gstreamer获取h264码流中SPS和PPS信息的方法 举个C语言例子

以下是使用 C 语言的 GStreamer API 获取 H264 码流中 SPS 和 PPS 信息的示例代码：

#include <gst/gst.h>

int main(int argc, char *argv[]) {
    GstElement *pipeline, *src, *h264parse, *capsfilter, *splitter, *queue_sps, *queue_pps, *sink;
    GstBus *bus;
    GstMessage *msg;
    GstCaps *caps;
    GstBuffer *buf;
    gboolean ret;
    GError *err = NULL;
    guint8 *sps_data = NULL, *pps_data = NULL;
    gsize sps_size = 0, pps_size = 0;

    /* Initialize GStreamer */
    gst_init(&argc, &argv);

    /* Create elements */
    pipeline = gst_pipeline_new("pipeline");
    src = gst_element_factory_make("filesrc", "src");
    h264parse = gst_element_factory_make("h264parse", "parse");
    capsfilter = gst_element_factory_make("capsfilter", "caps");
    splitter = gst_element_factory_make("splitter", "split");
    queue_sps = gst_element_factory_make("queue", "sps");
    queue_pps = gst_element_factory_make("queue", "pps");
    sink = gst_element_factory_make("fakesink", "sink");

    /* Set properties */
    g_object_set(G_OBJECT(src), "location", "test.h264", NULL);
    caps = gst_caps_from_string("video/x-h264, stream-format=byte-stream");
    g_object_set(G_OBJECT(capsfilter), "caps", caps, NULL);

    /* Build the pipeline */
    gst_bin_add_many(GST_BIN(pipeline), src, h264parse, capsfilter, splitter, queue_sps, queue_pps, sink, NULL);
    gst_element_link_many(src, h264parse, capsfilter, splitter, NULL);
    gst_element_link_many(splitter, queue_sps, sink, NULL);
    gst_element_link_many(splitter, queue_pps, sink, NULL);

    /* Start playing */
    ret = gst_element_set_state(pipeline, GST_STATE_PLAYING);
    if (ret == GST_STATE_CHANGE_FAILURE) {
        g_printerr("Failed to start pipeline\n");
        return -1;
    }

    /* Wait until error or state change */
    bus = gst_element_get_bus(pipeline);
    msg = gst_bus_timed_pop_filtered(bus, GST_CLOCK_TIME_NONE, GST_MESSAGE_ERROR | GST_MESSAGE_STATE_CHANGED);
    if (msg != NULL) {
        gst_message_unref(msg);
    }

    /* Get SPS and PPS data */
    while (sps_data == NULL || pps_data == NULL) {
        GstSample *sample;
        GstBuffer *buf;
        sample = gst_app_sink_pull_sample(GST_APP_SINK(queue_sps));
        if (sample != NULL) {
            buf = gst_sample_get_buffer(sample);
            sps_data = gst_buffer_extract_dup(buf, 0, gst_buffer_get_size(buf), &err);
            sps_size = gst_buffer_get_size(buf);
            gst_sample_unref(sample);
        }
        sample = gst_app_sink_pull_sample(GST_APP_SINK(queue_pps));
        if (sample != NULL) {
            buf = gst_sample_get_buffer(sample);
            pps_data = gst_buffer_extract_dup(buf, 0, gst_buffer_get_size(buf), &err);
            pps_size = gst_buffer_get_size(buf);
            gst_sample_unref(sample);
        }
    }

    /* Output SPS and PPS data */
    g_print("SPS:");
    for (int i = 0; i < sps_size; i++) {
        g_print(" %02x", sps_data[i]);
    }
    g_print("\n");

    g_print("PPS:");
    for (int i = 0; i < pps_size; i++) {
        g_print(" %02x", pps_data[i]);
    }
    g_print("\n");

    /* Stop playing */
    gst_element_set_state(pipeline, GST_STATE_NULL);
    gst_object_unref(pipeline);

    return 0;
}

这段代码与前面的 Python 代码类似，使用了 `h264parse` 元素将 H264 码流解析为 NAL 单元，使用 `capsfilter` 元素设置媒体格式，并使用 `splitter` 元素将 NAL 单元分离为 SPS、PPS 和 IDR 帧等单元。不同之处在于，这里使用了 `gst_app_sink_pull_sample()` 方法从队列中获取数据。由于 C 语言没有 Python 中的 `bytearray` 类型，所以这里使用了 `guint8 *` 类型的指针来保存 SPS 和 PPS 数据，并使用 `gsize` 类型的变量保存数据的大小。