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Encoding Settings - Picture Quality


ejstubbs

Question

I sometimes have to use the custom encoding settings to tell Toast to re-encode a programme recorded off digital TV, because the recording has a Group Of Picture (GOP) which does not comply with the DVD standard. (Toast used to manage this automatically but seems to have forgotten how in more recent versions - but that's another story that I'm taking up with Roxio Support.)

 

Can anyone recommend the optimum settings for encoding in situations like this?

 

Increasingly I am finding that a re-encoded programme has dreadful picture quality: things like stepped outlines on high-contrast edges within the image, and sometimes a sort of vertical striping effect which is rather reminiscent of the original John Logie Baird Televisor, if anyone has ever seen what the pictures on those used to be like. (No, I'm not that old! There's an example on Wikipedia)

 

Now, I know the the non-standard GOP is used by the broadcasters to squeeze a bit more picture quality out of a low-bitrate channel. But the original recording looks much better than the one burned to DVD, with many fewer of the sort of artifacts that Toast seems to be introducing. I usually try to set the bit rates to be as high as possible while keeping the programme fitting on a DVD. Is this not a good strategy?

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anything at or above 5 mbps for an average bit rate should look good. If you only have about an hour of material you can go as high as 8 mbps for the average bit rate.

Interesting. The maximum bit rate Toast allows me to set is 9Mbit/s. I was under the impression (IIRC, from reading the Toast documentation) that there was no point in making the average more than half the maximum, which would suggest that an average bit rate of 4.5Mbit/s would be the most that you would expect to see any benefit from. Have I been misinformed, or misunderstood? Any recommendations for setting maximum bit rate vs average bit rate would be most welcome.

 

Since these are captured from Digital TV you might use the capture application (I know this works with EyeTV software) to export the captured video as elementary streams. Then drag the resulting .m2v to Toast (Toast will match it with the audio stream). Sometimes this results in a better result.

I am using EyeTV. I can certainly give this a try.

 

You may also be able to avoid the need for re-encoding even though there is an issue with some GOPs.

The particular recording I am struggling with at the moment has a maximum GOP of 12 (according to the ProjectX utility) so shouldn't be a problem. I don't actually understand why Toast insists on re-encoding it and I have raised that question with Roxio. I am considering setting the re-encoding option to "Never" just to see what happens.

 

You've given me some ideas to try anyway, many thanks!

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Try turning on Half-Pel.

 

Other than that, the problem may be due to Toast's MPEG encoder rescaling the resolution to 720x480 (if this is NTSC). If you are using an EyeTV Hybrid or similar device to capture standard definition digital video streams to your Mac you may notice that many of those streams have a lower resolution. The quality of the encoder seems to make up for this. But Toast must rescale the image.

 

Out of curiosity you might try exporting one of the videos to DV to see how it looks when rescaled and not very compressed. If that looks okay use the DV file in Toast for encoding to video DVD. I don't know if this will look any better.

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Try turning on Half-Pel.

Half-PEL is on. It doesn't seem to make any difference.

 

Other than that, the problem may be due to Toast's MPEG encoder rescaling the resolution to 720x480 (if this is NTSC). If you are using an EyeTV Hybrid or similar device to capture standard definition digital video streams to your Mac you may notice that many of those streams have a lower resolution. The quality of the encoder seems to make up for this. But Toast must rescale the image.

Hmm, don't think so. I'm using PAL. The source video is 576x544 progressive scan. That shouldn't need upscaling, should it?

 

Out of curiosity you might try exporting one of the videos to DV to see how it looks when rescaled and not very compressed. If that looks okay use the DV file in Toast for encoding to video DVD. I don't know if this will look any better.

I can try but it might take a while on a G4 iMac... :)

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Hmm, don't think so. I'm using PAL. The source video is 576x544 progressive scan. That shouldn't need upscaling, should it?

Toast will rescale it to 720x576 when doing the MPEG 2 encoding. Still, I'm surprised you're seeing any effect from this. As for optimum settings anything at or above 5 mbps for an average bit rate should look good. If you only have about an hour of material you can go as high as 8 mbps for the average bit rate.

 

I don't have any experience with your type of source files so I can't say whether this is something entirely due to Toast's MPEG 2 encoder or may be due to something else.

 

Since these are captured from Digital TV you might use the capture application (I know this works with EyeTV software) to export the captured video as elementary streams. Then drag the resulting .m2v to Toast (Toast will match it with the audio stream). Sometimes this results in a better result. You may also be able to avoid the need for re-encoding even though there is an issue with some GOPs.

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