Problem with playback under arch linux.

[perlindgren]

Hi

When trying out the latest master I get.

cargo run --example beep
warning: field is never used: `can_pause`
   --> src/host/alsa/mod.rs:501:5
    |
501 |     can_pause: bool,
    |     ^^^^^^^^^^^^^^^
    |
    = note: `#[warn(dead_code)]` on by default

    Finished dev [unoptimized + debuginfo] target(s) in 0.31s
     Running `target/debug/examples/beep`
Error: A backend-specific error has occurred: buffer time could not be set: Invalid argument

I'm on arch Linux using Jack, all packages recently updated and other sound applications (Jack, pulseaudio, alsa) works as expected.

cargo run --example enumerate
warning: field is never used: `can_pause`
   --> src/host/alsa/mod.rs:501:5
    |
501 |     can_pause: bool,
    |     ^^^^^^^^^^^^^^^
    |
    = note: `#[warn(dead_code)]` on by default

   Compiling cpal v0.11.0 (/home/pln/rust/adder/cpal)
    Finished dev [unoptimized + debuginfo] target(s) in 1.92s
     Running `target/debug/examples/enumerate`
Supported hosts:
  [Alsa]
Available hosts:
  [Alsa]
ALSA
  Default Input Device:
    Some("default")
  Default Output Device:
    Some("default")
  Devices: 
  1. "jack"
    Default input stream format:
      Format { channels: 2, sample_rate: SampleRate(44100), data_type: F32 }
    All supported input stream formats:
      1.1. SupportedFormat { channels: 2, min_sample_rate: SampleRate(44100), max_sample_rate: SampleRate(44100), data_type: F32 }
    Default output stream format:
      Format { channels: 2, sample_rate: SampleRate(44100), data_type: F32 }
    All supported output stream formats:
      1.1. SupportedFormat { channels: 2, min_sample_rate: SampleRate(44100), max_sample_rate: SampleRate(44100), data_type: F32 }
ALSA lib pcm_dmix.c:1089:(snd_pcm_dmix_open) unable to open slave
ALSA lib pcm_dsnoop.c:641:(snd_pcm_dsnoop_open) unable to open slave
ALSA lib pcm_usb_stream.c:508:(_snd_pcm_usb_stream_open) Unknown field hint
ALSA lib pcm_usb_stream.c:508:(_snd_pcm_usb_stream_open) Unknown field hint
  2. "hdmi:CARD=HDMI,DEV=0"
Error: DeviceNotAvailable
ALSA lib pcm_usb_stream.c:508:(_snd_pcm_usb_stream_open) Unknown field hint
ALSA lib pcm_usb_stream.c:508:(_snd_pcm_usb_stream_open) Unknown field hint

I have a similar setup on my laptop, arch, Jack etc. And there it works, so either my setup is wrong, or I hit a bug in cpal.

Any thoughts/ideas. What to try next?

[mitchmindtree]

It seems the issue has something to do with the way we specify the desired buffer size on the ALSA backend.

The source of the error is here.

Specifically, the call to snd_pcm_hw_params_set_buffer_time_near.

[perlindgren]

Oki, but not sure what to do about it. Is there a problem with my underlying ALSA driver or is it to be considered a bug in cpal.

[alxdb]

I'm also having this issue, using arch linux and alsa -> pulseaudio -> jack with the use of cadence. same error.

[sniperrifle2004]

The alsa documentation suggests that the configuration space is empty. That seems odd for buffer_time. I would be interested to see the output of aplay --dump-hw-params for this device.

[alxdb]

just tried running aplay --dump-hw-params on my machine, it just hangs. Tried with jack both enabled and disabled.

[sniperrifle2004]

Its waiting for input. Unfortunately you can't actually just use that command bare to get the parameters. Try aplay --dump-hw-params <some wav file>. Sorry for the confusion. However I have since found out that this problem probably is (was?) actually a bug in alsa-lib: https://bbs.archlinux.org/viewtopic.php?pid=1870274#p1870274

Looks like I was a little bit to optimistic :(

[alxdb]

Here's a dump of running aplay --dump-hw-params with a wav file

Playing WAVE '/home/alxdb/music/rips/afx-analogue_bubblebath_3/audio_00.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo
HW Params of device "default":
--------------------
ACCESS:  MMAP_INTERLEAVED MMAP_NONINTERLEAVED MMAP_COMPLEX RW_INTERLEAVED RW_NONINTERLEAVED
FORMAT:  S8 U8 S16_LE S16_BE U16_LE U16_BE S24_LE S24_BE U24_LE U24_BE S32_LE S32_BE U32_LE U32_BE FLOAT_LE FLOAT_BE FLOAT64_LE FLOAT64_BE MU_LAW A_LAW IMA_ADPCM S20_LE S20_BE U20_LE U20_BE S24_3LE S24_3BE U24_3LE U24_3BE S20_3LE S20_3BE U20_3LE U20_3BE S18_3LE S18_3BE U18_3LE U18_3BE
SUBFORMAT:  STD
SAMPLE_BITS: [4 64]
FRAME_BITS: [4 640000]
CHANNELS: [1 10000]
RATE: [4000 4294967295)
PERIOD_TIME: (2 349525500)
PERIOD_SIZE: (0 4294967295)
PERIOD_BYTES: (0 4294967295)
PERIODS: (0 4294967295]
BUFFER_TIME: [1 4294967295]
BUFFER_SIZE: [1 4294967294]
BUFFER_BYTES: [1 4294967295]
TICK_TIME: ALL
--------------------

[sniperrifle2004]

I thought I had spotted the error, but it look it looks like I was wrong. I don't know why exactly, but the problem actually really just occurs for the jack device, with the plug alsa type as a default device. The underlying device and the jack device directly works fine.

Now what I can't understand is why it does work in aplay. That doesn't do things very differently from cpal, so its surprising. It also means that it is possible that the jack device directly would also not work with cpal (Since I was using aplay to test that, since the beep example doesn't have the luxury of using anything other than the default device)

EDIT: It's surprising but the order matters! You must first specify a period time and only then you can set the buffer time. Now there is something to be said for this (Because the buffer size must be at least large then a period. Preferably at least twice as large to prevent underruns), but for it to actually fail while trying to set the buffer time...

[est31]

9503ab7