Logitech M720 Triathlon mouse – long-term review

In this post I want to take a look at the Logitech M720 mouse after having used it for 2.5 years.

Specs and durability

The specs are pretty common for a mouse you get today, so lets start with the special features:

  • There are side buttons, which I find pretty handy for navigating front/ back in the browser or a file manager
  • It can be paired with up to 3 devices at the same time, which makes it easy to use with your PC, Laptop and Tablet
  • It supports both Bluetooth LE and the Logitech Wireless Receiver
  • It is powered by a single, replaceable AA battery

Especially the last two points make this seem to be future-proof product that you can use for a long time.

Logitech is currently replacing their Wireless Receiver dongles by Logitech Bolt, so in the near future the Wireless Receivers will go away. But thanks to the Bluetooth support you will still be able to use the mouse without having to occupy a USB port just for using it.

Then, using standard AA batteries means that you just use some nice rechargeable ones. This means that you will never have to wait for the mouse to charge and that the mouse can out-live the battery. As you are probably aware from using your phone, rechargeable batteries wear-out over time until the device cannot be properly used any more.

So we finally got a mouse for the years to come? Well..

Built-in obsolescence

Unfortunately, Logitech made some design decision that drastically shorten the life-span of the device, even though they must have known better.

Rubber coating

The most obvious one is likely the rubber coating of the mouse.

Note how the plastic buttons look still perfectly fine in comparison

I took the images for this post after cleaning the mouse. So the dirt you see there is not the skin from my greasy hands, but rather said rubber coating disintegrating.
This is caused by your sweat which is slightly acidic and thus takes hold of the rubber.
There is a reason that Gamepads do not have such coating, even though having good grip is even more important there.
Also, the way the coating is used here, all it does is making the mouse look greasy after some time.

Bad switches

The less obvious issue are the used switches i.e. the things that perform the clicks.
Did you ever notice that after some time your mouse does incorrect double clicks or releases the click while drag and dropping on its own? Well, that means the switch starts wearing out.

The mouse uses OMRON D2FC-F-7N micro-switches in a cheap variant that is only rated for 10 million clicks (10M). While this sounds a lot, it yields to 6850 clicks/ per day for 4 years, which is not all that much if you think about playing a shooter or using photoshop.
The crazy part is that going for the 20M rated variant (2x the durability) only costs 50 ct more (pack of 5 on amazon). This would make the mouse merely 1€ more expensive – probably way less even as Logitech can negotiate bulk discounts on these things.
Given that the mouse is priced at 50€, I do not think we can pass this off as cost optimization.

Introducing ODRS Browser

GNOME Open Desktop Ratings is the service that enables user ratings in various Linux app stores like the Snap-Store, Gnome Software and KDE Discover.

While it nowadays works for users by providing a mostly useful star rating, from a application developer perspective the story is very grim.

Basically one only gets the users view, which provides an average rating and some reviews in the current locale.
This means you might see something like “2 Stars from 80 Reviews” – but the 3 reviews in your current locale are all 4-5 Star.
To see something else you have to change the locale and restart the app store – which is inconvenient and confusing.
As a developer, seeing the negative reviews is crucial, as people often just post bug reports there and this is the only way to find out why the app did not work for them.

Therefore I quickly hacked together a web-based browser for the ODRS service, skillfully named

This allows accessing the ODRS service from the web and shows the reviews from multiple locales at once. The idea here is that often people write reviews in english – regardless of their current locale. Currently, ODRS has no logic to detect that.

Also, if your app is packaged in different formats like snap and flatpack and deb, you can see the reviews of all variants in the overview.

Unfortunately, ODRS currently does not set the CORS header which prevents browsers from accessing it directly. The data that you see right now was scraped with python script. But once this issue is fixed, the ODRS Browser will be able to use live data.

Debugging Python with GDB on Ubuntu

Lets say you want to debug a python process that is either already running or crashing in native code. Pythons PDB is of no help here and you will have to use low-level GDB debugger. Fortunately, it comes with support for debugging high level python scripts.

However, while the actual python-gdb commands are nicely described here, that page lacks important details on how to get python-gdb in the first place. We are merely told that a python-gdb.py is needed.

