(PAL Problem ONLY!!) - How to get an m2v file and ac3/lpcm file that will sync

[jaay]

i have read many conflicting posts in this forum and would like a difinitive way of adjusting ripped lpcm or ac3 files so that they will be in sync when imported into maestro. i know there are ways round this in maestro but there must be a way to do it before you import them.

[jaay]

here are some as yet flawless methods all tested on vobs with delays in either ac3 or lpcm sound:
1: with the vob on your computer or on the dvd use smatripper to demux the m2v file and sound file to separate files and when you import this into dvdmaestro the sound will be in sync despite any delays in the original vob.
2: if the above simple procedure isnt working simply rip the vobs to you hard disk and get them into the EXACT same state as you will have them after you have authored your dvd with menus etc. in maestro using ifoedit. then compile your maestro project and then simply replace the out of sync vobs in the video-ts dir maestro has created with the original ones you ripped from the dvd. they will now work perfectly with your menus you created in maestro. you can also load up your ifos in ifoedit and do get vts sectors just to be sure. so far this has worked flawlessly for me.
3: this works as well for re-encoded video too. simply mak the dvd fit on a dvd-5 with no menu using ifoedit (doom9 has a great guide :)) and then demux your vobs using smartripper and import into maestro. they should all be in sync, but if not dont worry just follow step 2 after compiling!

[benf2]

Do you think this will take care of the sync problem of the audio sync becoming worst as the movie goes on. I have had a few movies that play ok for the first 1/2-3/4 then seem to start losing sync. I use smart ripper to rip then use flask with the cce or lsx plugin giving me a m2v and ac3 which i use Maestro 2.915a to author.

I know others have the same problem, I even tried one suggest of using Maestro audio sync, but that didnt fix it either, then i saw one person said to insert a black .bmp file.

I have used smartripper for a while now and i must have overlooked it, but where is the demux option to rip and save as a m2v and ac3.

Thanks for your input on this issue!!
Ben

[jeffnoone]

when you select "movie" in Smartripper, you will see a tab called "stream processing"

Click on this and you will see a list of the streams in set of vob's

Hit "none", then select the 2 you want - video is the first one, and then select "demux" from menu on right
then select the audio you want, in English NTSC usually the first one (0x80- there is a description which gives language and format eg 6channel), again select "demux" from options on right

Start the process, and you will have 2 demuxed files, and a set of empty vob's -this will save automatically in .m2v and .AC3/DTS format, the audio file will have the delay incorporated in output name

I also change max file size to 8GB in Smartripper, as you otherwise will have 2 video files if bigger than the defaultt 4GB - not a major issue, as DVD2AVI will join the output anyway

[benf2]

Thanks, I will give it a try. All the time i have been using smartripper(i use the stream processing all the time), never new i could save a step and save as m2v and ac3 at this point.

[jeffnoone]

on the synching issue, a few comments

The lengths of the of the video and the audio as reported by DVDMaestro should be very close - this is a KEY issue.

On most movies this is different by 2-5 units(each unit in DVDMaestro being a frame, or 1/30 of a second)
When the difference in lenghts in longer, often the reported audio offset is larger: for example you may have a .ac3 marked with a delay of -280ms (or about 8 frames)

Usually the audio offset is so small, that it is difficult for my ear to confirm whether DVDMaestro exactly synchs or not, but it looks synched

Having Cinemaster 2000 codec installed to allow preview is essential

When the audio offset is larger (>100ms) or when the differnce in reported lenghts is greater than 3-5 frames, then I do try the various resynching options


1. "sync audio track" seems to work well and creates a second complete audio track which repalces original (quick process)

2. for large -ve offsets (eg -150ms), I add the 500ms (15 frames)black slide at start and do the math described elsewhere. This works well and works at times when I have found "sync audio" not to work

3. for large +offsets, the audio track can be manually delayed by dragging in DVDMaestro timeline

4. if I want to get rid of some of the beginnning of the movie, I do the following: use the DVDMaestro clip function to cut off beginning (eg 30 sec of studio intro ), then create "sync audio track". the result will be a second audio track which is smaller that the original - noticeable in windows explorer, and this track will be synced with the video. You cannot clip the audio directly in DVDMaestro, but this process shows quite clearly how effective the "sync audio" is, no matter how much is chopped off in intro credits

If the DVDMaestro-eported audio and video lengths are significantly different and if movie is NTSC, then I believe other options should be considered, such as whether an IVTC filter should have been used to correctly identify the video frames (and number of frfames) to be transcoded)

[jaay]

yes those are all good methods, but i am a perfectionist and like to use original vobs if i can, and i find that the method using smartripper produces the best all round results, although i am unclear as to whether smartripper adjusts the audio itself or inserts some sort of 'flag' that dvdmaestro uses to adjust the delay. either way it works.
i also have another way that is working well too. but only if you are happy with 2 speaker audio only, and that is to use besweet to adjust for the delay and produce a nice mp2 audio file.

