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--- ubuntu:video:rotate_videos_with_ffmpeg [2020/02/13 00:02] – created 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 13: / Line 22: @@
 Use **-vf "transpose=2,transpose=2"** for 180 degrees.
+</WRAP>
 ----
-Running
+If you don't want to re-encode your video AND your player can handle rotation metadata you can just change the rotation in the metadata using ffmpeg:
 <code bash>
-ffmpeg -filters
+ffmpeg -i input.m4v -metadata:s:v rotate="90" -codec copy output.m4v
 </code>
-shows this:
+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
+----
+===== Determine filters supported by ffmpeg =====
+Other filters that can be used.
+<code bash>
+ffmpeg -filters
+</code>
+returns:
 <code>
@@ Line 433: / Line 483: @@
-----
-<code>
-Filters:
-anull            Pass the source unchanged to the output.
-aspect           Set the frame aspect ratio.
-crop             Crop the input video to x:y:width:height.
-fifo             Buffer input images and send them when they are requested.
-format           Convert the input video to one of the specified pixel formats.
-hflip            Horizontally flip the input video.
-noformat         Force libavfilter not to use any of the specified pixel formats
- for the input to the next filter.
-null             Pass the source unchanged to the output.
-pad              Pad input image to width:height[:x:y[:color]] (default x and y:
-, default color: black).
-pixdesctest      Test pixel format definitions.
-pixelaspect      Set the pixel aspect ratio.
-scale            Scale the input video to width:height size and/or convert the i
-mage format.
-slicify          Pass the images of input video on to next video filter as multi
-ple slices.
-unsharp          Sharpen or blur the input video.
-vflip            Flip the input video vertically.
-buffer           Buffer video frames, and make them accessible to the filterchai
-n.
-color            Provide an uniformly colored input, syntax is: [color[:size[:ra
-te]]]
-nullsrc          Null video source, never return images.
-nullsink         Do absolutely nothing with the input video.
-</code>