timer: implement AV-sync

This is focused on keeping --on-the-fly-encoding in sync even
over long videos.  The existing code inevitably would fall into a
permanently negative pdata->avd value letting things get
increasingly out of sync and never correcting.

Before removing the vestigial negative avd "don't wait" logic
from get_frame when this permanently negative avd state was
entered, get_frame would just start sampling at an unregulated
fps.

The timer thread which drives get_frame now consults avd on every
tick, Depending on which which half is ahead, the timer will
either cause get_frame to drop frames by advancing the frameno by
more than one, or it will adjust its sleep delay in proportion to
the delta.

See comments in rmd_timer.c for more details.

Note that in testing especially with a loaded system I observed
some surprisingly large deltas where multi-second sleeps occurred
to let the sound catch back up.  I expect to revisit this issue
more in the future, but would just like to get things more
correct for now.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/rmd_encode_image_buffer.c b/src/rmd_encode_image_buffer.c
index 57ac5ce..d83c694 100644
--- a/src/rmd_encode_image_buffer.c
+++ b/src/rmd_encode_image_buffer.c
@@ -74,10 +74,13 @@ void *rmdEncodeImageBuffer(ProgData *pdata) {
 		while (theora_encode_packetout(&enc_data->m_th_st, 0, &enc_data->m_ogg_pckt1) > 0) {
 			pthread_mutex_lock(&pdata->libogg_mutex);
 			ogg_stream_packetin(&enc_data->m_ogg_ts, &enc_data->m_ogg_pckt1);
-			pdata->avd += pdata->frametime;
 			pthread_mutex_unlock(&pdata->libogg_mutex);
 		}
 
+		pthread_mutex_lock(&pdata->avd_mutex);
+		pdata->avd += pdata->frametime * n_frames;
+		pthread_mutex_unlock(&pdata->avd_mutex);
+
 		last_encode_frameno = encode_frameno;
 	}