alsa-lib/NOTES

Old versus new PCM API (values returned using indirect pointers)
================================================================

From the binary compatibility view, there is no change. For compilation,
1.0 ALSA applications do not need any change. The older applications must
use this include sequence:

#define ALSA_PCM_OLD_HW_PARAMS_API
#define ALSA_PCM_OLD_SW_PARAMS_API
#include <alsa/asoundlib.h>

If you use already the new API, you may remove old defines selecting
this API, because they are no longer used:

#define ALSA_PCM_NEW_HW_PARAMS_API
#define ALSA_PCM_NEW_SW_PARAMS_API


Verbose Error Messages
======================

Since version 1.0.8, assert() for some non-fatal errors are removed
and error messages are no longer shown to stderr as default.  Instead,
the error messages appear only when the environment variable
LIBASOUND_DEBUG is set (to a non-empty value).

When LIBASOUND_DEBUG=1 is set, the errors in hw_params configuration
will be dumped to stderr.  Note that this will show even the non-fatal
errors of plug layer (trial-and-error of parameters).
When LIBASOUND_DEBUG=2 is set, the default error message handler calls
assert() to catch with a debugger, in addition to parameter debugging.

This feature is disabled when --with-debug=no is passed to configure,
i.e. no strict checking is done in alsa-lib.