DVRMS(HD) to DVD... or, why I bought VideoReDo

[Gorganzola]

I had been successfully converting HD off-the-air content captured with ATI HDTV Wonder

and MCE to DVD-compliant mpegs using the following:

1.TMPGenc Mpeg Editor 2.0 to edit content of DVR-MS files and save as mpeg (HD).
2.TMPGEnc 2.5 to re-encode HD mpeg to DVD-compliant mpeg.

Until I ran into a snag. I noticed while editing this file in TMPGEnc Mpeg Editor 2.0 that a commercial break had unusually large GOPs (30 frames instead of 15). I'm not a whiz at video, but it appears this is because some tv studios don't have hd equipment and switch to standard def during local commercial breaks. This is easy to detect in
TMPGEnc Mpeg Editor 2.0 by the way it displays thumbnails. When I played the file after re-encoding in TMPGEnc 2.5, i found it had a huge audio sync gap beginning at the splice point where I took the above mentioned commercial out.

I downloaded and bought VideoRedo because it has quick stream fixing. I edited the same OTA DVR-MS file with VRD and saved it (it reported audio frame errors and input sequence errors) and it played fine! No audio gap. But wait! There's more...

After re-encoding in TMPGEnc 2.5, I found there was NO video after the splice described above... just black screen.

After trying every option in TMPGEnc 2.5 with no avail, I finally fixed the problem thusly:

I loaded the edited HD mpeg (output by VideoReDo) into TMPGEnc Mpeg Editor 2.0, navigated to the place where the problem was and found one unusually large GOP right at the splice point. I chopped it out, saved, and re-encoded with TMPGEnc to DVD compliant mpeg. Problem fixed!!

Now, after all that blather, I have a question for the kind creators of VideoReDo: Is there a way to detect and remove the larger GOP in VideoReDo like I did in TMPGEnc MpegEditor 2.0? Or is there another option in VRD that would eliminate this problem? I would like to be able to do everything in VRD. Please excuse my lack of technical expertise, but I hope I got the point across...

[phd]

You can set the maximum GOP length you wish to allow by clicking the Options button in the file save dialog box.

[Anole]

I'm wondering if changing the GOP in VRD will solve your problem.
It's a good theory.

I pre-set GOP size for all my editing (of non-standard satellite feed) with VRD to keep them down to a reasonable size.
You could use the QSF function only, to shorten the GOPs, or just edit as normal with VRD and have it save with shorter GOPs.
Either should work, but do try both if you run into a problem.
As a last resort, use QSF to write a new file, then load that into VRD for your edits.

[Gorganzola]

Thank you both for your comments. I did try phd's suggestion and set the output gop length to 15. Unfortunately, TMPGEnc still choked. So I loaded the new output from VRD (the one that failed in TMPGEnc 2.5) into TMPGEnc Mpeg editor 2.0 and went to precisely

where TMPGEnc coughed and began encoding audio + black screen. Again, because the thumbnails in TMPGEnc Mpeg editor 2.0 allow frame level exploring, it was easy to see that a couple of gops at the splice point had more frames in them than the rest. (Remember, I saved the VRD file with max gop length set at 15). The gops just before the splice had 17 or 18 frames. Again, I edited these gops out, and TMPGEnc 2.5 bought them and encoded the file successfully. Keep in mind though, that the reason I bought VRD was that TMPGEnc Mpeg editor 2.0 was unable to correctly edit the longer gops out until I first ran them through VRD with its stream fixing ability.

I really wish I knew more about this science of video compression but I don't. (I am presently stumbling through Peter Symes' book DIGITAL VIDEO COMPRESSION which is searching my mind for the math I once knew many years ago, but haven't used in a reeeealy long time). I am guessing that video transport streams such as what you get from digital TV are subject to a lot of opportunities for error, given the various paths they are subject to (network commerical breaks, local station breaks and commercials, untimely switching between the two, etc).

One more thing, for what it's worth: I have only had this problem with one local digital station, and it is the only one I watch that broadcasts in 720p. All the rest are 1080i. Don't know if this has anything to do with it, but I'm throwing it in anyway.

Appreciate all your help.