[quake2] Choppy sound with default (non-SDL) client

[Alexey Dokuchaev]

On Sat, Apr 27, 2013 at 01:24:18PM +0300, Ozkan Sezer wrote:
> On 4/27/13, Alexey Dokuchaev <danfe at nsu.ru> wrote:
> > I've heard several reports over quite some time that default (non-SDL)
> > client executable gives choppy sound on FreeBSD (that is, OSS).
> 
> It is because the SNDCTL_DSP_GETOSPACE ioctl is issued before setting
> other important parameters: if it is move to the place just below the
> mmaping it is fixed. See the patch I just cooked up (which contains a
> few additional bits)

I confirm that moving SNDCTL_DSP_GETOSPACE ioctl() call lower does fix the
problem for me here on FreeBSD 8.3, thanks!

May I ask a few questions on the remaining bits of the patch?

> @@ -76,7 +74,7 @@
>  	{
>  		seteuid(saved_euid);
> 
> -		audio_fd = open(snddevice->string, O_RDWR);
> +		audio_fd = open(snddevice->string, O_RDWR|O_NONBLOCK);

What happens when opening file in blocking mode?  I did not observe any
problems...  Although I've seen this change in some other quake engine
source code.

> -		if (fmt & AFMT_S16_LE) dma.samplebits = 16;
> +		if (fmt & AFMT_S16_NE) dma.samplebits = 16;
>  		else if (fmt & AFMT_U8) dma.samplebits = 8;
>  	}
> 
>  	if (dma.samplebits == 16)
>  	{
> -        	rc = AFMT_S16_LE;
> +        	rc = AFMT_S16_NE;

Do I understand correctly that using AFMT_S16_LE would break on big-endian
machines?  I.e., AFMT_S16_NE makes code CPU (endian) agnostic, ergo correct?

> +	mmaplen = info.fragstotal * info.fragsize;
> +	sz = sysconf (_SC_PAGESIZE);
> +	mmaplen += sz - 1;
> +	mmaplen &= ~(sz - 1);

What benefits forcing page size aligned mmaplen brings us here?

> +		munmap (dma.buffer, mmaplen);
> +		dma.buffer=NULL;

Fixing resource leaks are clear.

./danfe