Re: [xine-devel] issue with OSS output on RHL9

[Thibaut M. <tma...@no...>]

Hi Miguel,

On Thursday 03 April 2003 22:08, Miguel Freitas wrote:
> On Thu, 2003-04-03 at 16:34, Thibaut Mattern wrote:
> > I don't know if it's normal or not, but it's a known issue.
> > I'm trying to improve seeking speed, and this write() call is
> > problematic. I propose to add a new function to audio drivers to return
> > the number of byte or frame that could be written without blocking (i
> > guess this info is available for oss and alsa).
> > comments ?
>
> even when the api provides such info, we would still need to check if
> all drivers do implement it and if they do it right. it's not uncommon
> to find that these "more advanced" features of oss drivers (such as
> poll/select) are completely broken on some cards.

are you sure that the SNDCTL_DSP_GETOSPACE command is not suitable ?
It does'nt look like an "advanced" feature.
(mplayer uses it, i guess it's well tested)

=46rom audio_out.h :
  /*
   * write audio data to output buffer=20
   * audio driver must sync sample playback with metronom
   * return value:=20
   *   1 =3D> audio samples were processed ok
   *   0 =3D> audio samples were not yet processed,=20
   *        call write_audio_data with the _same_ samples again
   */
  int (*write)(ao_driver_t *this,
	       int16_t* audio_data, uint32_t num_samples);

The returned value is not checked in the ao_loop.
What about returning 0 if the buffer can't be written without blocking and=
=20
adding a simple while loop in ao_loop ?
something like that :
  pthread_mutex_lock( &this->driver_lock );
  while (!this->driver->write (this->driver, mem, step_frame )) {
    pthread_mutex_unlock( &this->driver_lock );
    usleep(10000);
    pthread_mutex_lock( &this->driver_lock );
  }
  pthread_mutex_unlock( &this->driver_lock );


> have you tried to just break the sample buffer and send smaller chunks
> to the sound card? we might use rate to calculate the maximum time we
> want it to block waiting.

it works, but i guess there is a little performance hit.

> regards,
>
> Miguel

cheers,
thibaut