一、简介

OpenHarmony-5.0 之前的版本播放器AVPlayer使用gstreamer引擎实现播放能力，可以支持http、https、hls网络协议，但还无法支持rtsp协议。本篇文章介绍如何基于gstreamer扩展支持rtsp协议。

二、前言

版本信息：OpenHarmony-4.0-Release标准32位系统（不同版本代码可能略有不同）
备注：下面代码中“+”代表新增行，“-”代表删除行，“增加”代表以下代码均需添加，“...”代表省略n行代码

三、说明

想要AVPlayer支持rtsp网络协议需要增加rtsp相关的gstreamer库，包括glib库，gstreamer基础能力库，rtsp、rtp、sdp基础库，rtsp、rtp、udp、tcp等插件库等，还需要修改AVPlayer框架层代码。

四、基础库

1、glib

（1）gio

后续与网络相关的插件库都需要依赖glib下的gio库，需要新增编译该库
third_party/glib/BUILD.gn 增加

config("gio_config") {
  visibility = [ ":*" ]
  include_dirs = [
    ".",
    "glib",
    "gobject",
    "gio",
    "gmodule",
    "//third_party/libffi/include",
    "//third_party/zlib/",
  ]
  cflags = [
    "-DG_LOG_DOMAIN=\"GIO\"",
    "-Wno-sign-compare",
    "-Wno-unused-function",
    "-Wno-int-conversion",
    "-DGIO_COMPILATION",
    "-DGIO_MODULE_DIR=\"system/lib/gio/modules\"",
    "-DHAVE_NETLINK",
    "-DLOCALSTATEDIR=\"system\"",
    "-DXDG_PREFIX=_gio_xdg",
   ]
}

ohos_source_set("gio_source") {
  source = [
    gio/xxx.c，
    ...
    gio/inotify/xxx.c,
    ...,
    gio/xdgmime/xxx.c,
    需要编译的C文件
  ]

  config = [ ":gio_config" ]
}

ohos_shared_library("gio") {
  deps = [
    ":gio_source",
    "glib"
    "gobject",
    "gmodule"
    "//third_party/libffi:ffi",
    "//third_party/zlib:shared_libz",
  ]

  part_name = "glib"
  subsystem_name = "thirdparty"
}

生成libgio.z.so，安装到/system/lib/ 目录

（2）glib_packages

third_party/glib/BUILD.gn 修改

group("glib_packages") {
  deps = [
    ":glib",
    ":gmodule",
    ":gobject",
+   ":gio",
  ]
}

2、gstreamer

（1）gstnet

后续的rtsp、udp插件等都需要依赖这个库，这里为了方便编译成了静态库被libgstreamer.z.so链接，后续其他库直接依赖libgstreamer.z.so即可，也可修改编译成动态库
third_party/gstreamer/gstreamer/BUILD.gn 增加

config("gstnet_config") {
  include_dirs = [
    ".",
    "libs",
    "//third_party/glib/glib",
    "//third_party/glib",
    "//third_party/glib/gmodule",
  ]

  cflags = [
    "-DHAVE_CONFIG_H",
    "-fno-strict-aliasing",
    "-Wno-sign-compare",
    "-Wno-builtin-requires-header",
    "-DG_LOG_DOMAIN=\"GStreamer-Net\"",
    "-DBUILDING_GST_NET",
  ]
}
ohos_source_set("gstnet_source") {
  sources = [
    "libs/gst/net/xxx.c",
    ...
  ]

  configs = [ ":gstnet_config" ]
}

ohos_static_library("gstnet") {
  deps = [ 
    ":gstnet_source"
    "//third_party/glib:gio",
  ]

  part_name = "gstreamer"
  subsystem_name = "thirdparty"
}

third_party/gstreamer/gstreamer/BUILD.gn 修改

ohos_shared_library("gstreamer") {
  deps = [
    ":gst_source",
    ":gstprintf",
+   ":gstnet",
    "//third_party/glib:glib",
    "//third_party/glib:gmodule",
    "//third_party/glib:gobject",
  ]

+  include_dirs = [
+    "./libs",
+  ]

  part_name = "gstreamer"
  subsystem_name = "thirdparty"
}

（2）fakesrc element

gstrtspsrc插件运行时会创建该元素，如果不存在会报错
third_party/gstreamer/gstreamer/BUILD.gn 修改

ohos_source_set("gstcoreelements_source") {
  sources = [
    "plugins/elements/gstcapsfilter.c",
    "plugins/elements/gstcoreelementsplugin.c",
    ...
    "plugins/elements/gsttypefindelement.c",
+   “plugins/elements/gstfakesrc.c”,
  ]

注册fakesrc插件
third_party/gstreamer/gstreamer/plugins/elements/gstcoreelementselements.h 修改

