I have a bug in ALSA somewhere; playback is corrupted. Nothing is pro-actively telling me of a problem (eg. underrun) I could use some assistance getting to the bottom of this. Listen to [1] for what it sounds like -- analogue recording from the output. Look at the waveform [2] in Baudlien and it seems both L+R channels geting zero'd for some buffer period of 2.5 or 5 milliseconds. This is Layla3G, snd-echo3g. This problem has been rare, but persisted for many years. I've finally got something reproducable to investigate. It began ~10 years ago where very occasionally recordings or playback would do this. This was a simple self-contained application in production use; written by me, using plughw:Layla3G,0,0 (no desktops, browsers, dmix etc.) Problems were frequent enough to be annoying, but infrequent enough that I just had to put it down to 'cosmic rays', with no useful bug report. These days I am on a desktop using dmix; and more recently with Google Chrome and found I can reliably 'trigger' it. To reset, I must close all applications using /dev/snd, and re-open. It seems to be: * whether or not Google Chrome is first to open the device * about 10-60 minutes after Chrome has opened the device * more prone to happening if other applications are using the dmix * not related to buffer sizes; I use larger sizes in the asoundrc it doesn't affect the likelihood, or the 'sound' when it does happen * I've seen two Layla's affected * I've had many kernels and PCs over the years There's a bug somewhere, and with nothing printed to dmesg, console etc., I'm at a loss here, imagining my problem could be anywhere between dmix, alsa-lib, snd-echo3g or even the firmware itself. Whatever the case, I've finally got some combination I can do in userland as a trigger. Below is: - .asoundrc describing today's setup (previously I used stereo with no route, still with problems) - output of the 'aplay' that produced the recording above; and - some other stats. [1] http://www.pogo.org.uk/~mark/tmp/layla-glitch.flac [2] http://www.pogo.org.uk/~mark/tmp/layla-glitch.png Many thanks -- Mark pcm.!default { type plug slave.pcm layla_multi } pcm.layla_multi { type route slave.pcm { type dmix ipc_key 1742 slave { pcm "hw:Layla3G,0,0" period_size 992 buffer_size 10912 channels 5 rate 48000 format S16_LE } } ttable { # Headphones 0.0 1 1.1 1 # Speakers 0.2 1 1.3 1 # Subwoofer; mono mix 0.4 0.5 1.4 0.5 } } $ uname -a Linux stax 4.18.5 #113 SMP PREEMPT Mon Sep 3 23:14:59 BST 2018 x86_64 Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz GenuineIntel GNU/Linux $ head -99l /proc/asound/Layla3G/pcm0p/sub0/* ==> /proc/asound/Layla3G/pcm0p/sub0/hw_params <== access: MMAP_INTERLEAVED format: S16_LE subformat: STD channels: 6 rate: 48000 (48000/1) period_size: 992 buffer_size: 10912 ==> /proc/asound/Layla3G/pcm0p/sub0/info <== card: 0 device: 0 subdevice: 0 stream: PLAYBACK id: Analog PCM name: Layla3G subname: subdevice #0 class: 0 subclass: 0 subdevices_count: 8 subdevices_avail: 7 ==> /proc/asound/Layla3G/pcm0p/sub0/prealloc <== 128 ==> /proc/asound/Layla3G/pcm0p/sub0/prealloc_max <== 256 ==> /proc/asound/Layla3G/pcm0p/sub0/status <== state: RUNNING owner_pid : 9250 trigger_time: 663739.627559736 tstamp : 680208.555428028 delay : -790500256 avail : 790511168 avail_max : 790511168 ----- hw_ptr : 790500256 appl_ptr : 0 ==> /proc/asound/Layla3G/pcm0p/sub0/sw_params <== tstamp_mode: ENABLE period_step: 1 avail_min: 1 start_threshold: 1 stop_threshold: 6142909891733356544 silence_threshold: 0 silence_size: 6142909891733356544 boundary: 6142909891733356544 $ aplay -vv all48000.wav Playing WAVE 'all48000.wav' : Float 32 bit Little Endian, Rate 48000 Hz, Stereo Plug PCM: Linear Integer <-> Linear Float conversion PCM (S16_LE) Its setup is: stream : PLAYBACK access : RW_INTERLEAVED format : FLOAT_LE subformat : STD channels : 2 rate : 48000 exact rate : 48000 (48000/1) msbits : 32 buffer_size : 10912 period_size : 992 period_time : 20666 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 992 period_event : 0 start_threshold : 10912 stop_threshold : 10912 silence_threshold: 0 silence_size : 0 boundary : 6142909891733356544 Slave: Route conversion PCM (sformat=S16_LE) Transformation table: 0 <- 0 1 <- 1 2 <- none 3 <- none 4 <- none 5 <- none Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_LE subformat : STD channels : 2 rate : 48000 exact rate : 48000 (48000/1) msbits : 16 buffer_size : 10912 period_size : 992 period_time : 20666 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 992 period_event : 0 start_threshold : 10912 stop_threshold : 10912 silence_threshold: 0 silence_size : 0 boundary : 6142909891733356544 Slave: Route conversion PCM Transformation table: 0 <- 0 1 <- 1 2 <- 0 3 <- 1 4 <- 0*0.5 + 1*0.5 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_LE subformat : STD channels : 6 rate : 48000 exact rate : 48000 (48000/1) msbits : 16 buffer_size : 10912 period_size : 992 period_time : 20666 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 992 period_event : 0 start_threshold : 10912 stop_threshold : 10912 silence_threshold: 0 silence_size : 0 boundary : 6142909891733356544 Slave: Direct Stream Mixing PCM Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_LE subformat : STD channels : 6 rate : 48000 exact rate : 48000 (48000/1) msbits : 16 buffer_size : 10912 period_size : 992 period_time : 20666 tstamp_mode : NONE tstamp_type : MONOTONIC period_step : 1 avail_min : 992 period_event : 0 start_threshold : 10912 stop_threshold : 10912 silence_threshold: 0 silence_size : 0 boundary : 6142909891733356544 Hardware PCM card 0 'Layla3G' device 0 subdevice 0 Its setup is: stream : PLAYBACK access : MMAP_INTERLEAVED format : S16_LE subformat : STD channels : 6 rate : 48000 exact rate : 48000 (48000/1) msbits : 16 buffer_size : 10912 period_size : 992 period_time : 20666 tstamp_mode : ENABLE tstamp_type : MONOTONIC period_step : 1 avail_min : 992 period_event : 0 start_threshold : 1 stop_threshold : 0 silence_threshold: 0 silence_size : 0 boundary : 6142909891733356544 appl_ptr : 0 hw_ptr : 807111136 ############################ + | 56%^C Aborted by signal Interrupt... aplay: pcm_write:2004: write error: Interrupted system call _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