On Ubuntu/ Debian, this file is included in the python3-dbg package:

sudo apt install python3.10-dbg

Installing that is sufficient, if you use the matching python3 package. You can go ahead and connect to some running python process via:

gdb -p <PID>
# verify that the script is loaded
(gdb) info auto-load
# get a python backtrace
(gdb) py-bt
Traceback (most recent call first):
  File "/usr/lib/python3.10/selectors.py", line 416, in select
    fd_event_list = self._selector.poll(timeout)
  File "/usr/lib/python3.10/socketserver.py", line 232, in serve_forever
...

In case Ubuntu is merely a host and you use coda, you can still use the host python-gdb.py – even if the python versions dont match. You will have to load the script manually though like:

(gdb) source /usr/share/gdb/auto-load/usr/bin/python3.10-gdb.py

Fix Steam Deck Input in Desktop Mode

While older SteamOS releases used to map the right trigger to the left mouse button by default, in current SteamOS you can only click by using the touchpad. However due to the way you hold the device it is really fiddly – especially if you try to drag and drop something.

Fortunately, there is a way to fix this via a setting in Steam. For this you need launch Steam when in Desktop Mode. There, switch to big picture mode and go to

Settings > Base configuration > Desktop Configuratiom

In this view you can configure the inputs to your liking

I suggest you to go with the following setup

  • Right trigger for left click (sounds counter-intuitive, but works well)
  • Left trigger for right click
  • Left touchpad for moving the mouse (doh)
  • Right touchpad for scroll wheel

With this configuration you can use the desktop mostly pain-free.

Using Docker with SLURM

The SLURM documentation provides you with the basic information that you can use Docker withing SLURM – as long as you use rootless Docker. However some crucial pieces are missing.

The issue that you will immediately run into is that the SLURM resource allocation is not propagated to docker at all. E.g. if you start your job with srun --gpus 1 docker ... all GPUs will be available to docker nevertheless.

The issue here is that Docker uses a manager daemon that the docker CLI communicates with. And that daemon does not know anything about SLURM or any resources it allocated for the job.

The solution is to start a daemon per job (instead of per user) as one user might want to run different jobs with different allocations on the same machine. The docker documentation gives you an idea on how to do that.

You will need to set at least the following parameters to make the daemon fully job-specific

# dockerd-rootless.sh requires XDG_RUNTIME_DIR
XDG_RUNTIME_DIR=/somewhere/including/$SLURM_JOB_ID
# export, so docker client sees it later on
export DOCKER_HOST=unix://$XDG_RUNTIME_DIR/docker.sock
dockerd-rootless.sh --host=$DOCKER_HOST --data-root=... --exec-root=...

Here, exporting DOCKER_HOST makes the docker CLI use the correct daemon.

The drawback of this method is that each job needs to pull the container again due to the separate data-root paths. Switching to podman might solve that.

Steam Deck SSD Upgrade

If you, like me, went with the entry level Steam Deck option with only 64 GB of internal storage, you likely realized quite soon that some games wont fit on it.

One option is to use the microSD expansion card slot. For current-gen games the throughput of only about 150 MB/s does not seem to degrade loading performance compared to a NVMe SSD.
However, given that the internal storage is upgradable, the only logical choice for keeping your PC master race status is to cram in the fastest NVME SSD inside that thing.

Specifically, you will need a one-sided SSD in the M.2 2230 for factor so it fits the space inside the Steam Deck.
I went with the KIOXIA Client-SSD BG5 512GB. Kioxia is the Toshiba spin-off for SSD drives, if you wonder about the brand. Although it is a PCIe 4.0 drive, its peak read throughput of 3.5 GB/s is within the practical limits of PCIe 3.0 of the Steam Deck.
Also, the active power consumption of 4.1W is quite close to the 3.8W drawn by the custom PHISON PS5013 E13 SSD that Valve uses.

You can follow the iFixit Guide for the steps to actually swap the SSD. Make sure to transfer the ESD shielding wrap to the new SSD.

To get Steam OS on the new drive, follow the official recovery instructions and select the “Re-image Steam Deck” script.
This will install Steam OS on the blank SSD – similar to how you would install Ubuntu from a live USB.

Benchmarking results

Next, I wanted to actually compare the speed of the upgraded NVMe SSD with the one of the stock eMMC memory. To this end I used KDiskMark – an open-source alternative to CrystalDiskMark that runs on Linux natively.

The tests were performed on SteamOS 3.3.1 using KDiskMark 2.3.0.


In short, the NVME offers roughly one order of magnitude faster throughput over the eMMC.
Whether you feel this in-game, highly depends on the given game. For older titles, even the eMMC is so fast, that you cannot read the hints on the loading-screen. However, for something like the Flight Simulator 2020 that shuffles huge assets around, it will surely be noticeable.