    #ifndef OHOS_EXT_FUNC
    /* ohos.ext.func.0032 remove the unused features */
    GST_ELEMENT_REGISTER_DECLARE (capsfilter);
    ...
    GST_ELEMENT_REGISTER_DECLARE (typefind);
    GST_ELEMENT_REGISTER_DECLARE (valve);
    #else
    GST_ELEMENT_REGISTER_DECLARE (capsfilter);
    GST_ELEMENT_REGISTER_DECLARE (fakesink);
+   GST_ELEMENT_REGISTER_DECLARE (fakesrc);
    ...
    GST_ELEMENT_REGISTER_DECLARE (typefind);
    #endif

third_party/gstreamer/gstreamer/plugins/elements/gstcoreelementsplugin.c 修改

    #ifndef OHOS_EXT_FUNC
    /* ohos.ext.func.0032 remove the unused features */
    ret |= GST_ELEMENT_REGISTER (capsfilter, plugin);
    ...
    ret |= GST_ELEMENT_REGISTER (streamiddemux, plugin);
    #else
    ret |= GST_ELEMENT_REGISTER (capsfilter, plugin);
    ret |= GST_ELEMENT_REGISTER (fakesink, plugin);
+   ret |= GST_ELEMENT_REGISTER (fakesrc, plugin);
    ...
    ret |= GST_ELEMENT_REGISTER (multiqueue, plugin);
    #endif

（3）gstaudio

后续插件依赖该库部分未编译的源码
third_party/gstreamer/gstplugins_base/BUILD.gn 修改

ohos_source_set("gstaudio_source") {
  sources = [
    "gst-libs/gst/audio/audio-buffer.c",
    "gst-libs/gst/audio/audio-channel-mixer.c",
    ...
    "gst-libs/gst/audio/streamvolume.c",
+   "gst-libs/gst/audio/gstaudiostreamalign.c"
  ]

（4）gstrtp-1.0

rtp基础库，后续插件依赖，源码库名为gstrtp，与后续插件库名冲突，必须修改库名，这里修改为gstrtp-1.0
third_party/gstreamer/gstplugins_base/BUILD.gn 修改

-    ohos_source_set("rtp_source") {
+    ohos_source_set("rtp-1.0_source") {
        sources = [
          "gst-libs/gst/rtp/gstrtcpbuffer.c",
          ...，
        ]

        configs = [ ":gst_plugins_config" ]
     }

-    ohos_shared_library("gstrtp") {
+    ohos_shared_library("gstrtp-1.0") {
        deps = [
-         ":rtp_source",
+         ":rtp-1.0_source",
          "//third_party/glib:glib",
          "//third_party/glib:gobject",
          "//third_party/gstreamer/gstreamer:gstbase",
          "//third_party/gstreamer/gstreamer:gstreamer",
       ]
      part_name = "gstreamer"
      subsystem_name = "thirdparty"
    }

编译生成libgstrtp-1.0.z.so，安装到/system/lib/ 目录

（5）gstrtsp-1.0

rtsp基础库，后续插件依赖，源码库名不能为gstrtsp
third_party/gstreamer/gstplugins_base/BUILD.gn 增加

ohos_source_set("rtsp-1.0_source") {
  sources = [
    "gst-libs/gst/rtsp/xxx.c",
     ...
  ]

  configs = [ ":gst_plugins_config" ]
}

ohos_shared_library("gstrtsp-1.0") {
  deps = [
    ":rtsp-1.0_source",
    "//third_party/glib:glib",
    "//third_party/glib:gobject",
"//third_party/glib:gio",
    "//third_party/gstreamer/gstreamer:gstbase",
    "//third_party/gstreamer/gstreamer:gstreamer",
":gstvideo",
":gstaudio",
  ]
  part_name = "gstreamer"
  subsystem_name = "thirdparty"
}

编译生成libgstrtsp-1.0.z.so，安装到/system/lib/ 目录

（6）gstsdp

sdp基础库，后续插件依赖
third_party/gstreamer/gstplugins_base/BUILD.gn 增加

ohos_source_set("gstsdp_source") {
  sources = [
    "gst-libs/gst/sdp/gstmikey.c",
    "gst-libs/gst/sdp/gstsdpmessage.c",
  ]

  configs = [ ":gst_plugins_config" ]
}

ohos_shared_library("gstsdp") {
  deps = [
    ":gstsdp_source",
    "//third_party/glib:glib",
    "//third_party/glib:gobject",
"//third_party/glib:gio",
    "//third_party/gstreamer/gstreamer:gstbase",
    "//third_party/gstreamer/gstreamer:gstreamer",
":gstvideo",
":gstaudio",
":gstrtp-1.0",
":gstpbutils",
  ]
  part_name = "gstreamer"
  subsystem_name = "thirdparty"
}

编译生成libgstsdp.z.so，安装到/system/lib/ 目录

（7）gstplugins_base_packages

third_party/gstreamer/gstplugins_base/BUILD.gn 修改

group("gstplugins_base_packages") {
  deps = [
    ":gstapp",
    ":gstaudioconvert",
    ":gstaudioresample",
    ...
    ":gstvideoscale",
+   ":gstrtp-1.0",
+   "gstrtsp-1.0",
+   "gstsdp",
+   "gstpbutils",
  ]
}

五、插件库

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