[MPlayer-dev-eng] [PATCH] New commands for loading/unloading audio filters at runtime

[Reimar Döffinger]

On Sun, Apr 11, 2010 at 12:16:39PM +0900, Jehan Pagès wrote:
> Hi,
> 
> and have you tried to load it at startup as well? As I said, some
> filters are problematic from the base. I tried lavcac3enc, and it
> crashes indeed when I load it at runtime, but mplayer crashes also
> when I load it at startup (with -af option) with basically the same
> error:
> 
> [ac3 @ 0xa35e360]No channel layout specified. The encoder will guess
> the layout, but it might be incorrect.
> [AO OSS] Can't set audio device /dev/dsp to ac3le output, trying s16le...
> AO: [oss] 44100Hz 2ch s16le (2 bytes per sample)
> [format] Sample format big-endian AC3 not yet supported
> [libaf] Reinitialization did not work, audio filter 'format' returned
> error code -2
> [libaf] Unable to setup filter system can not meet sound-card demands,
> please send bugreport.
> Couldn't find matching filter/ao format!
> Audio: no sound
> Video: no video
> 
> So I would say that the problem is from the filter.
> Tell me if this is any different for you.

Uh, I think he means crashing when he says "crashing", not just "does not play
audio".
Dynamically inserting lavcac3 just can not work (at least not this way) since
the ao does not get reconfigured, so the output at the very end of the
filter chain can not change.
This means two things: 1) adding or removing lavcac3 can not work since (at least
for adding) we would need a AC3 decoder filter somewhere to get back to the
same format
2) even if it worked, it wouldn't make any sense.

However the crash is an indication that the error-handling when the filter chain
after the change is unusable is insufficient.