如何使用gstreamer api提取H264中的sps和pps信息

使用GStreamer API提取H.264的SPS和PPS信息，需要使用h264parse元素来解析H.264码流，并从中提取SPS和PPS。以下是使用GStreamer API提取H.264中的SPS和PPS信息的示例代码：

#include <gst/gst.h>

int main(int argc, char *argv[]) {
    GstElement *pipeline, *h264parse;
    GstCaps *caps;
    GstBuffer *sps_buf, *pps_buf;
    GstMapInfo map_info;
    gboolean ret;

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

    /* Create the elements */
    pipeline = gst_pipeline_new("mypipeline");
    h264parse = gst_element_factory_make("h264parse", "myh264parse");

    /* Set the caps for h264parse element */
    caps = gst_caps_new_simple("video/x-h264",
                               "stream-format", G_TYPE_STRING, "byte-stream",
                               NULL);
    g_object_set(G_OBJECT(h264parse), "caps", caps, NULL);
    gst_caps_unref(caps);

    /* Add h264parse element to the pipeline */
    gst_bin_add(GST_BIN(pipeline), h264parse);

    /* Link the elements */
    if (!gst_element_link_many(h264parse, NULL)) {
        g_printerr("Failed to link elements\n");
        return -1;
    }

    /* Start the pipeline */
    gst_element_set_state(pipeline, GST_STATE_PLAYING);

    /* Wait for the SPS and PPS buffers to be emitted */
    ret = gst_element_get_state(h264parse, NULL, NULL, GST_CLOCK_TIME_NONE);
    if (ret != GST_STATE_CHANGE_SUCCESS) {
        g_printerr("Failed to get state of h264parse element\n");
        return -1;
    }
    ret = gst_element_query_position(h264parse, GST_FORMAT_TIME, NULL);
    if (ret != TRUE) {
        g_printerr("Failed to query position of h264parse element\n");
        return -1;
    }
    ret = gst_element_query_duration(h264parse, GST_FORMAT_TIME, NULL);
    if (ret != TRUE) {
        g_printerr("Failed to query duration of h264parse element\n");
        return -1;
    }
    ret = gst_element_query_latency(h264parse, GST_FORMAT_TIME, NULL, NULL);
    if (ret != TRUE) {
        g_printerr("Failed to query latency of h264parse element\n");
        return -1;
    }
    gst_element_send_event(h264parse, gst_event_new_seek(1.0, GST_FORMAT_TIME,
                                                         GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE,
                                                         GST_SEEK_TYPE_NONE, 0,
                                                         GST_SEEK_TYPE_NONE, GST_CLOCK_TIME_NONE));

    ret = gst_element_get_state(h264parse, NULL, NULL, GST_CLOCK_TIME_NONE);
    if (ret != GST_STATE_CHANGE_SUCCESS) {
        g_printerr("Failed to get state of h264parse element\n");
        return -1;
    }

    sps_buf = gst_buffer_new();
    pps_buf = gst_buffer_new();

    ret = gst_element_query_convert(h264parse, GST_FORMAT_TIME, GST_FORMAT_BUFFER, GST_SECOND, &sps_buf);
    if (ret != TRUE) {
        g_printerr("Failed to query convert SPS buffer\n");
        return -1;
    }

    ret = gst_element_query_convert(h264parse, GST_FORMAT_TIME, GST_FORMAT_BUFFER, 2 * GST_SECOND, &pps_buf);
    if (ret != TRUE) {
        g_printerr("Failed to query convert PPS buffer\n");
        return -1;
    }

    /* Extract the SPS and PPS data */
    gst_buffer_map(sps_buf, &map_info, GST_MAP_READ);
    /* map_info.data contains SPS data */
    gst_buffer_unmap(sps_buf, &map_info);

    gst_buffer_map(pps_buf, &map_info, GST_MAP_READ);
    /* map_info.data contains PPS data */
    gst_buffer_unmap(pps_buf, &map_info);

    /* Stop and cleanup the pipeline */
    gst_element_set_state(pipeline, GST_STATE_NULL);
    gst_object_unref(pipeline);

    return 0;
}

在上述代码中，我们创建了一个GStreamer管道，其中包含了h264parse元素。我们设置了h264parse的caps，然后将h264parse元素添加到管道中，并启动了管道。

我们使用gst_element_send_event()来发送一个seek事件，让h264parse元素从H.264码流中提取SPS和PPS信息。我们使用gst_element_query_convert()来获取SPS和PPS的缓冲区，并使用gst_buffer_map()和gst_buffer_unmap()来提取SPS和PPS数据。

请注意，在实际使用中，你需要根据需要修改代码，并添加适当的错误处理和释放资源的代码。