libsvtav1: Support crf quarter steps

Author: alexheretic

CHANGELOG.md

@@ -1,3 +1,7 @@
+# Unreleased (0.11)
+* libsvtav1: Support crf quarter steps. This requires svt-av1 >= v4.0.0, if using an older version
+  you may want to use crf-search `--crf-increment 1` for the old behaviour.
+
 # v0.10.4
 * Use ffmpeg `-fps_mode passthrough` for all sample encodes. This improves VMAF scores in some cases.
 * Use explicit pixel format in xpsnr calls, use highest quality format of the ref & distorted streams.

Cargo.lock

@@ -213,6 +213,8 @@ impl Encode {
                 _ => 0,
             };
             svtav1_params.push(format!("scd={scd}"));
+            // include crf in svtav1-params to support quarter-steps
+            svtav1_params.push(format!("crf={crf}"));
             // add all --svt args
             svtav1_params.extend(self.svt_args.iter().map(|a| a.to_string()));
         }
@@ -382,6 +384,7 @@ impl Encoder {
     pub fn default_crf_increment(&self) -> f32 {
         match self.as_str() {
             "libx264" | "libx265" => 0.1,
+            "libsvtav1" => 0.25,
             _ => 1.0,
         }
     }