The ALSA implementation can be found in the Read / Write transfer section. There are two basic behaviours of these functions - blocked and non-blocked (see the O_NONBLOCK flag for the standard C open function - see 'man 2 open'). Great article. Is Esperanto likely to survive in future? navigate here
Two times the period size seems to be a good initial write size? snd_pcm_sframes_tsnd_pcm_writei (snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size) Write interleaved frames to a PCM. The hardware parameters cannot be changed when the stream is running (active). Transfer align The read / write transfers can be aligned to this sample count. see here
I grabbed a sample here, $ wget http://freewavesamples.com/files/Roland-JD-990-Windchimes.wav I saved listing 3 as "listing3.c" and compiled, $ gcc $(pkg-config --cflags --libs alsa) listing3.c -o listing3 Then to test, $ cat Roland-JD-990-Windchimes.wav This function is a light version of snd_pcm_avail() . They depend on the start threshold software parameter. int snd_pcm_prepare ( snd_pcm_t * pcm) Prepare PCM for use.
My main issue is that I'm almost out of time to spend on this part of the project. :-( Thanks for your help. Here are some of the readings. The function snd_pcm_delay() returns the delay in samples. Snd_pcm_drain Transfer methods in UNIX environments In the UNIX environment, data chunk acknowledges are received via standard I/O calls or event waiting routines (poll or select function).
Examples: /test/pcm.c. intsnd_pcm_open_lconf (snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode, snd_config_t *lconf) Opens a PCM using local configuration. ok I just found it. http://stackoverflow.com/questions/23092895/alsa-buffer-underrun-on-snd-pcm-writei-call From your comment I gather that right after playing the sound, which is only a few milliseconds in length, I have to drain and close the connection instead of keeping it
I'll try and upgrade to Fedora 12, and then try again. Snd_pcm_hw_params_set_channels The opposite function is snd_pcm_unlink(). rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0); looking at the API reference for this call we see that the last parameter in this call is int mode. Note: the caller is requested to release the returned value via snd_pcm_free_chmaps().
It is built on top of the control interface. have a peek at this web-site [email protected] Kudoos and hats off for the Article Submitted by Anonymous on Wed, 02/17/2010 - 02:18. Alsa Pcm Example Examples: /test/latency.c. Snd_pcm_writei Example Puzzle similar to 15-puzzle but more moveable pieces?
Anything I record is messed up in random data. http://phabletkeyboards.com/error-codes/snd-pcm-readi-error-codes.php One digital value is called sample. Display format Submitted by MikeW (not verified) on Thu, 09/22/2005 - 11:56. The raw interface works directly with the MIDI events, and the programmer is responsible for managing the protocol and timing. Snd_pcm_recover
The overrun can happen when an application does not take new captured samples in time from alsa-lib. -ESTRPIPE This error means that system has suspended drivers. Why does Fleur say "zey, ze" instead of "they, the" in Harry Potter? For this reason the function takes a pointer to an unsigned integer, so it can change the value of our rrate variable to reflect the actual rate set. http://phabletkeyboards.com/error-codes/snd-pcm-write-error-codes.php That way, you have a buffer of slack.
A period stores frames, each of which contains the samples captured at one point in time. Alsa Error Codes Example: tee:hw,'/tmp/out.raw',raw File device The file device is file plugin with null plugin as slave. The Application Buffer Over and Under Run When a sound device is active, data is transferred continuously between the hardware and application buffers.
A channel map is represented by an integer array, beginning with the channel map type, followed by the number of channels, and the position of each channel. This is a really handy structure, because the first thing we do is grab the associated device handle from it. You can find examples of all communication schemes for playback in Sine-wave generator example. Snd_pcm_wait After reading through web, I found that snd_pcm_drop() should also work similar to snd_pcm_close().
undocumented == BAD MOJO! The devices might be virtual, physical or a mix of both. Did I participate in the recent DDoS attacks on Dyn's DNS service? http://phabletkeyboards.com/error-codes/soap-api-error-codes.php Sequencer interface: a higher-level interface for MIDI programming and sound synthesis than the raw MIDI interface.
There's one last step we have to take: prepare the device: snd_pcm_prepare (pcm_handle); Now we can write! So when we've been through all this trouble to set up our device, we want to actually start playing. In this case, application should do next event waiting using poll() or select(). Please don't fill out this field.
for code Submitted by Elie (not verified) on Tue, 12/30/2008 - 00:24. Try running Listing 4 and redirecting the output to a file. The poll desctiptor array should have the size returned by ::snd_pcm_poll_descriptors_count() function.