2009/12/2 pl bossart <bossart.nospam@xxxxxxxxx>
> Hi,
> I have been having issues for a while now with PulseAudio running on
> an older Thinkpad X41. PulseAudio relies on snd_pcm_avail() to detect
> underflows and increases the timer watermark when they happen. There
> are actually no audible underflows though...
> So I instrumented both PulseAudio (enabling DEBUG_TIMING in the
> alsa-sink.c code) and the kernel (latest alsa-kernel git) by adding
> the following printk in pcm.h:
>
> static inline snd_pcm_uframes_t snd_pcm_playback_avail(struct
> snd_pcm_runtime *runtime)
> {
> snd_pcm_sframes_t avail = runtime->status->hw_ptr +
> runtime->buffer_size - runtime->control->appl_ptr;
> if (avail < 0)
> avail += runtime->boundary;
> else if ((snd_pcm_uframes_t) avail >= runtime->boundary)
> avail -= runtime->boundary;
> //plb
> if(avail > runtime->buffer_size) {
> snd_printk(KERN_ERR "avail %d hw_ptr %d buffer %d appl_ptr %d
> \n",
> avail, runtime->status->hw_ptr,
> runtime->buffer_size, runtime->control->appl_ptr);
> }
> return avail;
> }
>
> In my tests this error condition where avail is larger than the ring
> buffer happens fairly often. The dmesg log show messages such as
> [ 834.524479] ALSA include/sound/pcm.h:600: avail 16403 hw_ptr 24351
> buffer 16384 appl_ptr 24332
> [ 835.266937] ALSA include/sound/pcm.h:600: avail 16407 hw_ptr 55841
> buffer 16384 appl_ptr 55818
> and these messages are correlated with the times when PulseAudio
> detects underflows.
> The full log can be found at http://pastebin.com/f210aa108.
>
> I believe the issue is the accuracy of the hw_ptr reported by
> snd_intel8x0_pcm_pointer. If indeed such a condition occurred, it
> should be flagged as underflow, shouldn't it? There's been some
> changes in this part of the code to avoid extremely large values, here
> the issue seems more subtle, the pointer is only slightly off in most
> cases. This does screw-up PulseAudio though, the timer watermark keeps
> increasing and low-latency isn't possible.
>
> I'd be more than happy to run more experiments, however I have no idea
> what the hardware does to report the position of the hw pointer.
> Thanks for your feedback
> - Pierre
>
>
I: main.c: This is PulseAudio 0.9.21-296-gd2ab2
1. D: alsa-util.c: Trying front:0 with SND_PCM_NO_AUTO_FORMAT ...
2. D: alsa-util.c: Managed to open front:0
3. D: alsa-util.c: Maximum hw buffer size is 371 ms
4. D: alsa-util.c: Set buffer size first (to 4408 samples), period size
second (to 1102 samples)
What is the purpose of these buffer-size and period size during the probing
phase ?
