= Introduction to GStreamer in Buildroot

An embedded solution may require a custom multimedia streaming solution. Buildroot and GStreamer makes for an efficient lightweight solution. 

This guide will walk you through the necessary steps to create a bootable image containing the ability to:
- capture/playback/encode/decode Video
- capture/playback/encode/decode Audio

= Building the demo image

== Recommended hardware

- Ventana board with video input and video output (ie GW5404)
- 1080p HDMI monitor
- Mini HDMI cable to HDMI (for connecting the board and monitor together)
- Power cables


== Building
Procedure:
{{{#!bash
# clone buildroot
git clone https://github.com/buildroot/buildroot.git
cd buildroot
# fetch and apply patch that adds ventana defconfig files
wget http://trac.gateworks.com/raw-attachment/wiki/buildroot/gstreamer/0000-package-add-gst-gateworks-apps.patch
wget http://trac.gateworks.com/raw-attachment/wiki/buildroot/gstreamer/0001-configs-add-various-Gateworks-Ventana-configs.patch
wget http://trac.gateworks.com/raw-attachment/wiki/buildroot/gstreamer/0002-board-gateworks-add-overlay-for-Gateworks-Ventana-bo.patch
git am *.patch
# build the gwventana-gst image
make distclean
make imx6-gwventana-gst_defconfig
make
ls output/images/
}}}

The patch adds the following:
 * board/gateworks/ventana/rootfs_overlay/bin/media-ctl-setup - media-ctl helper script for configuring video capture devices
 * configs/imx6-gwventana-gst_defconfig - defconfig for GStreamer based image

You can use the following filesystem images:
 * output/images/rootfs.ubi for 2K page size flash geometries (256MB flash or newer 2GiB flash parts)
  - if you are looking for a ubi image suitable for 4K page size flash geometries (the Micron 2GiB part) change the following via menuconfig:
{{{#!bash
BR2_TARGET_ROOTFS_UBIFS_LEBSIZE=0x3e000
BR2_TARGET_ROOTFS_UBIFS_MINIOSIZE=0x1000
BR2_TARGET_ROOTFS_UBIFS_MAXLEBCNT=8192
BR2_TARGET_ROOTFS_UBI_PEBSIZE=0x40000
BR2_TARGET_ROOTFS_UBI_SUBSIZE=0
}}}
 * output/images/rootfs.tar - refer to [wiki:/linux/blockdev this page] to create a bootable block storage device using the created tarball
 * output/images/sdcard.img - disk image suitable for copying to a removalbe block storage device (see [wiki:/linux/blockdev])


= Running the Demos

Login as "root"

Example Demos:
 * Video Display of test pattern:
{{{#!bash
gst-launch-1.0 videotestsrc ! autovideosink
}}}
 * Capture, encode, and stream Analog Video
{{{#!bash
media-ctl-setup adv7180 > setup
. ./setup
gst-launch-1.0 v4l2src device=$DEVICE ! \
        $GST_CONVERT output-io-mode=dmabuf-import ! \
        v4l2h264enc output-io-mode=dmabuf-import ! \
        rtph264pay ! udpsink host=$SERVER port=5000
}}}
  - view on $SERVER with:
{{{#!bash
gst-launch-1.0 udpsrc port=5000 caps=application/x-rtp,payload=96 ! rtph264depay ! decodebin ! autovideosink
}}}
 * Capture, encode, save Analog audio:
{{{#!bash
amixer -c 1 sset "Capture Mux" LINE_IN # LINE_IN vs MIC_IN, default MIC_IN
amixer -c 1 sset "Capture" 8 # 0-15, default 0
gst-launch-1.0 alsasrc device="sysdefault:CARD=sgtl5000audio" ! audioconvert ! filesink location=file.mp3
}}}
 * Decode and Playback audio to Analog out:
{{{#!bash
gst-launch-1.0 filesrc location=file.mp3 ! mpegaudioparse ! mpg123audiodec ! alsasink device="sysdefault:CARD=sgtl5000audio"
}}}
 * Capture, encode, and stream Analog Audio:
{{{#!bash
amixer -c 1 sset "Capture Mux" LINE_IN # LINE_IN vs MIC_IN, default MIC_IN
amixer -c 1 sset "Capture" 8 # 0-15, default 0
gst-launch-1.0 -v alsasrc device="sysdefault:CARD=sgtl5000audio" ! \
          audioconvert ! \
          lamemp3enc ! \
          rtpmpapay ! udpsink host=$SERVER port=5000
}}}
  - play on $SERVER with:
{{{#!bash
gst-launch-1.0 udpsrc port=5000 caps=application/x-rtp,payload=96 ! rtpmpadepay ! decodebin ! autoaudiosink
}}}
 * Stream, decode, playback audio:
{{{#!bash
gst-launch-1.0 playbin uri=http://server/myfavoritesong.mp3
}}}

= Conclusion
This concludes how to build and install the GStreamer demo in buildroot. Using "make menuconfig" many additional applications and gstreamer plugins can be built into buildroot for other needs.