[alsa-devel] snd_pcm_hw_params_set_buffer_time_near: invalid argument

[Jean-Yves Avenard]

Hi

On 9 March 2011 23:29, Jaroslav Kysela <perex at perex.cz> wrote:

> What is your dir argument (last one) for the near functions? If it's NULL or
> value is zero, it means you request the exact value which may not be
> available. Use -1 to request specified or smaller value or 1 to request
> specified or bigger value.

It is zero.

That still doesn't explain the difference in behaviour I'm seeing
between 400ms or 500ms request. Neither of those are possible with a
64kB buffer.

What you are describing isn't what is happening in practice:
Requesting 500ms with the dir=0 (or NULL) provides a buffer of 371ms.
So it doesn't return an exact value, not even close (I found that with
dir=0 or NULL always return a value equal or less than what is
requested. If less the value returned is the maximum allowed by the
prealloc value)

JY