Bass amp problem

[ralphy]

Should this subject be moved to another thread ?

Yes, I thought the same thing when I last replied.

Created Community Build Radio Firmware thread and replied there.

[mrw]

Applet: ALSA buffer size - An effective work-around to the Bass amp problem

I have updated this Applet to work around a problem encountered with playback of 22050 Hz sample rate streams, which was reported a while back.

You may be asked to restart your Radio after installing the update.

There are no other changes, so need to rush unless you use a 22050 Hz stream.

Original post: https://forums.slimdevices.com/showt...l=1#post933926

As an added bonus, to those of you who remain irritated by 'jittery/bouncing' scrolling menu displays on your Squeezebox Controller, I have uploaded a patch that I have found to be effective. I see no reason why I shouldn't share it. Install it by using the 'Patch Installer' applet under Settings/Advanced/Patch Installer and look for the item titled Fix up misaligned and/or jittery text after horizontal scrolling.

This work-around patch modifies a couple of lua scripts within SqueezePlay, and applies to all SqueezePlay devices, not just the Controller. But only the Controller actually jitters, other devices just show a slight menu misalignment. Ideally we would modify the binary, and I have a source code patch that should do the job, if someone wishes to test it.

[slartibartfast]

After months with no issues I have had the bass issue a couple of times over the past few days. This morning playback started normally then the bass disappeared after a couple of seconds. Strange.

Sent from my Pixel 3a using Tapatalk

[slartibartfast]

After months with no issues I have had the bass issue a couple of times over the past few days. This morning playback started normally then the bass disappeared after a couple of seconds. Strange.

Sent from my Pixel 3a using Tapatalk

Just happened again. Turned on Radio then pressed the preset for Radio 2 and for the first few seconds sound was normal then the bass dropped out.

Sent from my Pixel 3a using Tapatalk

[mrw]

Just happened again. Turned on Radio then pressed the preset for Radio 2 and for the first few seconds sound was normal then the bass dropped out.

I've not had it for a long while. Is your ALSA buffer size set to 30ms ?

I've been running a different 'solution' for the last four months or so (a modified jive_alsa binary) which seems to be fine and absolutely stops the bass drop out. Perhaps it's time to offer it up. I must check how the patch installer applet handles modified binaries.

[slartibartfast]

I've not had it for a long while. Is your ALSA buffer size set to 30ms ?

I've been running a different 'solution' for the last four months or so (a modified jive_alsa binary) which seems to be fine and absolutely stops the bass drop out. Perhaps it's time to offer it up. I must check how the patch installer applet handles modified binaries.

Yes. I have been running a buffer size of 30ms ever since you released the patch. It had been fine for ages but just recently both Radios have suffered in the last week.

Sent from my Pixel 3a using Tapatalk

[mrw]

I must check how the patch installer applet handles modified binaries.

Well, the answer is that it won't handle a modified jive_alsa. So a little installation applet and/or a "do it by hand" instruction is required.

[slartibartfast]

I've not had it for a long while. Is your ALSA buffer size set to 30ms ?

I've been running a different 'solution' for the last four months or so (a modified jive_alsa binary) which seems to be fine and absolutely stops the bass drop out. Perhaps it's time to offer it up. I must check how the patch installer applet handles modified binaries.

This is happening a lot now invariably when I press the Radio 2 preset with the dash iPlayer stream after a restart. I will try a buffer of 40ms to see if it improves.

Sent from my Pixel 3a using Tapatalk

[mrw]

Replacement jive_alsa: A work-around to the Bass amp problem

UPDATE:

The modifications to jive_alsa announced in this post are present in the Community Firmware for Squeezebox Radio announced here. Users of that firmware will not wish to install the modified jive_alsa presented here.


Having investigated the issue further over the last few months, somewhat sporadically, I have pursued an alternative approach to the problem. It appears to be effective, and has, in some form, been running on my Radios for the last five months or so without any obvious adverse effects.