[benf2]

:D :D Well, I just tried the demux from the dvd with smartripper of the m2v and ac3 files and compiling with Maestro and burned a dvd. It plays great on my stand alone dvd player. Thanks for the shortcut in this process!!

[Alphaloop]

Well, even with the risk to destroy your smartripper-dreams: ;)
I tried the 7th chapter of the Blade 1 Widescreen Edition ('cause of a nice scene, where something falls on the floor and brings a nice sync sound). Delay by ripping/demuxing was -272ms. Put into Mestro, compiled, watched the result, which _IS_ definately not in sync!

[SATANIC1]

I too just tried the method as described by JAAY on Devils Advocate. The audio and video are out of sync. I am looking for a SURE method on the cure for the delay set up by demuxing process. I also tried to decode the audio since that proved to not a delay to the extracted audio stream. But, alas, that didn't work also.

Fortunately, I was able to preview the work in Maestro before making a coaster. Any help on the sync problem would be appreciated.

[Alphaloop]

Well, after a lot of tries and experiments, here are my results:

a) If I rip a chapter from within a movie, no sync at all. Don't know why, probably broken ac3 within a movie? Never mind, just experiments, not really necessary for serious backup rips...

b) Correct rip from the start of the movie: Maestro takes ac3 with its PTS and syncs it to the video stream, but rounds to full frames. (-80, -40, 0, 40 80, ... ms in my 25 fps PAL movie tries). Worst case scenario would be a +/-19ms, if I calc correctly... ;)

btw: I "fc /b"'ed a smartripper demux and a vobedit demux of a ac3: no differences at all. It hasn't to do with smartripper, just make sure the demux prog doesn't change the PTS of the ac3.

PS: Please excuse my awful English, it's my now quite ancient school knowledge. (school time, how many years ago...? *lugubriously counting...*

[Matthew]

Here's the way I do it for negative audio delays.

We know AC3 delay corrector cuts in single frames. Each frame is 32 ms in length.

The other day I had an AC3 with negative delay (according to DVD2AVI) of -80 ms. I changed the delay in AC3 Delay Corrector to the smallest multiple of 32 that would result in a positive delay. That is -96. So Ac3 Delay Corrector cut off 3 frames and made a file with delay +16 ms.

In Maestro I zoomed in to the most detailed view and then dragged the AC3 file approx half a frame to the right (with PAL there are 25 frames per sec, hence 1 frame = 40 ms, 0.5 frame = 20 ms).

I then compiled the project for a few secs, then unchecked the compile box (result is one vob of 60 MB or whatever). Opened the vob in DVD2AVI and demuxed. The delay was like 26 ms so I dragged the AC3 to the left a bit in Maestro, compiled for a few secs, then demuxed the vob in DVD2AVI (no need to reopen DVD2AVI or the vob in it either). Repeated this until sync was correct. Best I could get the delay was either 15 or 17 ms (mouse wouldn't move in smaller increments) but 1 ms out of sync is impossible to detect.

Whole process only took a few mins ;)

And for positive delays, just drag to right in maestro, compile a bit, and use DVD2AVI until sync is exact (or close to it).

[Alphaloop]

To detect the delays I use Tsunamis' streams.exe. Just a CLI tool, but very useful.

[SATANIC1]

@Matthew

Most of my delays have been in the negative region thus far. For Devils Advocate I get -917ms after the rip. Therefore based on your method I would use 928 in the Corrector in order to get to +11ms...right? Then I would move my audio to the right about a half a frame. I will give it a try tonight and post my results.

One question regarding your pseudo compile. What exactly is that supposed to accomplish...

compiled for a few secs, then demuxed the vob in DVD2AVI (no need to reopen DVD2AVI or the vob in it either). Repeated this until sync was correct. Best I could get the delay was either 15 or 17 ms (mouse wouldn't move in smaller increments) but 1 ms out of sync is impossible to detect

When you demux the vob in DVD2AVI from the pseudo compile, are you then using the resulting files from the demux in Maestro? In other words, are you using the pseudo compiled files in Maestro to replace the original avi or m2v's?

