Re: [alsa-devel] snd_pcm_set_params faild on set_buffer_time_near and set_period_time_near

Hi Raymond,

Output parameters with custom logs: set_buffer_time_near: -22 set period time: 12517 get period size: 276 set buffer size: 1104 get buffer size: 1104

ACCESS: RW_INTERLEAVED FORMAT: S16_LE SUBFORMAT: STD SAMPLE_BITS: 16 FRAME_BITS: 32 CHANNELS: 2 RATE: 22050 PERIOD_TIME: (12517 12518) PERIOD_SIZE: 276 PERIOD_BYTES: 1104 PERIODS: 4 BUFFER_TIME: (50068 50069) BUFFER_SIZE: 1104 BUFFER_BYTES: 4416

What do you mean, are latency always <= 50ms? In what cases?

Martin

On 25.07.2015 04:01, Raymond Yau wrote:

2015-07-24 19:16 GMT+08:00 Martin Geier <martin.geier@streamunlimited.com mailto:martin.geier@streamunlimited.com>:

Patch with fixed name and description.

Martin



On 24.07.2015 10:21, Takashi Iwai wrote:

    On Fri, 24 Jul 2015 09:52:14 +0200,
    Martin Geier wrote:

        Thanks for help,

        in attachment is patch with suggest change.
        Is the patch acceptable?

    I prefer a bit clearer name like params_saved or such, but
    yes, it's
    what I had in my mind, too.  Could you tidy it up and resubmit
    with
    the more description -- why it's needed and what does it? 
    Last but
    not least, it'd be helpful if you give also signed-off-by tag.


    thanks,

    Takashi

        Martin

        On 23.07.2015 10:11, Takashi Iwai wrote:

            On Tue, 21 Jul 2015 10:52:01 +0200,
            Martin Geier wrote:

                Hallo,

                I tried to configure alsa device with
                snd_pcm_set_params function,
                requested
                parameters was:
                channel 2, rate: 22050, soft_resample: 1, latency:
                50000

                Function snd_pcm_hw_params_set_buffer_time_near and
                snd_pcm_hw_param_set_near
                is called with:
                min: 50000, max: 50000, mindir: 0, maxdir: -1

                and input params was:

                ACCESS:  RW_INTERLEAVED
                FORMAT:  S16_LE
                SUBFORMAT:  STD
                SAMPLE_BITS: 16
                FRAME_BITS: 32
                CHANNELS: 2
                RATE: 22050
                PERIOD_TIME: (362 743039)
                PERIOD_SIZE: [8 16384]
                PERIOD_BYTES: [32 65536]
                PERIODS: [2 19]
                BUFFER_TIME: (725 1486078)
                BUFFER_SIZE: [16 32768]
                BUFFER_BYTES: [64 131072]
                TICK_TIME: ALL

                unfortunately, this function fails, on function
                snd_pcm_hw_param_set_first:

                ALSA ERROR hw_params: set_near (BUFFER_TIME)
                              value = 50000 : Invalid argument
                ACCESS:  RW_INTERLEAVED
                FORMAT:  S16_LE
                SUBFORMAT:  STD
                SAMPLE_BITS: 16
                FRAME_BITS: 32
                CHANNELS: 2
                RATE: 22050
                PERIOD_TIME: (4580 5533)
                PERIOD_SIZE: NONE
                PERIOD_BYTES: [404 488]
                PERIODS: 10
                BUFFER_TIME: (50022 50023)
                BUFFER_SIZE: 1103
                BUFFER_BYTES: 4412
                TICK_TIME: ALL

                This shouldn't be problem because in
                snd_pcm_set_params is
                snd_pcm_hw_params_set_period_time_near called.
                This function should be called with same params as
                snd_pcm_hw_params_set_buffer_time_near
                but the input params are:

                snd_pcm_hw_param_set_near: min: 12500, max: 12500,
                mindir: 0, maxdir: -1
                hw_params: snd_pcm_hw_param_set_near (PERIOD_TIME)
                ACCESS:  RW_INTERLEAVED
                FORMAT:  S16_LE
                SUBFORMAT:  STD
                SAMPLE_BITS: 16
                FRAME_BITS: 32
                CHANNELS: 2
                RATE: 22050
                PERIOD_TIME: (4580 5533)
                PERIOD_SIZE: NONE
                PERIOD_BYTES: [404 488]
                PERIODS: 10
                BUFFER_TIME: (50022 50023)
                BUFFER_SIZE: 1103
                BUFFER_BYTES: 4412
                TICK_TIME: ALL

What is the period time and buffer time after applied your patch ?

Are latency always <= 50ms ?