@Ninthony , the ProRes 4444 codec is known for generating large file sizes due to its high-quality, near-lossless or lossless nature, designed to retain the utmost amount of information. While this is advantageous for preserving both quality and transparency, it is not conducive for minimizing file size, streaming, or smooth scrubbing.
Given that smooth scrubbing and transparency are critical for your project, along with iOS compatibility, here are a few alternative strategies for managing transparent videos on iOS while potentially achieving smaller file sizes. While I haven't tested these methods personally, they might be worth exploring:
HEVC with Alpha Channel:
HEVC (High Efficiency Video Coding, also referred to as H.265) supports alpha channel encoding, offering a more efficient alternative to ProRes 4444. This codec has the potential to reduce file size while retaining transparency.
ffmpeg -i {input_video}.mp4 -vf "format=yuva420p,scale=-1:1080" -c:v libx265 -pix_fmt yuva420p -crf 20 -preset slow -g 6 -keyint_min 6 -movflags +faststart -an {output_video}_scrub.mov
AV1 with Alpha Channel:
AV1 is a newer, open-source codec with support for alpha channel encoding, and is more efficient than ProRes 4444. However, be aware that support for AV1 on iOS devices might still be limited, Apple AV1 Support - Bitmovin
ffmpeg -i {input_video}.mp4 -vf "format=yuva420p,scale=-1:1080" -c:v libaom-av1 -crf 20 -g 6 -keyint_min 6 -movflags +faststart -an {output_video}_scrub.mkv
Optimized ProRes 4444:
It's possible to reduce the file size of ProRes 4444 videos by either lowering the resolution or tweaking other settings, although such alterations might impact video quality
ffmpeg -i {input_video}.mp4 -vf "scale=-1:720" -c:v prores_ks -profile:v 4444 -pix_fmt yuva444p10le -movflags +faststart -an {output_video}_scrub.mov
It may need some experimentation and testing to ascertain the optimal balance for your specific needs.