This "solution" requires installation of a modified jive_alsa that eliminates the possibility of ALSA subsystem under-runs. In my experience a "Bass Amp problem" is invariably preceded by an ALSA under-run, and I believe that some of these under-runs, for unknown reasons, trigger the problem. So, eliminate the under-run and the problem goes away.

Update December 2020: Well, I find that the problem may still occur, so elimination of ALSA under-runs does not entirely cure the issue. But it has helped. I've had one instance in the last 10 months.

There is a small downside, in that any time that an under-run would have otherwise occurred, we will get a small, audible, click in the playback. I haven't particularly become aware of this in "real use".

The replacement jive_alsa can be operated with or without adjusting the ALSA buffer size. I have been running it with a buffer size set to 30 milliseconds for some months now, to good effect.

Unfortunately the "Patch Installer" applet cannot install this replacement binary file, so manual installation is the only option at present. In due course I shall endeavour to make up an "Installer Applet" that will do the job.

It is possible that the replacement jive_alsa may expose an undiscovered defect in the firmware, or trigger an issue that I am simply unaware of. I haven't become aware of any issues, but installation is at your own risk.

Manual installation

Enable Remote Login on your radio, note the password, and log in using ssh or your tool of choice. On a Linux or macOS system this would be:

ssh -l root your_radio

Then execute the following commands on the Radio. Lines preceded with '#' are not intended to be executed, these are just comments:

# Fetch the replacement jive_alsa
wget http://mrw-applets.s3-website-us-east-1.amazonaws.com/jive_alsa_fix_bass_dropout_1.0.zip
unzip jive_alsa_fix_bass_dropout_1.0.zip

# Verify checksum of extracted file
echo "c14cb5b9ad789e53eb18c8dd3322a7d2  jive_alsa_fix_bass_dropout_R_2020_04_11"|md5sum -c

# Make executable
chmod +x jive_alsa_fix_bass_dropout_R_2020_04_11

# Check that it appears to work:
./jive_alsa_fix_bass_dropout_R_2020_04_11

# If all ok:
# Move existing jive_alsa to one side
mv /usr/bin/jive_alsa /usr/bin/jive_alsa.original
# Install new version
mv jive_alsa_fix_bass_dropout_R_2020_04_11 /usr/bin/jive_alsa
# Again, check that it appears to work:
/usr/bin/jive_alsa

# If ok, tidy up and restart the radio
rm jive_alsa_fix_bass_dropout_1.0.zip
sync
reboot

The expected dialogue is as follows:

# wget http://mrw-applets.s3-website-us-east-1.amazonaws.com/jive_alsa_fix_bass_dropout_1.0.zip
Connecting to mrw-applets.s3-website-us-east-1.amazonaws.com (52.217.13.59:80)
jive_alsa_fix_bass_d 100% |******************************************************************************************************************************************************************************************************************| 28054  00:00:00 ETA
# unzip jive_alsa_fix_bass_dropout_1.0.zip
Archive:  jive_alsa_fix_bass_dropout_1.0.zip
  inflating: jive_alsa_fix_bass_dropout_R_2020_04_11
# echo "c14cb5b9ad789e53eb18c8dd3322a7d2  jive_alsa_fix_bass_dropout_R_2020_04_11"|md5sum -c
jive_alsa_fix_bass_dropout_R_2020_04_11: OK
# chmod +x jive_alsa_fix_bass_dropout_R_2020_04_11
# ./jive_alsa_fix_bass_dropout_R_2020_04_11
Usage: ./jive_alsa_fix_bass_dropout_R_2020_04_11 [-v] -d <playback_device> [-c <capture_device>] -b <buffer_time> -p <period_count> -s <sample_size:24|16> -f <flags>
Patched to mitigate against 'bass drop out'. Release 11 April 2020.
# mv /usr/bin/jive_alsa /usr/bin/jive_alsa.original
# mv jive_alsa_fix_bass_dropout_R_2020_04_11 /usr/bin/jive_alsa
# /usr/bin/jive_alsa
Usage: /usr/bin/jive_alsa [-v] -d <playback_device> [-c <capture_device>] -b <buffer_time> -p <period_count> -s <sample_size:24|16> -f <flags>
Patched to mitigate against 'bass drop out'. Release 11 April 2020.
# rm jive_alsa_fix_bass_dropout_1.0.zip
# sync
# reboot

The Radio will be restarting itself at this point.

