From 1f010daf520794f4cb2d131957b1c95c0fd8c3b3 Mon Sep 17 00:00:00 2001
From: Kuba Orlik <kontatk@kuba-orlik.name>
Date: Mon, 20 Sep 2021 16:31:17 +0200
Subject: [PATCH] New version using (a)trim + concat

As suggested here: https://trac.ffmpeg.org/ticket/9430#comment:2
---
 dziurkacz-fast.mjs | 93 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 81 insertions(+), 12 deletions(-)

diff --git a/dziurkacz-fast.mjs b/dziurkacz-fast.mjs
index e2642bb..acf967c 100755
--- a/dziurkacz-fast.mjs
+++ b/dziurkacz-fast.mjs
@@ -73,19 +73,19 @@ current_piece.end = all_frames[all_frames.length - 1];
 pieces.push(current_piece);
 
 // this approach is using a filter, so it requires reencoding the entire video, but lets us be very precise:
-const filter = pieces
-  .map(
-    ({ start, end }) =>
-      `between(t,${(start / FRAMERATE).toFixed(5)},${(end / FRAMERATE).toFixed(
-        5
-      )})`
-  )
-  .join("+");
+// const filter = pieces
+//   .map(
+//     ({ start, end }) =>
+//       `between(t,${(start / FRAMERATE).toFixed(5)},${(end / FRAMERATE).toFixed(
+//         5
+//       )})`
+//   )
+//   .join("+");
 
-await $`ffmpeg -i ${video} \
-               -vf ${`select='${filter}',setpts=N/FRAME_RATE/TB`} \
-               -af ${`aselect='${filter}',asetpts=N/SR/TB`} \
-               ${video + ".cut.mp4"}`;
+// await $`ffmpeg -i ${video} \
+//                -vf ${`select='${filter}',setpts=N/FRAME_RATE/TB`} \
+//                -af ${`aselect='${filter}',asetpts=N/SR/TB`} \
+//                ${video + ".cut.mp4"}`;
 
 // let ffmpeg_args = [];
 // const parts = [];
@@ -114,3 +114,72 @@ await $`ffmpeg -i ${video} \
 // await $`ffmpeg -f concat -safe 0 -i /tmp/vdlist.txt -c copy -y ${
 //   video + "final.mp4"
 // } `;
+
+function range(n) {
+  return [...Array(n).keys()];
+}
+
+for (let piece of pieces) {
+  console.log(piece);
+}
+
+const ns = range(pieces.length);
+
+const sample_rate = parseInt(
+  (
+    await $`ffprobe odc25proxy.mp4 2>&1 | grep 'Audio:' | grep --only-matching --extended-regexp '[0-9]+ Hz' | sed 's/ Hz//'`
+  ).stdout
+); // in Hz
+
+const samples_per_frame = sample_rate / FRAMERATE;
+
+function generateSplit(pieces, prefix = "") {
+  return `[0] ${prefix}split=${pieces.length} ${ns
+    .map((n) => `[copy${n}${prefix}]`)
+    .join("")}`;
+}
+
+function generateFilter(pieces, prefix = "") {
+  return pieces
+    .map(
+      (piece, n) =>
+        `[copy${n}${prefix}]${prefix}trim=start_frame=${piece.start}:end_frame=${piece.end},setpts=PTS-STARTPTS [copy${n}t${prefix}]`
+    )
+    .join("; ");
+}
+
+function generateAudioFilter(pieces) {
+  return pieces
+    .map(
+      (piece, n) =>
+        `[copy${n}a]atrim=start_sample=${
+          piece.start * samples_per_frame
+        }:end_sample=${
+          (piece.end + 1) * samples_per_frame
+        },asetpts=PTS-STARTPTS [copy${n}ta]`
+    )
+    .join("; ");
+}
+
+// version with audio, that doesn't work yet:
+// const filter = `${generateSplit(pieces)}; ${generateSplit(
+//   pieces,
+//   "a"
+// )}; ${generateFilter(pieces)}; ${generateAudioFilter(pieces)}; ${ns
+//   .map((n) => `[copy${n}t]`)
+//   .join("")} concat=n=${pieces.length} [out_video]; ${ns
+//   .map((n) => `[copy${n}ta]`)
+//   .join("")} concat=n=${pieces.length} [out_audio]`;
+
+// video-only version
+const audio_filter = `${generateSplit(pieces, "a")}; ${generateAudioFilter(
+  pieces
+)};`;
+
+const filter = `${generateSplit(pieces)}; 
+${generateFilter(pieces)}; 
+${audio_filter} 
+${ns.map((n) => `[copy${n}t][copy${n}ta]`).join(" ")} 
+concat=n=${pieces.length}:v=1:a=1 [out_video] [out_audio]`;
+
+await $`ffmpeg -i ${video} -filter_complex ${filter} -map '[out_video]' -map '[out_audio]' ${`${video}.cut-complex.mp4`}`;