问如何减少使用ALSA读取音频时的延迟？

EN

/** Set the current thread's priority
\param priority <0 implies maximum priority, otherwise must be between sched_get_priority_max and sched_get_priority_min
\return 0 on success, error code otherwise
*/
static int changeThreadPriority(int priority){
  int ret;
  pthread_t thisThread = pthread_self(); // get the current thread
  struct sched_param origParams, params;
  int origPolicy, policy = SCHED_FIFO, newPolicy=0;

  if ((ret = pthread_getschedparam(thisThread, &origPolicy, &origParams))!=0)
    return ALSA::ALSADebug().evaluateError(ret, "when trying to pthread_getschedparam\n");
  printf("ALSA::Stream::changeThreadPriority : Current thread policy %d and priority %d\n", origPolicy, origParams.sched_priority);

  if (priority<0) //maximum priority
    params.sched_priority = sched_get_priority_max(policy);
  else
    params.sched_priority = priority;

  if (params.sched_priority>sched_get_priority_max(policy))
    return ALSA::ALSADebug().evaluateError(ALSA_SCHED_PRIORITY_ERROR, "requested priority is too high\n");
  if (params.sched_priority<sched_get_priority_min(policy))
    return ALSA::ALSADebug().evaluateError(ALSA_SCHED_PRIORITY_ERROR, "requested priority is too low\n");

  if ((ret = pthread_setschedparam(thisThread, policy, &params))!=0)
    return ALSA::ALSADebug().evaluateError(ret, "when trying to pthread_setschedparam - are you su or do you have permission to set this priority?\n");
  if ((ret = pthread_getschedparam(thisThread, &newPolicy, &params))!=0)
    return ALSA::ALSADebug().evaluateError(ret, "when trying to pthread_getschedparam\n");
  if(policy != newPolicy)
    return ALSA::ALSADebug().evaluateError(ALSA_SCHED_POLICY_ERROR, "requested scheduler policy is not correctly set\n");
  printf("ALSA::Stream::changeThreadPriority : New thread priority changed to %d\n", params.sched_priority);

  return 0;
}