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pion / mediadevices

Go implementation of the MediaDevices API.
https://pion.ly/
MIT License
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audio-call codec driver face-recognition go golang livestream machine-learning mediadevices mediadevices-api p2p rtp streaming video-call voip webrtc

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Pion MediaDevices

Go implementation of the MediaDevices API

Slack Widget GitHub Workflow Status Go Reference Coverage Status License: MIT


mediadevices provides access to media input devices like cameras, microphones, and screen capture. It can also be used to encode your video/audio stream to various codec selections. mediadevices abstracts away the complexities of interacting with things like hardware and codecs allowing you to focus on building appilcations, interacting only with an amazingly simple, easy, and elegant API!

Install

go get -u github.com/pion/mediadevices

Usage

The following snippet shows how to capture a camera stream and store a frame as a jpeg image:

package main

import (
    "image/jpeg"
    "os"

    "github.com/pion/mediadevices"
    "github.com/pion/mediadevices/pkg/prop"

    // This is required to register camera adapter
    _ "github.com/pion/mediadevices/pkg/driver/camera" 
    // Note: If you don't have a camera or your adapters are not supported,
    //       you can always swap your adapters with our dummy adapters below.
    // _ "github.com/pion/mediadevices/pkg/driver/videotest"
)

func main() {
    stream, _ := mediadevices.GetUserMedia(mediadevices.MediaStreamConstraints{
        Video: func(constraint *mediadevices.MediaTrackConstraints) {
            // Query for ideal resolutions
            constraint.Width = prop.Int(600)
            constraint.Height = prop.Int(400)
        },
    })

    // Since track can represent audio as well, we need to cast it to 
    // *mediadevices.VideoTrack to get video specific functionalities
    track := stream.GetVideoTracks()[0]
    videoTrack := track.(*mediadevices.VideoTrack)
    defer videoTrack.Close()

    // Create a new video reader to get the decoded frames. Release is used 
    // to return the buffer to hold frame back to the source so that the buffer 
    // can be reused for the next frames.
    videoReader := videoTrack.NewReader(false)
    frame, release, _ := videoReader.Read()
    defer release()

    // Since frame is the standard image.Image, it's compatible with Go standard 
    // library. For example, capturing the first frame and store it as a jpeg image.
    output, _ := os.Create("frame.jpg")
    jpeg.Encode(output, frame, nil)
}

More Examples

Available Media Inputs

Input Linux Mac Windows
Camera ✔️ ✔️ ✔️
Microphone ✔️ ✔️ ✔️
Screen ✔️ ✔️ ✔️

By default, there's no media input registered. This decision was made to allow you to play only what you need. Therefore, you need to import the associated packages for the media inputs. For example, if you want to use a camera, you need to import the camera package as a side effect:

import (
    ...
    _ "github.com/pion/mediadevices/pkg/driver/camera"
)

Available Codecs

In order to encode your video/audio, mediadevices needs to know what codecs that you want to use and their parameters. To do this, you need to import the associated packages for the codecs, and add them to the codec selector that you'll pass to GetUserMedia:

package main

import (
    "github.com/pion/mediadevices"
    "github.com/pion/mediadevices/pkg/codec/x264"      // This is required to use H264 video encoder
    _ "github.com/pion/mediadevices/pkg/driver/camera" // This is required to register camera adapter
)

func main() {
    // configure codec specific parameters
    x264Params, _ := x264.NewParams()
    x264Params.Preset = x264.PresetMedium
    x264Params.BitRate = 1_000_000 // 1mbps

    codecSelector := mediadevices.NewCodecSelector(
        mediadevices.WithVideoEncoders(&x264Params),
    )

    mediaStream, _ := mediadevices.GetUserMedia(mediadevices.MediaStreamConstraints{
        Video: func(c *mediadevices.MediaTrackConstraints) {},
        Codec: codecSelector, // let GetUsermedia know available codecs
    })
}

Since mediadevices doesn't implement the video/audio codecs, it needs to call the codec libraries from the system through cgo. Therefore, you're required to install the codec libraries before you can use them in mediadevices. In the next section, it shows a list of available codecs, where the packages are defined (documentation linked), and installation instructions.

Note: we do not provide recommendations on choosing one codec or another as it is very complex and can be subjective.

Video Codecs

x264

A free software library and application for encoding video streams into the H.264/MPEG-4 AVC compression format.

mmal

A framework to enable H264 hardware encoding for Raspberry Pi or boards that use VideoCore GPUs.

openh264

A codec library which supports H.264 encoding and decoding. It is suitable for use in real time applications.

vpx

A free software video codec library from Google and the Alliance for Open Media that implements VP8/VP9 video coding formats.

vaapi

An open source API that allows applications such as VLC media player or GStreamer to use hardware video acceleration capabilities (currently support VP8/VP9).

Audio Codecs

opus

A totally open, royalty-free, highly versatile audio codec.

Benchmark

Result as of Nov 4, 2020 with Go 1.14 on a Raspberry pi 3, mediadevices can produce video, encode, send across network, and decode at 720p, 30 fps with < 500 ms latency.

The test was taken by capturing a camera stream, decoding the raw frames, encoding the video stream with mmal, and sending the stream through Webrtc.

FAQ

Failed to find the best driver that fits the constraints

mediadevices provides an automated driver discovery through GetUserMedia and GetDisplayMedia. The driver discover algorithm works something like:

  1. Open all registered drivers
  2. Get all properties (property describes what a driver is capable of, e.g. resolution, frame rate, etc.) from opened drivers
  3. Find the best property that meets the criteria

So, when mediadevices returns failed to find the best driver that fits the constraints error, one of the following conditions might have occured:

Failed to find vpx/x264/mmal/opus codecs

Since mediadevices uses cgo to access video/audio codecs, it needs to find these libraries from the system. To accomplish this, pkg-config is used for library discovery.

If you see the following error message at compile time:

# pkg-config --cflags  -- vpx
Package vpx was not found in the pkg-config search path.
Perhaps you should add the directory containing `vpx.pc'
to the PKG_CONFIG_PATH environment variable
No package 'vpx' found
pkg-config: exit status 1

There are 2 common problems:

Roadmap

The library can be used with our WebRTC implementation. Please refer to that roadmap to track our major milestones.

Community

Pion has an active community on the Slack.

Follow the Pion Twitter for project updates and important WebRTC news.

We are always looking to support your projects. Please reach out if you have something to build! If you need commercial support or don't want to use public methods you can contact us at team@pion.ly

Contributing

Check out the contributing wiki to join the group of amazing people making this project possible

License

MIT License - see LICENSE for full text