A delay of -9ms cannot be fixed? eac3to

[DanDare1983]

Hi, whilst demuxing films using the popular tool eac3to I seem to encounter a lot of audio delays explaining that several ms cannot be fixed. In the latest case its telling me -9ms cannot be fixed. Could anyone tell me or break this down simply as I'm not sure if it will mess up the remux? Also seems to happen with alot of seamless branching films aswell with extended cut etc.

[Richard1485]

It won't mess up your remux. -9ms is a fraction of a video frame, which is 41.7ms for 23.976fps content. The warning occurs because unless you re-encode the audio stream, eac3to can cut only to the nearest "frame", which limits the precision of the delay that it can apply. For AC-3, a "frame" is 32ms; for DTS, it's 10.67ms; eac3to works out the delay to the nearest "frame" and lets you know the remainder. If you repeat the demuxing and decode the track to wav or w64 (instead of extracting it), the warning will go away because eac3to can now apply the delay to the precise ms.

Either way, it's nothing to worry about. The difference will always be less than a frame of video and therefore not noticeable.

[DanDare1983]

Hi,

Thank you for the very informative breakdown. Would this also apply to +ms? So basically if the video is 23.97fps anything below 41.7ms won't effect the audio enough for anyone to notice? Also an I right in saying that if their is a delay of any sort e.g -9ms and I extracted to dts core or converted to ac3 or any other audio codec the delay will go away as it can then be to the precise ms?

[Richard1485]

Would this also apply to +ms?

Yes.

So basically if the video is 23.97fps anything below 41.7ms won't effect the audio enough for anyone to notice?

Yes.

Also an I right in saying that if their is a delay of any sort e.g -9ms and I extracted to dts core or converted to ac3 or any other audio codec the delay will go away as it can then be to the precise ms?

In the case of the core, you are still extracting an existing track, so the delay remains.

In the case of conversion to AC-3, the delay is applied down to the ms and therefore "goes away".

But the -9ms is not a problem anyway; eac3to knows what it is doing, and unless your audio is noticeably out of sync, just let it get on with it. :)

[DanDare1983]

Thanks for the help, much appreciated.

I now have a decent insight on how everything works in regards to frames, delay etc.