I have used the delay corrector, BeSweet and other AC3 utilities to get this sync problem solved and I am about explode. Last night I started the whole process all over starting in square 1 and ended up in the same place. So I know the process I am following from the guides is ok (or maybe I am consistent with the way I am forgetting something). Do you think that the problem could be because of multiple PGC's? I don't think so but maybe it does. On other DVD's I have done, I had no problems with them but they were single PGC's.

I have access to Scenarist, do you know if Scenarist has better control in this area of syncronicity? I wish there was a cure for this sync issue.

Thanks for your reply...

[Alphaloop]

>When you demux the vob in DVD2AVI from the pseudo compile, are you then using the resulting files from the demux in Maestro? In other words, are you using the pseudo compiled files in Maestro to replace the original avi or m2v's?

No, he just loads the created vob into dvd2avi and chose save avi. At the moment where the codec is requested he clicks on cancel, but has the already demuxed ac3-filename. That's just what he wanted, because the delay is included in the filename. After that he deletes the file and continues with the files he still/already has in Maestro. The dvd2avi stuff is just dummy for looking on the delay. Am I right, Matthew? ;)

[Matthew]

Yes that's right Alphaloop, except I use save project not save AVI ;) The purpose of the exercise is trial and error (looking at delay in AC3 filenames) until I get the sync as close as possible.

SATANIC1 you would indeed use a 928 negative delay in the Corrector so you'd get a fixed AC3 with +11 ms delay. But you'd drag it approx a quarter of a frame (not half) as there are 40 ms in one frame (PAL - 1000ms/25, it's a little different for NTSC).

I have little idea about PGCs etc as I don't need to. I just make a DVD with the re-encoded video stream + ac3(s) + subs and set the movie as the first play in maestro. No extras/menus = better quality video stream, and less effort to boot. But my syncing method should work the same if you are trying to do a reconstruction of the original DVD.

I have use Scenarist a little, but I haven't played around with it much (no need to, Maestro does all I need). But as I understand it you could use the above method as the AC3 can be dragged to the right.

[SATANIC1]

It worked! Thanks to all on this thread for the help especially Matthew and Alphaloop. I followed the procedure as detailed by Matthew and could not believe it only took 6 mins to get the files in sync. I was sooo close.

However, (it seems there is always a 'however') the TDK DVD-R I used is not playable on my set top Sony player. It plays well using MSI DVD 5.1 and other PC players but not on my set top. I used Nero 5.8 to burn the DVD-ROM (ISO). I have always used this method with no problems. Any suggestions?

Thanks again

[Taz69]

Sorry for jumping into the middle (or possibly just after a solution has been found) but I only noticed this thread whilst looking for something else.

The way that I have been demuxing the audio & video for use within Maestro is to use the d2v file generated by Smartripper rather than bothering with DVD2AVI and I have NEVER had a problem with audio & video being out of sync in Maestro...

I had been using VFAPIConv to create a dummy avi for CCE but since I've just upgraded to the later version of 2.64 I have started to use Avisynth and had no problems with that either.

I must admit that I normally rip PAL DVDs and don't need to worry abut Forced Film or IVTC. As the few NTSC DVDs that I have done I've just left at 29.970 and everything has come out okay.

I hope I don't cloud the issue but it might just be worth giving Smartripper's d2v a try sometime.

If anyone is prepared to try it I would be interested as to how you get on TTFN.

[Alphaloop]

@Satanic1:
>However, (it seems there is always a 'however') the TDK DVD-R I used is not playable on my set top Sony player. It plays well using MSI DVD 5.1 and other PC players but not on my set top. I used Nero 5.8 to burn the DVD-ROM (ISO). I have always used this method with no problems. Any suggestions?

I heard that some of the first 5.8.xx Versions of Nero had problems with writing 100% correct udf file system which caused some (or many?) standalones to refuse o play. Try upgrading to the latest version or try to burn from inside Maestro.

[Matthew]

Nice to see that it worked, the disc not playing thing would be certainly unrelated to the sync method though...maybe it's Nero, maybe it's due to problems replicating the DVD structure. For burning I create an image in maestro then use RecordNow DX to burn.

Taz69, does smartipper produce a d2v such that frames are cut off (for positive audio delay) or added (for negative audio delay) to the video stream? Otherwise I can't see how there wouldn't be a sync issue like there are with dvd2avi.

[Taz69]

I think this varies as I think with ac3 the sync is actually encoded in the ac3. As I have not had any problems with sound I have not really paid much attention.

I have recently done a SVCD > DVD conversion where the 3 parts of the movie overlapped. Originally I was off to use mp2 sound but I ended up convering my audio to ac3 because Maestro lost sync after the second & third parts were shortened and mp2 was unable to keep the audio in sync. With ac3 Maestro automatically retaind sync automatically dispite the shorening of my 3 clips to gain a seamless join.

