Comcast/Moto 6412 - How to fix/avoid corrupt .TS captures?

[Tiernan]

I've been firewire capturing (via CapDVHS) .TS streams from the Comcast DVR for quite some time now, but since the start of the new fall season, have been doing more captures from the network broadcasts, and have had more failures than successes, in terms of the ability to cap, downconvert to DVD format and author to DVD. The problem, most often, seems to be related to corruption in the initial .TS stream that is being recorded on the DVR. From there, DVHSCap can obviously only do so much to correct the corruption on the fly.

Here's the process: I take the captures into VideoRedo (if it will load them in the first place), edit the commercials, then save back to .TS and/or .mpv/ac3 (to keep video/audio synch), then use FFMPEG to downconvert to 720X480. It's usually during this part of the process that it fails, when FFMPEG seems to choke on bad data in the .TS files (and freezes/causes an error in XP and shuts down)

Does anyone have a suggestion about how to fix or avoid corruption in the data stream when capturing from the Comcast/Moto DVR?

[Krispy Kritter]

Try having it replaced. The DVR either works or it doesn't, there isn't anything you can do to control how the hardware inside works.

[Tiernan]

OK, then...

Assuming that I'm stuck with whatever the DVR is outputting via the firewire port (and the quality of this output has NOT been consistant)...

Is there a TS/HD - MPG conversion program out there that is more hardy and forgiving of corrupt transport streams?

[jman98]

I have Comcast too and sometimes they drop frames. Usually they don't, but it happens on the HD broadcasts from time to time. Since it's a problem at the Comcast level, there's no fix nor is there anything you can do. If it's a DVR problem then perhaps replacing it will help, but you'll need to watch the broadcast at the time of broadcast to catch if frames are being dropped then or if the DVR is messing up.

VideoReDo (not free, but you can try before you buy) can do wonders with fixing corrupt transport streams, but some are so messed up even VideoReDo can't fix them. I use CapDVHS too and VideoReDo can usually fix what Comcast corrupts.

[oldandinthe way]

Comcast in the boston area pixilates, drops frames and shows other problems of inadequate bandwidth.

If one wants to do something about it here, the answer is Verizon Fios.

[edDV]

The issue is local to your neighborhood and probably not a DTC-6412 issue. If you see a quality drop complain. They are always balancing bitrates to fit more in. If your local neighborhood Comcast is only a 550MHz system expect more and more compression until they go 750MHz to 1 GHz.

[justastu]

I am also using CapDVHS with a Comcast\Moto 6412. I have just started downloading and out of the 15 episodes of a 30min animated series, I've had 3 bad streams. If I go back and re-capture, it has worked on 2 of the 3. The third one I didn't do a 3rd time, I just used fix stream in VideoReDo, and it looks and sounds good.

Based on what I am seeing, it's not the Recording, nor Comcast. It seems to be either CapDVHS, the 6412's firewire download, or my laptop that I'm capturing it to.

If I narrow down the problem, I'll let you know!

Steve

[edDV]

I am also using CapDVHS with a Comcast\Moto 6412. I have just started downloading and out of the 15 episodes of a 30min animated series, I've had 3 bad streams. If I go back and re-capture, it has worked on 2 of the 3. The third one I didn't do a 3rd time, I just used fix stream in VideoReDo, and it looks and sounds good.

Based on what I am seeing, it's not the Recording, nor Comcast. It seems to be either CapDVHS, the 6412's firewire download, or my laptop that I'm capturing it to.

If I narrow down the problem, I'll let you know!

Steve

Is your disk getting full or are you doing other applications while capturing? A laptop shares the same disk for capture and OS/application needs. They conflict. Where OS meets capture interrupt priority, the OS always wins.

[slipperyone]

I've been having similar problems. I've used VLC to capture the TS. If I play it back using VLC or Nero Showtime, the streams play great! If I try any type of transcoding, I get sync problems. If I demux and remux the stream, and play the resulting stream in VLC or Nero, I get the same sync problems. In addition, I get GOP length errors, which means some transcoders will barf, while others will allow it.

If I produce an mpeg from the TS using something like projectX, this also plays fine, but again, de/remuxing or transcoding gives me sync problems.

The streams I'm recording are sports broadcasts, and the places I start having trouble is when they splice in a new feed, like going to commercial or studio.

My theory is that the problem is caused by timestamps in the TS. Since the TS spec is designed for continous streaming, where the receiver can jump in at any moment, there are timestamps in both the audio and video stream to sync them together. I believe the video stream is sent slightly ahead of the audio stream, so that the receiver has time to decode the video frame, and then the sound arrives just in time.

In any case, when the broadcast has splices, this messes with the two streams. Since the splice happens at one moment, some of the audio that should have been sent for the last couple of frames gets clipped, since it is always lagging (by design). This doesn't cause a problem, since the receiver can sync the audio and video back together using the timestamps.

However, when a demuxer splits the TS, it apparently just writes off all the video and audio it finds. Since some of the audio is missing, the two streams are written out of sync. Why the demuxer doesn't account for the timestamps is beyond me. It can obviously be done, since VLC can play the TS just fine, and projectX can convert it (not transcode it) to an mpeg just fine. Since demuxing is generally the first step in transcoding, it's no wonder that these don't come out right either.

I've tried every program I can find to fix the TS, but most produce a mangled TS that is worse than when I de/remux.

I think that adding TS support is generally an afterthought. Most (all?) programs were developed to manipulate program streams, where there generally is no timestamp issue or missing data.

If anyone knows how to solve this problem, I'd appreciate you replying to this post.

[videohelpPete]

Try the following programs that have TS stream fixers:

VideoRedo v4 ($75 / 15 day trial) has a function called "Quickstream fix":
http://www.videoredo.net/msgBoard/showthread.php?t=15759

TS Doctor (30 euro / 30 day trial):
http://www.cypheros.de/dvb_e.html

[slipperyone]

I've been having the same problem with TS files, especially long ones. Some shorter TS files will actually come out OK when remuxed, but most will be out of sync. I've tried TS Doctor, and while the resulting TS will play fine in VLC, if I use any remuxer, (e.g. TSmuxer) the resulting file will be out of sync. Haven't tried Video Redo yet.

[slipperyone]

I've now tried the VideoRedo 4.20's quickstream fix under Vista. It cranked away so long I went to bed. The next day, Vista had closed the process, and the resulting stream was almost twice as big as the original. I couldn't find a player that could play the file.

So far, I've tried a lot of tools and none seem to help this problem. The only way I've found to get around this is to try to find all the places where the audio gets out of sync, split the file into these pieces, and then use some tool to re-sync the audio in that section. It takes so long to do this that it's generally not worth the effort.

[Khaver]

I've had no problems with ffmpeg down converting HD TS captures to VOB. On some channels, pixelation is a problem, but ffmpeg seems to handle them very good and keeps the audio in sync.

I used to run the TS files through comskip to generate an edl then run it through mencoder to get the VOB. This caused too many audio sync problems.

Now I run the whole TS file through ffmpeg to get the VOB. Run the VOB through comskip that generates a script for VideoRedo, then run the VOB through VideoRedo. This has worked the best for me.