[MPlayer-dev-eng] [PATCH] Online audio stream switching

[D Richard Felker III]

On Mon, Feb 28, 2005 at 12:31:13PM -0600, Joey Parrish wrote:
> On Mon, Feb 28, 2005 at 10:37:53AM -0500, D Richard Felker III wrote:
> > > > A single keypress will make it horribly crash unless the new audio
> > > > track has exactly the same codec and format as the old one. This is
> > > > very bad. Consider DVDs that have some tracks as 2.0 AC3 and others as
> > > > 5.1 AC3, or a mix of AC3, PCM, and DTS. Unless you work out all the
> > > > mess to close down and reinitialize the audio layer for the newly
> > > > selected audio track, a patch like this (which only works on a very
> > > > limited number of files and crashes on all the rest) is not
> > > > acceptable. I know it's very hard to do this right (that's why no one
> > > > has done it yet..) but that's the way it is. Sorry..
> 
> > > Well, the patch already knows about the difference between AC3, PCM and DTS
> > > and switches only between streams of the same format. Switching
> > > between 2.0 AC3 and 5.1 AC3 did not make problems here but please
> > > send me a sample where it does.
> 
> > do you have a 5.1 setup? if not, it will just decode both as 2.0 so no
> > problem should arise...but i wonder what happens if you have 5.1
> > output available..
> 
> Well, if it checks the format to ensure no crashing, I say it's a very
> good thing to have.  What's the down side when compared to no switching
> at all?

If it's safe, I agree, it's ok to add. But I'm still worried about
cases that might seem safe but not be, e.g. switching between
apparently-compatible vorbis streams when they actually have different
dictionaries or whatever crap goes in the global header.

Of course for this patch vorbis is irrelevant since it's MPEG-only, so
we're probably safe. But if we want to do this kind of switching in
more generality, it needs to do full reinit of the audio system, IMO.

Rich