Broken Pipe with SNDRV_PCM_IOCTL_WRITEI_FRAMES

[Ryan McClue]

I've update my loop to:

struct

snd_xferi

transfer

=

{};
  transfer.buf = (u8 *)buffer;
  transfer.frames = num_base_samples;

int

res = ioctl(fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &transfer);

if

(res == -EPIPE) {
    ioctl(fd, SNDRV_PCM_IOCTL_PREPARE);

This removes the Broken Pipe, however no sound is heard.
--
Ryan McClue, Sydney

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, September 26th, 2021 at 7:01 PM, Ryan McClue <re.mcclue at protonmail.com> wrote:

> Hello again.
> I'm using alsa-kernel.
> My configuration:
> SNDRV_PCM_HW_PARAM_ACCESS = SNDRV_PCM_ACCESS_RW_INTERLEAVED
> SNDRV_PCM_HW_PARAM_FORMAT = SNDRV_PCM_FORMAT_S16_LE
> SNDRV_PCM_HW_PARAM_SUBFORMAT = SNDRV_PCM_SUBFORMAT_STD
> SNDRV_PCM_HW_PARAM_CHANNELS = 2
> SNDRV_PCM_HW_PARAM_RATE = 48000
>
> I have a vsynced game loop that is running at 60fps:
>
>> int num_base_samples = 48000 * (1 / 60);
>> int num_samples =  num_base_samples * 2;
>> int16_t buffer[num_samples] = {};
>>
>> while (true) {
>>   int16_t *samples = buffer;
>>   for (int sample_i = 0; sample_i < num_base_samples; sample_i++) {
>>     *samples++ = 0x33;
>>     *samples++ = 0x33;
>>   }
>>
>>   struct snd_xferi transfer = {};
>>   transfer.buf = buffer;
>>   transfer.frames = num_base_samples;
>>   ioctl(fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &transfer);
>>
>>   // ioctl(fd, SNDRV_PCM_IOCTL_DRAIN);  --> NECESSARY???
>>   // ioctl(fd, SNDRV_PCM_IOCTL_PREPARE);  --> NECESSARY???
>> }
>
> On the first iteration of SNDRV_PCM_IOCTL_WRITEI_FRAMES I get no error.
> All subsequent iterations, I get Broken Pipe error.
> So, to counteract this at the end of each frame I call SNDRV_PCM_IOCTL_DRAIN and SNDRV_PCM_IOCTL_PREPARE.
> This removes the Broken Pipe error however slows the program down by half and no sound is heard.
> How best to solve this issue?
>
> Thanks again
> --
> Ryan McClue, Sydney