Sync problems after encoding

[Fadenoid]

Having recently purchased a DVD writer I have been experimenting with backing up VHS to DVD-R/RW without success. The raw MPEG2 grabbed from a VCR (approximately 30 minutes in length) is in sync from beginning to end (at 2, 4 or 6MBS all in half D1 mode).

However, after using TMPGEnc to encode, the converted MPEG2 file (for DVD PAL) gradually goes out of sync after about 5 minutes when played back on either Media Player, WinDVD or Power DVD (audio after video). Interestingly, a 10 minute raw MPEG2 file can be rendered with TMPGEnc without problem and looks like it stays in sync after encoding when played on either of the above.

I have also used ULead DVD Workshop with similar results. One theory I have is the 25fps frame rate that the raw MPEG2 is grabbed in may not be exactly 25 fps, but when I check it with bit rate monitor everything looks ok. Also, the demultiplexed audio, after being converted to 48KHz, 384Kbps also is the correct length. Is this a software player issue ie is the codec at fault here?

Anybody else suffering from this and if so are there any possible solutions? Any help would be appreciated.

Cheers

[Prashanth Enukonda]

hi buddy
use software - avid or hardware cannopus vhs to dvd converter.
visit cannopus website.
They have got the audio locking features ......
ok good luck
byebye

[Fadenoid]

Thanks Prashanth for the prompt reply. I'll have a butchers at the cannopus site!

[Betamax]

Using a "Matrox RT2500" this is what I know about creating DVD's from analogue material (like vcr's).
You could get the "Canopus ADVC-100", an external device that converts analogue video to IEEE1394 (FireWire) DV-video, keeping the video and audio sync'd (very important I think).
You can capture directly into MPEG-2, using I-Frames only (at max. of 7Mbps).

Then feed this avi/mpg (I didn't try that yet myself) to DVDit! It seems DVDit encodes it to the correct MPG-2 format for DVD, so you don't have to worry about TMPGenc anymore.

[holistic]

Fadenoid,

I believe your problem lies here :

Just a guess but i believe if you captured at 16bit/44Khz audio
then by reencoding to 48khz (DVD spec) i believe you have induced an 'time shift' in the audio track

have a read.....
http://www.sospubs.co.uk/sos/mar01/articles/pcmusician.asp

[Fadenoid]

Thanks everybody for all the help.

An important point I think I didn't make was that I've grabbed the video in MPEG2 format using an external hauppage PVR device. The quality probably isn't as great as some of the other capture cards, but the raw mpeg stream is all in sync prior to encoding and is ok for my purposes.

Holistic I think that you're right about timeshifting being introduced by re-encoding audio at 48KHz and I'm going to have a look at the article shortly. I think the bit I'm confused about is that I would expect to see the audio track extend beyond the length of the video track (eg when I open it up with say media player) however this does not seem to be the case. I even thought of putting a stopwatch against it!

I'm also assuming that when ULead DVD Workshop reconverts the audio stream to 48KHz also as I'm getting a similar effect with this.

Anyway, thanks again to everybody for their advice and I'll let you know if I get a result.

Fadenoid

[MartenF]

I posted the same issue in the Advanced Conversion section. I am having the same problem.

[Fadenoid]

Hello to everybody who has replied to my previous postings,
Sorry for the delay in replying but I now appear to have solved the sync problem. After demultiplexing the audio from an unencoded file, then demultiplexing the apparently faulty encoded one, I viewed these using goldwave, which reported that the audio length was the same (original 44.1K PCM, encoded 48K 384kbps). It therefore looked to me that what was actually happening was the video was running fast so the longer the mpeg file, the worse the sync error got.

I then loaded the unencoded file into TMPGEnc (Ver. 2.53) it was an MPEG2 1/2 D1 4MBs stream approximately half an hour long with 44.1K audio setting (note I'm using a laptop with a Hauppage PVR-USB MPEG2 capture unit). I loaded the DVD template then ticked the "do not modify frame rate" box in Advanced and the resultant encoded file was perfectly in sync when played back on WM player and WinDVD. I was then able to drop this mpeg file into Ulead DVD Movie factory trial version which recognised the format and did not need to re-encode it, and it burnt the rendered file on to a DVD-RW which played perfectly on my Pioneer Stand-alone.

I've just attempted using a different template with a higher Bit Rate setting and also used the source range to see if editing may cause a problem with the audio sync, but these appear to work ok also. All I need to find out now is the optimum template for doing this conversion. I've read that 2 pass variable gives better results than the ones I've used so far but I'll need to experiment.

Anyway, I don't know if this setting will work for everybody but it certainly worked for me.

Thanks again for the help.

Fadenoid