Does librav1e Support Two-Pass Encoding?

This article explains whether the librav1e AV1 encoder library supports two-pass encoding for optimal file size distribution. You will learn how two-pass encoding functions within this library, why it is beneficial for targeting specific file sizes, and how to implement it using FFmpeg.

Yes, librav1e (the library interface for the rav1e AV1 encoder) fully supports two-pass encoding. This feature is highly valuable for creators and developers who need to meet strict target file sizes or bandwidth limits without sacrificing visual quality.

During two-pass encoding, the encoder processes the video in two distinct stages:

1. First Pass: The encoder analyzes the entire video sequence to identify motion, scene cuts, and overall complexity. It writes this analysis into a temporary statistics log file. No actual video is output during this stage.
2. Second Pass: The encoder reads the statistics log file and uses the data to allocate the available bitrate. It distributes more bits to complex, high-motion scenes and fewer bits to static, simple scenes, resulting in an optimized final video file that meets the target bitrate.

To use two-pass encoding with librav1e via FFmpeg, you run two consecutive commands.

First Pass Command:

ffmpeg -i input.mp4 -c:v librav1e -b:v 2000k -pass 1 -f null -

Second Pass Command:

ffmpeg -i input.mp4 -c:v librav1e -b:v 2000k -pass 2 output.mkv

Using two-pass encoding with librav1e ensures the most efficient distribution of data across your video, preventing quality drops in action-heavy scenes while maintaining a highly predictable final file size.