I found a number of audio related changes that make MX-21 worse than MX-19, in my opinion.
Regarding audio quality, I have not been able to tell any difference between MX-21 and MX-19 (provided the audio levels are equal). However, there are other things about the way MX-21 handles the audio that makes me question how the audio interface is accomplished. I want to keep this brief so I'll present one.
I tested with MX-21 beta2 on installed hardware with the most current updates as of 7 September 2021. That includes the Firefox 92.0 update today (the issue was also present on the previous 91.0.2) version.
I am using self-powered speakers that are fed with a digital signal from a USB port into a DAC (I am not using the motherboard analog audio output).
The MX-21 pavucontrol audio mixer "Configuration" tab with the heading "PCM 2704 16-bit stereo audio DAC" is set to "Digital Stereo (IEC958) Output" in the "Profile" drop-down menu.
The problem, anomaly, issue (however one wants to look at it) is when Firefox is playing audio from a Youtube video causing the mixer Playback slider position to change its set position. This will also change the output audio level (volume). This varies based on the video being played. Note that this slider always remains fixed at its set position when Chrome is playing any video (I have only tested with Youtube, Firefox and Chrome). Also note that in MX-19, the same mixer Playback slider always remains at its fixed position for both Firefox and Chrome when playing any audio source.
To duplicate the issue:
- Use Firefox and play a Youtube video.
- Open the mixer to the "Playback" tab and when a video is playing adjust the playback slider to 100%.
- Now move to another time on the Youtube video being played. If the video has audio that causes this issue off 100%, changing the playback time will change the mixer Playback slider position.
There are other actions that will cause the issue, for example removing the audio (pause, mute) for at least 6 seconds (if the audio resumes in less than ~5 seconds then the slider will remain where it was).
As I said, not every video will change the Playback slider in the mixer. It seems like the "Normalized" value in a Youtube video has something to do with this. That value can be seen by right-clicking on a Youtube video and selecting "Stats for nerds" where "Volume / Normalized" can be seen. The first value (Volume) is the setting of the Youtube audio output (always 100% for me). The second value "Normalized" is determined by the audio of the uploaded video.
Here are four videos to demonstrate the issue. The two numbers (xxx/xxx) after the URL correspond to "Volume / Normalized" respectively, followed by where the mixer Playback slider will go when Firefox is used. In Chrome in MX-21, the slider will always remain at its set position, whatever that position is.
https://youtu.be/GdCsMIRsyrg 100/100, slider stays at 100%
https://youtu.be/tXiIpzC74iQ 100/81, slider goes to 91%
https://youtu.be/5bQUqTsC0JA 100/96, slider goes to 99%
https://youtu.be/SC4AhA76DgU 100/88, slider goes to 96%
Further, in Firefox when a Youtube video is muted on the Youtube video screen, the Playback slider will go to 0% (silence), however in Chrome the slider will always remain at whatever its set position is.
Is this the intended behavior of the mixer Playback slider?