Player skips start of audio

Question

I knew that some DVD players fail to play the very beginning of a timeline, so I left the first 15-20 frames in my PPro timelines blank, and things seemed to work fine with the players I tested it on.  Then Murphy's Law kicked in - after I had 1000 DVDs replicated and a good chunk of them distributed to sales points, I bought a cheap portable DVD player to use for demos and discovered that the player fails to play the first bit of the audio on some of my tracks (music videos, so the audio is important - a song intro with the first beat missing is pretty annoying).  Well, not only would I like to burn a demo disk that will sound right on my portable, but I also need to learn for the future.
In Encore, I tried moving the audio and video over on the timeline to leave blank space at the beginning, but that didn't work - it just pauses longer before playing my video with the beginning of the audio clipped off.  Before I go to the trouble of going back to PPro, editing to increase the dead time there and re-encoding a bunch of these tracks, I would like to know if (a) there is some way in Encore to do it, and (b) how much dead time is needed to be safe for most players?  Naturally I don't want to leave more space than is needed - many players respond quite slowly to commands (or end actions going from one track to another), so I don't want to make it any more sluggish than it needs to be.  And although sliding things around on an Encore timeline and burning another coaster is somewhat frustrating,  if I have to go back and re-encode a bunch of tracks every time I want to test a slightly different timing, that's an even bigger time-waster.  And my portable is only one example of a sluggish player, so it would be helpful if someone can share a rule of thumb for most players, and/or an explanation of what is going on "under the hood" that causes the problem and why moving the clips over on the Encore timeline doesn't solve it.

