如何使用tee插件创建含不同FPS并行分支的GStreamer流水线

你的代码存在3个核心错误，和命令行的流水线逻辑不匹配，导致出现卡顿：

• 分支元素链接顺序错误
  命令行中每个分支的逻辑是queue→videorate→帧率约束→nvvideoconvert→autovideosink，你的C++代码中把nvvideoconvert放在了videorate前面，顺序完全颠倒，会引发格式协商异常。
• 缺少显式的帧率Caps约束
  仅设置videorate的rate属性是按比例缩放帧率，无法保证输出帧率固定，你需要新增capsfilter元素显式指定输出帧率，和命令行逻辑对齐。
• 无独立的分支缓冲隔离
  你代码中两个分支的queue没有配置合理的缓冲参数，两个分支处理速度不一致时会互相阻塞，引发整体卡顿。

修复代码示例 #

1. 第一分支修改 #

//First Branch creation
GstPadTemplate *templ;
templ = gst_element_class_get_pad_template (GST_ELEMENT_GET_CLASS (tee), "src_%u");
GstPad *teepad1 = gst_element_request_pad (tee, templ, NULL, NULL);

queue1 = gst_element_factory_make ("queue", NULL);
videorate1 = gst_element_factory_make("videorate",NULL);
// 新增capsfilter用于指定输出帧率
GstElement *caps1 = gst_element_factory_make("capsfilter", NULL);
conv1 = gst_element_factory_make ("nvvideoconvert", NULL);
sink1 = gst_element_factory_make ("autovideosink", NULL);

// 配置1fps的帧率约束
GstCaps *fr_caps1 = gst_caps_from_string("video/x-raw(ANY), framerate=1/1");
g_object_set(G_OBJECT(caps1), "caps", fr_caps1, NULL);
gst_caps_unref(fr_caps1);
// 配置queue缓存避免阻塞
g_object_set(queue1, "max-size-buffers", 10, "max-size-bytes", 0, "max-size-time", 0, NULL);

gst_bin_add_many (GST_BIN (pipeline), queue1, videorate1, caps1, conv1, sink1, NULL);
// 调整链接顺序和命令行对齐
if (!gst_element_link_many (queue1, videorate1, caps1, conv1, sink1, NULL))
{
g_error ("Failed to link first branch elements");
}

GstPad *sinkpad = gst_element_get_static_pad (queue1, "sink");
gst_pad_link (teepad1, sinkpad);
gst_object_unref (sinkpad);
//First Branch creation ends

2. 第二分支修改 #

//Second Branch
GstPadTemplate *templ2;
templ2 = gst_element_class_get_pad_template (GST_ELEMENT_GET_CLASS (tee), "src_%u");
GstPad *teepad2 = gst_element_request_pad (tee, templ2, NULL, NULL);

queue2 = gst_element_factory_make ("queue", NULL);
videorate2 = gst_element_factory_make("videorate",NULL);
// 新增capsfilter用于指定输出帧率
GstElement *caps2 = gst_element_factory_make("capsfilter", NULL);
conv2 = gst_element_factory_make ("nvvideoconvert", NULL);
sink2 = gst_element_factory_make ("autovideosink", NULL);

// 配置30fps的帧率约束
GstCaps *fr_caps2 = gst_caps_from_string("video/x-raw(ANY), framerate=30/1");
g_object_set(G_OBJECT(caps2), "caps", fr_caps2, NULL);
gst_caps_unref(fr_caps2);
// 配置queue缓存避免阻塞
g_object_set(queue2, "max-size-buffers", 10, "max-size-bytes", 0, "max-size-time", 0, NULL);

gst_bin_add_many (GST_BIN (pipeline), queue2, videorate2, caps2, conv2, sink2, NULL);
// 调整链接顺序和命令行对齐
if (!gst_element_link_many (queue2, videorate2, caps2, conv2, sink2, NULL))
{
g_error ("Failed to link second branch elements");
}

GstPad *sinkpad2 = gst_element_get_static_pad (queue2, "sink");
gst_pad_link (teepad2, sinkpad2);
gst_object_unref (sinkpad2);
//Second brach creation ends

内容的提问来源于stack exchange，提问作者goldfish