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

[Feng Wei]

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.

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



-- 
Wei.Feng (irc wei_feng)
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