How to understand drift when synchronizing the audio

[busybeeCS]

The function aout_DecSynchronize first calls aout_OutputTimeGet to get the drift time and then does

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drift += mdate () - dec_pts;

.

Can anybody explain the meaning of drift to me?

[Rémi Denis-Courmont]

In that context, it's the difference between the intended and the estimated actual audio playback time.

[busybeeCS]

In that context, it's the difference between the intended and the estimated actual audio playback time.

then,what is the estimated actual audio playback time and what the intended one?
is the dec_pts estimated?
how to understand :drift += mdate () - dec_pts;

[Rémi Denis-Courmont]

dec_pts is the intended time and mdate() is the current time.

[busybeeCS]

dec_pts is the intended time and mdate() is the current time.

do u mean mdate() is the estimated playback time?
why is there an accumulation in variable drift?

[edwardw]

dec_pts is the estimated time to play this sample. mdate() is the current time. So mdate() - dec_pts is Δtime, or in other words, drift.

And drift is needed in order to ensure that playback is synchronized. This could have many causes, like different decoder speed, or audio output, etc.