Linux 5.15 will introduce a new control element "Playback Pitch 1000000" (commit 6fec018 ("usb: gadget: u_audio.c: Adding Playback Pitch ctl for sync playback") which provides feedback mechanism for playback direction of USB Audio Gadget. The control operates in the same way as the existing control element "Capture Pitch 1000000".
This patch adds support for this feature.
Signed-off-by: Pavel Hofman pavel.hofman@ivitera.com --- alsaloop/pcmjob.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/alsaloop/pcmjob.c b/alsaloop/pcmjob.c index 7b47c40..59ca0ff 100644 --- a/alsaloop/pcmjob.c +++ b/alsaloop/pcmjob.c @@ -1064,6 +1064,7 @@ static int set_rate_shift(struct loopback_handle *lhandle, double pitch) snd_ctl_elem_value_set_integer(lhandle->ctl_rate_shift, 0, pitch * 100000); err = snd_ctl_elem_write(lhandle->ctl, lhandle->ctl_rate_shift); } else if (lhandle->ctl_pitch) { + // 'Playback/Capture Pitch 1000000' requires reciprocal to pitch snd_ctl_elem_value_set_integer(lhandle->ctl_pitch, 0, (1 / pitch) * 1000000); err = snd_ctl_elem_write(lhandle->ctl, lhandle->ctl_pitch); } else { @@ -1241,7 +1242,10 @@ static int openctl(struct loopback_handle *lhandle, int device, int subdevice) lhandle->prateshift_name); exit(EXIT_FAILURE); } - } + } else + openctl_elem(lhandle, device, subdevice, "Playback Pitch 1000000", + &lhandle->ctl_pitch); + set_rate_shift(lhandle, 1); if (lhandle->loopback->controls) goto __events; return 0; @@ -1388,7 +1392,7 @@ int pcmjob_init(struct loopback *loop) loop->id = strdup(id); if (loop->sync == SYNC_TYPE_AUTO && (loop->capt->ctl_rate_shift || loop->capt->ctl_pitch)) loop->sync = SYNC_TYPE_CAPTRATESHIFT; - if (loop->sync == SYNC_TYPE_AUTO && loop->play->ctl_rate_shift) + if (loop->sync == SYNC_TYPE_AUTO && (loop->play->ctl_rate_shift || loop->play->ctl_pitch)) loop->sync = SYNC_TYPE_PLAYRATESHIFT; #ifdef USE_SAMPLERATE if (loop->sync == SYNC_TYPE_AUTO && loop->src_enable)