By converting the sound to ac3. After I shortened the 2nd & 3rd clips sync was retained and I think this was because ac3 has a time code encoded into it.

One place where problems may arise could be if the audio is ripped from SmartRippers film processing mode (this would be just the film)and the d2v is generated from the VOBs (ie VTS_01_1-VTS_04_4) with DVD2AVI as sometimes the VOBs relevant to the film might also include additional frames such as the blank screens which are often included. This is a pretty wild guess as to where the problems are coming from though.

All I can suggest is you give it a try on your next project if it works Problem solved. If not then you'll have to sync the audio manually again but you won't have lost anything ;)

If it works okay for you let me know and I might try doing an alternative guide to help anyone else who is having problems.

[SATANIC1]

First off, thanks again for the responses.

Alphaloop...I re-burned using Nero 5.8 but this time I set it up as DVD-ROM UDF/ISO. This worked perfectly. Strange though?? I never had to use that mode before. I also have 5.9 but haven't seen a need as yet. Maybe now is a good time to "play" with it. As for burning with Maestro, gave that a try with no luck many moons ago (but that was when I was first getting into this). Maybe its re-visit time. What the heck, it's done.:D

TAZ69...I used the SmartRipper method as you described on my last try and that is what made it out of sync. I will check my settings and note them to see if there is a difference with other settings and post any info that may help others. I also use the VFAPI method because I had some trouble setting up the script for Avisynth. There were numerous guides I reviewed on the script for Avisynth before I tried it but no go for me. I was especially interested in the claims of Avisynth's speed over VFAPI. Since you use that process, is there a noticeable differance in speed? I have CCE Pro 2.5 and it should use the Avisynth process just fine but like I said, I get errors. I think I will look into it again just to know another method in case I should need it.

I would be intersted in your analysis of CCE SP 2.64. The writeup is great. you mentioned that you "upgraded" to it. I looked on their site for an upgrade from my version but could only find the trial version of CCE 2.64. Is this the one you are talking about?

Well, enough of this chatting. Time to get back and burn with different processes in mind. I will post results. Thanks...

[Matthew]

"I think with ac3 the sync is actually encoded in the ac3."

Well when I've used smartripper to demux it gives the delay in the filename. Plus if smartripper adds/removes frames to achieve sync I would think it's going have the same problem as AC3 Delay corrector - it can only cut in single frames, and each of those are 32ms.

Not meaning to have a go at you, just trying to figure out a rationale as to why using smartripper would result in perfect sync.

@SATANIC1

avisynth is faster than vfapi in every instance.

CCE 2.64.01.10 supports avs files, the versions in between 2.5 and this version don't (you have to use the slower vfapi). AFAIK the video quality is unchanged from 2.5 (it was as at the earlier build of 2.64). The problem with 2.64.01.10 is that it stops after vaf creation and after each pass, unless you use a fix. But using the fix before vaf creation means you can't put the iframes encoded into the video (which means chapter points will be a few frames off).

So I encode the vaf, CCE stops, then I start the mpv creation after using the fix (which is simply deleting and readding the avs in the edit->settings of the avs file. If I don't do this, mpv creation will stop 25 % of the way through (I use 4 pass VBR).

But 2.64.01.10 is more stable on my machine, I was getting freezing problems with 2.5.

As for the avs script, for DVD source all you need is something like this:

LoadPlugin("E:\PROGRA~1\MPEG2Dec\mpeg2dec.dll")
MPEG2source("H:\beautifulsample\beaut.d2v")

[Holomatrix]

Hi guys, sorry to bud in, but how do you find the delay in DVD2AVI? I have this movie that there is silence about the first minute of the movie because of some dedications and stuff. I've been trying to mess with muxing audio delay with TMPEG and have the synce pretty close (-46500 ms). I will try the smartripper idea to see if it gives me the exact delay but is there a way to load the VOB in DVD2AVI and find out what the actual starting delay is so I'm not guessing ???
Thanks

[Taz69]

SATANIC1 With regards to CCE I upgraded from 2.64.01.02 to 2.64.01.10 and the main diference is that 2.64.01.10 works with Avisynth (I am using 2.05 and it is working quite nicely :D) and yes I am using the trial version.

I'm sorry but I cannot really comment on the difference in speed yet because I used Avisynth to scale from 480*480 to 720*480 as well as feeding CCE and it seemed to be about as quick as using VFAPI to do a straight encode.

From this it looks like Avisynth is quicker (as I was scaling and encoding at about the same rate) but I can't say as yet as to how much quicker.

