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Old June 9th, 2009, 08:47 AM   #1
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Compression - How much can I get away with

I am producing a event video (in this case a Dance Recital) that is being sold to people that have pre-ordered it. If I am just over the limit for given disc, what level of compression (if any) is accecptable?

Note: I am talking about an event that is definitely over the 2 hour limit (2:20) for a DL disc, so with no compression, my options are
1. 3 single layer disc
2. 1 DL disc and 1 SL disc
3. 1 DL disc, with a small compression ration calculated by Studio 12

While proofing a different event, I dialed in about 40% compression in order to squeeze 1:40 onto a DVD+RW. Even running at 60% of optimal, I was hard-pressed to see any differences

Last edited by Vince Pachiano; June 9th, 2009 at 10:02 AM. Reason: emphasize that it is definately over the 2 hour limit
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Old June 9th, 2009, 09:38 AM   #2
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A dance recital means relatively much movement, so high bitrates are required to maintain good quality. But 2 hours should fit on either a DL or two single layer DVD's, especially if you encode the audio to AC3. Stereo @ 192 Kbps, 5.1 @ 256 Kbps.

Maybe use a bitrate calculator to find optimal settings, like this one:
DVD-HQ : Bitrate & GOP calculator
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Old June 9th, 2009, 10:06 AM   #3
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Definately over the 2 hour limit

Quote:
Originally Posted by Harm Millaard View Post
A dance recital means relatively much movement, so high bitrates are required to maintain good quality. But 2 hours should fit on either a DL or two single layer DVD's, especially if you encode the audio to AC3. Stereo @ 192 Kbps, 5.1 @ 256 Kbps.
I will look into that.
I should have emphasized in my original post that the total run time definitely exceeds the time limit for a DL disc with NO compression. Pinnacle has an option where it calculates the compression ration required to fit, say 2:20 onto a DL disc. My original question remains, how much (if any) is acceptable for final output?
I will probably just burn a DL + SL disc and call it a day, but I know it would be more convenient for customers to have just a single DL disc
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Old June 10th, 2009, 08:47 AM   #4
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2 hours of uncompressed footage would never fit on a dual layer DVD.

It's not a matter of if you compress the footage, it's how much. Using the maximum bitrate allowable, for DVD video specs, you can fit 2 hours of video on a dual layer DVD. You don't have to compress a whole lot more to fit 2:20 on a dual layer DVD. Using a good encoder, the quality should still be excellent. A lot of Hollywood feature films have been released on DVD, with considerably more compression than that.
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Old June 10th, 2009, 09:10 AM   #5
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You can easily go with 384kbps audio and still be around 7000kbps for video on a dual layer disk, which would produce excellent results.

It's not unreasonable to consider compressing down to something in the neighborhood of 3500kbps for video, to fit on a single layer disk, and still likely get acceptable results.

Use 2-pass VBR encoding. You might want to use a better compressor than whatever comes with Pinnacle though. A very low cost option, for a good compressor, is TMPGEnc.
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Old June 11th, 2009, 02:25 AM   #6
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You could even do that length of time on a single layer disc. I had an event that ran over two and a half hours and the budget called for single layer discs. While it wasn't the best image I've seen on a DVD, it certainly wasn't bad.

My advice would be to run a few tests at different bitrates. Perhaps encode a two minute segment at different bitrates and place them back to back on a DVD. Let your eyes be the judge.
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Old June 11th, 2009, 09:16 AM   #7
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Vince,

I know that post # 1 is often overlooked. You mentioned a duration of 2:20 hours.

Here are the results you could have found had you used the calculator I linked to, so there is no need to experiment with other, lesser settings. These are the best settings to fit it all on a single DL DVD:
Attached Thumbnails
Compression - How much can I get away with-11-06-2009-16-12-19.jpg  
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Old June 11th, 2009, 09:23 AM   #8
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I wouldn't push the audio bitrate down to 192kbps, for a dual layer DVD. The video would still be over 7000kbps with 384kbps audio, and 7000kbps video should look excellent (assuming a good compressor is used). It might make sense to push the audio bitrate down to 192kbps for a single layer DVD though.
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Old June 11th, 2009, 11:27 AM   #9
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For stereo AC3 I see no reason to go beyond 192. For a dance recital with heavy movement my preference would be the video quality rather than the audio quality. Anyway, this is just an example, showing the advantage of using a bitrate calculator. If the OP wants better audio at the detriment of the video, he has the opportunity to play around and see what it does to different encoding rates.
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Old June 11th, 2009, 12:48 PM   #10
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As a practical matter, there probably wouldn't be a perceptible difference one way or the other. Increasing bitrates over 192kbps for stereo AC3 and 7000kbps for SD MPEG-2 video produces very little return in quality. Either way, the OP will likely get great results.
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Old June 13th, 2009, 07:57 AM   #11
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I would not use DL discs as they have poor compatibility. Most reproduction shops will not use and certainly the one that I use will not reproduce on DL. I have put 2 hour 26 min dance recital on a single disc, 2 pass VBR 3650 average, 8000 max, 2000 min with AC3 224. Encoded with TMPGenc4Xpress ( there is a difference depending on what encoder you use I don't use the encoder in Edius or Vegas for these lower bit rates). You only have high movement in dance if you use a lot of closeups not something most dance enthusiasts actually like as they want to see the full movement. Small children are different and the parents need to see their faces but they are usually not moving about the stage too much!! Remember most of the stage is likely black not much i-frame change. It's not like encoding running water or leaves or grass most of the image is stationary. Unless of course you keep moving the camera around. Switch cameras, limit zoom and pan you will make life easier on the encoder later. Can I see a difference if I encode at CBR6000? Sure I can, but then I am a lot more critical than the average viewer. It is much more convenient for the user to have 1 disc with full menus.

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Old June 13th, 2009, 11:35 AM   #12
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I've never tried TMPGenc 4. I simply will not install any software that requires a constant internet connection to run. I'm pretty sure TMPGenc 2.5 would yield better quality than Pinnacle though. I do know that 2 pass VBR ~3500mbps can produce a reasonably good quality image with most footage.
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Old June 13th, 2009, 12:47 PM   #13
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TMPGenc doesn't need a constant connection just a license verification when needed so could just be connected when it asks for verification. Not sure of the time frames but it is not every time I use it. The nice thing about TMPGenc is one can see how the disc is filling up so I usually set data rate so that the disc is usually just over 4G mark, not full.

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Old June 14th, 2009, 11:24 AM   #14
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I don't see any reason why 2:30 wouldmt go on a DL disc without good results. I think the issue of getting someone to reproduce the disc for you is a non-starter. If the disc run is low enough, it wouldn't appear to be economcal to make pressed discs and as for 'burned' discs, it's not out of the question to do that them yourself.
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Old June 14th, 2009, 11:51 AM   #15
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Image quality (due to compression) isn't really anything akin to a serious issue (assuming a good encoder), as far as putting a little over 2 hours onto a DL disk. DL disks are more problematic than single layer disks though, as far as getting good burns, as well as compatibility issues with DVD players.
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