Hi Philippe, My reason for using ioctl()'s is to better understand how ALSA works. I'm very close to achieving my goal of playing pcm with ioctl()'s. I want to make the code public so everyone can gain better knowledge of linux sound. In regards to using alsa-lib, I can equate my example to snd_pcm_writei() and snd_pcm_prepare() As I understand it, the EPIPE indicates a buffer underrun. However, I'm recovering with prepare. Why would there be total silence? -- Ryan McClue, Sydney ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Monday, September 27th, 2021 at 7:21 PM, Philippe Bekaert <linux@xxxxxxxxxxx> wrote: > Hi Ryan, > > I realize this is probably not the answer you are waiting and hoping for, but why do you use the ioctl interface directly in the first place? > People on this list will likely be more alarmed if you had problems with audio I/O, when done as explained on > https://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html > and illustrated in the examples. > > Best, > > Philippe. > >> On 27 Sep 2021, at 01:21, Ryan McClue <re.mcclue@xxxxxxxxxxxxxx> wrote: >> >> 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@xxxxxxxxxxxxxx> 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
