audioConstraints on mimeType: 'audio/webm;codecs=pcm',

[ddaydd]

Hello,

I record a stream with these options

options: {
      audio: true,
      video: false,
      mimeType: 'audio/webm;codecs=pcm',
      audioConstraints: {
        mandatory: {
          sampleRate: { exact: 16000 },
          channelCount: { exact: 1 },
        },
      },
    },

and when I do a

ffprobe ./debug_audio.webm

on the output file, I get this result

Stream #0:0(eng): Audio: pcm_f32le, 44100 Hz, 2 channels, flt , 2822 kb/s (default)

What am I missing, the sampleRate and channelCount are not what I expect?

[lorikku]

@ddaydd this is actually a mistake in the code:

puppeteer-stream/extension/options.js

Lines 48 to 65 in 5ce56d0

	const stream = await navigator.mediaDevices.getUserMedia({
	video: video && {
	...video,
	mandatory: {
	...video?.mandatory,
	chromeMediaSource: "tab",
	chromeMediaSourceId: streamId,
	},
	},
	audio: audio && {
	...audio,
	mandatory: {
	...audio?.mandatory,
	chromeMediaSource: "tab",
	chromeMediaSourceId: streamId,
	},
	},
	});

As you can see, neither videoConstraints nor audioConstraints are being used, and the values are being read from audio and video which are just booleans so that doesn't make any sense either. It should have been something like

const stream = await navigator.mediaDevices.getUserMedia({
	video: video && {
		...videoConstraints,
		mandatory: {
			...videoConstraints?.mandatory,
			chromeMediaSource: "tab",
			chromeMediaSourceId: streamId,
		},
	},
	audio: audio && {
		...audioConstraints,
		mandatory: {
			...audioConstraints?.mandatory,
			chromeMediaSource: "tab",
			chromeMediaSourceId: streamId,
		},
	},
});

[ddaydd]

Thanks for the reply,
but i don't think navigator.mediaDevices.getUserMedia works with chrome headleass, right?

Edit : sorry I just saw your other post where you talk about tabCapture.capture, thanks

[ShivaTomar24]

            {
                audio: true,
                    video: false,
                        audioConstraints: {
                    mandatory: {
                        sampleRate: { exact: 16000 },
                        channelCount: { exact: 1 },
                    },
                },
                mimeType: 'audio/webm;codecs=opus'
            }

ffprobe: output-file.webm

Still shows:

Input #0, matroska,webm, from 'output-file.webm':
  Metadata:
    encoder         : Chrome
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0(eng): Audio: opus, 48000 Hz, stereo, fltp (default)

Channel and Sample Rate has no effect

@lorikku Isn't this issue fixed?

[lorikku]

@ShivaTomar24 the merged PR fixed passing args, but the fact that it does not work that your Hz is not changing is not linked to the plugin. Chrome only accepts 48000 Hz as its sample rate. You can check the browser's 'acceptance parameters' by calling getCapabilities on a MediaStramTrack.

https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamTrack/getCapabilities

You can check yourself by pasting

navigator.mediaDevices
  .getUserMedia({ video: true, audio: true })
  .then((stream) => {
    const tracks = stream.getTracks();
    tracks.map((t) => console.log(t.getCapabilities()));
  });

in any tab (and accepting the video/audio perms), after which the capabilities will be logged into the console. For me Chrome gave this:

AUDIO CAPABILITIES

{
  "autoGainControl": [
      true,
      false
  ],
  "channelCount": {
      "max": 1,
      "min": 1
  },
  "deviceId": "61fb94b26b2af3a1dd3b37148074b88ef61c31617ffeec5baa2768daf19efac5",
  "echoCancellation": [
      true,
      false
  ],
  "groupId": "96581f81c5d3eb6cb69d7bd34bcdfcae6037396ebe765eabfb50ec71eaa59248",
  "latency": {
      "max": 0.085333,
      "min": 0.002666
  },
  "noiseSuppression": [
      true,
      false
  ],
  "sampleRate": {
      "max": 48000,
      "min": 48000
  },
  "sampleSize": {
      "max": 16,
      "min": 16
  },
  "voiceIsolation": [
      true,
      false
  ]
}

VIDEO CAPABILITIES

{
    "aspectRatio": {
        "max": 1920,
        "min": 0.0005208333333333333
    },
    "deviceId": "a20dd190960df2504d8c972171ed0fe149cc07b684eff72c7f6c8b7eee5b89a1",
    "facingMode": [],
    "frameRate": {
        "max": 30,
        "min": 0
    },
    "groupId": "927cdffba91d13a5984c2779319d713d4827f4687d044c8f322aed7b1ca56201",
    "height": {
        "max": 1920,
        "min": 1
    },
    "resizeMode": [
        "none",
        "crop-and-scale"
    ],
    "width": {
        "max": 1920,
        "min": 1
    }
}

As you can see, the min and max for sampleRate is 4800 Hz (set by Chrome), so that's the only value you can use unfortunately. Other browsers might have other options.

Edit: these values may also be set/limited by your hardware (microphone/pc) or OS, I don't know exactly if this is the case so you might want to go ahead and research further.

[ShivaTomar24]

@lorikku Thank you for the reply. Really appreciated.

[bdegomme]

thank you @lorikku!
Shouldn't channelCount: { exact: 1 } have led to a mono file instead of stereo? Any clue how to end up with a mono file?