[tebasuna51]

Originally Posted by madshi

Or am I missing/misunderstanding something?

Isn't a bug,

[-pad #] Start-of-stream padding
            The AC-3 format uses an overlap/add cycle for encoding
            each block.  By default, Aften pads the delay buffer
            with a block of silence to avoid inaccurate encoding
            of the first frame of audio.  If this behavior is not
            wanted, it can be disabled.  The pad value can be a
            1 (default) to use padding or 0 to not use padding.

Each frame uses the last 256 samples from precedent frame to encode the actual frame (time -> frequency domain). This is a problem for first frame, there are two methods:

With -pad 1 (default), the first 256 samples (delay buffer) are already filled with silence (and introduce a 5.33 ms delay if 48 KHz.) and the real samples are encoded properly.

With -pad 0 [if(!opts.pad_start)] the first 256 samples are filled with real samples, without delay but with something like a fade-in in first 5.33 ms.