Finally, the peak read performance of 3.5GB/s is not reached. This might be due to the PCIe 3.0 bottleneck – I did not bother putting the drive in a PCIe 4.0 device. Still, there is a significant advantage in writing performance over the older Kioxia BG4 series, that only do 1.4 GB/s.

Drifting with WLtoys 284131 Mini RC-Car

In this post I will discuss how to convert the WLToys 284131 (new K989) into a drift-car.

Overview

This car is the latest iteration of the K989 (rally car) platform, of which there is also variant specifically for drifting, namely the K969 porsche.
However you still should go with the more recent 284131 as it comes with an upgraded radio that has no dead-zone when compared to the previous one. This will give you better control of the car.
Additionally, the 284131 now has metal ball-heads on the shocks and on the servo horn which allow those parts to move more smoothly.
Then, it comes with a preinstalled light-kit, that helps guessing the direction of the car from far away.
Also, some adjustments were made compared to the K989, to cope with the heat generated by the motor; the transmitter module was rotated by 90° to move it away from the motor and the motor pinion is now all brass, making it more heat resistant.

The only downside is really the ugly hoonitruck chassis, but at least this will be authentic after we do the drift-conversion.

The included battery lasts for about 20min and can be fully charged in about 25min, if your USB charger can deliver 2.5W. If you use an USB port older than 3.0 charging will take much longer.
Note, that even if you get a kit with multiple batteries you should take a break of about 10min between runs to allow the motor to cool down. Otherwise it will break much faster.

Drift conversion

Out of the box, the 284131 is tuned for fast acceleration and handling at high speed

  • The differentials are so stiff, that you can consider them locked. This gives you best acceleration
  • The turning-radius is limited which prevents flipping over at high speed
  • The stiff shocks reduce body-lean, additionally lowering the risk of flipping
  • Traction is mainly achieved by the grippy rubber-tires

For drifting however, we generally run at lower speed and need precise handling there. This basically means undoing all of the choices listed above.

Drifting with the changes suggested in this post

Some of the changes are easy to do, others are more involved

  • Replace the rubber-tires by some hard-plastic ones. We must get rid of some grip to be able to slide sideways. I suggest just going with the K969 tires, that only cost about 5€.
  • Remove the spacers from both front and back suspension to make it soft. This will increase forward grip while drifting.
  • Use the upper hole on the servo-horn to get a tighter turning-radius. Unfortunately the stock ball-head does not fit in the upper hole and you cannot get the old servo-horn any more. I suggest using the “MINI-Q 3.5mm ball-head” instead. It will set you off by about 3€.
  • Most crucially, we need locked differentials in the back and opened differentials in the front. The locked differential will cause the back to lose traction and drift. Contrary, the open differential will keep traction and allow us to control the drift.
    This is a difference to the K969, where both differentials are locked and the car merely slides (like on ice) instead of drifting.

The good news is that the stock diffs are so stiff that you can just keep them in the back and they will behave as if they were locked.

Making differentials work

The bad news is that getting actually working (i.e. open) differentials is not that easy. The cheapest option is to dissemble the stock one and loose it up. For this, I recommend using a (3mm) drill to widen the diff housing. If you try to use sandpaper on the diff arms, you will probably not make it uniform enough to run smoothly.


One thing to watch out when adjusting the diff is that both diff-arms have the same resistance. You can hold down the center and rotate each arm to test this by hand. Also, when assembled, the car should accelerate in a straight line.

If you dont want to go through the hassle, you can also just buy the Mini-Z MD005 diff (15€) and a pair of extended 11mm swing-shafts (10€) to compensate for the shorter diff arms.

If you want the best diff possible, you can go for the Mini-Z MDW018 ball diff or the MDW017 one way diff. Especially the latter gives you even better controls for drifting. However each of those costs as much as the whole 284131 RTR kit.

Lipo tester for storing the batteries

When ordering stuff anyway, make sure to also get a Lipo tester. Those cost about 2€ and allow monitoring the charge of the battery. This is useful when you want to take a break for a few days. In this case the battery should be at 3.8V per cell. Otherwise you risk permanently damaging the battery. To get there, you can keep the tester connected to the white-plug while driving and set the beeper to that voltage. If the beeper is too loud, you can dampen it by putting some cotton wool into the housing.

