editing mp2?

[cnelson87]

I'm using ADS Instant USB to capture directly to mpeg2. Mostly some TV shows (Stargate and South Park, yeah!) and some old VHS tapes. Quality is excellent, IMO. The MPEG Cutter works great for cutting out commercials and trimming the beginning and end.
Or so I thought.
I'm just dragging the mpg's into Toast and creating DVDs to watch later. Now I'm discovering that about 50% loses audio sync. I'm assuming this has to do with either dropped frames during capture or MPEGCutter not doing it's job quite right. What's odd is the trimmed files play perfectly in QT and VLC. But after the demux-remux process, whammo! Out of sync. Not just Toast, but Sizzle amd MPEG2Works too (which is why I'm assuming the problem lies in the capture or edit process).
The included authoring app, CaptyTV, is a frustrating unintuitive POS that actually solves the problem by totally re-encoding the audio. Ugh.
What to do?

[pbs666]

Usually you can avoid this problem by using the "Export mpeg to..." function of PixeDV on your cut mpegs. The soundtrack will end up as an aiff file which you might want to convert to ac3 or even back to mp2, which you can then use in Sizzle without the sync problems. Time consuming, but sometimes necessary if you want to use Sizzle or Toast instead of Capty.

[cnelson87]

yeah, well...
I DO appreciate the suggestion, but I would prefer not to re-encode the audio so as to avoid further loss of quality.
It just seems strange that this device produces a perfectly cromulent mp2, but lacks the ability to use it.

[t_shirley]

I had the same problem and found the only way to solve it was to bring the mpeg2 into CaptyDVD and author the dvd from there. It's another step to go through and takes forever on my G3 but it does the job. PixeDV and CaptyDVD are supplied together with Ads Instant DVD so they obviously seem to work well together.

[Frobozz]

I spent a lot of time trying to make sense of what PixeDV and CaptyDVD do. One bit of enlightenment came when I used bbDemux to separate the audio and video of PixeDV mpegs. If I recorded at the maximum 6 mbps the demuxed audio and video were of significantly different lengths. This difference was small at 5.5 mbps or less. This is on a 933 mhz G4 so it isn't that the Mac can't handle the encoding speed.

So my theory is that 6 mbps is not an option. Don't use it. My companion theory is there is something really weird about PixeDV-encoded mpegs.

I haven't had any sound sync problems in Toast or CaptyDVD except with the highest bit rate setting. My guess is that is the setting you were using.

[cnelson87]

yeah, I've done that and it DOES work, but it does it by re-encoding the audio (decreasing audio quality) and totally negating any reason to capture in mp2 format in the first place.
All this thing needs is just a little tighter editing and it would be better than oxygen.

I had the same problem and found the only way to solve it was to bring the mpeg2 into CaptyDVD and author the dvd from there. It's another step to go through and takes forever on my G3 but it does the job. PixeDV and CaptyDVD are supplied together with Ads Instant DVD so they obviously seem to work well together.

[mhar4]

I have had this sync problem even at low bitrates, and I have done the Export mpeg to.. to get an m2v and an aiff which I convert to ac3. I prefer ac3 anyway, but the extra step is a drag.

I have tried MPEG Streamclip to demux the original PixeDV mpgs and then author in Sizzle. I did my brain trying to tell if there was still a sync problem, which means if there was it was only slight, but sometimes it's hard to tell. I concluded that it was still a little bit out, but maybe I was imagining it in a crazed sync-induced paranoia.

[cnelson87]

I have come up with a solution. Sort of. It's a royal PITA and isn't perfect but works without having to re-encode the audio.
After demuxing, remux and import back into PixDV. Do not delete the original streams! Open the same remuxed file in either QT (or VLC). Play the file in QT and note the first time it goes out of sync. (I've noticed that the audio is delayed from the video, which would indicate that it's dropping frames during capture, damnit!) Make a single frame cut in PixDV at the same point. If the audio gets further out of sync later on, then make further cuts at the appropriate time. For a one hour show with 6 commercial breaks cut out, I've only had to do one or two re-cuts (so far, knock on wood). Export and demux. Remux the old video with the new audio and test.
As I said, a total PITA and takes more time but I'm getting good results. If your audio is early compared to the video you will have to use the new video and the old audio, or recut from the original capture.

I'm also considering converting to uncompressed aif to edit a little more precisely, and then encode to ac3. maybe...

[tmw]

I haven't used a mac in years, but the video camera I use produces mpeg2, and some people who own it use mac's, which has challenges. I saw this novel method for editing mpeg2, which may be applicable to your world...

http://www.jackbrown.us/camera/viewtopic.php?t=222

Basically, you use Virtual PC to run Womble Mpeg Video Wizard and do the editing there.

Supposedly, it works pretty well, although not the most efficient method.

[DUDIRENO]

cnelson87

Why is it so important for everybody to take there clips and import them into other programs? What am I missing here? Yea Capty and PixeDV are a little annoying. But what can't it do that makes everybody feel the need to use other programs? Is it speed?