The PA server seem use different values
1. I: sink.c: Created sink 0 "alsa_output.pci-0000_00_1e.2.analog-stereo"
with sample spec s16le 2ch 44100Hz and channel map front-left,front-right
2. I: sink.c: alsa.resolution_bits = "16"
3. I: sink.c: device.api = "alsa"
4. I: sink.c: device.class = "sound"
5. I: sink.c: alsa.class = "generic"
6. I: sink.c: alsa.subclass = "generic-mix"
7. I: sink.c: alsa.name = "Intel ICH6"
8. I: sink.c: alsa.id = "Intel ICH"
9. I: sink.c: alsa.subdevice = "0"
10. I: sink.c: alsa.subdevice_name = "subdevice #0"
11. I: sink.c: alsa.device = "0"
12. I: sink.c: alsa.card = "0"
13. I: sink.c: alsa.card_name = "Intel ICH6"
14. I: sink.c: alsa.long_card_name = "Intel ICH6 with AD1981B at irq
22"
15. I: sink.c: alsa.driver_name = "snd_intel8x0"
16. I: sink.c: device.bus_path = "pci-0000:00:1e.2"
17. I: sink.c: sysfs.path =
"/devices/pci0000:00/0000:00:1e.2/sound/card0"
18. I: sink.c: device.bus = "pci"
19. I: sink.c: device.vendor.id = "8086"
20. I: sink.c: device.vendor.name = "Intel Corporation"
21. I: sink.c: device.product.id = "266e"
22. I: sink.c: device.product.name = "82801FB/FBM/FR/FW/FRW (ICH6
Family) AC'97 Audio Controller"
23. I: sink.c: device.form_factor = "internal"
24. I: sink.c: hal.udi =
"/org/freedesktop/Hal/devices/pci_8086_266e_sound_card_0"
25. I: sink.c: hal.product = "Intel ICH6 with AD1981B Sound Card"
26. I: sink.c: hal.card_id = "Intel ICH6 with AD1981B"
27. I: sink.c: device.string = "front:0"
28. I: sink.c: device.buffering.buffer_size = "65536"
29. I: sink.c: device.buffering.fragment_size = "65536"
30. I: sink.c: device.access_mode = "mmap+timer"
31. I: sink.c: device.profile.name = "analog-stereo"
32. I: sink.c: device.profile.description = "Analog Stereo"
33. I: sink.c: device.description = "Internal Audio Analog Stereo"
34. I: sink.c: alsa.mixer_name = "Analog Devices AD1981B"
35. I: sink.c: alsa.components = "AC97a:41445374"
36. I: sink.c: module-udev-detect.discovered = "1"
37. I: sink.c: device.icon_name = "audio-card-pci"
intel8x0 does not has hdmi , it seem PA hardcode hdmi for all sound cards
instead of using namehint for playback device
1. D: alsa-mixer.c: Looking at profile output:hdmi-stereo
2. D: alsa-mixer.c: Checking for playback on Digital Stereo (HDMI)
(hdmi-stereo)
3. D: alsa-util.c: Trying hdmi:0 with SND_PCM_NO_AUTO_FORMAT ...
4. I: (alsa-lib)conf.c: Unknown parameters 0
5. I: (alsa-lib)pcm.c: Unknown PCM hdmi:0
6. I: alsa-util.c: Error opening PCM device hdmi:0: Invalid argument
Is it possible to add timestamp in alsa-sink.c: Wrote 31792 bytes (of
possible 31792 bytes) statement for debugging
1. D: alsa-sink.c: Loop
2. D: alsa-sink.c: Buffer time: 371 ms; Sleep time: 351 ms; Process time:
20 ms
3. hwptr 7948 buffer 16384 appl 16384, avail=7948
4. D: alsa-sink.c: avail: 31792 (samples 7948)
5. D: alsa-sink.c: 191.29 ms left to play; inc threshold = 0.00 ms; dec
threshold = 100.00 ms
6. D: alsa-sink.c: Filling up
7. hwptr 7948 buffer 16384 appl 16384, avail=7948
8. hwptr 7948 buffer 16384 appl 16384, avail=7948
9. D: alsa-sink.c: Wrote 31792 bytes (of possible 31792 bytes)
10. hwptr 7960 buffer 16384 appl 24332, avail=12
11. D: alsa-sink.c: avail: 48 (samples 12)
12. D: alsa-sink.c: 371.25 ms left to play; inc threshold = 0.00 ms; dec
threshold = 100.00 ms
13. D: alsa-sink.c: Not filling up, because too early.
14. D: alsa-sink.c: Wakeup from ALSA!
15. D: alsa-sink.c: Loop
16. D: alsa-sink.c: Buffer time: 371 ms; Sleep time: 351 ms; Process
time: 20 ms
17. hwptr 24351 buffer 16384 appl 24332, avail=16403
18. E: alsa-util.c: avail 16403 delay -19
19. D: alsa-sink.c: avail: 65536 (samples 16384)
20. D: alsa-sink.c: 0.00 ms left to play; inc threshold = 0.00 ms; dec
threshold = 100.00 ms
21. D: alsa-sink.c: Filling up
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