I would be interested in knwing if you are having sync problems with most things or is this an isolated problem with certain films. Also please let me know if you are doing PAL or NTSC DVDs as I have the PAL version of Blade and would be happy to see if I have any problems encoding it (or part of it) if it would help.

Also I can't comment on the differences between 2.50 & 2.64 as I have not used 2.50.

[SATANIC1]

Taz69: Thanks for the info. I just dl'd the trial version and I will give it a go with Avisynth. I discovered that my test avs script was missing a quote for the filename so I fixed that and the script now works. So I will test with a file on my next rip.

The DVD I was having a problem with, The Messenger, is NTSC, frame rate 23.976, video type film 99%.

Regards...

[dannyv]

[QUOTE]Originally posted by SATANIC1

However, (it seems there is always a 'however') the TDK DVD-R I used is not playable on my set top Sony player.


This may not be a problem with the disk but with the sony player. Most of the older sony players were not dvd-r compatible. I had a sony which was 2 years old and not dvd-r compatable and so could not play dvd-r on it. I recently got a panasonic which is cd-r and dvd-r compatable and my dvd-r's play fine on it.
You may want to consult the players owners manual on it's compatibility.

[Mr Zippy]

I have also been researching the AC3 delay, reading several forums and seeing different views.

I have tested 2 films partially in the follwing way..

1. Demux video and audio to hard drive with DVD Decryptor.

2. Import video and audio into DVDMaestro timeline in the following ways (video was simply dragged into the timeline on all 3 occations)...
a) Drag AC3 file into the timeline
b) Using Create Sync Audio without 'sync to timecode' selected
c) Using Create Sync Audio with 'sync to timecode' selected

3. Complile Movie in DVDMaestro

3. Create and ISO image with Nero

4. Load ISO image with Daemon Tools

5. Demux video and audio from the DVD image loaded on the Daemon virtual drive

6. Compare the delay figure from the demuxed audio from the original DVD to the DVD image loaded on the virtual DVD drive...

Movie 1 Original Delay -111ms
Method a) -80ms
Method b) -80ms
Method C) -80ms

Movie 2 Original Delat 0ms
Only tested method c) result 0ms

It would appear from this limited test that DVDMaestro detects the timecode within the orignal AC3 file and rounds this to a full frame as another user of this forum said.

The question is, as I am a perfectionist, how can we get DVDMaestro to correctly sync with the original delay, or what authoring program correctly syncs with AC3 delay?

Lets face it the DVDs were created in the first place with AC3 delay - how?

[Matthew]

Mr Zippy, what's wrong with using the method I prescribe? It's easy and the only 'butchering' it involves is cutting a few frames off the front of the AC3 audio track(s). Which is hardly something to write home to mummy about.

[mpucoder]

Here's something to check, but it will not be easy as VobEdit does not display these fields. In each NAV pack (DSI packet) there are 2 "audio gaps" for each of the eight audio tracks. This is to allow for cell sync, especially when using non-seamless interleaving (where the disparity between 16.7ms video frames and 32ms audio frames can be a problem). The gaps are specified in terms of the 90KHz system clock, so they have very fine granularity.
These fields start at offset 0x43B, and are described at http://www.mpucoder.com/DVD/dsi_pkt.html

As for DVDMaestro rounding to the nearest audio frame, this would suggest that it does not utilize the audio gap for fine sync.

[auenf]

Originally posted by Mr Zippy
It would appear from this limited test that DVDMaestro detects the timecode within the orignal AC3 file and rounds this to a full frame as another user of this forum said.

The question is, as I am a perfectionist, how can we get DVDMaestro to correctly sync with the original delay, or what authoring program correctly syncs with AC3 delay?

Lets face it the DVDs were created in the first place with AC3 delay - how?

perhaps everyone is forgetting this:

http://www9.brinkster.com/sportschook/?ac3timecode.jpg

as for how they were created in the first place, the video and audio were created with the same timecode embedded within the stream, you are reencoding the video and giving it a new timecode, but the ac3 is keeping its old timecode.

Enf...

[Mr Zippy]

Thanks for that, I did not realize that you could disable use of the embedded ac3 timecode. Using the AC3 Delay corrector to remove the delay, then ignoring the timecode would probably be the best solution.

The reason I was not keen on adding/removing audio frames, was because I thought if you remove the frames to make the AC3 0ms delay, then DVDMaestro would still see the original delay, therefore it would still be slightly out of sync.

One other thought
Does the demuxed AC3 file actually have a delay recorded within it that needs to be removed, or is it just the timecode the creates a delay, therefore simply ignoring the AC3 timecode would be enough.

