[xine-devel] Re: [xine-cvs] CVS: xine-lib/src/xine-engine osd.c,1.23,1.24

[James Courtier-D. <Ja...@su...>]

Heiko Schaefer wrote:

>Update of /cvsroot/xine/xine-lib/src/xine-engine
>In directory sc8-pr-cvs1:/tmp/cvs-serv12622
>
>Modified Files:
>	osd.c 
>Log Message:
>seems the closedir doesn't break passthrough anymore
>  
>
Closedir() never was the cause. I suspect that the problem was XRUNs and 
removing "closedir()" just modified the scheduling enough to fix the 
apparent problem.

As you may have noticed, I rewrote some of "audio_out.c" recently, so 
that when it is used with alsa, it is actually approximating a 
"callback" audio model.
I also changed the buffer and period setting code a bit.
Now, the "audio out loop" will sit waiting blocked by the kernel in the 
write function. The kernel will only schedule audio out loop when there 
is free space in the audio buffer. When audio out does get scheduled, it 
immediately does a write to the audio card, thus reducing the amount of 
XRUNs as much as possible, it then goes round the loop, and decides 
which audio samples to use next time, then returns to the blocked state, 
waiting for the audio buffer to free up enough samples again.
The current state of xine audio out (xine-lib CVS) seems to work well, 
so I don't think I have broken anything.
There are some improvements I could still make, like making sure that 
there are always enough samples waiting to be written to the sound card 
immeadiately each time it unblocks, instead of the current method of 
just holding what ever samples are left from the current fifo buffer. At 
the moment, we can still get XRUNs, because we could have a fifo buffer 
with 1536 samples in it. The first write could send 1500 samples, 
leaving only 36 samples to go.
So, we sit blocked until the buffer is free enough and then try to write 
only 36 samples, we then have to go all round the loop again before we 
can find the other 1464 samples that the sound hardware requires.
A better approach would be to make sure that we always have 2*period 
samples ready to write to the sound card at each "block". This would 
mean re-writing all the audio out plugins, and change the api a bit there.
The api would change the "write" function (e.g. in audio_alsa_out) into 
a function that makes "callbacks" to xine-engine/audio_out.c
I am pretty sure that I could get this working for oss and alsa, but I 
have no way of testing of even knowing if it is possible to do this with 
the other audio plugins. Can anyone advise me?

Cheers
James


Cheers
James