Video Codec V4L2 Use Description with C3V buildroot system

Introduction

This document is about the video codec used with V4L2 on the C3V platform.

Environment

This feature needs to make some changes to GStreamer and FFmpeg source code to adapt to the v4l2 codec interface and we will provide the patches for the changes. And the kernel also needs to do some config to support the video codec V4L2 driver.

Get the patches

The C3V project source code and the patches of the GStreamer and FFmpeg can be obtained from GitHub.

The gstreamer patch files are in path “code_root/linux/rootfs/initramfs/buildroot/package/gstreamer1” .

The ffmpeg patch files are in path “ code_root/linux/rootfs/initramfs/buildroot/package/ffmpeg” .

Patch files will be applied automatically during process of building buildroot. If you just want to apply patch without rebuild action of buildroot, you can take reference to below steps.

Apply the patches

Here we assume that you have already configured GStreamer and FFMPEG in the buildroot and have built it successfully.

GStreamer

Apply the gst1-plugins-good-1.20.1.diff to <buildroot>/output/build/gst1-plugins-good-1.20.1/ by the command:

Then rebuild the plugin:

The modified library is libgstvideo4linux2.so.

FFmpeg

Apply the ffmpeg-4.4.2.diff to <buildroot>/output/build/ffmpeg-4.4.2/ by command:

Then rebuild the FFmpeg:

The modified library is libavcodec.so*.

After the build, copy the modified libraries to the C3V master rootfs.

Kernel support

Run the command make kconfig on the C3V master to configure the kernel.

video hardware codec driver

Device Drivers > Multimedia support > Media drivers > Video hardware codec

Open

Then rebuild the C3V master and boot the platform.

Use

Here just introduce the basic usage with default parameters for H.264 and JPEG. If you need to change the codec parameters, please follow the usage of GStreamer and FFmpeg.

V4L2 Sample

Test sample:

This test needs a YUV source file, you can use the GStreamer to generate one:

Open

H.264 Encode

The command will encode the file 1080p.yuv to a file called stream.h264.

The file can be played by PC tools like PotPlayer and VLC media player.

H.264 Decode

The command will decode the file stream.h264 to a file called test.yuv.

The file can be played by PC tools like Elecard YUV viewer and YuvEye.

GStreamer

H.264 Encode

Fake live stream:

Local file:

H.264 Decode

JPEG Encode

JPEG Decode

FFmpeg

H.264 Encode

H.264 Decode

JPEG Encode

JPEG Decode