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--- howto:convert-images [2024/07/28 12:56] – [high quality conversion to mp4] Wuff
+++ howto:convert-images [2025/05/20 11:23] (current) – [lossy conversion of png to jpg] Wuff
@@ Line 28: / Line 28: @@
 </code>
-===== lossless changing containers between webm/mov/mp4/mkv =====
+===== lossy conversion of png to jpg =====
+Converts all png files in the directory recursively to jpg
+<code>
+find . -iname '*.png' | while read i; do mogrify -format jpg "$i" && rm "$i"; echo "Converted $i to ${i%.*}.jpg"; done
+</code>
+===== png to ico =====
+To create favicon ico files, the following command creates multiple sizes and stores them in the ico file and keeps transparency. Adjust as required.:
+<code>
+convert logo.png -define icon:auto-resize=256,64,48,32,16 favicon.ico
+</code>
+===== lossless changing containers between webm/mov/mp4/mkv/m4v =====
-webm/mov/mkv/mp4 are container formats and can contain various encoded video or audio streams. To change the container between each other, the following command can be used, provided the used codecs inside the containers are compatible:
+webm/mov/mkv/mp4/m4v are container formats and can contain various encoded video or audio streams. To change the container between each other, the following command can be used, provided the used codecs inside the containers are compatible:
 <code>
 ffmpeg -i file.webm -c:a copy -c:v copy file.mkv
@@ Line 38: / Line 50: @@
 #find . -type f -iname '*.webm' -delete
-#lossless change container mkv, webm, mov -> mp4
+#lossless change container mkv, webm, mov, m4v -> mp4
-find . -type f \( -iname "*.mkv" -o -iname "*.webm -o -iname "*.mov\) | while read f; do
+find . -type f \( -iname "*.mkv" -o -iname "*.webm" -o -iname "*.mov" -o -iname "*.m4v" \) | while read f; do
     ffmpeg -i "$f" -codec copy "${f%.*}.mp4"
 done
@@ Line 196: / Line 208: @@
 done
 IFS=$SAVEIFS
+</code>
+===== 3D VR SBS to 2D =====
+https://blog.interstellar.co.jp/en/2022/06/21/converting-vr180-videos-to-2d-videos-with-ffmpeg/
+<code>
+ffmpeg -i input.mp4 -vf v360=input=equirect:output=flat:ih_fov=180:iv_fov=180:h_fov=93:v_fov=121:in_stereo=sbs:w=960:h=640 -codec:v h264 output.mp4
+</code>
+https://video.stackexchange.com/questions/21084/how-to-convert-a-3d-movie-to-2d-using-ffmpeg
+<code>
+ffmpeg -i input.mkv -vf stereo3d=sbsl:ml -metadata:s:v:0 stereo_mode="mono" output.mkv
+</code>
+Use sbsl2:ml or  -aspect 16:9 if the aspect ratio is wrong
+https://stackoverflow.com/questions/66960003/unwarping-180-vr-footage-with-ffmpeg-v360-filter
+https://github.com/paulpaul999/vr-video-notes/blob/main/vr-to-flat/README.md
+<code>
+ffmpeg -i equirectangular.mp4 -filter:v "v360=input=hequirect:output=flat:in_stereo=sbs:out_stereo=2d:d_fov=125:w=1920:h=1080:pitch=+5" -map 0 -c copy -c:v h264 -pix_fmt yuv420p flat.mp4
+</code>
+===== Mono to Stereo MP3 =====
+Conversion using ffmpeg -ac 2 reduces volume by 3db, apparently to keep perceived loudness the same. To maintain the same volume use pan as below.
+<code>
+for i in {01..33}; do
+  ffmpeg -i "Chapter "$i".mp3" -af "pan=stereo|c0=c0|c1=c0" "Chapter "$i"s.mp3";
+done
 </code>