[cnelson87]

Good question! I really don't have a good answer, except to say I can be a right picky b*st*rd.
CapTY re-encodes the audio, which decreases it's quality. It's like taking an mp3, turning it into a wav or aif, and then re-encoding it to mp3. There WILL be a loss of quality, the real question is how bad is that quality loss, does it really make that much of a difference?
Being the self-torturing perfectionist that I am, the answer is YES.

cnelson87

Why is it so important for everybody to take there clips and import them into other programs? What am I missing here? Yea Capty and PixeDV are a little annoying. But what can't it do that makes everybody feel the need to use other programs? Is it speed?

[DUDIRENO]

OK.

I have never noticed a sound problem. I am more distracted by the quality of my source video quality. Sound always seems to come out fine. Just my thoughts. I do wish I could make a larger disc image that I could shrink with DVD2one. Then I would use other applications. In general I just make it so the video plays right when I insert the disc into my player and ADS Instant DVD makes those really well once I got my settings how I like.

[mhar4]

Good question! I really don't have a good answer, except to say I can be a right picky b*st*rd.
CapTY re-encodes the audio, which decreases it's quality. It's like taking an mp3, turning it into a wav or aif, and then re-encoding it to mp3. There WILL be a loss of quality, the real question is how bad is that quality loss, does it really make that much of a difference?
Being the self-torturing perfectionist that I am, the answer is YES.

cnelson87

Why is it so important for everybody to take there clips and import them into other programs? What am I missing here? Yea Capty and PixeDV are a little annoying. But what can't it do that makes everybody feel the need to use other programs? Is it speed?

I like the simplicity of the first version of Sizzle. I don't feel the need for menus and navigation.

As for loss of sound quality with the extra compression stage, I don't think it's really a problem with broadcast or video tape material, especially if you are going over to ac3 anyway.

[cnelson87]

Ah hell, I think you're right. It's just a cable TV capture. I think I'm gonna give up and just let CapTY re-encode. Apparently my latest "fix" isn't working quite as well as I had originally thought. By fixing one sync problem I'm creating new ones. Plus, it takes a LOT longer and all I wanna do is capture, burn, and watch.

As for loss of sound quality with the extra compression stage, I don't think it's really a problem with broadcast or video tape material, especially if you are going over to ac3 anyway.

[AntnyMD]

If I'd known this thread was about video captured with the ADS box I would have chimed in earlier ... I am a frequent user of the box and have never had sync issues with any of my encodes save one that I let run for hours while I went out to the mall.

I really would suggest not using the 6Mbps setting, and when using MPEG2, I wouldnt suggest using constant bit rate on anything above 4Mbps. Also periodically unplug the box from power then replug it. I would also not suggest letting it capture content without stopping for more than 3 hours at a time.

[DUDIRENO]

Why do you suggest not using the constant bit rate? Just curious

I always seem to use it. I admit because it works and I am lazy. I like to balme it on being so busy.

I have used someones suggestions on this forum for settings and I thought it was yours AntnyMD. I will have to go back and look at the old posts.

[DUDIRENO]

OK AntnyMD I went back and saw that you usually use a 2.5Mbps VBR. And you adjust the slider to 100 and it will actually give you between 2.5 and 5Mbps. So would I actaully get better quality if I used a setting of 5Mbps at CBR? Or will I just get a bigger file?

[AntnyMD]

A bigger file and maybe better quality. However, most scenes dont require a 5Mbps constantly.

I suggest not using constant bitrate because it just seemed I got better overall results from the software using variable bitrate. It could be just me, but I noticed on some constant bitrate encodes it would just make stuff blocky since it couldnt occasionally spike upward during an action-packed scene.

[cnelson87]

thanks for the tips. i agree about 6mbps, it seems to choke. i've been capturing at 4.5mbps vbr but will try using cbr (can't remember audio settings, maybe 224 or 256). 4.5 for video seems just about right to record three 45 min shows to dvdr.
i let it run for about 5 hrs one night when i went out. damn that was one big video! and the box was HOT! but usually i only use it up to two hrs at a time.

If I'd known this thread was about video captured with the ADS box I would have chimed in earlier ... I am a frequent user of the box and have never had sync issues with any of my encodes save one that I let run for hours while I went out to the mall.

I really would suggest not using the 6Mbps setting, and when using MPEG2, I wouldnt suggest using constant bit rate on anything above 4Mbps. Also periodically unplug the box from power then replug it. I would also not suggest letting it capture content without stopping for more than 3 hours at a time.

[Frobozz]

I agree with AntnyMD that VBR seems to make cleaner captures than does CBR with the ADS box. Also, the box's heat can cause problems. I mistakenly sat the box on a carpet which caused videos longer than 45 minutes to have problems. Try to keep the box reasonably cool.

My brother had a Dazzle analog-to-digital box which he happily donated to the county dump. In order to use it he had to first put it in his freezer for awhile. That box had serious heat issues. I suggest putting the ADS box on a little stand and turning on a fan when doing long captures. It may be overkill, but who wants to do these captures over again? Don't get me wrong, my ADS box has never overheated to the point where it was a hazard; it only does a poorer job capturing video glitch-free when it is fairly warm.