is there an example of a full-duplex ALSA connection in C? I've read that it is supported, but all the introductory examples I saw did either record or play a sound sample, but I'd like to have one handler that can do both for my VoIP-app.
Big thanks for help, Jens
一些名叫艾伦的人发表了这篇很好(但很旧)的教程, 全双工ALSA ,用C写的。
You provide a link to both handles and pump them in turn. Here's alan's code elided and commented.
// the device plughw handle dynamic sample rate and type conversion.
// there are a range of alternate devices defined in your alsa.conf
// try:
// locate alsa.conf
// and check out what devices you have in there
//
// The following device is PLUG:HW:Device:0:Subdevice:0
// Often simply plug, plughw, plughw:0, will have the same effect
//
char *snd_device_in = "plughw:0,0";
char *snd_device_out = "plughw:0,0";
// handle constructs to populate with our links
snd_pcm_t *playback_handle;
snd_pcm_t *capture_handle;
//this is the usual construct... If not fail BLAH
if ((err = snd_pcm_open(&playback_handle, snd_device_out, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
fprintf(stderr, "cannot open output audio device %s: %s\n", snd_device_in, snd_strerror(err));
exit(1);
}
// And now the CAPTURE
if ((err = snd_pcm_open(&capture_handle, snd_device_in, SND_PCM_STREAM_CAPTURE, 0)) < 0) {
fprintf(stderr, "cannot open input audio device %s: %s\n", snd_device_out, snd_strerror(err));
exit(1);
}
then config and pump them.
A ring mod could do the job: http://soundprogramming.net/programming_and_apis/creating_a_ring_buffer or you could use alans way outlined above.
It was my first requirements to a Linux/Unix VoIP projects where I need to know about all of the available audio devices capability and name. Then I need to use these devices to capture and playback the audio.
For everyone's help I have made a (.so) library and a sample Application demonstrating the use of this library in c++.
The output of my library is like-
[root@~]# ./IdeaAudioEngineTest
HDA Intel plughw:0,0
HDA Intel plughw:0,2
USB Audio Device plughw:1,0
The library provides functionality to capture and playback real-time audio data.
Full source with documentation is available in IdeaAudio library with Duplex Alsa Audio
Library source is now open at github.com
See also latency.c
, included in alsa-lib
source; on the ALSA wiki:
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.