To verify that the replacement jive_alsa is running, log into the radio again, and look for the tell tale trace message in the log:

grep squeezeplay /var/log/messages
Jul 10 13:19:44 squeezeplay: main:1265 This is a modified version of jive_alsa that mitigates against 'bass drop out'. Release version 11 April 2020.

[b]Plus possibly some other lines of text.[/b]

Note: Other lines of text may also appear, but they are not important. The presence of this line of text provides the verification that we seek.

To remove the replacement jive_alsa, either restore factory settings by pressing the "MORE|+" key while powering up the Radio, or put back the original jive_alsa that we saved during installation:

mv /usr/bin/jive_alsa.original /usr/bin/jive_alsa
sync
reboot

Remember to disable remote login when you are all done.


The changes made to jive_alsa

I have published the changes that I have made to a forked version of Squeezeplay. The changes are in a git tree named baby_bass_drop_out and may be found here: https://github.com/mw9/squeezeplay/t...drop_out_final

The binary was built using the same build system, squeezeos, as was used to create the original firmware. As far as I can tell, it would also work on a regular "UE" Radio firmware, but I haven't checked that.

I have converted the changes into squeezeos form, these may be found here: https://github.com/mw9/squeezeos/tree/baby_bass_dropout


Any comments or feedback welcome.

[mrw]

This is happening a lot now invariably when I press the Radio 2 preset with the dash iPlayer stream after a restart. I will try a buffer of 40ms to see if it improves.

My guess is that you are seeing what I think have seen, that increasing the buffer size just does not seem to be as effective when a stream is first started up. I won't attempt to speculate on why you have been recently "afflicted".

See my previous post today for an additional approach.

[slartibartfast]

My guess is that you are seeing what I think have seen, that increasing the buffer size just does not seem to be as effective when a stream is first started up. I won't attempt to speculate on why you have been recently "afflicted".

See my previous post today for an additional approach.

I'll try that with one Radio to start with. Could it be because the stream is 320kbps? Then again it always has been. Maybe something in iPlayer changed.

Sent from my Pixel 3a using Tapatalk

[mrw]

Could it be because the stream is 320kbps? Then again it always has been.

Quite possibly contributory, because more decoding work. But then again...

Possibly delays in stream start up at the BBC end. I've found it impossible to diagnose, I end up speculating.

[slartibartfast]

Quite possibly contributory, because more decoding work. But then again...

Possibly delays in stream start up at the BBC end. I've found it impossible to diagnose, I end up speculating.

The strange thing is it plays normally for a few seconds before the bass disappears.

Sent from my Pixel 3a using Tapatalk

[mrw]

The strange thing is it plays normally for a few seconds before the bass disappears.

Perhaps a "post start up glitch" at the BBC, or perhaps something else. BBC iPlayer setting Seconds to delay start live stream ? Mine is at 10 seconds.

As an aside, I find the Radio menu navigation noticeably sluggish when streaming BBC 320kbs AAC.

I have recently disabled "Native AAC" [1] on LMS, so now they are transcoded into flac. Menu navigation is noticeably more sprightly, and no drawbacks that I've noticed, so far at least.

[1] Server settings|Advanced|File Types

[slartibartfast]

Perhaps a "post start up glitch" at the BBC, or perhaps something else. BBC iPlayer setting Seconds to delay start live stream ? Mine is at 10 seconds.

As an aside, I find the Radio menu navigation noticeably sluggish when streaming BBC 320kbs AAC.

I have recently disabled "Native AAC" [1] on LMS, so now they are transcoded into flac. Menu navigation is noticeably more sprightly, and no drawbacks that I've noticed, so far at least.

[1] Server settings|Advanced|File Types

I have delay set to zero. Can't say I have noticed the menus being sluggish but I will watch out for it. I might try disabling AAC before trying the replacement alsa.

Sent from my Pixel 3a using Tapatalk