[alsa-devel] hw_ptr accuracy with intel8x0 -> PulseAudio issue

[Raymond Yau]

2009/12/4 pl bossart <bossart.nospam at gmail.com>

> Hi Raymond,
> comments below.
> - PL
>
> On Wed, Dec 2, 2009 at 8:26 PM, Raymond Yau <superquad.vortex2 at gmail.com>
> wrote:
> >   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
>
> This is a red herring, PulseAudio tries to open multiple profiles and
> finds out which ones make sense. You want to look at the result below
> which is the final configuration.
>
> >   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
>
> Yes, PA will try all possible profiles. Not that smart but unrelated
> to my problem.
>
>
> > Is it possible to add timestamp in alsa-sink.c: Wrote 31792 bytes (of
> > possible 31792 bytes) statement for debugging
>
> Not sure why this is needed. In that case the driver reports 7948
> frames are available, which translates to 31792 bytes.
> The problem shows in the next call to snd_pcm_avail down to the kernel
> level, PA only uses the misleading information reported by the driver.
>


>   17. hwptr 24351 buffer 16384 appl 24332, avail=16403

appl pointer is behind hwprtr (  underrun ) , need timestamp to find out
whether PA is unable to write audio data in time since

>   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

did it adjust the sleeping time when it think too early ?


>
> >   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
>