dtv capture glitches

[jmac698]

Does anyone experience glithces when capturing dtv? From ota or firewire? Just wondering, I wrote a tool to fix them by comparing multiple copies. It's never been tested though.

[Ghitulescu]

I use DVB-T/S here in Europe. It has built-in error correction mechanism. Which passes however through is definitively lost. The only way of getting rid of this is a better reception.
If those glitches occur due to firewire transfer, then I think you should check the gears for grounding, a common cause for errors.

[jmac698]

Oh, no it's a known problem with the firmware in some cable boxes. If capturing a recording from DVR, you can just playback the bad part and cap it again to patch. That's what the program does.

[Ghitulescu]

It's not the reception, it's not the firewire-transfer, it's a broken FW. Recapping I assume it works only with a PVR (a STB with HDD).
Does the glitch occur at the same position (say number of bytes, duration) or it's arbitrary, and is it possible to have a glitch-free transfer (after 99 tries :) )?
My PVRs have USB and network (with integrated ftp server), so transferring files are also protected from errors.
Maybe you can change the way you transfer, for instance using another interface or simply removing the HDD, as we did in Europe before the USB-enabled PVRs.

[jmac698]

Well, it's not really my problem, I can cap with no errors, but some others in a forum reported such problems. These boxes have no usable USB functionality, but some work with external drive and eSata - however the files are encrypted. The glitches might happen every 5 minutes. They are in a different spot on each capture. If you can cap a live program and it's repeat, that could also work. The internal HD is hard to get to, there are security screws and tabs, and often these boxes are rented, not owned.
I should try the ethernet though..

[Ghitulescu]

From my experience (and some other guys in Germany): it's highly improbable that a re-airing of a programme fits perfectly the previous airing. It might be that the first airing is say at 1:00AM and has a higher parental level while the next one is during the day and is cut to fit a lower parental level. It may also miss seconds, maybe minutes, due to longer commercial breaks. It's also highly probable that the re-encoding of the material (to fit the transponder) is completely different, even at the same duration, which will force you to re-encode the material once again.

I would advise you therefore to try the utmost to get a clean capture from the STB in the first place, rather than trying to fix broken ones. This is also my philosophy for analog captures: fixing something at the HW level is much simpler and more effective than fixing the same in SW; also faster ;).

PS: from info gathered from other fora, it appears to be that the firewire output of selected STBs is indeed not copy protected, while other I/O are. Strange federal law vs copyright law issues.

[Mounir]

What brand / model of hard drive do you use jmac698 , out of curiosity

[jmac698]

It's a law in USA that local broadcasts must be unencrypted, and the box must provide a way to access it digitally, thus the firewire outputs. The first DVR was the D-VHS which used VHS tape. It had a firewire connection.

Some people tried some tricks to get less glitches and it sometimes works.

But that's interesting that there's different rating versions, I'd never considered that. Anyhow having different encodings is a good thing - I found a way to combine them to get better quality. For example the P after I,B looks good. Especially on film and 720p, you can get 3 of the same frames, and pick one with the best quality. I guess for you you get double of each film frame.

And I have a bunch of ST31500341AS
63.6-136.1MB/s, 104.5MB/s avg, 15.4ms
63.3-138.5MB/s, 105.9MB/s avg, 14.9ms
I find some operations drive to drive is faster than SSD. The latest 3TB drives have 170MB/s, and dgindex between drives for example is very fast.

[Mounir]

ST31500341AS aka the infamous code for Seagate Barracuda series i knew it ! That's the likely culprit (i own two of such drives) Have a look Here (ST31500341AS) for more infos