Answer 1

OsakaWebbie wrote:
Thanks for your replies, guys - I gave you both "Helpful post" marks, but surprisingly, what you recommended didn't quite work, either.  Read on...
I went back into PPro and looked at when my various music content started in each clip.  If some devices need as much as 2 seconds, then my portable isn't quite as bad as I thought, because the clips that start okay have only around 20-25 frames of space.  (The ones that didn't had around 10-15 frames before the music started.)  Since my real products for this project are already pressed, so these edits are only for my portable, I adjusted the rest of the PPro timelines by moving everything over until the musical content started at 25 frames or later.  Two days and a lot of computer time later (17 timelines needed fixing,  but due to stupid mistakes I had to re-encode some as many as three times!), I had 17 overwritten, slightly longer timelines, and in Encore I stretched them out, deleted and replaced the audio parts (for some reason I can't just lengthen the end of the audio clip in the Encore timeline in the same way as the video), and burned another disk ... er, COASTER!  Within my ability to detect just with subjective hearing, I had the same skipping at the start as before I re-encoded all those clips!  Does there have to be some small audio "content" on the PPro timeline in that area (a little noise at -50dB or something)?  Since some of my tracks were working, I assumed not, but all that work came to nothing.  Then...
(Jeff) Some AC3 decoders...  (Neil) ...the recommended figure from Dolby Labs... (emphasis mine)
I picked up this subtle hint from statements both of you made - apparently the problem relates only to AC3 audio, not PCM.  For this project I have extra space, so I right-clicked on each of the audio clips in the Project pane, selected "Revert to Original" (I don't know what that does, but it un-disables the "Transcode Settings" menu item), then selected "Transcode Settings" and changed it from Automatic to Don't Transcode.  They play correctly in that format, which I guess is expected.  (So now the dead space on the beginning of my clips is unneeded, but truncating them by 15 frames in Encore causes the ends of the video tracks to get shorter also for some weird reason, so I stopped doing that.)
AARGH.
You overwrote the original files using the same file names, didn't you?
That will never work, and also attempting any form of trimming in Encore will not work either.
What you need to do is this:
1 - Remove the Dolby Digital files/streams from your Encore project completely, and delete them from the assets list.
If this means deleting all AVI files then so be it.
Once this is done, clear/clean the media cache files.
2 - Go back to Premiere, and make certain your 2 seconds of silence is there at the start, preferably accompanied by Videoblack as well.
Export your AVI files in the normal manner. Make absolutely certain that they have a different name to the originals.
3 - Go back into Encore & reimport your new assets. Do *not* attempt to replace them using the "replace/locate missing assets" dialogue, as this may well result in incorrect references with regards to file lengths & end up with truncation.
Now rebuild your Encore project. If it were me, I would completely delete the old one and start over with a new project name, but then I ma all too familiar with Sonic compilers & their occasionally flaky operation.
OsakaWebbie wrote:
This is the first time I have forced audio to stay PCM in Encore. Is this something I should do more often when space allows, or are there side effects I will run into (like the data rate overrunning the player's ability - I tend to encode my video pretty high when there is room to do so - VBR with a max of 8)?
That depends on how highly you value Audio quality. Quite simply, Dolby Digital sounds terrible to me. You are throwing away 11/12 of your data, and there is no way you can realistically expect it to sound as good, and it doesn't.
Also bear in mind that a poor film can be saved by great sound, whereas the reverse does not hold. Poor sound will never make a good film no matter how well encoded & lush the video looks.
VBR with a max of 8 is meaningless without the average & min figures. If you're looking at an average of 7, then CBR will do a great job.
Another thing to consider is the final output - if you will be outputting to written discs then be aware that there are far too many players out there that cannot handle a combined bitrate much over 7Mbps.- higher than this can result in unpredictable playback.
OsakaWebbie wrote:
I think that shifting the audio in En just adds a separate silent clip at the beginning of the timeline and does nothing to address the decoding of your original audio clip.
Does that mean that if I had multiple clips on one timeline in Encore, each clip would have the same problem?  I have no multi-clip timelines in this project (although before writing to the forum I did consider creating a one-second silent black clip and trying that), but I might have them in the future, so I would want to know.
I have lost count of the discs I own where the first second or two of audio is cropped either on menus or the main timeline.
Yikes - you mean I'm in "good company", that the real pros overlook this?  My normal player doesn't have the problem, so I don't notice.
2 seconds is the recommended figure from Dolby Labs - slower decoders
have to lock onto the stream, start decoding & get the output
through the onboard DAC to the speakers. And some are better/faster
than others.
It would be useful to know how common players are that need a whole 2 seconds - if that type of player is rare, perhaps 1 second (or even 25 frames) is good enough.  I'm thinking it might be best to apply the same principles to this as to web design - if a better design works for 99% of the browsers, and it can be designed such that for even the 1% it doesn't completely fall apart, there is no need to force a poorer solution on everyone.  Same thing with DVDs perhaps - if only 1% of the players need more than 1 second to lock on, then making the other 99% wait 2 seconds to see the video they selected may be counter-productive.  Does anyone know any statistics on that?  Before I bought my portable, I had used this DVD on about 5 set-top players, and although I wasn't specifically listening for this problem, I think I would have noticed if something had been missing at the start of the music - the very first song in the list (and my favorite) was one of the worst offenders on the portable.  So it would seem that many players are quick enough to lock onto the audio in less than 10 frames.
Anyway, a key point is that for some reason, sometimes adding silent space, even in PPro, doesn't work, but that PCM doesn't have the problem, and a key question is what the conventional wisdom is regarding using PCM on real DVDs when space allows.
PCM will not have the problem because it does not need to go through a complex decoder like Dolby Digital and also DTS do.
Ergo, no lag, no delay in the player locking down on the stream, feeding the Dolby/DTS stream to the decoder chip and outputting audio - in sync.
To fix the problems with DD, you need to prepare the source files correctly, and please for the love of all the gods, never overwrite an asset.
To suggest that it is not worth bothering because it only affects a small number of players is a terrible solution. Of course it is worth bothering.
All you do is add 2 seconds of videoblack at the head of the file in Premiere Pro before rendering.
No problem, no chance at all of cut off audio - and I can tell you this irritates the life out of me when I pay good money for a DVD to find the author could not be bothered to get the details right.
How fast a player locks down & begins to decode audio is a massive variable.
It depends on the player, the decoder, where the decoder is located (amplifier or DVD player), speed of the CoAxial line in the amplifier (something as silly as a 50 microfarad capacitor across the ground line in the decoder circuit can fix a problem with slow lockdown, but this is just an example to give as to how complex the procedure is), speed of the decoder, speedd the amp or player gets the decoded audio out to the rest of the system etc.
At the end of the day, Dolby Labs recommend 2 seconds at the head - so just do it!
As far as a "solution" that is "Good Enough" goes.
There is a wonderful poen by a chap called Edgar Guest, called "Good Enough". It's first 2 lines read
"My Son, beware of "good enough"
It isn't made of sterling stuff"
and ends with
"For this is true of men and stuff
Only the best is good enough" - google for it. Sorry to ram this point home, but really. Your clients (who are paying your wages) deserve the best you can give them.
Finally, Re Multiple clips on the same timeline in Encore.
You'll need to check this, but in CS3 stacked clips that got encoded to Dolby Digital lost timing. This is because Dolby Digital encodes in fixed block sizes, and I am not certain if thisproblem was corrected in CS4, CS4.1 or not yet at all.
I will check & post back on this one.