Re: [PATCH 01/10] alsa_stream: port changes made on xawtv3

[Hans de Goede <hdegoede@redhat.com>]

Hi,

Lots of good stuff in this thread! It seems Mauro has answered most
things, so I'm just going to respond to this bit.

On 09/07/2011 05:37 AM, Devin Heitmueller wrote:

<Snip>
>> We've added a parameter for that on xawtv3 (--alsa-latency). We've parametrized
>> it at the alsa stream function call. So, all it needs is to add a new parameter
>> at tvtime config file.
>
> Ugh.  We really need some sort of heuristic to do this.  It's
> unreasonable to expect users to know about some magic parameter buried
> in a config file which causes it to start working.  Perhaps a counter
> that increments whenever an underrun is hit, and after a certain
> number it automatically restarts the stream with a higher latency.  Or
> perhaps we're just making some poor choice in terms of the
> buffers/periods for a given rate.

This may have something to do with usb versus pci capture, on my bttv card
30 ms works fine, but I can imagine it being a bit on the low side when
doing video + audio capture over USB. So maybe should default to say
50 for usb capture devices and 30 for pci capture devices?

In the end if people load there system enough / have a slow enough
system our default will always be wrong for them. All we can do is try to
get a default which is sane for most setups ...

Regards,

Hans