How to convert .avc videos to .264 format.
Converting MPEG-4 Advanced Video Coding Movie Format directly to Ripped Video Data Format (.avc to .264 conversion) is certainly possible and should be quite straightforward, even though your options are limited.
Your best bet appears to be using the Freemake Video Converter, which allows users to import AVC videos and export them in 264 format.
A video converting tool
One of the most popular and successful free video conversion softwares