Slightly sloooow audio

[motorcity909]

Hi all

Bit of a funny one. Over the past few weeks, I've noticed audio plays ever so slightly slow. It's almost imperceptible; we're not talking a cassette Walkman with the batteries running out! It's just very very slight and barely noticable unless you know the song very well. I mainly noticed it from playing the same songs on CD or my iPod in the car.

This slowness is apparent when playing audio/video files (mp3, avi, mp4, etc), YouTube videos and BBC Iplayer too.

Does a soundcard have, for want of a better word, a "clock" which has maybe lost a milli-second or two?

I'm just using the integrated sound output from the motherboard. My graphics cards has a HDMI output but I don't use it.

If it helps, this is the output from

lspci -v | grep -A7 -i "audio"

-

00:14.2 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] SBx00 Azalia (Intel HDA)
Subsystem: ASUSTeK Computer Inc. Device 8445
Flags: bus master, slow devsel, latency 64, IRQ 16
Memory at fcff4000 (64-bit, non-prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: snd_hda_intel

00:14.3 ISA bridge: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0/SB8x0/SB9x0 LPC host controller
--
01:00.1 Audio device: NVIDIA Corporation GF108 High Definition Audio Controller (rev a1)
Flags: bus master, fast devsel, latency 0, IRQ 19
Memory at feaf8000 (32-bit, non-prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: snd_hda_intel

02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)
Subsystem: ASUSTeK Computer Inc. P8P67 and other motherboards


Any help will be very much appreciated
Dave

[motorcity909]

Quick update. I changed a setting in /etc/pulse/daemon.conf - I changed default-sample-rate from 44100 to 48000 and I think it's worked. Although now I'm listening to a song and thinking 'is that too fast?'.

This may well drive me mad!!

Any other thoughts will be much appreciated.

Cheers
Dave

[tgalati4]

Sound chips are controlled by crystal oscillators that tend to slow down over time. Your 44.1 KHz oscillator is probably slow so going to 48 KHz provides some correction, but now your music is a semitone (or more) higher pitch. If you have a smartphone, load a guitar tuner app. Make some 1-minute audio test files in audacity. Use the sine wave generator at 440 Hz (A key). Play it through your speakers and have the phone app show you the key and frequency. If it is not exactly 440, then you have a problem.

The music player audacious has an effects setting that allows you to make slight corrections to the audio clock. Play with that so you can see how much you are off from being "in tune".

speaker-test will also generate tones on the fly:

tgalati4@Mint14-Extensa ~ $ speaker-test -t sine -f 440

speaker-test 1.0.25

Playback device is default
Stream parameters are 48000Hz, S16_LE, 1 channels
Sine wave rate is 440.0000Hz
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 192 to 2097152
Period size range from 64 to 699051
Using max buffer size 2097152
Periods = 4
was set period_size = 524288
was set buffer_size = 2097152
0 - Front Left

[motorcity909]

That is a really helpful post, many many thanks.

I did as you advised and the guitar tuner app showed 439.9.

So would that -0.1 make the almost imperceptible slowness I can feel/hear?

If so, I guess that brings me to the need for a longer term solution. I'm guessing buying and installing a stand-alone sound card?

[Yellow Pasque]

Try this:

echo "options snd-hda-intel enable_msi=1" | sudo tee -a /etc/modprobe.d/alsa-base.conf

See if there's a difference in your next boot.

[motorcity909]

Will do. What is that meant to do?

Oh, one other thing - between my second post and your first reply (the tuning app idea), I had changed the /etc/pulse/daemon.conf back to 48000, so my test with the guitar tuning app was with the 48000 figure restored.

I changed it because I was hearing a slight speed up, which you confirmed was probably a semitone higher pitch.

So, with the 48000 setting back, does that change your suggested command?

Thanks for all your help
Dave

[tgalati4]

A 440 Hz tone should be 440 Hz regardless of the clock speed. If not, then there is a problem. Now .1 Hz may be within tolerance of the crystal oscillator, that you will have to research.