Bad upgrades

There are also some bad upgrades you can buy. Those either are wither unnecessary or actually worse than the stock parts. Particularly, this concerns the metal replacement parts. Metal parts are harder to manufacture at high precision, so you might actually degrade the performance by installing them. Also, they make the car heavier and thus decrease acceleration.

Generally, I would say that you do not need any of them for drifting. However, if you do touring and any of the plastic parts break, you might consider replacing those with a metal equivalent.

All metal ball differentials

Stock diff, good pinion – Metal diff, eaten pinion

You can get a all-metal ball diff on Aliexpress for about 8€. After some run-in those work very well and are smoother than what you get by fixing the stock ones.
Unfortunately those all-metal cogs (which are also shorter then stock) will eat-up the plastic center-shaft pinion in no time as we have high traction on the front wheels when drifting.

RunCam Thumb on the Tinyhawk II Freestyle

In this post I will show you how you can shoot some cinematic footage with your TH II Freestyle by mounting a RunCam Thumb on top. This cam only weights 13g including the mount and thus does not impact the flight-time and performance much.
Also, it is easy to remove it again in case you want the full performance back.

The procedure is quite simple as you only need to solder two wires and can use the stock parts for the rest. You need the package that includes the 3D-printed mount though.

Note that there is a new “naked” RunCam Thumb variant now, which only weights 6.6g that you can use to further reduce the weight.

Mounting

First, we need to solder-on the power-connector. For this, remove the top plate so you get an easier access to the pins.

We will use the 5V connection coming from the controller-board, which also powers the VTX. The images below show the result and the board schematic for an overview.

To keep the power-cable away from the rotors, you should route it behind the VTX antenna.

The camera-mount itself, can be attached by using the screws that hold the top plate – they are long enough to keep both in place.
Note, that I shifted the mount to the left to keep the center of mass and the lens closer to the middle of the quad.

Gyroflow Results

There are some reports about issues when using Gyroflow with the RunCam Thumb recorded data.

Below are the results of the v2.1.0 firmware with Gyroflow v1.1. I disabled the zoom and increased the FOV to include the invalid regions so you can see the gyro compensation in action

You can see how Gyroflow removed the radial distortion and keeps the image-center steady by shifting the frame based on the gyro data. So the gyro based stabilization definitely works.

Getting into FPV with the Tinyhawk III RTF Kit

After being absent from the RC world for some time, I recently took another look at the advances FPV drones have made. The last time, I was mainly into RC helicopters as FPV flight seemed a fiddly and expensive thing to do.

But progress did not stop and nowadays there are multiple options to get a complete FPV kit for 200-300€. I picked the Tinyhawk III RTF kit and here are some impressions of using it and how it compares to alternatives.

Drone: Tinyhawk III

Coming from RC helicopters it is amazing how durable the drone is. I literally learned flying using stock parts only and keep on flying them as of today.

When getting used to maneuver the drone, I found the default tune in the 3 flight modes Angle, Horizon and Air quite helpful.
In Angle Mode the drone tilt is limited to about 20° so you wont get too fast and you can focus on throttle and momentum control while flying inside.
Switching to Horizon mode is a nice intermediate step. The Angle is no longer limited so you can go fast. This requires you to actively break like in Air mode. However, as the drone still auto levels you can safely fly inside.
After flying Horizon mode inside, going outside and using Air mode was surprisingly easy for me.

In total it took me about 2 Weeks going from bumping into the ceiling and floor on Angle mode to confidently flying Air mode outside.

The only casualty is a small dent in the lower right prop, which I did not bother switching so far.

Goggles: Transporter 2

The part that made me choose this particular RTF Kit are the Googles as they are very well though out.


First, you can adjust the focal-length in 3 steps. This is useful if you are near-sighted or if you want to adjust the FOV from immersive to a tunnel view.

Then, the display resolution of 800×480 px is a good fit for analog FPV, where video is transmitted via NTSC (720×480 px). The internal DVR records precisely this resolution when set to D1 mode. There is also a HD mode, but you will not get anything out of it as the incoming image is the bottleneck.
Speaking of which; the RunCam Nano 4 on the Tinyhawk has a resolution of 800 TVL (800×600 px) which again fits in nicely.

Note that the DVR recording is quite bad as it saves white frames as soon as there is some noise in the image, but it gets the job done if you want to review your flight or need to find the drone.

Ultimately, the detachable display unit can be re-purposed once you decide to upgrade to better Goggles – even though I think one can stick with the Transporter 2 Goggles for a while.

