Disc ID calculation with gstreamer

discid.c

#include <stdlib.h>
#include <stdio.h>

#include <glib.h>
#include <gst/gst.h>
#include <gst/tag/tag.h>
#include <gst/audio/gstaudiocdsrc.h>

int main(void) {
        GstElement *source, *pipeline, *sink;
        GstBus *bus;
        GstMessage *msg;
        GstTagList *tags;
        gchar *device;
        gchar *discid = NULL;
        gchar *discid_full = NULL;
        char **hex_offsets;
        int i, count;

        gst_init(NULL, NULL);
        printf("gstreamer version: %s\n", gst_version_string());

        source = gst_element_make_from_uri(GST_URI_SRC, "cdda://", NULL, NULL);
        pipeline = gst_pipeline_new(NULL);
        sink = gst_element_factory_make("fakesink", NULL);
        bus = gst_pipeline_get_bus(GST_PIPELINE (pipeline));
        if (!source || !pipeline || !sink || !bus) {
                fprintf(stderr, "aborted!\n");
                return 1;
        }

        g_object_get(G_OBJECT (source), "device", &device, NULL);
        g_print("device name: %s\n", device);
        g_free(device);

        gst_bin_add_many(GST_BIN (pipeline), source, sink, NULL);
        gst_element_link(source, sink);

        gst_element_set_state(pipeline, GST_STATE_PAUSED);
        while(1) {
                msg = gst_bus_pop(bus);
                if (msg && GST_MESSAGE_TYPE (msg) == GST_MESSAGE_TAG) {
                        gst_message_parse_tag(msg, &tags);
                        gst_tag_list_get_string(tags,
                                        GST_TAG_CDDA_MUSICBRAINZ_DISCID,
                                        &discid);
                        gst_tag_list_get_string(tags,
                                        GST_TAG_CDDA_MUSICBRAINZ_DISCID_FULL,
                                        &discid_full);
                        if (tags) gst_tag_list_free(tags);
                        break;
                }
                if (msg) gst_message_unref(msg);
        }
        g_print("discid: %s\n", discid);
        /* display discid_full in readable form (non-hex) */
        hex_offsets = g_strsplit(discid_full, " ", 0);
        count = g_strv_length(hex_offsets);
        g_print("discid full: ");
        for (i = 1; i < count; i++) {
                g_print("%ld ", strtol(hex_offsets[i], 0, 16));
        }
        g_print("\n");
        return 0;
}

Makefile

CFLAGS=`pkg-config --cflags gstreamer-plugins-base-1.0`
LIBS=`pkg-config --libs gstreamer-plugins-base-1.0`

discid: discid.c
        gcc -Wall $^ -o $@ $(CFLAGS) $(LIBS)