mjpeg-decoder v1.0.3
mjpeg-decoder
A NodeJS M-JPEG decoder which can be used to retrieve individual JPEG frames or take a snapshot from a IP/network camera which serves M-JPEG video stream.
Installation
npm install mjpeg-decoderor
yarn add mjpeg-decoderUsage
Typically, you use the mjpeg-decoder to read JPEG frames from an M-JPEG video stream.
const fs = require('fs');
const MjpegDecoder = require('mjpeg-decoder');
// create a decoder which delivers a JPEG frame
// via the 'frame' event every 3 seconds.
const decoder = new MjpegDecoder(
'<your stream url>', { interval: 3000 }
);
decoder.on('frame', (frame, seq) => {
fs.writeFileSync(`${seq}.jpg`, frame);
});
decoder.start();But sometimes, you just want to take a snapshot of the M-JPEG video stream, and then forget. In this case, you can do like this:
// create a decoder which takes a snapshot and forget
const decoder = new MjpegDecoder(
'<your stream url>', { maxFrames: 1 }
);
const frame = await decoder.takeSnapshot();
fs.writeFileSync('snapshot.jpg', frame);Or, you can use the MjpegDecoder.decoderForSnapshot shorthand method to create the decoder instance:
const decoder = MjpegDecoder.decoderForSnapshot('<your stream url>');
const frame = await decoder.takeSnapshot();
fs.writeFileSync('snapshot.jpg', frame);API
Options
MjpegDecoder.MjpegDecoderOptions
interval: Specify the time interval in which the frames will be delivered (default:0)maxFrames: Specify the max frames to consume before stopping (default:0)timeout: Specify the timeout before the http connection is aborted (default:10000ms)
Constructor
constructor(url: string, options?: Partial<MjpegDecoder.MjpegDecoderOptions>)url: url of the M-JPEG video stream source.options: control how the decoder will work as expected.
How to find the url of the camera? The camera user manual should usually mention the URL, or searching the camera model number should get you a result as well. You can also try this tool http://skjm.com/icam/mjpeg.php or this tool https://www.ispyconnect.com/man.aspx.
decoderForSnapshot
static decoderForSnapshot(
url: string,
options?: Partial<MjpegDecoder.MjpegDecoderOptions>
): MjpegDecoderCreate an instance of MjpegDecoder used to take a onetime snapshot of the video stream.
url: url of the M-JPEG video stream source.options: control how the decoder will work as expected.
start
start(): voidStart the M-JPEG decoder and begin consuming the M-JPEG video stream. Listen for 'frame' event to get the decoded JPEG frames sequently.
stop
stop(): voidStop consuming the M-JPEG video stream.
takeSnapshot
takeSnapshot(): Promise<Buffer>Take snapshot of the M-JPEG video stream.
Events
frame
on(event: 'frame', listener: (frame: Buffer, seq: number) => void): thisAdd listener for frame event which is emitted when a JPEG frame is decoded. The event listener takes the decoded JPEG frame and sequence number as the parameters.
abort
on(event: 'abort', listener: (reason: MjpegDecoder.AbortReason, error?: Error) => void): thisAdd listener for abort event which is emitted for some reason. The decoder will stop consuming the video stream in the following cases:
timeout: network timeout while connecting to the video stream source at the given url.http_error: when a network error or http error occuredinvalid_mjpeg_stream: if the source is not a valid M-JPEG video streamend: when you call thestopmethod of the decoder or the max frames have been delivered.max_buffer_size_exceeded: when the internal data buffer size reached the limit, and this might be caused by the M-JPEG decoding problem. If you accountered this error, please create an issue.
Capture M-JPEG snapshot the other ways
Use wget:
$ wget <url> -O snapshot.jpgUse ffmpeg:
ffmpeg -f MJPEG -y -i <url> -r 1 -vframes 1 -q:v 1 snapshot.jpg