[DSPguru]

i guess it's possible to update AC3's timecode without re-encoding anything.

i once wrote a small tool that updates AC3's dialog normalization tag and then updates the crc1&crc2 tags.

[Mr Zippy]

I think someone who knows a bit about DVD authoring and AC3 timecode should investigate AC3 Delay in depth, below is what I've found out.

I found this link http://arbor.ee.ntu.edu.tw/~jackei/dvd2avi/doc/issue.html to information on how DVD2AVI calucates AC3 Delay, basically the delay is simply when the first audio packet is played in relation to the first video packet and is a relative figure.

The AC3 file I belive has no physical delay in it, just a timecode within it that reflects the original delay.

What is the best way to sync the relative PTS timecode differences in demuxed AC3/M2V streams?

Theoretically if you demux a VOB file then drag the M2V and AC3 into an authoring program such as DVDMaestro it should read the timecodes and sync correctly - yet I find in my tests the output is 39ms different to the orignal delay, maybe this is OK as there article I reference above states less than 80ms should be undetectable to the human ear.

If you transcode the M2V you write a new timecode, will this affect the relative delay when syncing?

[benf2]

Still, think the biggest problem i encounter is delays that start in the last 1/3 of the movie. Its like, how do u fix the last 1/3 without affecting the first 2/3?

Have not seen a good(dependable) method for this yet?

[Mr Zippy]

Can I clarify yesterdays post...

The AC3 delay is calculated, if you start ripping from the second I frame, as difference from this 2nd I frame to the first audio frame.

Would I be correct in thinking that DVD Decryptor and DVD2AVI both start ripping at the 2nd I frame then, and either both the M2V and AC3 files either keep the orginal timecodes or are relativly adjusted for future syncing?

If this is true then the delay is directly relative to the start of the ripped M2V file, and you may as well just let DVDMaestro use the built in video and audio timecodes to sync, in my test this resulted in 31ms differnce, but the article I read says that the perceptial tolerance for delay skew is 80ms, so well within this.

[Mr Zippy]

Explain this....

I used my -111ms AC3 test track, which when re-authrored with no editing shows a delay of -80ms (as shown in previous post).

I used delay corrector to try and cut the delay, it removed 3 full frames (96ms).

I re-authrored in DVDMaestro once ignoring the AC3 Timecode, and 2nd time using the AC3 timecode... Both times the resulting output according to DVD2AVI STILL had a -80ms delay.

Now this is stupid, as whatever I do the re-authored movie has an audio delay of -80ms.

If I actually drag the audio in the timeline this DOES affect the AC3 delay, I dragged 5 frames forward, now the delay is 113ms.

All very odd.

How can the delay stay the same if you ignor the AC3 timecode and cut frames from the AC3 file???

[DVD__GR]

Originally posted by DSPguru
i guess it's possible to update AC3's timecode without re-encoding anything.

i once wrote a small tool that updates AC3's dialog normalization tag and then updates the crc1&crc2 tags.


It would be really generous of you posting that program:) :) :) :) :)

[Mr Zippy]

Does noone have any comments on my post?

Form my tests DVDMaestro reads the timecode from the M2V and AC3 files, so this means most comments in this thread are useless.

Did anyone actually demux their created DVDs to see what the delay showed? I think not.

I have tired Sonic ReelDVD and DVDMaestro, both seem to read the orignal timecode, although both round this to a whole figure in my -111ms test, both gave -80ms output.

[Matthew]

With Ocean's Eleven the delay was -96 ms but when the untouched m2v and ac3 were reauthored in Maestro the delay came out at -80ms. Which is consistent with what you have found.

Also, recently I reauthored a DVD losslessly, by extracting the m2v with smartripper and AC3 with DVD2AVI. Regardless of whether the ignore AC3 timecode box was checked, the correct delay of -80ms came up after muxing in Maestro (without fiddling with the audio). This is equal to 2 frames (PAL).

However, when I re-encoded the video stream the delay came up as 0ms after muxing in Maestro. On further investigation it was clear that the re-encoded stream had 2 less frames at the beginning. So my solution in that instance is to use AC3 delay corrector to cut off 3 frames (96 ms) then have a positive audio delay of ~16 ms by dragging the AC3 to the right in Maestro.

