Clemens Ladisch <cladisch <at> fastmail.net> writes:
>
> Akio wrote:
> > Right now, we are using a arm box with linux kernel 2.6.14 to
> > develop a voip solution. After the rtp connection was
> > connected at first 20 secs, there is no delay. As the timing passing
> > by, the delay will going longer and longer. After 16 hours, the
> > delay will up to 12 secs.
>
> If the sending and the receiving computers don't use the same clock,
> there will be a small difference in the sample rate. You have to
> measure this and adjust the data accordingly (by re-sampling or just
> adding/dropping some samples).
Thank you very much. I think the CPU power is so tight, there is no room to
do that
conversion.
> > Because the alsa lib application can't detect any alsa device,
>
> I'd guess that either the device nodes in /dev/snd/ or the configuration
> files in /use/share/alsa/ are missing.
Could you can show me how to build the right structure to make alsa lib to work?
May be this is the right way to void voice delay.
> HTH
> Clemens
BTW, after many tests. I find the following combination that seems make the
delay disappear
in read direction, but in write direction, there will be some extra space
been added. Right now,
I find two points to suppress voice delay via the following method.
1. in sound/core/oss/pcm_oss.c, in snd_pcm_oss_read3(), mark the break branch
which
after snd_pcm_oss_capture_position_fixup().
the original code is like :
ret = snd_pcm_oss_capture_position_fixup();
if (ret < 0)
break;
to the following one:
ret = snd_pcm_oss_capture_position_fixup();
//if (ret < 0)
// break;
2.in snd_pcm_oss_capture_position_fixup(), change the delay calculation
method. from the original
one:
if (*delay <= (snd_pcm_sframes_t)runtime->buffer_size) break;
frames = (*delay - runtime->buffer_size) + runtime->period_size - 1;
frames /= runtime->period_size;
frames *= runtime->period_size;
to the following one:
if (*delay <= (snd_pcm_sframes_t)runtime->period_size) break;
frames = (((*delay + runtime->period_size - 1) / runtime->period_size)) *
runtime->period_size;
Does the modification will cause other side effect or not?
How to solve the extra space in write space?
Thanks in advance.
Best Regards,
Akio
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