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--- ubuntu:video:rotate_videos_with_ffmpeg [2020/02/13 00:08] – peter
+++ ubuntu:video:rotate_videos_with_ffmpeg [2023/06/06 18:30] (current) – peter
@@ Line 1: / Line 1: @@
 ====== Ubuntu - Video - Rotate Videos with FFmpeg ======
+===== Software Encoding =====
 <code bash>
 ffmpeg -i in.mov -vf "transpose=1" out.mov
 </code>
+<WRAP info>
+**NOTE:**  This will re-encode the audio and video parts.
+  * You can usually copy the audio without touching it, by using **-c:a copy**.
+  * To change the video quality, set the bitrate (for example with **-b:v 1M**) or have a look at the H.264 encoding guide if you want VBR options.
 For the transpose parameter you can pass:
@@ Line 14: / Line 23: @@
 Use **-vf "transpose=2,transpose=2"** for 180 degrees.
-<WRAP info>
-**NOTE:**  This will re-encode the audio and video parts.
-You can usually copy the audio without touching it, by using **-c:a copy**.
-To change the video quality, set the bitrate (for example with **-b:v 1M**) or have a look at the H.264 encoding guide if you want VBR options.
 </WRAP>
@@ Line 30: / Line 32: @@
 ffmpeg -i input.m4v -metadata:s:v rotate="90" -codec copy output.m4v
 </code>
+Check the rotate metadata first with:
+<code bash>
+ffmpeg -i input.m4v 2>&1 | grep rotate
+</code>
+----
+To rotate the picture clockwise you can use the rotate filter, indicating a positive angle in radians. With 90 degrees equating with PI/2, you can do it like so:
+<code bash>
+ffmpeg -i in.mp4 -vf "rotate=PI/2" out.mp4
+</code>
+for counter-clockwise the angle must be negative
+<code bash>
+ffmpeg -i in.mp4 -vf "rotate=-PI/2" out.mp4
+</code>
+It is possible to get finer-grained resolution of radians, because * behaves as multiplication:
+<code bash>
+ffmpeg -i in.avi -vf "rotate=-8*PI/40" -q 1 out.avi
+</code>
+(slightly less rotation than -PI/4 = -10*PI/40