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VBR not varying
Hey all, there might be big problem with the way the MainConcept codec encodes VBR 2-pass in Ppro 2.0
I have a 2-hour show. Nothing special here. Source is DV 4:3 from Sony PD-170. For export in Adobe Media Encoder, I basically chose the ‘NTSC 4:3 DVD VBR 2-pass 4mbps’ preset, and modified the bitrates. Here are some settings:
DVD MPEG-2
Codec quality: 5.0
VBR 2-pass
Min bitrate: 1.5000 mbps
Avg bitrate: 5.1200 mbps
Max bitrate: 7.7000 mbpsEverything else such as Lower Field are verified.
The problem is that the M2V output file is very much “flat” in bitrate when checked in Bitrate Viewer. Here are a couple of screenshots: https://jshare.johnshopkins.edu/bli3/public_html/vbr01.gif
https://jshare.johnshopkins.edu/bli3/public_html/vbr01.gifThe graph is flat for the whole 2 hours. You can see that the ‘avg’ is about 4800, and ‘peak’ is about 5200. Since it’s so flat, it never reaches 7700max and 1500min as I specified. As a result, I see artifacts and “blocks” in high-motion and low-light scenes.
This wasn’t an issue in Ppro 1.5. The output M2V for DVD always had great variation in bitrate, with the same settings used. Perhaps there was a bug introduced when Adobe updated 1.5 to 2.0?
Any help is greatly appreciated.
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3 Replies
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The biterate used is also a product of the ammount of footage being encoded vs space, use a bitrate calculator to find the bitrate recommended for the size of the file being used, you maybe bumping against a ceiling.
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I actually used a bitrate calculator before I encoded. The 5.12 mbps average was just right for my 2-hr show to fit on a 4.7 GB disc.
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The content dictates the variance from average. If your content is all talking heads or all football there is not going to be enough places to “save” bits during low motion scenes or not enough places to “spend” these bits during action.
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