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

[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



_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

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

[Zhao Zhili]

> 在 2025年3月20日，上午3:35，Steve Rance <steverance@outlook.com> 写道：
> 
> 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.

This mailing list is for ffmpeg development, not user support.

There is no such framerate 23.986, it’s 24 * 1000/1001.

> 
> 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
> 
> 
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

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

[Steve Rance]

Sorry, yes, that was a typo on my part, but still even with 24*1000/1001 that would give a non-integer/fractional sample rate which ffmpeg will round.
I will locate the correct group.
Thank you.
Steve


-----Original Message-----
From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Zhao Zhili
Sent: Wednesday, March 19, 2025 06:05 PM
To: ffmpeg-devel@ffmpeg.org
Cc: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] 24 FPS to 23.975 Conversion with Audio


> 在 2025年3月20日，上午3:35，Steve Rance <steverance@outlook.com> 写道：
> 
> 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.

This mailing list is for ffmpeg development, not user support.

There is no such framerate 23.986, it’s 24 * 1000/1001.

> 
> 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
> 
> 
> 
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 
> To unsubscribe, visit link above, or email 
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".

_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel

To unsubscribe, visit link above, or email
ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".