Another case, I was losslessly reauthoring the last half of a title so it has a -255 ms delay (tends to happen in those instances). I cut the AC3 by 8 frames (256 ms) so delay should have been +1 ms after I dragged it to the right in Maestro. But it was -79 ms as a -80ms timecode was embedded somewhere (only because I hadn't re-encoded the video stream). So I simply dragged the AC3 to the right by another 79ms (or as close to it as I could get) until DVD2AVI reported a delay of +1ms. I could have also re-cut the AC3 by 6 frames (192 ms) and I would have had an AC3 with delay -63ms. As there was an embedded delay of -80ms I just had to drag the AC3 by 17ms to the right (so afterwards DVD2AVI would report a delay of -80ms + 17 ms = -63 ms). But I couldn't be bothered cutting the AC3 again so I just did it the other way. Either method would suffice, 2 less frames of audio is nothing.

Now provided that DVD2AVI is accurate in reporting delays all of this is academic is it not?

The loss of a couple of frames at the beginning does however have possible implications for the exact placement of chapter points.

[Mr Zippy]

I'm still a bit confused as to the best solution.

The AC3 Delay is givin so that we can correctly mux the video and audio back together in sync, yet no DVD authoring software seems to be available that lets you specifiy the AC3 delay for correct muxing - I note I have seen several DVD-DivX programs that DO let you input the AC3 delay for correct sync.

Now from my brief tests with DVD Maestro and ReelDVD they both seem to get a timecode from somewhere to make the delay -80ms whatever I seem to do, even if I remove frames with AC3 corrector.

What we need is a custom DVD muxing program, like there is for DivX, then we can use the supplied AC3 delay as I was meant, for 100% correct sync of the audio - commercial programs will never offer this as the delay is only for our reference when we come to re-sync the M2V and AC3.

[mpucoder]

Originally posted by Mr Zippy
yet no DVD authoring software seems to be available that lets you specifiy the AC3 delay for correct muxing

No mystery there, the "audio delay" was invented by someone after the fact. I'm not even sure how that measurement is defined, as there seems to be several ways to compute it. But it is not an input parameter for proper muxing. To achieve proper muxing, get the timecodes correct, and then programs like Maestro, Scenarist, StreamWeaver, and IfoEdit will do the rest.

[Mr Zippy]

I have posted a link within one of my posts in this thread as to how DVD2AVI works out AC3 delay, and as I said I know that AC3 delay is for our use only when re-muxing VOB files - so it would not be catered for in professional programs.

What we need is a program that will mux M2V, AC3, DTS and Subtitle streams, allowing us to use the very useful AC3 Delay figure to ensure the correct sync is preserved.

There are DivX programs that allow you to give the AC3 delay for correct sync when muxing, I would assume DVD2AVI would have been written with DivX in mind, hence why DivX muxing programs allow input of the AC3 delay.

[mpucoder]

I agree, since avi has no timecode, that the delay is useful for Divx, until someone comes up with an integrated encoder/muxer that goes from vob or demuxed streams straight to avi.
But for DVD the timecodes are all that is needed. What is needed here is a program to restore the original timecodes in m2v files. While they're at it, restore the original rff/tff (pulldown) flags, and it would also be nice to reinsert several other pieces of data that get stripped out, like CC and Pan/Scan position.

[Mr Zippy]

Would I be right in thinking if the timecodes were correct in the M2V and AC3 eveything would sync correctly?

If so when you transcode the M2V in CCE you can specifiy a timecode, so maybe this could be fixed by specifiying the correct timecode instead of 00:00:00:00.

Athough this does not follow, as if you just demux the VOB then remux the delay is still different.

I am really surprised more people have not looked into this, and written a nice program to help us, I support DVD writers have only just become mainstream.

[Matthew]

Originally posted by Mr Zippy
Athough this does not follow, as if you just demux the VOB then remux the delay is still different.

Exactly. AFAIK timecodes go to frame level only, no smaller.

I still don't understand why there are any problems with using the method I prescribed.

[Mr Zippy]

As I have said using AC3 Delay corrector shows no difference when I have tested, see my other posts.

Whatever I do with my -111ms test movie, the remuxed DVD authored with DVDMaestro always had a delay of -80ms, unless I physically drag the AC3 forward a couple of frames in the DVDMaestro timeline.

As I have said using AC3 corrector seems to be a waste of time, at least in my test, possibly as DVDMeastro is using the embedded AC3 timecode, whether I tell DVDMaestro to ignor it or not.

Cutting frames using AC3 corrector still shows the same delay, when tested, as if I had not cut any frames.

Did you read the page I linked to that explained how DVD2AVI calcualtes delay?

[Mr Zippy]

I see IFOEdit can remux M2V, AC3 etc. and you can specify the AC3 delay.

The only problem is negative delay gives an error and the program crashes.

I took my test -111ms audio track and muxed that entering a delay of 111ms just to test, the output showed a delay of 31ms.

