sync: work-around players with broken edit list support

This adds a preset key AlignAVStart that enables this work-around. When
enabled, blank frames are inserted or frames are dropped to force
alignment of the initial timestamp of every audio and video stream.
Aligning the start times minimizes the impact of broken edit list
support in players.

Closes #763.

Squashed:

sync: improve alignment when passthru audio is present

presets: enable AlignAVStart for General and Gmail presets

LinGui: Improve AlignAVStart tooltip

sync: avoid inserting a black frame < nominal frame duration

sync: fix start alignment when doing p-to-p encoding

sync: add comments

1 files changed, 8 insertions, 0 deletions

diff --git a/libhb/common.h b/libhb/common.h
index 04a969221..d25bcbdb3 100644
--- a/libhb/common.h
+++ b/libhb/common.h
@@ -607,6 +607,14 @@ struct hb_job_s
     int             mux;
     char          * file;
 
+    int             align_av_start;     // align A/V stream start times.
+                                        // This is used to work around mp4
+                                        // players that do not support edit
+                                        // lists. When this option is used
+                                        // the resulting stream is not a
+                                        // faithful reproduction of the source
+                                        // stream and may have blank frames
+                                        // added or initial frames dropped.
     int             mp4_optimize;
     int             ipod_atom;