PulseAudio:线程主循环数据回调

时间:2013-03-20 22:03:41

标签: callback pulseaudio

我有一个关于如何使用线程主循环数据回调功能的问题。我一直在看文档并试一试。   为了尝试数据回调,我采用了AsyncDeviceList示例,将mainloop更改为线程化的mainloop并尝试在此处进行回调,使用pa_threaded_mainloop_signal(ml,1)和pa_threaded_mainloop_accept()。我不确定我是否将信号(ml,1)放在错误的位置,但程序对我来说很重要。我注意到的是从回调调用signal(1)之后,当wait()唤醒时,get_state()的返回值仍然是OPERATION_RUNNING。   根据我的理解,这是有道理的,因为需要调用accept()以使信号进展。但是,文档的数据回调示例是以这种方式编码的,因此我对如何正确地进行此操作感到有点迷茫。   一些帮助和澄清会有所帮助。此外,我将在解析时将此示例添加到pulseaudio wiki页面。

P.S。我复制了下面的代码。 编译: 'gcc -Wall -o pulsedevicelist pulsedevicelist.c -lpulse' 资源: http://freedesktop.org/software/pulseaudio/doxygen/threaded_mainloop.html http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/Samples/AsyncDeviceList

#include <stdio.h>
#include <string.h>
#include <pulse/pulseaudio.h>
#include <pulse/stream.h>

// Field list is here: http://0pointer.de/lennart/projects/pulseaudio/doxygen/structpa__sink__info.html
typedef struct pa_devicelist {
        uint8_t initialized;
        char name[512];
        uint32_t index;
        char description[256];
} pa_devicelist_t;

void pa_state_cb(pa_context *c, void *userdata);
void pa_sinklist_cb(pa_context *c, const pa_sink_info *l, int eol, void *userdata);
void pa_sourcelist_cb(pa_context *c, const pa_source_info *l, int eol, void *userdata);
int pa_get_devicelist(pa_devicelist_t *input, pa_devicelist_t *output);

pa_threaded_mainloop *pa_ml;

int main(int argc, char *argv[]) {
    int ctr;

    // This is where we'll store the input device list
    pa_devicelist_t pa_input_devicelist[16];

    // This is where we'll store the output device list
    pa_devicelist_t pa_output_devicelist[16];

    if (pa_get_devicelist(pa_input_devicelist, pa_output_devicelist) < 0) {
        fprintf(stderr, "failed to get device list\n");
        return 1;
    }

    for (ctr = 0; ctr < 16; ctr++) {
        if (! pa_output_devicelist[ctr].initialized) {
            break;
        }
        printf("=======[ Output Device #%d ]=======\n", ctr+1);
        printf("Description: %s\n", pa_output_devicelist[ctr].description);
        printf("Name: %s\n", pa_output_devicelist[ctr].name);
        printf("Index: %d\n", pa_output_devicelist[ctr].index);
        printf("\n");
    }

    for (ctr = 0; ctr < 16; ctr++) {
        if (! pa_input_devicelist[ctr].initialized) {
            break;
        }
        printf("=======[ Input Device #%d ]=======\n", ctr+1);
        printf("Description: %s\n", pa_input_devicelist[ctr].description);
        printf("Name: %s\n", pa_input_devicelist[ctr].name);
        printf("Index: %d\n", pa_input_devicelist[ctr].index);
        printf("\n");
    }

    return 0;
}

int pa_get_devicelist(pa_devicelist_t *input, pa_devicelist_t *output) {
    // Define our pulse audio loop and connection variables
    //pa_threaded_mainloop *pa_ml;
    pa_mainloop_api *pa_mlapi;
    pa_operation *pa_op;
    pa_context *pa_ctx;

    pa_operation_state_t temp;

    // We'll need these state variables to keep track of our requests
    int state = 0;
    int pa_ready = 0;

    // Initialize our device lists
    memset(input, 0, sizeof(pa_devicelist_t) * 16);
    memset(output, 0, sizeof(pa_devicelist_t) * 16);

    // Create a mainloop API and connection to the default server
    pa_ml = pa_threaded_mainloop_new();
    pa_mlapi = pa_threaded_mainloop_get_api(pa_ml);
    pa_ctx = pa_context_new(pa_mlapi, "test");

    //pa_stream *s = pa_stream_new(pa_ctx, "stream", &ss, &map);

    // This function connects to the pulse server
    pa_context_connect(pa_ctx, NULL, PA_CONTEXT_NOFLAGS, NULL);

