mirrors/alsa-lib
1
0
Fork 0
mirror of https://github.com/alsa-project/alsa-lib.git synced 2025-10-29 05:40:25 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

More updates

Browse source
This commit is contained in:
Jaroslav Kysela 2001-10-24 14:13:49 +00:00
parent de592e7c22
commit caa8d5372e
1 changed files with 26 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

28
doc/pcm.doxygen
View file

@ -197,8 +197,10 @@ returns 24 in the case.
There are two methods to transfer samples in application. The first method
is the standard read / write one. The second method, uses the direct audio
buffer to communicate with the device while ALSA library manages this space
itself. You can find example of all communication schemes for playback
in \ref example_test_pcm "Sine-wave generator example".
itself. You can find examples of all communication schemes for playback
in \ref example_test_pcm "Sine-wave generator example". To complete the
list, we should note that \link ::snd_pcm_wait \endlink function contains
embedded poll waiting implementation.
\subsection alsa_pcm_rw Read / Write transfer
@ -336,6 +338,17 @@ samples - \link ::snd_pcm_status_get_overrange \endlink. The last two
parameters - avail_max and overrange are reset to zero after the status
call.
\subsection pcm_status_fast Obtaining fast device status
The function \link ::snd_pcm_avail_update \endlink updates the current
available count of samples for writting (playback) or filled samples for
reading (capture).
<p>
The function \link ::snd_pcm_delay \endlink returns the delay in samples.
For playback, it means count of samples in the ring buffer before
the next sample will be sent to DAC. For capture, it means count of samples
in the ring buffer before the next sample will be captured from ADC.
\section pcm_action Managing the stream state
These functions directly and indirectly affecting the stream state:
@ -381,6 +394,17 @@ functions can conditionally start the stream -
\link ::SND_PCM_STATE_RUNNING \endlink. They depend on the start threshold
software parameter.
\section pcm_sync Streams synchronization
There are two functions allowing link multiple streams together. In the
case, the linking means that all operations are synchronized. Because the
drivers cannot guarantee the synchronization (sample resolution) on hardware
lacking this feature, the \link ::snd_pcm_info_get_sync \endlink function
returns synchronization ID - \link ::snd_pcm_sync_id_t \endlink, which is equal
for hardware synchronizated streams. When the \link ::snd_pcm_link \endlink
function is called, all operations managing the stream state for these two
streams are joined. The oposite function is \link ::snd_pcm_unlink \endlink.
\section pcm_examples Examples
The full featured examples with cross-links: