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--- ffmpeg:conversions:convert_h264_to_av1:libaom:constrained_quality [2023/06/14 16:56] – created peter
+++ ffmpeg:conversions:convert_h264_to_av1:libaom:constrained_quality [2023/06/14 16:59] (current) – peter
@@ Line 1: / Line 1: @@
 ====== ffmpeg - Conversions - Convert H264 to AV1 - libaom - Constrained Quality ======
+**libaom-av1** has a constrained quality (CQ) mode that will ensure that a constant (perceptual) quality is reached while keeping the bitrate below a specified upper bound or within a certain bound.
+  * This method is useful for bulk encoding videos in a generally consistent fashion.
+----
+<code bash>
+time ffmpeg -i a.mp4 -c:v libaom-av1 -crf 30 -b:v 2000k -f mp4 out.mp4
+</code>
+returns:
+<code bash>
+...
+real	104m57.062s
+user	599m4.884s
+sys	0m32.345s
+</code>
+<WRAP info>
+**NOTE:**
+  * Input test size:  75.5M
+  * Output test size:  4.8M
+</WRAP>
+<WRAP info>
+**NOTE:**  The quality is determined by the **-crf**, and the bitrate limit by the **-b:v** where the bitrate MUST be non-zero.
+  * **crf**:  This value can be from 0–63.
+    * Lower values mean better quality and greater file size.
+    * 0 means lossless.
+    * A CRF value of 23 yields a quality level corresponding to CRF 19 for x264 (source), which would be considered visually lossless.
+</WRAP>