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Old 12th February 2005, 00:20   #101  |  Link
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Re: audio delay question/request

Quote:
Originally posted by bob0r
Is it possible to sync the .mpa file with DGMPGDec?
It's on the development list but has a low priority. Is it so hard to set the offset in nandub?
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Old 12th February 2005, 00:23   #102  |  Link
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@zeus163

Up to a couple hundred meg is fine. I don't care where or how you get the file. All I care about is that I can duplicate your issue using it. Please put it up there soon so I can work on it when I get home.
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Old 12th February 2005, 00:25   #103  |  Link
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@cw_uk

The information is all the same, but is more readable. I didn't print the VOB cell id either, because I think it is useless for what DGParse is used for.
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Old 12th February 2005, 04:29   #104  |  Link
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@zeus163

I was hoping to work on this tonight. Any chance?

I'd really like to release 1.2.0, but can't while your issue is hanging fire.
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Old 12th February 2005, 05:29   #105  |  Link
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Its got another 45 minutes or so. The clip is 150 megs or so and FlashFXP shows that I'm at 53% complete.

I'm sorry it took so long to get to this. Since the grandparents were watching the kids tonight, it was date night for an early Valentines. As soon as I got home I got to this.

I also included a text file with some info for you. If you have any questions there is an email in there you can use.

I hope this gets there soon enough!
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Old 12th February 2005, 14:15   #106  |  Link
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Thank you, zeus163. I'll get right on it.
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Old 12th February 2005, 15:44   #107  |  Link
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@zeus163

That sure was an interesting issue. Your stream is extremely weird but you did uncover a real problem. The stream now has a home in the "Weird" subdirectory of my test file suite.

Your stream has no GOP headers, at all! That's legal of course. But the stream also doesn't use the temporal reference field properly.

I try to get the temporal reference of the first I frame. But now I realize that it should be the first I frame after a GOP header, because the GOP header resets the temporal reference to 0. So I do that now. Also, if there is no GOP header, I then do not use the temporal reference adjustment in the delay calculation.

While this gives me a delay of -404ms now for your stream, I'm still concerned that your stream does not use the temporal reference field properly, i.e., it doesn't increment for each frame in display order until reset by a GOP header, as required by the MPEG2 spec. And it has large values like 0x268. That won't throw me off, unless a GOP header comes along and the next I frame has a bad temporal reference. I do check for the value to be reasonable (less than 18), and I don't use it if it isn't. The worst thing that can happen is that the delay value given is wrong or absent, but this will occur only for illegal streams.

I'll put up an RC4 shortly with this change.

Last edited by Guest; 12th February 2005 at 16:28.
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Old 12th February 2005, 15:53   #108  |  Link
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I know the difference in audio delay between tracks demuxed with FF and those without it is really small, but which value should we trust for muxing?
Regards
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Old 12th February 2005, 16:07   #109  |  Link
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Quote:
Originally posted by loni_blues
I know the difference in audio delay between tracks demuxed with FF and those without it is really small, but which value should we trust for muxing?
Regards
There is no difference in RC4. I was using the FF adjusted frame rate when I should have been using the MPEG2 encoded frame rate.

Thank you for pointing out that issue.
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Old 12th February 2005, 16:24   #110  |  Link
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1.2.0 RC4

Here's RC4. The only change is to the delay calculation as described. I also included the 1.2.0 DGVfapi.vfp.

http://neuron2.net/fixd2v/dgmpgdec120rc4.zip

I sure would like to release this today or tomorrow.
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Old 12th February 2005, 17:39   #111  |  Link
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I am getting audio delays of -66ms in 2 tracks demuxed from the same vob with rc4 when I used to get different values of 0ms and 66ms with rc3 and no ff. Is this to be expected?
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Old 12th February 2005, 18:53   #112  |  Link
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I'm glad that my weird stream was of some help. I seem to recall that somebody once wrote streams with no GOP headers can't be opened properly in Project X. Which would explain why I couldn't open that stream up in that program or open it up properly to cut out commercials. I now think that several HD stations that I receive send out their streams without any GOP headers. But with your work, I should be able to handle that problem now. Thanks for taking the time to look at that file I sent you. I appreciate it.

I will try the latest version out today when I do another cap from the same station. I'm going to guess that the stream will have no GOP headers as well.

thanks!
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Old 12th February 2005, 19:39   #113  |  Link
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Quote:
Originally posted by loni_blues
I am getting audio delays of -66ms in 2 tracks demuxed from the same vob with rc4 when I used to get different values of 0ms and 66ms with rc3 and no ff. Is this to be expected?
Without seeing the stream, I can't tell you what is expected. Do the delays appear correct?

You know where my FTP server is. Hint, hint.

Last edited by Guest; 12th February 2005 at 19:53.
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Old 13th February 2005, 01:31   #114  |  Link
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@neuron2

I ran RC4 on the complete .ts file that I started with. I used the delay value that it came up with on the .ac3 file and it worked perfectly when I muxed it back with the encoded file.

Thanks a bunch!
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Old 13th February 2005, 01:47   #115  |  Link
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@zeus163

You're welcome. Thank you for the feedback. It makes it all worth while for me.
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Old 13th February 2005, 01:51   #116  |  Link
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Quote:
Originally posted by zeus163
I seem to recall that somebody once wrote streams with no GOP headers can't be opened properly in Project X. Which would explain why I couldn't open that stream up in that program or open it up properly to cut out commercials. I now think that several HD stations that I receive send out their streams without any GOP headers.
Interesting. Fortunately for us, DGIndex spits out a new "GOP line" at each I frame, otherwise the limit of 499 pictures would have killed us. The real limit is 499 frames between I frames.
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Old 13th February 2005, 14:34   #117  |  Link
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Hi Don,

I just tested RC4 and noticed that the delay is incorrect for my MPEG2 -captures. The delay reported for the original clip was -124ms, in earlier versions it's -44ms. The delay for the cut sample file (see below) is -80ms but it's still way off.

I'd say the delay should be closer to zero for both clips although it's hard to determine. Nevertheless, -124ms and -80ms sound off to my ears, the audio runs too early.

I uploaded a sample clip to my webspace as I couldn't log on to your FTP site.

http://www.saunalahti.fi/sam08/delayclip.mpg
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Old 13th February 2005, 17:37   #118  |  Link
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@Boulder

Greetings from the quantum vacuum!

Ha, ha, I had already fixed that in my local build in preparation for release. It gives 0ms for the uploaded clip.

Try this one:

http://neuron2.net/fixd2v/dgmpgdec120rc5.zip
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Old 13th February 2005, 17:49   #119  |  Link
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Thank you, Sir, will try it ASAP

The wonders of hybrid NTSC->fieldblended PAL conversion..grr
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Old 14th February 2005, 20:14   #120  |  Link
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A bugreport from elsewhere : the filter BlindPP() doesn't work anymore. When you load a script with BlindPP() in VDub, it just vanishes. Also it probably has the same postprocessing bugs that MPEG2Source() had.

Just thought I'd report it since some people are using it, not me though
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