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primarykey
Id
11372584
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0
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0
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3
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2012-07-07T05:38:52.113
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2012-07-07T05:38:52.113
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416224
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11347346
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2
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2
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text
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Using ALSA directly is overly complicated, so I hope a Gstreamer solution is fine to you too. Gstreamer gives a nice abstraction to ALSA/OSS/Pulseaudio/you name it -- and is ubiquitous in the Linux world. I wrote a little library that will open a <code>FILE</code> object where you can fwrite PCM data into: <a href="https://github.com/Kijewski/gstreamer_file" rel="nofollow">Gstreamer file</a>. The actual code is less than 100 lines. Use use it like that: <pre><code>FILE *output = fopen_gst(rate, channels, bit_depth); // open audio output file while (have_more_data) fwrite(data, amount, 1, output); // output audio data fclose(output); // close the output file </code></pre> I added an <a href="https://github.com/Kijewski/gstreamer_file/blob/master/mpg123_example.c" rel="nofollow">mpg123 example</a>, too. Here is the whole file (in case Github get's out of business ;-) ): <pre><code>/** * gstreamer_file.c * Copyright 2012 René Kijewski <rene.SURNAME@fu-berlin.de> * License: LGPL 3.0 (http://www.gnu.org/licenses/lgpl-3.0) */ #include "gstreamer_file.h" #include <stdbool.h> #include <stdlib.h> #include <unistd.h> #include <glib.h> #include <gst/gst.h> #ifndef _GNU_SOURCE # error "You need to add -D_GNU_SOURCE to the GCC parameters!" #endif /** * Cookie passed to the callbacks. */ typedef struct { /** { file descriptor to read from, fd to write to } */ int pipefd[2]; /** Gstreamer pipeline */ GstElement *pipeline; } cookie_t; static ssize_t write_gst(void *cookie_, const char *buf, size_t size) { cookie_t *cookie = cookie_; return write(cookie->pipefd[1], buf, size); } static int close_gst(void *cookie_) { cookie_t *cookie = cookie_; gst_element_set_state(cookie->pipeline, GST_STATE_NULL); /* we are finished */ gst_object_unref(GST_OBJECT(cookie->pipeline)); /* we won't access the pipeline anymore */ close(cookie->pipefd[0]); /* we won't write anymore */ close(cookie->pipefd[1]); /* we won't read anymore */ free(cookie); /* dispose the cookie */ return 0; } FILE *fopen_gst(long rate, int channels, int depth) { /* initialize Gstreamer */ if (!gst_is_initialized()) { GError *error; if (!gst_init_check(NULL, NULL, &error)) { g_error_free(error); return NULL; } } /* get a cookie */ cookie_t *cookie = malloc(sizeof(*cookie)); if (!cookie) { return NULL; } /* open a pipe to be used between the caller and the Gstreamer pipeline */ if (pipe(cookie->pipefd) != 0) { close(cookie->pipefd[0]); close(cookie->pipefd[1]); free(cookie); return NULL; } /* set up the pipeline */ char description[256]; snprintf(description, sizeof(description), "fdsrc fd=%d ! " /* read from a file descriptor */ "audio/x-raw-int, rate=%ld, channels=%d, " /* get PCM data */ "endianness=1234, width=%d, depth=%d, signed=true ! " "audioconvert ! audioresample ! " /* convert/resample if needed */ "autoaudiosink", /* output to speakers (using ALSA, OSS, Pulseaudio ...) */ cookie->pipefd[0], rate, channels, depth, depth); cookie->pipeline = gst_parse_launch_full(description, NULL, GST_PARSE_FLAG_FATAL_ERRORS, NULL); if (!cookie->pipeline) { close(cookie->pipefd[0]); close(cookie->pipefd[1]); free(cookie); return NULL; } /* open a FILE with specialized write and close functions */ cookie_io_functions_t io_funcs = { NULL, write_gst, NULL, close_gst }; FILE *result = fopencookie(cookie, "w", io_funcs); if (!result) { close_gst(cookie); return NULL; } /* start the pipeline (of cause it will wait for some data first) */ gst_element_set_state(cookie->pipeline, GST_STATE_PLAYING); return result; } </code></pre>
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1. POALSA equivalent to /dev/audio dump?
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1. USkay
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