lavcac3enc broken?

Hi there,
I am a long term user of mplayer, and my "custom" usage is to reencode 
audio streams to ac3 to feed my "old" amplifier.

Since version 1.5, it seems that the audio chain having:

-af lavcac3enc 1:x:y

is broken as soon as the stream is not ac3 (it used to work with any 
stream pre-version 1.5).

Here the errors popping out, for instance from an eac3 audio channel:

[ac3_fixed @ 0x7f72fd553760]Specified sample format s16p is invalid or 
not supported
Couldn't open codec ac3, br=448000.
[libaf] Reinitialization did not work, audio filter 'lavcac3enc' 
returned error code -2
Error at audio filter chain pre-init!

Same error reading from an audio channel in aac:

[ac3_fixed @ 0x7fd154b53760]Specified sample format s16p is invalid or 
not supported
Couldn't open codec ac3, br=448000.
[libaf] Reinitialization did not work, audio filter 'lavcac3enc' 
returned error code -2
Error at audio filter chain pre-init!

I am happy to give more information or test patches.

PS: tested mpv (which also has the lavac3enc filter, and it works fine 
for those very same audio streams).

Cheers,
chris.