 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1316 pblack:99 pts:1317316 t:43.910533 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1317 pblack:99 pts:1318317 t:43.943900 type:P last_keyframe:1290
                * [Parsed_blackframe_0 @ 0x54f7960] frame:1318 pblack:99 pts:1319318 t:43.977267 type:P last_keyframe:1290
                *
                * Pick the split point as the last frame in a block with the highest percentage of black pixels, in this case
                * it would be on the first line as it has pblack=100 for a single frame.
                */

                if (!file_exists({{%scenes}})) {
                    return;
                }

                $frames = file({{%scenes}}, FILE_IGNORE_NEW_LINES);

                $chunks = [];

                // Split into chunks of blackish frames
                $chunk = [];
                $last_frame = 0;
                foreach ($frames as $frame) {
                    if (preg_match('/frame:(\d+) pblack:(\d+) pts:(\d+) t:([\d\.]+) type:(.+) last_keyframe:(\d+)$/', $frame, $info)) {
                        list ($void, $_frame, $_pblack, $_pts, $_t, $_type, $_last_keyframe) = $info;
                        if ($_frame > $last_frame+1) {
                            // Add the chunk if its a new block
                            if (count($chunk)>0) {
                                $chunks[] = $chunk;
                                $chunk = [];
                            }
                        }
                        // Store chunk data
                        $chunk[] = (object)[
                            'frame' => $_frame,
                            'pblack' => $_pblack,
                            'time' => $_t
                        ];
                        $last_frame = $_frame;
                    }
                }
                // Save the last chunk
                if (count($chunk)>0) {
                    $chunks[] = $chunk;
                }

                // Process chunks and find best split points
                $last_time = 0;
                $scenes = [];
                foreach ($chunks as $chunk) {
                    // Find split
                    $best_black = 0; $best_time = 0;
                    foreach ($chunk as $frame) {
                        if ($frame->pblack >= $best_black) {
                            $best_black = $frame->pblack;
                            $best_time = $frame->time;
                        }
                    }
                    $scenes[] = [ $last_time, $best_time ];
                    $last_time = $best_time;
                }

                // Split it up
                $input = {{%input}};
                $output = {{%output}};

                $outdir = dirname($output);
                $outext = pathinfo($output, PATHINFO_EXTENSION);
                $outfile = basename($output, ".{$outext}");

                foreach ($scenes as $_index=>$scene) {
                    list($_start,$_end) = $scene;
                    $_duration = $_end-$_start;
                    $cmdl = sprintf("ffmpeg -ss %s -i '%s' -t %s -codec copy '%s/%s-%d.%s' 2>/dev/null", 
                        $_start, 
                        $input, 
                        $_duration, 
                        $outdir, $outfile, $_index+1, $outext
                    );
                    printf("Exec: %s\n", $cmdl);
                    exec($cmdl, $out, $ret);
                }