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Jittery mpeg-2; pulldown problem maybe?

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Joe Murray
Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 1:42:36 am

I'm trying to encode mpeg-2 multiplexed files from uncompressed Quicktime or AVI standard definition footage. These are finished spots, shot on film at 24 and transferred to 29.97 fps for editing. I'm not sure if the issue is the 3:2 pulldown or not, but the motion in the spots is real jittery and the problem seems to be field related. I'm using high VBR settings (average 15000 kbps, 2 pass encodes) and have tried both upper and lower field first in some tests. I've also tried using a couple of different apps to encode: Main Concepts mpeg encoder and Tmpgencode from Pegasus. Neither Cleaner nor Compressor seem to have a high enough bit rate available for what i need to accomplish.

I'll be doing some more tests with footage that has no pulldown, but does anyone have any suggestions as to what this problem could be?

Thanks in advance-

Joe Murray


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Charles Simonson
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 2:22:37 am

Were they "jerky" when they were transfered to 29.97 and edited? Are you using the telecined transfers for the compression? If so, and the telecined clips weren't jerky, then the initial 3:2 pulldown does not sound like the issue (and I don't see much benefit doing a reverse pulldown and then another pulldown when encoding). Just make sure when you are encoding that you are selecting the same framerate as the source.

As far as your bitrate, there really is no reason that you should encode to 15000kbps, especially if using 2-pass. I doubt that the quality is any better for 15 compared to 7, 8, or 9 for MPEG-2 SD. At 15000kbps, you may even be taxing your hardware too much to play back the MPEG-2 files at full framerate, hence the "jerkiness".

Basically, if you are getting errors with all of the apps you mentioned, then there is something wrong on your end. Because I would expect MainConcept (are you using the mac version?) to be able to compensate in most cases where the others you named would not.


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Joe Murray
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 11:33:03 am

>>>Were they "jerky" when they were transfered to 29.97 and edited?

No, just normal 3:2 pulldown, film motion

>>>Are you using the telecined transfers for the compression?

I've edited the spots in FCP 10 bit uncompressed using the telecined transfers, then exporting either an uncompressed Quicktime or uncompressed AVI (the Pegasus encoder doesn't take Quicktime). Using the same framerate when encoding...

>>>As far as your bitrate, there really is no reason that you should encode to 15000kbps, especially if using 2-pass. I doubt that the quality is any better for 15 compared to 7, 8, or 9 for MPEG-2 SD. At 15000kbps, you may even be taxing your hardware too much to play back the MPEG-2 files at full framerate, hence the "jerkiness".

By hardware do you mean the computer? I don't try to play them back via a software player. My test of the encodes is to burn them to DVD so I can watch them on a decent NTSC monitor. I'm encoding these spots for digital delivery to stations including national networks, and I'm following the specs of the company that does the actual delivery to stations...minimum 10000 kbps, max 25000, average 15000. I'll try a lower bitrate to see if that helps, but quality is THE issue. It's not just ending up on DVD, it's going straight to air/cable from the file I create.

>>>Basically, if you are getting errors with all of the apps you mentioned, then there is something wrong on your end. Because I would expect MainConcept (are you using the mac version?) to be able to compensate in most cases where the others you named would not.

I'm sure you're correct about where the problem is; I'm certainly not looking to blame the software. This is a new process to me so I expect my inexperience is indeed the problem. I'll do some more tests with non-telecined footage and lower bitrates and report back. Are there any other apps you would recommend instead of Main Concept or Pegasus TMPGEncode?

Thanks for your response-

Joe Murray


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Charles Simonson
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 3:23:24 pm

The only other apps I would recommend are Compression Master 3.1 and Canopus ProCoder 2, although I don't think they will be much different in this situation.

Per the bitrate, while the specs of the broadcast require 10000kbps minimum, quality really does reach its saturation point with SD MPEG-2 encoding at about 8 or 9mbps and a good two-pass software encoder. I understand your need though to generate files at that high of a bitrate, but unfortunately, you will not be able to effectively test on most DVD players your encodes burned to a disc. That is because the DVD spec only guarantees playback of full mulitplexed streams at under 9 - 9.5mbps. And when you are you using DVD-/+R media, that number is more like 8 - 8.5mbps to be on the safe side. So, it is entirely possible that your encodes are fine, but that your playback device (DVD STB) can not handle the bitrate they are encoded at because it is taxing the decoder chip too much.

The sad thing is, that while you have to deliver these spots at these high bitrates, in reality, when they are broadcast you will be lucky if they are transmitted at even half the encoded bitrate.


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Ben Waggoner
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 5:58:26 pm

Half that bitrate for DBS? I wish. Almost all digital cable and digital satellite uses half-D1 (352x480) resolution, at around 1 Mbps VBR. THEY STINK!

You're right that the 15 Mbps peak is rather insane. When I'm targeting a set top player, I try to keep my peak to 6.5 Mbps or lower for video+audio, so typically 6.3 Mbps CBR video and 192 Kbps AC-3 audio.

Compressor 2 can provide stunning quality with 24p content at 6.3 CBR in Best quality mode - in my tests, it's almost indistinguishable from the source.


My Book: http://www.benwaggoner.com/books.htm
Squeeze and ProCoder tutorials: http://www.classondemand.net/benwaggoner/
Compression Class at Stanford: http://www.digitalmediaacademy.org/compression.html


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Joe Murray
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 6:50:00 pm

I understand the points about excessive bitrate. I'm just going off the spec sheet I was sent by the spot distribution company. Their minimum is 10 Mb/s and PREFERRED is 25. Is there a good mpeg-2 player that will output to NTSC, for instance through the AJA IO or Kona 2? Maybe that way I could check the files without involving a DVD.

Basically I've got to be able to guarantee to my clients that this will look just as good as if I sent a DBeta to one of the big networks. I know cable and satellite clip the bandwidth severely, but network is a whole different issue in terms of QC requirements.

Thanks again for all the help with this-

Joe Murray


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Charles Simonson
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 25, 2005 at 8:35:31 pm

Yes, saying half was mighty generous of me, but I didn't really want to get into too much detail in that aspect. BTW, most of the digital cable streams that I have seen and ripped were 528x480 at 1.5 to 3.5mbps. As always, thanks for calling me out on it Ben. ;)


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geoff
Re: Jittery mpeg-2; pulldown problem maybe?
on Aug 26, 2005 at 6:20:01 pm

Sounds like the client wants an MPEG 2 Transport stream. Different then what you create for a DVD. That is what is used for Digital Cable/Satellite and VOD. Main concept will let you make a transports stream but I am not sure what the maximum bit rate is. Duma Video and Tandberg make hardware based encoders but they are expensive. I am not sure about a software encoder.

Geoff


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Chris Tomberlin
Re: Jittery mpeg-2; pulldown problem maybe?
on Sep 22, 2005 at 2:11:42 am

Joe,

Did you ever get this worked out? I'm using MainConcept and having the same problem. I'm trying to do the exact same thing you are and would really like to know if you found out the best way to do it.

Thanks
Chris


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Joe Murray
Re: Jittery mpeg-2; pulldown problem maybe?
on Sep 22, 2005 at 2:14:39 am

I had to set that aside when a project came in, so I never really got it working. I also tried to get some tech help from Main Concept but never got anywhere with that. If I make any progress I'll post back to this thread.

Joe Murray


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