Fixing Timecode Breaks

[Wyatt Riot]

A friend of mine played on public access and got a DVD of the performance. It's now my job to put 4 of his songs in a different order and add a nice menu.

I ripped the DVD using MTR and it looks/sounds great in DVD Player.

But when I convert the VOB to DV using MPEG Streamclip I get a split-second skip in the audio track every minute. (When looking at the DVD, it looks like the television station automatically created a new chapter every minute.) This is after using the "Fix Timecode Breaks" option. Not using that option won't work because, until I fix the timecode breaks, MPEG Streamclip only recognizes the first minute of the VOB.

I also tried using Drop2DV to convert. That, at least, recognizes all of the chapters on the VOB, but I still get the skip after every chapter. I know that some people have had problems with MPEG Streamclip, but Drop2DV is supposed to use ffmpeg, but I'm getting the same problems.

What am I missing here?

If it matters, I'll be using iMovie and iDVD for the final editing and DVD creation. I'd like to maximize video and audio quality if at all possible.

[pianoman719]

Is the skipping audible if you play the original DVD through a set top box and use headphones? Or is it completely absent until you get to the DV conversion? Try this:

- Download Yade X and use it to rip the main title on the DVD to elementary streams. That should give you an .m2v video file, and an audio file that's either .ac3, .mp2, or .pcm. (Let us know which.)

- In MPEG Streamclip preferences, check the box that says Fix Timecode Breaks.

- In Streamclip, open only the *audio file*, do a Cmd-F to fix any timecode breaks, and just listen to it carefully through headphones. Is there any skipping?

- Now in the Finder, put the video file and audio file in a new folder together, and make sure they have the same names but different extensions, like this:

Concert.m2v
Concert.ac3 (or .mp2 or .pcm)

- In Streamclip, open the video file. Streamclip will automatically load the audio file as well. You will see a progress bar as Streamclip muxes them on the fly.

- Do a Cmd-F, then play the file in Streamclip and listen carefully. Is there any skipping?

- Still in Streamclip, use Convert To MPEG to write out a new file with fresh timecode containing both the video and audio tracks.

- Now open the .mpeg file that Streamclip just wrote. You should not need to do a Cmd-F because the new .mpeg should have fresh, continuous timecode. Try using that to export to DV.

However, you should consider whether there's a way to do your project using cuts-only editing of the original MPEG2 footage (no quality loss), rather than converting to DV and then recoding to MPEG2 again later. In Streamclip, you could extract each of the four desired songs as a smaller .mpeg, then rejoin them in a different order. I've found this to work pretty well. YMMV

If you still have the skipping audio problem, there are other things you can try, but let's take it one step at a time. -Pianoman

[Wyatt Riot]

Okay, homework done.

Tried playing the DVD on my standalone and I hear the skips. Went back to my MTR rip and I now hear the skips as well. Not sure how I missed them before, except maybe I know they're there and so I listen for them.... (I'm hoping that a casual lister wouldn't catch them, but we'll see if my friend wants to proceed with the project if I can't fix the audio.)

As for that: now that I figured out it's a human issue (me!) and not a software issue, is there anything I can do about fixing the skips? Separating the audio, trying to clean it up, and then sync it?

Pianoman: Sorry to make you go to so much work when it wasn't really necessary.

Edit: by the way, ripped to elementary streams in both Yade X and MTR, got M2V and AC3. The AC3 won't open in MPEG Streamclip or even VLC. Maybe that has something to do with the crappy audio? Non-compliant or something?

[pianoman719]

I'm sure you know that to open an audio file in Streamclip you need to choose Open Files: Audio Files. Since an AC3 elementary stream ripped by Yade X will usually open in Streamclip 1.5.1, that plus the skips suggest the AC3 is defective.

Previously, you did get Streamclip to open a .vob with video and audio. You can do that again, and Demux To Aiff, which will give you an uncompressed audio file you can try and edit with such tools as:

Audacity (freeware)
Amadeus II (shareware)
SndSampler (shareware)

One simple freeware tool you haven't thrown at the AC3 yet is mAC3dec. It may be able to convert the AC3 to an .aiff file at 48 kHz.

This may sound wacky, but sometimes an AC3 with some pops in it gets mellowed out when in Streamclip you Demux To M1A. But first in Preferences set the MP2 Encoding Bitrate to 384 kbps.

