[Embedded] Buildroot -- 建置 gstreamer 的流程

本篇說明如何編譯gstreamer以及相關檔案。為了簡單，僅記錄使用 buildroot 的編譯步驟，如下：

 1. 安裝 buildroot

a. 安裝 buildroot，安裝過程可參考此篇  。

b. 執行下列指令，試試 buildroot 建立的image是否正確。 

$ cd output/images
$ QEMU_AUDIO_DRV=alsa qemu-system-arm -kernel zImage \ -M vexpress-a9 -m 512 -drive file=rootfs.ext2,if=sd,format=raw \ -dtb ./vexpress-v2p-ca9.dtb \ --append "root=/dev/mmcblk0 console=ttyAMA0,115200" -nographic

2. 編譯 gstreamer

a. 設定 gstreamer 選項，再次編譯

$ cd buildroot/buildroot-2017.11
$ make menuconfig

b. ToolChain 設定修改成 glib 

Toolchain -> C library -> glibc  

c. 選擇 gstreamer 

Target packages -> Audio and video applications -> gstreamer 1.x
為了方便使用，建議開啟 gst1-libav, gst1-rtsp-serve 

 

另外 gst1-plugins-base, gst1-plugins-good 也要選擇自己需要的，例如選擇rtsp, alsa, souphttpsrc, videoconvert

d. 重新編譯

$ make clean;make 

e. Test Gstreamer 

$ QEMU_AUDIO_DRV=alsa qemu-system-arm -kernel zImage \ -M vexpress-a9 -m 512 -drive file=rootfs.ext2,if=sd,format=raw \ -dtb ./vexpress-v2p-ca9.dtb \ --append "root=/dev/mmcblk0 console=ttyAMA0,115200" -nographic
$ gst-launch-1.0 -v fakesrc num_buffers=5 ! fakesink 

輸出結果如下：到達此步驟，表示編譯成功。
Pipeline is PREROLLING ...
Pipeline is PREROLLED ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
Got EOS from element "pipeline0".
Execution ended after 0:00:00.003942000
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...
Setting pipeline to PAUSED ... 

若是剛剛編譯有加入 souphttpsrc則可以試試此命令 

$ gst-launch-1.0 souphttpsrc is-live=true location=http://devimages.apple.com/iphone/samples/bipbop/bipbopall.m3u8 ! hlsdemux ! decodebin ! videorate ! videoconvert ! ximagesink

3. 編譯成功後，若要在嵌入式平台上使用，則要注意相關 library 是否都已存在於平台內。

$ arm-linux-gnueabihf-readelf -d ./gst-launch-1.0
Tag                Type                               Name/Value
0x00000001 (NEEDED)                     Shared library: [libgstreamer-1.0.so.0]
0x00000001 (NEEDED)                     Shared library: [libgobject-2.0.so.0]
0x00000001 (NEEDED)                     Shared library: [libgmodule-2.0.so.0]
0x00000001 (NEEDED)                     Shared library: [libglib-2.0.so.0]
0x00000001 (NEEDED)                     Shared library: [librt.so.1]
0x00000001 (NEEDED)                     Shared library: [libdl.so.2]
0x00000001 (NEEDED)                     Shared library: [libpthread.so.0]
0x00000001 (NEEDED)                     Shared library: [libc.so.6]

參考資料：

• 編譯方式
• https://github.com/GStreamer/gstreamer
• http://www.armadeus.org/wiki/index.php?title=Gstreamer

• 線上程式碼 
• https://cgit.freedesktop.org/gstreamer/gstreamer/tree/scripts/

• API用法 
• http://artistehsu.pixnet.net/blog/post/280809115-gstreamer-安裝與使用
• https://blog.gtwang.org/programming/gstreamer-hello-world-streaming/
• https://github.com/GStreamer/gstreamer/blob/master/tests/examples/helloworld/helloworld.c

• 測試範例
• https://gist.github.com/bot11/64026a09128b2e3de794 
• https://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/gst-running.html