One upgrade you can do straight away though, is replacing the linear antennas by a set of polarized ones. This will reduce interference due to reflected signals in closed spaces. A possible choice here are a pair of Foxeer Lollipops that you can get for about 18€.

Battery and Charger

The weakest part is probably the battery & charger. For starters it only comes with one battery which the bundled charger takes about 90 min to charge (likely at 0.3A). Also, you can only charge two batteries at a time.

Fortunately the required 450mAh HV batteries are quite cheap. If you order a pack of 5 from China you can get them for about 4.5€ per piece. You should do that.

As for upgrading to a better charger, the VIFLY WhoopStor for about 33€ is an affordable option. It can charge up to 6 batteries at up to 0.9A. This allows charging the 450mAh batteries at 2C speeding up charging by 3x compared to the bundled charger. On top, it supports checking the battery voltage as well as storage-charging for when you need some days off from flying.
The only thing it lacks compared to a “big” charger is resistance measurement of the batteries.

WhoopStor (left) and bundled charger (right)

Alternatively, you can get a serious charger, like the ISDT 608AC straight away. But that alone is about 65€ and needs an a serial, balanced charging cable that is about 5€ on top. With this setup you will have to always charge exactly 4 batteries at a time.
Having that charger makes moving to actual 4S in the long run easy though.

Remote: E8 Transmitter

The Transmitter only supports the FrSky D8 and D16 protocols – although there is really no reason to switch it to D16 as there are only 8 channels on the remote and telemetry is shown in your video signal anyway.

More importantly, it is usable as Joystick when connected to the PC, where each channel is reported as a separate axis – so it will work fine with all FPV Simulators.

Also notable: the radio uses a standard 18650 battery that is compatible with other radios and is worth about 10€.

It would have been nice to have a module bay to be able to attach a ELRS module – however none of the comparable RTF kits in the price range offer this. There cost needs to be cut somewhere I guess.

Speaking of ELRS; you are not really missing out on that with a tinywhoop. D8 still allows you to go for about 1km. The limiting factor will be more likely the tiny RX antenna on the drone and the VTX power. Also, even if you could manage to get that far with the Tinyhawk, retrieving it if it something goes wrong will be a PITA. ELRS really only starts making sense with GPS powered drones, where you got return to home as a failsafe.

I keep hearing that one should go ELRS from the start or you will end up swapping your RX modules on the drones if you only decide to go ELRS later. This is BS as you can just continue using the old remote for the old drones or get a remote that supports both ELRS and D8, like e.g. the Commando 8.

Alternatives

The following alternative Kits that are in a similar price-range and are all brushless, as brushed motors are really not worth the money you save.

EMAX EZ Pilot Pro

This saves you 60$, while you get the same Radio and almost the same Goggles and Drone.
The Goggles have no DVR though and you will not get the nice carrying case.

BETAFPV Cetus Pro

This is also about 60$ cheaper than the Tinyhawk 3. However, the Goggles are way worse: no DVR, fixed focal-length and fixed screen.

What you get here is an easier Angle mode, with altitude-hold and hover-stabilization. The flipside of it is that it is not compatible with the betaflight configurator which is the standard when it comes to tuning the drone – in case you wanted to e.g. configure the OSD content.

Additionally, the drone uses the more modern BT2.0 connector/ batteries. However, the 1S setup does not draw enough Amps for this to make an actual difference. Also, as it is only used on BETAFPV Drones there is less choice of batteries and they are currently more expensive. Then there is the even more modern GNB27 connector at the horizon..
If you prefer Apple products, the above will probably not bother you though.

GEPRC TinyGo

This is a 2S drone, so you get more power, which makes it better outdoors but worse indoors.
Much worse radio; requires 4xAA batteries, has worse gimbals and most importantly does not work as a Joystick when connected to a PC.
Worse Goggles; there is a DVR, but the focal-length is fixed as is the screen.

The deal-breaker is the used FHSS (Futaba) protocol though. This is virtually not used by any other Drone on the market, so you cannot just get another BNF drone to fly with the same radio. And if you upgrade the Radio you will have to go for a multi-protocol version to still be able to fly the drone instead of being able to get the cheaper D8/ D16 only variant.

Where to go next

The following BNF drones are compatible with the Radio and also run on the 450mAh PH2 batteries that you likely piled up while flying.

