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igorzwx

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Registered: 2024-05-06

Posts: 342  

How to change PreferredSampleRate in Firefox's about:config

The top secret settings in Firefox's about:config are invisible. For example:

// Allows to get something non-default for the preferred sample-rate
media.cubeb.force_sample_rate

media.cubeb.backend
media.cubeb.output_device

_https://searchfox.org/firefox-main/source/dom/media/CubebUtils.cpp

#define PREF_VOLUME_SCALE "media.volume_scale"
#define PREF_CUBEB_BACKEND "media.cubeb.backend"
#define PREF_CUBEB_OUTPUT_DEVICE "media.cubeb.output_device"
#define PREF_CUBEB_LATENCY_PLAYBACK "media.cubeb_latency_playback_ms"
#define PREF_CUBEB_LATENCY_MTG "media.cubeb_latency_mtg_frames"
// Allows to get something non-default for the preferred sample-rate, to allow
// troubleshooting in the field and testing.
#define PREF_CUBEB_FORCE_SAMPLE_RATE "media.cubeb.force_sample_rate"
#define PREF_CUBEB_LOGGING_LEVEL "logging.cubeb"
// Hidden pref used by tests to force failure to obtain cubeb context

Open a new tab in Firefox. Type about:config in the address bar.
Type into "Search preference name"

media.cubeb.force_sample_rate

Select "Number"
Press "+"
Type "48000", then Enter

You have a new entry in Firefox's "hidden preferences":

media.cubeb.force_sample_rate        48000

Restart Firefox. Type about:support in the address bar.

Name 	Firefox
Version 	140.4.0esr
...
Media
Audio Backend	alsa
Max Channels	10000
Preferred Sample Rate	48000

Reference media files:

Hi-Res Music 32 Bit - Greatest Audiophile Collection - Natural Beat Records
_https://rutube.ru/video/b54c962301787eb1f2758ac8ba97f5bf/

Best Audiophile Vocal 24 bit - Hi-Res Music 2025 - Audiophile Voices
_https://www.youtube.com/watch?v=uO6jfQ5tQHM
_https://youtu.be/uO6jfQ5tQHM

$ youtube-dl -F "https://youtu.be/uO6jfQ5tQHM" | grep "audio only"
249          webm       audio only audio_quality_low   54k , webm_dash container, opus  (48000Hz), 30.39MiB
250          webm       audio only audio_quality_low   71k , webm_dash container, opus  (48000Hz), 39.87MiB
140          m4a        audio only audio_quality_medium  129k , m4a_dash container, mp4a.40.2 (44100Hz), 72.39MiB
251          webm       audio only audio_quality_medium  137k , webm_dash container, opus  (48000Hz), 76.97MiB

$ firefox 2>&1 youtube.com/watch?v=uO6jfQ5tQHM
Input:  44100 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 1764
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  44100 --> 48000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

Input:  44100 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 1764
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  44100 --> 48000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

Input:  48000 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 1920
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  48000 --> 48000 (J: 0.00%, T: None, W: Planar)
Ok.

Input:  44100 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 1764
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  44100 --> 48000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

$ firefox 2>&1 rutube.ru/video/b54c962301787eb1f2758ac8ba97f5bf
Input:  44100 Hz, 2 ch, 's32_le' (0xa): dummy = 0, period = 1764
Output: 48000 Hz, 2 ch, 's16_le' (0x2): dummy = 0, period = 1920
Rates:  44100 --> 48000 (J: 0.00%, T: FFT, W: Vorbis)
Ok.

The same is for PreferredSampleRate = 44100
It does not change Firefox's playback with ALSA.
You may test it with apulse

apulse firefox 2>&1

What has changed is that you can now see Preferred Sample Rate 48000 in about:support

The statement "The deaf may try a blind test. The blind may try a deaf test" is a philosophical observation about perspective, not a literal one. It points to the idea that people with different life experiences and challenges can gain new understanding by experiencing things from another's point of view.

Last edited by igorzwx (2025-10-23 05:25:56)