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--- appwiki:ffmpeg [2021/06/18 19:12] – created ying
+++ appwiki:ffmpeg [2022/12/07 07:21] (current) – [Common Convertion] ying
@@ Line 1: / Line 1: @@
-====== REF ======
-  * https://ottverse.com/trim-cut-video-using-start-endtime-reencoding-ffmpeg/
 ====== FFmpeg - the core command app of open source transcoder ======
@@ Line 52: / Line 50: @@
 ffmpeg.exe -i "d:\out\me.mpg" -c:v libx264 -c:a libfaac -crf 20 -preset:v veryslow "d:\out\me_out.mov"
 </code>
+  * copy portion of video <code>
+# about -ss before -i and after -i  difference, which can make cut video works or not works
+# ref: https://ottverse.com/trim-cut-video-using-start-endtime-reencoding-ffmpeg/
+ffmpeg.exe -i video.mp4 -c copy -ss 00:00:09 -to 00:00:21 video_cut.mp4
+# -ss in front means: start time (from 9s), duration time (21s)
+ffmpeg.exe -ss 00:00:09 -i video.mp4 -c copy -to 00:00:21 video_cut.mp4
+</code>
+  * combine list of videos into 1 video
+    * ref: https://stackoverflow.com/questions/7333232/how-to-concatenate-two-mp4-files-using-ffmpeg
+  * gif maker <code>
+ffmpeg -i input.mp4 -vf "fps=10,scale=640:-1:flags=lanczos,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" -loop 0 output.gif
+</code>
+  * 2x2 stack <code>
+#ref: https://ottverse.com/stack-videos-horizontally-vertically-grid-with-ffmpeg/
+ffmpeg -i input0.mp4 -i input1.mp4 -i input2.mp4 -i input3.mp4 -filter_complex "[0:v][1:v]hstack=inputs=2[top]; [2:v][3:v]hstack=inputs=2[bottom]; [top][bottom]vstack=inputs=2[v]" -map "[v]" finalOutput.mp4
+</code>
+  * image to square size (like convert image to texture size format) <code>
+ffmpeg -i image.jpg -vf "scale=1024:1024:force_original_aspect_ratio=decrease,pad=1024:1024:-1:-1:color=white" -q:v 1 tex_image.jpg
+# longest side, so basically original size with padding to square
+ffmpeg -i image.jpg -vf "scale=max(iw\,ih):max(iw\,ih):force_original_aspect_ratio=decrease,pad=max(iw\,ih):max(iw\,ih):-1:-1:color=white" -q:v 1 tex_image.jpg
+</code>
+====== GIF related ======
+  * use every 1 from out of 10 frame from a huge frame-by-frame gif recording, and save as a 600px width gif <code dos>
+ffmpeg.exe -i big_recording.gif -vf "select=not(mod(n-1\,10)),scale=600:-1" -vsync vfr light_10th_600w.gif
+</code>