Happymodel Mobula 7 1S HD

The drone is very similar to the Tinyhawk III, however it comes with the RunCam Split 3 lite. On top of FPV streaming, it can simultaneously record the video as 1080p @ 60fps to a microSD card. The drone provides gyro logging too, so you can further stabilize the results with gyroflow at the PC.
So if you want to produce nicer videos, this is a good upgrade.

Notably, the drone comes with a serial, balanced charging board as discussed in the charger section above.

EMAX Tinyhawk II Freestyle

This is the drone to upgrade to if you prefer to fly outdoors. It is larger and heavier than the Tinyhawk III. Also it is more powerful as it flies on 2S. The latter is realized using the battery connector, so you still can use the 1S batteries.

If you like tinkering, you can also get nicer videos out of it by packing a RunCam Thumb on top. The drone is powerful enough to carry to extra ~12g of weight.
Note, that this requires soldering-on a power connector for the camera to the flight-controller as the cam has no internal power-supply.

Usage with Ubuntu

If you want to use the betaflight-configurator on Ubuntu, make sure that you have permissions to access the USB serial device by being in the dialout group as:

sudo usermod -a -G dialout $USER

The Remote is just plug-and-play (as a USB HID Gamepad) and is correctly recognized by e.g. FPV.SkyDive, which itself nicely runs on Linux through Steam/ Proton.

BlueJay ESC firmware

People online ™ are telling that one can get increased flight-time by replacing the ESC Firmware by BlueJay and enabling the bidirectional DShot protocol.

However, the TH III already comes with the JESC 2.3 48Khz ESC firmware, where the 48Khz part is what matters for flight-time. Therefore, you will not get any benefit here.

Actually, my flight-time decreased by 15% (from 4:44 min to 4:02 min) when switching to bluejay & bidirectional DSHOT300.

Youtube Channels to follow

Unfortunately there are a lot of youtube channels with a wide reach that have no clue what they are talking about. Dudes sitting in a basement that get a commission when something is sold is not a good combination. Here are some channels that are actually good

Computing replaygain for your Music library

TLDR; command at the end of post

If you want a equal loudness for your Music library the go to solution and the de-facto standard is ReplayGain.
If you are using a music streaming service, the provider is typically taking care of that for you – but maybe you want to migrate towards your own streaming solution.

ReplayGain analyses your audio files and stores their deviation from the baseline loudness as a tag. A compatible audio player can then read the tag and correct the playback volume so all you tracks have the same loudness.

Of course things get messy once you look at details like what the baseline loudness should be and how to determine loudness in the first place. Therefore we set the baseline once and for all as 89db and consider even tracks of the same album individually. If you disagree, feel free to branch off reading up the details now.

The next issue is that ReplayGain was born in a time where mp3 was synonymous to digital music, hence the algorithm was first implemented as the mp3gain CLI tool. Nowadays you also need aacgain and vorbisgain to cover all your formats, which is cumbersome to automate.

The larger issue with ReplayGain is that it defines loudness of a track by its peak volume. While a sane choice in theory, in practice the music and advertising industries raced to increase the perceived loudness without raising the peak volume. As broadcasters also used peak volume normalization, one could blow your eardrum with that very special advertisement.
Therefore the EBU R 128 was proposed which at its core is RMS based, meaning it is considering the average volume of the track.

Remember that ReplayGain merely adds a correction value to the tracks? This allows us to compute that correction value based on the R128 algorithm for a better normalization, which is exactly what the <a href="https://github.com/desbma/r128gain">r128gain</a> tool does.
Being written in modern day, r128gain also processes all possible audio files by hooking into ffmpeg as a filter.

So, without further ado, this is the command to normalize your Music library:

# pip3 install r128gain
r128gain -p -r Music/

This will preserve "-p" the file timestamps and recursively "-r" process all files in the given directory.

Trouble shooting

Note that if you previously used mp3gain, your files might contain non-standard lower-case replaygain_* tags, while r128gain will only write REPLAYGAIN_* tags.
To avoid confusing players with different values, you should remove the non-standard tags. This can be automated with eyeD3

eyeD3 -Q --remove-frame RGAD --preserve-file-times --user-text-frame=replaygain_track_gain: --user-text-frame=replaygain_track_peak: --user-text-frame=replaygain_album_gain: --user-text-frame=replaygain_album_peak: Music/

Refer to its documentation for the meaning of the parameters. For RGAD see here.

Header Image: “volume” by christina rutz (CC-BY-2.0)