[FFmpeg-devel] 24 FPS to 23.975 Conversion with Audio

[Steve Rance]

Hello developers, my first post, if I have posted to the wrong place please point me in the right direction

I'm attempting to use ffmpeg to convert 24FPS media to 23.986 - Video is good but the audio slips.

From my research I need a fractional sample rate for the audio. To be precise I need 48000 × (23.976/24) ≈ 47952.047952 Hz. However, since FFmpeg’s asetrate only accepts an integer value, ffmpeg ends up using 47952 exactly. I have tried many if not all of the options available and the result remains the same.

Here are the slippage rates ...
Approximately 172.63 samples error per hour
Approximately 2.88 samples error per minute.
Approximately 20.85 seconds must elapse for each 1 sample error.
Approximately 11 hours and 35 minutes before the audio is one full frame off.

I'm using Windows and need advice on how I could try to acheive perfect audio sync.

Thank you for reading.
Steve