How to Encode Video to AVS3 Using FFmpeg

This guide provides a straightforward walkthrough on how to transcode video files into the third-generation Audio Video Coding Standard (AVS3) format using FFmpeg. You will learn how to verify if your FFmpeg build supports AVS3 encoding, the basic commands required for conversion, and how to configure key encoding parameters for optimal quality and file size.

Prerequisites

To transcode videos to AVS3, your FFmpeg installation must be compiled with the libuavs3e library, which is the open-source encoder for the AVS3 video standard.

You can check if your FFmpeg installation supports the AVS3 encoder by running the following command in your terminal:

ffmpeg -encoders | grep uavs3

If the output lists libuavs3e, your version of FFmpeg is ready. If it does not appear, you must download or compile an FFmpeg binary configured with the --enable-libuavs3e flag.

Basic AVS3 Transcoding Command

To convert an existing video (such as an MP4 or MKV file) into an AVS3 video stream, use the following basic command structure:

ffmpeg -i input.mp4 -c:v libuavs3e output.avs3

In this command: * -i input.mp4 specifies your source video file. * -c:v libuavs3e selects the AVS3 encoder for the video stream. * output.avs3 is the resulting raw AVS3 elementary stream.

Containerizing AVS3 Video

Raw .avs3 streams do not contain audio or metadata container structures. To package the AVS3 video stream into a standard container like MP4 alongside audio, use the following command:

ffmpeg -i input.mp4 -c:v libuavs3e -c:a aac output.mp4

Note: Ensure your media player supports AVS3 playback inside the MP4 container, as player compatibility for this newer standard is still evolving.

Adjusting Quality and Bitrate

To control the file size and visual quality of your AVS3 output, you can set the video bitrate using the -b:v flag.

Constant Bitrate (CBR) Encoding

To target a specific average bitrate (for example, 5 Megabits per second):

ffmpeg -i input.mp4 -c:v libuavs3e -b:v 5M output.mp4

Controlling Group of Pictures (GOP) Size

To set the keyframe interval (GOP size), which is useful for streaming optimization, use the -g flag:

ffmpeg -i input.mp4 -c:v libuavs3e -b:v 4M -g 60 output.mp4

This command sets a keyframe to occur every 60 frames.