Check 880 and 1760 as well. Higher frequencies will magnify the error and that may be audible. Concert tuning is typically 441, 442, 443 Hz after an hour of playing. This is to compensate for the strings and wood instruments stretching during a performance so they stay in tune with the brass (which don't change much). So I would say a 1 to 2 Hz difference is audible, but a 0.1 Hz is probably not. Remember, each device has an oscillator and there will be slight differences.

Create some WAV or mp3 tracks with pure tones 220, 440, 880, 1760. Burn them to a CD or put them on your ipod and mp3 players and you will see slight differences between them.

More than you want to know about crystal oscillators: http://en.wikipedia.org/wiki/Crystal...or_frequencies

Typical audio oscillators are run at:

45.1584 MHz Used in CD-DA systems and CD-ROM drives; allows binary division to 44.1 kHz (1024×44.1 kHz), 22.05 kHz, and 11.025 kHz. Also allows integer division to common UART baud rates up to 115200. Available as a TCXO. Frequencies also used are 11.2896 MHz, 16.9344 MHz, 22.5972 MHz and 33.8688 MHz.

[motorcity909]

Interestingly, using the tuning app on 880 and 1760 files showed them exactly at their respective numbers. Not even a 0.1 deviation like with 440 file.

I'm wondering if it's all just in my head!!

BTW, what is that command

echo "options snd-hda-intel enable_msi=1" | sudo tee -a /etc/modprobe.d/alsa-base.conf

meant to do?

Thanks again
Dave

[tgalati4]

That is a switch:

tgalati4@Mint14-Extensa ~ $ modinfo snd-hda-intel
filename: /lib/modules/3.5.0-39-generic/kernel/sound/pci/hda/snd-hda-intel.ko
description: Intel HDA driver
license: GPL
srcversion: 56BA5E778974145B901C998
.
.
.
depends: snd-hda-codec,snd-pcm,snd,snd-page-alloc
intree: Y
vermagic: 3.5.0-39-generic SMP mod_unload modversions
parm: index:Index value for Intel HD audio interface. (array of int)
parm: id:ID string for Intel HD audio interface. (array of charp)
parm: enable:Enable Intel HD audio interface. (array of bool)
parm: model:Use the given board model. (array of charp)
parm: position_fixMA pointer read method.(0 = auto, 1 = LPIB, 2 = POSBUF, 3 = VIACOMBO, 4 = COMBO). (array of int)
parm: bdl_pos_adj:BDL position adjustment offset. (array of int)
parm: probe_mask:Bitmask to probe codecs (default = -1). (array of int)
parm: probe_only:Only probing and no codec initialization. (array of int)
parm: single_cmd:Use single command to communicate with codecs (for debugging only). (bool)
parm: enable_msi:Enable Message Signaled Interrupt (MSI) (bint)
parm: patchatch file for Intel HD audio interface. (array of charp)
parm: beep_mode:Select HDA Beep registration mode (0=off, 1=on, 2=mute switch on/off) (default=1). (array of int)
parm: power_save:Automatic power-saving timeout (in second, 0 = disable). (int)
parm: power_save_controller:Reset controller in power save mode. (bool)
parm: align_buffer_size:Force buffer and period sizes to be multiple of 128 bytes. (bint)
parm: snoop:Enable/disable snooping (bool)

By setting it to "1" the switch enables something called Message Signaled Interrupt. I have no idea what it does, but you could probably search the web for it.

[motorcity909]

Okay, thanks again.

Not sure I want to run a command that I'm not sure of what it will do.

I'm now thinking of trying a USB sound card and bypassing the internal sound card altogether.

I may start another thread to ask about recommedations for any particular such soundcard. Oddly enough, there is a very little out there on the web about good USB cards to use with (X)Ubuntu. I'm guessing (hoping) that's because they simply work.

Many thanks once again for all your help with this.

Dave