    // This function defines a callback so the server will tell us it's state.
    // Our callback will wait for the state to be ready.  The callback will
    // modify the variable to 1 so we know when we have a connection and it's
    // ready.
    // If there's an error, the callback will set pa_ready to 2
    pa_context_set_state_callback(pa_ctx, pa_state_cb, &pa_ready);
    pa_threaded_mainloop_start(pa_ml);
    // Now we'll enter into an infinite loop until we get the data we receive
    // or if there's an error
    for (;;) {
        // We can't do anything until PA is ready, so just iterate the mainloop
        // and continue
        if (pa_ready == 0) {
            //pa_mainloop_iterate(pa_ml, 1, NULL);
            continue;
        }
        // We couldn't get a connection to the server, so exit out
        if (pa_ready == 2) {
            pa_context_disconnect(pa_ctx);
            pa_context_unref(pa_ctx);
            pa_threaded_mainloop_free(pa_ml);
            return -1;
        }
        // At this point, we're connected to the server and ready to make
        // requests
        switch (state) {
            // State 0: we haven't done anything yet
            case 0:
                // This sends an operation to the server.  pa_sinklist_info is
                // our callback function and a pointer to our devicelist will
                // be passed to the callback The operation ID is stored in the
                // pa_op variable

                pa_threaded_mainloop_lock(pa_ml);

                pa_op = pa_context_get_sink_info_list(pa_ctx,
                        pa_sinklist_cb,
                        output
                        );

                 while (pa_operation_get_state(pa_op) == PA_OPERATION_RUNNING) { // MF
                     temp = pa_operation_get_state(pa_op); // MF
                     pa_threaded_mainloop_wait(pa_ml); // MF
                 } // MF
                // Update state for next iteration through the loop
                state++;
                break;
            case 1:
                // Now we wait for our operation to complete.  When it's
                // complete our pa_output_devicelist is filled out, and we move
                // along to the next state
                if (pa_operation_get_state(pa_op) == PA_OPERATION_DONE) {
                    pa_operation_unref(pa_op);


                    pa_threaded_mainloop_accept(pa_ml); // MF
                    pa_threaded_mainloop_unlock(pa_ml); // MF

                    // Now we perform another operation to get the source
                    // (input device) list just like before.  This time we pass
                    // a pointer to our input structure
                    pa_threaded_mainloop_lock(pa_ml);

                    pa_op = pa_context_get_source_info_list(pa_ctx,
                            pa_sourcelist_cb,
                            input
                            );

                    // Update the state so we know what to do next
                    state++;
                }
                break;
            case 2:
                if (pa_operation_get_state(pa_op) == PA_OPERATION_DONE) {
                    // Now we're done, clean up and disconnect and return
                    pa_operation_unref(pa_op);
                    pa_context_disconnect(pa_ctx);
                    pa_context_unref(pa_ctx);
                    pa_threaded_mainloop_free(pa_ml);
                    return 0;
                }
                break;
            default:
                // We should never see this state
                fprintf(stderr, "in state %d\n", state);
                return -1;
        }
        // Iterate the main loop and go again.  The second argument is whether
        // or not the iteration should block until something is ready to be
        // done.  Set it to zero for non-blocking.
        //pa_mainloop_iterate(pa_ml, 1, NULL);
    }
}

// This callback gets called when our context changes state.  We really only
// care about when it's ready or if it has failed
void pa_state_cb(pa_context *c, void *userdata) {
        pa_context_state_t state;
        int *pa_ready = (int *)userdata;

        state = pa_context_get_state(c);
        switch  (state) {
                // There are just here for reference
                case PA_CONTEXT_UNCONNECTED:
                case PA_CONTEXT_CONNECTING:
                case PA_CONTEXT_AUTHORIZING:
                case PA_CONTEXT_SETTING_NAME:
                default:
                        break;
                case PA_CONTEXT_FAILED:
                case PA_CONTEXT_TERMINATED:
                        *pa_ready = 2;
                        break;
                case PA_CONTEXT_READY:
                        *pa_ready = 1;
                        break;
        }
}

// pa_mainloop will call this function when it's ready to tell us about a sink.
// Since we're not threading, there's no need for mutexes on the devicelist
// structure
void pa_sinklist_cb(pa_context *c, const pa_sink_info *l, int eol, void *userdata) {
    pa_devicelist_t *pa_devicelist = (pa_devicelist_t *)userdata;
    int ctr = 0;

    // If eol is set to a positive number, you're at the end of the list
    if (eol > 0) {
        pa_threaded_mainloop_signal(pa_ml, 1); // MF
        return;
    }

    // We know we've allocated 16 slots to hold devices.  Loop through our
    // structure and find the first one that's "uninitialized."  Copy the
    // contents into it and we're done.  If we receive more than 16 devices,
    // they're going to get dropped.  You could make this dynamically allocate
    // space for the device list, but this is a simple example.
    for (ctr = 0; ctr < 16; ctr++) {
        if (! pa_devicelist[ctr].initialized) {
            strncpy(pa_devicelist[ctr].name, l->name, 511);
            strncpy(pa_devicelist[ctr].description, l->description, 255);
            pa_devicelist[ctr].index = l->index;
            pa_devicelist[ctr].initialized = 1;
            break;
        }
    }

}

// See above.  This callback is pretty much identical to the previous
void pa_sourcelist_cb(pa_context *c, const pa_source_info *l, int eol, void *userdata) {
    pa_devicelist_t *pa_devicelist = (pa_devicelist_t *)userdata;
    int ctr = 0;

    if (eol > 0) {
        return;
    }

    for (ctr = 0; ctr < 16; ctr++) {
        if (! pa_devicelist[ctr].initialized) {
            strncpy(pa_devicelist[ctr].name, l->name, 511);
            strncpy(pa_devicelist[ctr].description, l->description, 255);
            pa_devicelist[ctr].index = l->index;
            pa_devicelist[ctr].initialized = 1;
            break;
        }
    }

}

0 个答案:

没有答案