[FFmpeg-devel] About guess_correct_pts / AVFrame.best_effort_timestamp

Nicolas George nicolas.george
Wed Feb 16 16:52:30 CET 2011

L'octidi 28 pluvi?se, an CCXIX, M?ns Rullg?rd a ?crit?:
> How did you obtain those timestamps?

The transcode line I pasted plus ffprobe, plus awk to keep only the
timestamps in the output of ffprobe.

>					Whatever the answer, they are
> different from the original.  They should not be.

The original declares time_base = 1/1000 and frame_rate = 24000/1001.

The transcoded declares time_base = 1/24000, and same frame_rate.

The timestamps in the input are rounded to the insufficient accuracy of its
time base.

The timestamps in the output are perfect.

> Good would be equal.  These are not equal, and therefore not good.

This is not merely good, this is better: it does not dumbly copies the
timestamps, it unrounds them and restores them to their perfect accuracy.
This is not good, this is better.

> The timestamp of a decoded frame is _exactly_ what the container says it
> is, nothing else.

Except that containers can say it in various ways.

>		    The current code mangles the values from the
> container in unpredictable ways.

This is not true. Please read the code before making such statements.

> If an API function does something, that something is part of the API.

So if a new function gets committed with a stupid bug, the bug becomes part
of the API and should not be fixed? This is stupid.

The API is what the documentation says.

> There is an "algorithm" where there should be none.

How do you select which one, among the PTS and the DTS from the container,
should be used?

> I did exactly that and convinced several others.

Then why are they still discussing the question with me?


  Nicolas George
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