[pulseaudio-discuss] pa_mix 32Bit write for S16NE format

[kuldeep ghan]

On Wed, Aug 17, 2011 at 1:51 PM, Arun Raghavan <
arun.raghavan at collabora.co.uk> wrote:

> On Wed, 2011-08-17 at 13:34 +0530, kuldeep ghan wrote:
> > Hi,
> >
> >   I am working on a setup which has Linux Kernel running and I have
> > pulseaudio as Sound server. ASoc Alsa driver snd_pcm_mmap function
> > returns me
> >  Virtual Memory mapped to physical memory which is strictly 32 Bit
> > Aligned.
>
> Out of curiosity, what platform is this?
>
I am using OMAP4 platform.

>
> >   When I am trying to Mix two streams with gst-launch, pa_mix function
> > tries to write 16Bit mixed samples to this physical memory resulting
> > in Bus error.
> >
> >   As a work around I am trying following code which is trying to write
> > two Mixed 16Bit samples write making it a 32Bit write.
> > src/pulsecore/sample-util.c
> >
> >              //  *((int16_t*) data) = (int16_t) sum;
> >                 if(j==0) {
> >                        temp[0]=(int16_t) sum;
> >                        j=1;
> >                } else {
> >                         temp[1]=(int16_t) sum;
> >                          j=0;
> >                         sum = ((temp[1] << 16) | (0x0000FFFF &
> > temp[0]));
> >
> >                         data = (uint8_t*) data - sizeof(int16_t);
> >                        *((int32_t*) data) = (int32_t) sum;
> >                         data = (uint8_t*) data + sizeof(int16_t);
> >                }
> >
> > With this I am able to mix a gst-launch stream and already loaded
> > sample from pulseaudio played with play-sample from pacmd.
> > But not able to mix two streams with gst-launch.
>
> What is the error you see when playing 2 streams? Do two instances of
> paplay work fine together?
>
The error I see is
"Unhandled fault: external abort on non-linefetch (0x1818) at 0x40013000"


>
> BTW, Another potential workaround (if your hardware supports it), is to
> force the default sample spec to use S32NE samples (you can edit the
> default value in /etc/pulse/daemon.conf). The downside is obviously that
> you're transferring 2x the amount of data that you'd have done with
> S16LE samples and the format conversion cost for just about every
> client.
>

I have tried using S32NE as default format but it Causes
under-runs/over-runs.
As I am new to ALSA subsystem and PulseAudio I am yet to figure out how to
get those under-runs/over-runs solved?


>
> Unless there's more hardware out there with this sort of limitation (I
> don't believe there is), I wouldn't be too keen on adding this sort of
> workaround upstream.
>
> Regards,
> Arun
>
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> http://lists.freedesktop.org/mailman/listinfo/pulseaudio-discuss
>

Thanks,
Kuldeep
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