[pulseaudio-discuss] [PATCH] Fix unused buffer size to avoid xrun

[Feng Wei]

2012/4/5 David Henningsson <david.henningsson at canonical.com>:
> On 04/05/2012 10:59 AM, Feng Wei wrote:
>>
>> David,
>> I'd met xrun on some embedded platform, which will only report hw_ptr
>> at period boundary. Maybe it shouldn't use tsched, I'm not sure. Sorry
>> for inconvenience.
>
>
> Actually it does raise an important question about how we deal with
> platforms that have bad hw_ptr granularity. We don't to that very well
> today.
>
> Also is there much difference, powersave wise, between running in non-tsched
> and tsched mode? If there isn't, maybe using non-tsched for your particular
> device is the best option (if it works).
No much difference, but tsched is the default way. Non-tsched mode
works well on my device.
I think it's better to provide capability like "accurate hw_ptr" in
alsa driver so that we can determine schedule mode at runtime.

>
>
>>
>> 2012/4/5 David Henningsson<david.henningsson at canonical.com>:
>>>
>>> On 04/05/2012 10:22 AM, Feng Wei wrote:
>>>>
>>>>
>>>> When set latency is less than period time, we will assgin working
>>>> buffer less than a period size, which will cause unnecessary xrun
>>>> and wrong message indicating alsa driver bug.
>>>
>>>
>>>
>>> NAK, I don't think this is correct.
>>>
>>> This is tricky stuff though, so don't take my word for it! ;-)
>>>
>>> On what machine was this solving a problem for you?
>>>
>>> Have you verified it leads to better behaviour (or at least not worse) on
>>> both tsched and non-tsched systems?
>>>
>>> I e, try a VOIP call with ~20 ms of latency, on a desktop machine that
>>> has 2
>>> x 1s periods, running in tsched mode. I'm guessing the latency will be
>>> unacceptable with this patch applied.
>>>
>>>>
>>>> Signed-off-by: Feng Wei<feng.wei at linaro.org>
>>>> ---
>>>>  src/modules/alsa/alsa-sink.c   |    6 +++---
>>>>  src/modules/alsa/alsa-source.c |    6 +++---
>>>>  2 files changed, 6 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
>>>> index 5a4b606..a53fb6f 100644
>>>> --- a/src/modules/alsa/alsa-sink.c
>>>> +++ b/src/modules/alsa/alsa-sink.c
>>>> @@ -953,10 +953,10 @@ static int update_sw_params(struct userdata *u) {
>>>>
>>>>              b = pa_usec_to_bytes(latency,&u->sink->sample_spec);
>>>>
>>>>
>>>> -            /* We need at least one sample in our buffer */
>>>> +            /* We need at least one period and one sample in our buffer
>>>> to avoid underflow */
>>>>
>>>> -            if (PA_UNLIKELY(b<    u->frame_size))
>>>> -                b = u->frame_size;
>>>> +            if (PA_UNLIKELY(b<    u->frame_size + u->fragment_size))
>>>> +                b = u->frame_size + u->fragment_size;
>>>>
>>>>              u->hwbuf_unused = PA_LIKELY(b<    u->hwbuf_size) ?
>>>> (u->hwbuf_size - b) : 0;
>>>>          }
>>>> diff --git a/src/modules/alsa/alsa-source.c
>>>> b/src/modules/alsa/alsa-source.c
>>>> index 27fd3b9..8c41ca6 100644
>>>> --- a/src/modules/alsa/alsa-source.c
>>>> +++ b/src/modules/alsa/alsa-source.c
>>>> @@ -876,10 +876,10 @@ static int update_sw_params(struct userdata *u) {
>>>>
>>>>              b = pa_usec_to_bytes(latency,&u->source->sample_spec);
>>>>
>>>>
>>>> -            /* We need at least one sample in our buffer */
>>>> +            /* We need at least one period and one sample in our buffer
>>>> to avoid overflow */
>>>>
>>>> -            if (PA_UNLIKELY(b<    u->frame_size))
>>>> -                b = u->frame_size;
>>>> +            if (PA_UNLIKELY(b<    u->frame_size + u->fragment_size))
>>>> +                b = u->frame_size + u->fragment_size;
>>>>
>>>>              u->hwbuf_unused = PA_LIKELY(b<    u->hwbuf_size) ?
>>>> (u->hwbuf_size - b) : 0;
>>>>          }
>>>
>>>
>>>
>>>
>>>
>>> --
>>> David Henningsson, Canonical Ltd.
>>> http://launchpad.net/~diwic
>>
>>
>>
>>
>
>
>
> --
> David Henningsson, Canonical Ltd.
> http://launchpad.net/~diwic



-- 
Wei.Feng (irc wei_feng)
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