diff options
| -rw-r--r-- | sys/dev/sound/usb/uaudio.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/sys/dev/sound/usb/uaudio.c b/sys/dev/sound/usb/uaudio.c index 99369ca..1a530f2 100644 --- a/sys/dev/sound/usb/uaudio.c +++ b/sys/dev/sound/usb/uaudio.c @@ -2084,9 +2084,23 @@ uaudio_chan_play_sync_callback(struct usb_xfer *xfer, usb_error_t error) * Use feedback value as fallback when there is no * recording channel: */ - if (ch->priv_sc->sc_rec_chan.num_alt == 0) - ch->jitter_curr = temp - sample_rate; + if (ch->priv_sc->sc_rec_chan.num_alt == 0) { + int32_t jitter_max = howmany(sample_rate, 16000); + /* + * Range check the jitter values to avoid + * bogus sample rate adjustments. The expected + * deviation should not be more than 1Hz per + * second. The USB v2.0 specification also + * mandates this requirement. Refer to chapter + * 5.12.4.2 about feedback. + */ + ch->jitter_curr = temp - sample_rate; + if (ch->jitter_curr > jitter_max) + ch->jitter_curr = jitter_max; + else if (ch->jitter_curr < -jitter_max) + ch->jitter_curr = -jitter_max; + } ch->feedback_rate = temp; break; |