Best of luck! -Pianoman

[terryj]

It has moreso to do with the fact that AC3 is a compressed
audio format and, requires that the file be decoded
before it can be used by itself. It plays fine muxed,
as evidenced by your ability to play the rip through
DVD Player on your mac.

google "QuickTime AC3 Decoder", and download and
install the plugin for QT. Then try playing the file in QT.
(plugin should still be over at sourceforge)

As for fixing the skips, yes, but you will need to after
installing the plug-in, re-save ( export) the audio to
an AIFF file from Quicktime, and then use an audio
editor such as Amadeus II to edit the waveform
and clean up the audio. from there, you can then
save it ( as an AIFF, 48KHZ, 16bit uncompressed file).

then getting it synced will be the next step...

[Frobozz]

Just to let you know that you didn't need to rip that DVD with MTR. You could have opened the VOB's directly from the DVD in MPEG Streamclip or you could have dragged the VIDEO_TS from the DVD to your hard drive to copy it. I'm certain from your description that the DVD is not copy protected so MTR is unneeded.

[Wyatt Riot]

Pianoman and Terryj: Cool, I'll just convert to AIFF and see what I can do. I usually use Felttip Sound Studio for audio work, so I hope that works. If I need any help converting back and syncing I'll post an update.

Frobozz: Yeah, I technically can do that, but I usually rip everything with MTR anyways. It tells me if the DVD is damaged, which dragging doesn't always do. (I've backed up tons of CDs over the years, but just recently started using xACT to verify them while doing so. I sometimes wonder how many of those CDs have audible errors that the Finder didn't notice.)

Thanks for the help, everyone! I love this place!

[pianoman719]

Maybe what Terry's saying is that in a muxed file, the player can get the timecode from the video and fit in the AC3 audio, even if the audio's a bit choppy. So if you can open the muxed file in Streamclip and do a Convert To MPEG With MP2 Audio, you may be pleasantly surprised. (Maybe not.)

Terry, could you please clarify the exact name of the QuickTime AC3 codec you're recommending, and which versions of QT it works with? There is more than one AC3 codec out there, and some of them apparently only work with AVI files and do not give QuickTime general AC3 compatibility. Thanks.

I think there's a difference between media players and converters/processors. A media player is designed to try and keep playing even if there is missing data, while a converter/processor will often balk at data errors. I have defective audio CDs which are impossible to rip, but they will play tolerably well in a CD player because the player is designed to accept data errors and carry on regardless.

Regarding the ongoing debate about whether it's helpful to use a ripper like Mac The Ripper or Yade X to bring in video from a non copy-protected DVD... I think it can be helpful for choosing to rip only part of a DVD (Yade X lets you preview the frames). Also, I wonder if MTR is more fault tolerant than the native Mac copy routines? If the DVD is a bit scratched, are there cases where the Finder would just give up, but MTR will keep trying to read the data, and make an effort to reconstruct the VOBs in spite of some data errors?

-Pianoman

[terryj]

Maybe what Terry's saying is that in a muxed file, the player can get the timecode from the video and fit in the AC3 audio, even if the audio's a bit choppy. So if you can open the muxed file in Streamclip and do a Convert To MPEG With MP2 Audio, you may be pleasantly surprised. (Maybe not.)

Terry, could you please clarify the exact name of the QuickTime AC3 codec you're recommending, and which versions of QT it works with? There is more than one AC3 codec out there, and some of them apparently only work with AVI files and do not give QuickTime general AC3 compatibility. Thanks.

google "QuickTime AC3 Decoder", and download and
install the plugin for QT. Then try playing the file in QT.
plugin should still be over at sourceforge)
addition: Works with QT 6.52, QT 7.01

Also, I wonder if MTR is more fault tolerant than the native Mac copy routines? If the DVD is a bit scratched, are there cases where the Finder would just give up, but MTR will keep trying to read the data, and make an effort to reconstruct the VOBs in spite of some data errors?

-Pianoman

MTR has a "force" option built in since, oh I think it was 2.66,
but don't quote me,

that will force through a heavily scratched DVD to process
and often does the job.

[pianoman719]

Thanks Terry, I should have read your post more carefully. I found the download here and here:

http://www.macupdate.com/info.php/id/14633
http://sourceforge.net/projects/qtac3codec

MacUpdate Description:

"AC3 Codec is a QuickTime component which allows the playback of AC3 audio in AVI files. The component uses the liba52 library for the AC3 decompressing, you can get more information on this library at http://liba52.sourceforge.net/.

REQUIREMENTS
QuickTime 6.0 or later, DivX 5.x."

Has anyone been able to play .mpg and .ac3 files in QuickTime Player with this codec, or does it only decode the audio in AVI files?