Huge PTS underflow?

[aav]

On all the video files I'm exporting from VRD, I get what seems to be a HUGE PTS underflow number, like the following:

PTS underflow: 40252
Audio async frames removed: 81
Video output frames: 42264
Audio output frames: 70440

I have searched the forum and read the docs on this issue, but the docs only mention "small" PTS underflows being ok. The weird thing is, I've never had a problem with the resulting files... they work fine in the rest of my processing, and look/sound great on my stationary DVD player after I've remuxed the m2v+mp2.

Maybe I should mention that I always demux the m2v and mp2 (using TMPGEnc's MPEG Tools) after editing in VRD, and I just throw away the "padding" stream. It doesn't seem to be needed. I re-encode the m2v in CCE SP, and use the mp2 as-is and let TMPGEnc DVD Author mux the two streams together when authoring the disc. This has worked for several tapes with no desynchronization whatsoever.

Still, the PTS underflow bugs me a bit, what could cause it and could I get bitten by it later somehow?

The original unedited MPG's (PAL, interlaced) that i load into VRD come directly from my WinTV PVR-250 card and WinTV 2000. (I'm using the CBR 12mbit preset with 384 kbps stereo sound)

[DanR]

On all the video files I'm exporting from VRD, I get what seems to be a HUGE PTS underflow numberThe problem is VRD is currently hardcoded to output SCR timestamps at a max bitrate of 10.8 Mbps which is the max acceptable for DVDs. Since you are recording a 12MBps CBR its natural that you'll the system clock (at 10.8 Mbps) isn't keeping up with the PTS which are correct. Although your DVDs play well, you might want to consider reducing the bit rate in order to stay withiin DVD specs.

Do me a favor, please. Open the file and click on Tools>Show Program Info. What bitrate is displayed?

Finally, why don't you simply output elementary streams directly from VideoReDo and save the TmpGenc demux step?

[aav]

Ah, I see... the thing is though, I'm re-encoding the video later down to DVD compliance level at 6-9 mbit VBR. So I'm using VRD to edit the original captured stream. It would be great if VRD could support this properly. Currently it seems to work anyway, maybe the tools I'm using are lenient enough to ignore the problem?

The toolchain is currently:

- Capture MPG at 720x576 CBR 12mbit in WinTV 2000. (preset, into a Program Stream)
- Edit video/audio streams together with VideoReDo.
- Demux into m2v/mp2 with TMPGEnc Plus.
- Frameserve m2v through AVISynth, doing levels adjustment etc.
- Re-encode .avs video with CCE SP at VBR 6mbit avg, 9mbit max.
- Remux in TMPGEnc DVD Author while authoring, pairing the new video with the old audio stream.
- Burn the VIDEO_TS using Nero 6.

All seems to work fine.

Actually, I hadn't even seen that VRD could output elementary streams, i'll do that in the future. Should save some considerable time. Thanks for the tip. :)

Tools>Show Program Info shows 12.000 Mbps as it should.

[DanR]

Tools>Show Program Info shows 12.000 Mbps as it should.I'll look into removing the hard code limit on the timestamp. Why are you recording at such a high bit rate? One could make an argument that anything over ~6Mbps is wasted with bitstreams recorded off the air. Since you're down converting later to 6Mbps VBR, why not just record at that rate? (Incidently, I record at 6 Mbps VBR with my PVR-250 ).

Re-encode .avs video with CCE SP at VBR 6mbit avg, 9mbit max.This explains why you aren't having DVD authoring issues. Based on feedback from VRD users, I've found that many DVD players today will handle bitrates > 10Mbps just like they will handle other out-of-spec conditions like GOPS > 18 frames.

[aav]

'll look into removing the hard code limit on the timestamp.

Thanks!

Why are you recording at such a high bit rate? One could make an argument that anything over ~6Mbps is wasted with bitstreams recorded off the air. Since you're down converting later to 6Mbps VBR, why not just record at that rate? (Incidently, I record at 6 Mbps VBR with my PVR-250 ).

Well, the video, even after the PVR-250's noise filtering, still contains difficult noise etc in some scenes... and I trust CCE far more than the realtime hw encoder of the card. I did experiment with 8mbit/s "DVD preset" captures, and I guess they looked fine, but I figured that since I'm reencoding anyway I should have the source material in as high quality as possible. Also, given the nostalgic value of this home movie material I'm maximizing quality in any way I can. VBR at 6 mbit looks fine on current TV's - and works out to give me ~1.5 hours per 4.7GB DVD, but I'll be archiving the 12 mbit files too if I ever want to reprocess them in the future. No telling how long the VHS tapes will last...

[aav]

Dan,

To my surprise build 220 no longer gives me any PTS underflow messages, did you add a fix? In any case, I'm happy. Thanks again!

[DanR]

To my surprise build 220 no longer gives me any PTS underflow messages, did you add a fix? There weren't any fixes for the PTS underflow. Are you outputting directly to elem streams? PTS is only used with program streams.

[aav]

Doh, that was it of course. I'm sorry, haven't had my first cup of coffee yet.