Subtitle timeslip

Begonnen von jaydear, Februar 24, 2021, 07:09:32

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jaydear

I've been using MKVtoolnix for a few years to add subtitles back into my edited files. I've always had millisecond accuracy with the files from TSD except when  I make a mistake entering the delay ::)  My editing method tells me the exact amount of delay I need to enter into MKVtoolnix. Since late last year I occasionally have big errors in the order of 1 - 2 secs yet playing the edited files shows no timing error. I'm having trouble tracking down the source of the slippage. I've tried some old versions of MKVtoolnix, but they all give the same result so I think something is tricking it. Has TSD changed any subtitle parameters recently?
The.Doctor is the ants' pants :)

Cypheros

The timing of the subtitle tracks has not been changed on TS-Doctor side, maybe on the broadcasters side.
Does this concern the DVB subtitles or the teletext subtitles?
Check the offsets in the settings under Settings/Options/Teletext/Subtitles .

jaydear

I think I have just discovered where it is happening. This is a simplified explanation: I use VidCoder, a Handbrake GUI, to convert certain problem files to the end format before I edit them. It looks like Handbrake is adding up to a few seconds of black frames to the start of these conversions, perhaps to cope with their IDR frames. That screws up my timings as you can imagine, so I currently think the problem is in HB not TSD.
The.Doctor is the ants' pants :)

jaydear

I'm still not sure how to identify whether srts are from dvb or teletext, but I think they are all teletext here. Always very ugly big blocky text on black background when watching the off-air programs. Don't really know though. I have TSD set to extract both types in ENG with zero offsets. I get [801] & [888] srt files from TSD and both seem identical.
The.Doctor is the ants' pants :)

Cypheros

Three-digit numbers are probably teletext subtitles. DVB subtitles are bitmaps and need OCR to be converted to SRT.

jaydear

I understand a little more now, thanks. I'm guessing that teletext files are inherently more accurate than DVB subs and quicker for TSD to process.

The subtitle timing problem is unfortunately still an issue. I'm 99.9% sure now that it's only happening with recordings from one source. I have discovered that files from that source that have been processed by TSD will not play in VLC x64. I've un- and re-installed VLC and tried other versions, but the result is consistent - it won't play them. The original recordings do play in VLC, but they consistently freeze at or near the start for a second or two!! Recordings from other sources play properly in VLC whether they have been processed in TSD or not.

The TSD files that won't play in VLC are also the ones that cause problems in Handbrake/VidCoder which either adds lots of black frames at the start or adds lots of one frozen frame a few seconds in from the start. I can send you samples to investigate if you like.
The.Doctor is the ants' pants :)

Cypheros

Yes, sure. If you have a sample to reproduce the issue, I would like to investigate the source of the problem.

jaydear

OK, weird stuff happening! I used Raw Cutter to make a small sample of a file that won't play in VLC. Checked it and it plays in VLC! Re-checked the original file and it still doesn't. Then I copied the big file into another folder and it plays!! I'm going to get a bigger shovel and dig deeper :-\

The.Doctor is the ants' pants :)

jaydear

Hours later I'm not having much luck getting to the bottom of this. I'm trying to find out why simply copying a file with Windows File Explorer from one folder to another on the same drive makes it playable in VLC. I've been viewing files in TSD's cutting window and I can't see any difference except to say there is playback disturbance of one form or another in all TSD's files at the start, even though they appear to begin with an I-frame. Having mentioned that, the little I-frame box in the Cutting Window is not working, so I've had to check for I-frames in other software. Can you restore that function please?

Maybe TSD is not writing some tiny bit of information at the start of it's files and is causing VLC and Handbrake to misbehave. Merely copying a file to another place fixes it as far as VLC goes. I haven't had time to try a copied file in HB as more than half the day is gone and I need to keep my wife a bit happy :D
The.Doctor is the ants' pants :)

Cypheros

Do you know that VLC has a bug, well known for year but never been fixed?

VLC tries to open and read any text file in the same directory like it's part of the transport stream and hang.
So you need to delete all text files (.txt, .log, etc.) TS-Doctor creates in the same directory.

Don't use VLC, because it's really buggy. Better use Mediaplayer Classic BE: https://www.videohelp.com/software/MPC-BE

jaydear

ZitatDo you know that VLC has a bug...
I do now >:(

It's the srt file/s. Changing as little as one character in their filename fixes it. VLC ignores the ".[xxx]" part. I've learnt something :D
The.Doctor is the ants' pants :)


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