MP4Recorder
class NatML.Recorders.MP4Recorder : IMediaRecorder
The
MP4Recorder records *.mp4 video files. This is currently the most common video format, and as such practically every device in the world has hardware encoding support for it.The
MP4Recorder uses the H.264 AVC codec for video and the AAC codec for audio.The
MP4Recorder is not supported on WebGL./// <summary>
/// Create an MP4 recorder.
/// </summary>
/// <param name="width">Video width.</param>
/// <param name="height">Video height.</param>
/// <param name="framerate">Video framerate.</param>
/// <param name="sampleRate">Audio sample rate. Pass 0 for no audio.</param>
/// <param name="channelCount">Audio channel count. Pass 0 for no audio.</param>
/// <param name="videoBitRate">Video bit rate in bits per second.</param>
/// <param name="keyframeInterval">Keyframe interval in seconds.</param>
/// <param name="audioBitRate">Audio bit rate in bits per second.</param>
MP4Recorder (
int width,
int height,
float framerate,
int sampleRate = 0,
int channelCount = 0,
int videoBitRate = 10_000_000,
int keyframeInterval = 2,
int audioBitRate = 64_000
);
The
MP4Recorder can be created to record video with optional audio. To record video only, simply provide the video width, video height, and video framerate.// Record video only at 1080p60
var recorder = new MP4Recorder(1920, 1080, 60);
To record video with audio, you will provide the audio format along with the video format. The audio format comprises of the
sampleRate and channelCount.// Record 720p video with 48KHz stereo audio
var recorder = new MP4Recorder(1280, 720, 30, 48000, 2);
You can additionally specify the output video bitrate (in bits per second) and keyframe interval (in seconds).
// Record 720p60 video only with custom compression settings
var recorder = new MP4Recorder(
1280,
720,
60,
bitrate: 6_000_000, // bits per second
keyframeInterval: 3 // seconds
);
The
videoBitRate and keyframeInterval are important for controlling the output video file size.On Windows, the
MP4Recorder will always output audio with a 192kbps bitrate.- Set the
sampleRatetoAudioSettings.outputSampleRate. - Set the
channelCountto(int)AudioSettings.speakerMode.
/// <summary>
/// Video size.
/// </summary>
(int width, int height) frameSize { get; }
Some devices, especially Android devices, will fail to record when either the
width or height is not divisible by two. In general, it is best to stick with a standard recording size like 1280x720 or 1920x1080./// <summary>
/// Commit a video pixel buffer for encoding.
/// The pixel buffer MUST have an RGBA8888 pixel layout.
/// </summary>
/// <param name="pixelBuffer">Pixel buffer containing video frame to commit.</param>
/// <param name="timestamp">Pixel buffer timestamp in nanoseconds.</param>
void CommitFrame<T> (T[] pixelBuffer, long timestamp) where T : unmanaged;
The spacing between consecutive
timestamp values determines the actual video frame rate. The value passed to the constructor is merely a hint to the encoder.Committed timestamps must be strictly monotonic. Not meeting this condition will cause recording to fail.
/// <summary>
/// Commit an audio sample buffer for encoding.
/// </summary>
/// <param name="sampleBuffer">Linear PCM audio sample buffer, interleaved by channel.</param>
/// <param name="timestamp">Sample buffer timestamp in nanoseconds.</param>
void CommitSamples (float[] sampleBuffer, long timestamp);
/// <summary>
/// Finish writing and return the path to the recorded media file.
/// </summary>
Task<string> FinishWriting ();
Last modified 6mo ago