[pulseaudio-discuss] 'Failed to find a working profile' for firewire sound devices

[Raymond Yau]

>
> > How accurate are the hwptr playback/capture position ?
>>
>>
>> e,g, USB audio send in URB packet
>>
>> the position is only updated in one ms
>
>
> There is a chance to update the position every 2 msec. But it differ
depending on sampling rate, size of period and streaming mode.
>

Do you mean the card have internal memory of FIFO to hold 1 packet of data ?

Can the driver run with one periods per buffer or need two or more periods ?

Why periods_min = 1 ?

http://www.freedesktop.org/wiki/Software/PulseAudio/Backends/ALSA/BrokenDrivers/

>
>
>> Do you mean firewire driver 's pcm_pointer callback does not report
>> playback/capture positon in realtime ?
>
>
> Within the 2 msec, I mean it.
>
>
>> there is alway one packet 's uncertainty
>
> >
> > are the any minimum size of the packet ?
> >
> > e.g. usb audio send in urb
>
> There is uncertainty. But not one packet.
>
> Every 2 msec, the drivers queue some packets for transferring. So
uncertainty is the number of the packets.
>
> Currently this number is fixed by 16. See 'INTERRUPT_INTERVAL' macro in
'amdtp.c'.
> (In IEE1394, 8000 packets are transferred per sec. So 16 packets equal 2
msec.)
>
>

Do the driver need to use larger value for pulseaudio's rewind_safeguard as
it use more channels than the other cards ?

https://bugs.freedesktop.org/show_bug.cgi?id=72396
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