Now if this program or similar worked correctly we'd have what we need, a program that will sync the video and audio back to have the orginal initial delay of the source VOB file. All we'd have to check is that the transcoded video is the same number of frames, which with CCE it is not, but I have read the dropped frames are at the end of the movie, so should not affect the delay sync settings.

[Matthew]

Okay I'll try to deal with this point by point.

"As I have said using AC3 Delay corrector shows no difference when I have tested, see my other posts."

Using AC3 delay corrector will not affect the recorded delay after muxing, what it does is adjust the AC3 so the delay is different. e.g. on a film with - 96 ms delay you cut 3 frames off and mux in Maestro. The delay will be 0ms according to DVD2AVI but that is fine as you have cut the AC3 to remove the delay. Similarly on a film with an -80 ms delay if you cut 3 frames the delay will now be +16 ms (-80ms + 96 ms), and you can make it as that in Maestro by dragging the AC3 to the right.

"Whatever I do with my -111ms test movie, the remuxed DVD authored with DVDMaestro always had a delay of -80ms, unless I physically drag the AC3 forward a couple of frames in the DVDMaestro timeline."

In my experience this is on account of 2 black frames at the start of the video stream which disappear when you re-encode the video stream. With CCE there are more lost frames but those are at the end of the movie. And those 2 frames at the start are only there to disappear where there is an appropriate delay (e.g. -80 ms, -96ms, - 111ms). With 0ms they are not there.

So here is what you do in the case of a re-encoded video stream, where the -80ms thing is a non-issue:
Cut the AC3 by the smallest number of frames that results in a positive delay. i.e. 4 x 32 = 128. That means your delay is now -111 + 128 = + 17 ms after cutting 4 frames using AC3 delay corrector. Drag the AC3 in maestro to the right by that much. As I said, you have re-encoded the video stream the -80ms won't come into it.

In the case of a non-re-encoded stream then after doing the above your delay according to DVD2AVI will actually be 17-80 = -63 ms. So what you do is drag the audio 3 frames to the right to make it +17ms like you want it to be.

Alternatively, you can cut only 1 frame off the AC3 (111-80 = 31, which is just less than 1 frame). The delay will then be -111 + 32 = -79 ms. As a -80ms delay is there to start with just drag the AC3 by 1 ms to the right (tiny tiny bit).

"As I have said using AC3 corrector seems to be a waste of time, at least in my test, possibly as DVDMeastro is using the embedded AC3 timecode, whether I tell DVDMaestro to ignor it or not.

Cutting frames using AC3 corrector still shows the same delay, when tested, as if I had not cut any frames."

Hope I explained these statements above.

"Did you read the page I linked to that explained how DVD2AVI calcualtes delay?"

Just tried to but page won't load ("cannot find server")

That delay in IFOedit makes sense. Embebbed delay of -80 + 111ms = 31 ms. If your case you would put in -31 ms. -80 - 31 = -111. But I prefer Maestro, it's more powerful ;)

[Mr Zippy]

Am I right in thinking that both the demuxed AC3 and M2V files start at 0ms, therefore I need to move the audio AC3 either ahead (- ms) or behind (+ ms) the video to ensure the correct sync. The method to do this is to change the 1st audio frame in the AC3 file to the frame that would have been played at the specified delay by adding/removing frames, rather than changing the time at which the first audio frame is played. So the physcial calculated delay should be 0ms (if the orginal delay is divisable by 32ms audio frames), but the audio frame that is played with the first video frame is still the same as in the orginal VOB.

I have a question on your method I quoted below,

"So here is what you do in the case of a re-encoded video stream, where the -80ms thing is a non-issue:
Cut the AC3 by the smallest number of frames that results in a positive delay. i.e. 4 x 32 = 128. That means your delay is now -111 + 128 = + 17 ms after cutting 4 frames using AC3 delay corrector. Drag the AC3 in maestro to the right by that much. As I said, you have re-encoded the video stream the -80ms won't come into it."

Now in my test dragging audio forward in the timeline adds postive delay ie. moves the audio behind, thefore you would end up making your +17ms AC3 track +37ms if you dragged foward half a frame in the timeline, as you would have moved it behind another 20ms.

Am I missing something, I'm getting confused now, as we are changing the first frame in the AC3 file by cutting frames, but then physically moving the whole AC3 file forward in the timeline also changing the actual physical delay.


Google cached page on how DVD2AVI works out delay....
http://216.239.39.100/search?q=cache:g36FDyAwRKkC:arbor.ee.ntu.edu.tw/~jackei/dvd2avi/doc/issue.html+dvd2avi+ac3+pts+delay&hl=en&ie=UTF-8