Does real time RENDERING affect my final ENCODING output??

[JackoFluent]

I'm trying to burn the highest quality 30 min DVDs (so no issue on disk space) using Final Cut Pro (recently converted from Windows and loving it) and DVD Studio, and the results I get are reasonably good (wildlife documentary/travel stuff).

However, I'm trying to squeeze the very highest quality output from the uncompressed DV tapes I've captured, and I've now run into a brain teaser.

Basically I'm confused about the difference between RENDERING during the editing process to see my edits and effects in real time during the editing process, and how that may or may not affect my final output files during the ENCODING process.

Are these totally separate functions, and my final quality only rests on the encoding settings, which should convert my edited uncompressed AVI/DV to MPEG-2 files, OR can I mess up the quality of the uncopressed DV by rendering filters/transitions/titles etc etc during editing??

I have burned a few minutes of DVD footage to test, and it seems that clips that have had a high degree of filters and effects applied (and then rendered during editing to see results) are of a poorer quality after encoding than the un'effected' raw footage. I'm using the highest bitrates available under the DVD Studio encoder (after exporting through Apple's Compressor) - so that is a constant for both types of clip (ones that basically were unrendered vs ones that were rendered several times)

Anyone care to help me with words of wisdom on this? ie does rendering during editing affect output quality regardless of encoding?

Many thanks, Nick

[edDV]

...

Basically I'm confused about the difference between RENDERING during the editing process to see my edits and effects in real time during the editing process, and how that may or may not affect my final output files during the ENCODING process.

Are these totally separate functions, and my final quality only rests on the encoding settings, which should convert my edited uncompressed AVI/DV to MPEG-2 files, OR can I mess up the quality of the uncopressed DV by rendering filters/transitions/titles etc etc during editing??....

Anyone care to help me with words of wisdom on this? ie does rendering during editing affect output quality regardless of encoding?

Many thanks, Nick

I'll give it a try.

Processing the DV input with FCP before encoding will affect the quality vs a simple MPeg2 encode, yes. Proper procedures will limit the quality compromises.

Process 1 (FCP processing + encoding)

DV is decompressed to YUV and is either processed in YUV (e.g. levels filters ) or converted to RGB for other types of processing. YUV to RGB to YUV conversion can have loss. Processing algorithms (filters) may each have quality tradeoffs. When the filtering and effects processes are done rendering, everything is converted back to uncompressed YUV and passsed to the MPeg2 encoder. Improper technique may add a recompression to DV format only to have the encoder decompress again before encoding the MPeg2. PAL DV (4:2:0) has more recompression loss than NTSC DV (4:1:1).

Process 2 (simple encoding)

DV is decompressed to YUV and passed to the MPeg2 encoder.

I hope this addresses your question.

[JackoFluent]

OK we are getting somewhere down my path of enlightenment - thanks edDV! I suspected there were some pitfalls to avoid. So .. questions:

1) How do I force FCP to stay within YUV and not go through the intermediary of RGB?
2) What 'improper technniques' should I avoid so I don't go down a 'recompression to DV format' route?
3) I'm working in PAL which you suggest is more vulnerable - is there anyway around this? Or should I just be happy that PAL has intrinsically a slightly higher resolution (or doesn't that make a difference anyhow!?)
4) I think I understand that certain rendered effects/filters (eg brightness/contrast?) may reduce quality by removing data - rather than say RGB tweaks that might just substitute - BUT - is there any information source out there that lists filters and effects to avoid and those to employ in order not to compromise quality? Or maybe you have some additional suggestions?

Really appreciate your input on this. Cheers

[edDV]

OK we are getting somewhere down my path of enlightenment - thanks edDV! I suspected there were some pitfalls to avoid. So .. questions:

1) How do I force FCP to stay within YUV and not go through the intermediary of RGB?
2) What 'improper technniques' should I avoid so I don't go down a 'recompression to DV format' route?
3) I'm working in PAL which you suggest is more vulnerable - is there anyway around this? Or should I just be happy that PAL has intrinsically a slightly higher resolution (or doesn't that make a difference anyhow!?)
4) I think I understand that certain rendered effects/filters (eg brightness/contrast?) may reduce quality by removing data - rather than say RGB tweaks that might just substitute - BUT - is there any information source out there that lists filters and effects to avoid and those to employ in order not to compromise quality? Or maybe you have some additional suggestions?

Really appreciate your input on this. Cheers

Everything I said above was generic to all the mid-level DV based editing systems (e.g. FCP, AVID, Premiere Pro, Vegas, etc.). All these companies are less than forthcoming on internal processing details unless they are revealed during problem solving in advanced forums. For this reason you need to spend time in advanced dedicated forums and ask alot of questions like you are.

1) You must learn which filters use RGB. I can only guess for FCP
2) Usually if you use the internal MPeg2 encoder, or "frameserve" to another encoder, you avoid the additional recompression. If you save to a DV format file, you are recompressing but only if the image was processed.
3) PAL DV has multigeneration issues due to 4:2:0 rather than 4:1:1 chroma encoding. 4:2:0 chroma is reinterpolated each generation.
4) Only thing I can suggest is spend time in advanced FCP forums.

[JackoFluent]

4) Only thing I can suggest is spend time in advanced FCP forums.[/quote]

OK edDV, fair points - I'll try and find some more specialised forums (fora?) for FCP. Thanks for the initial ball-roll.

Meanwhile...if anyone within this VideoHelp.com forum has specific FCP domain knowledge in this complex area I'd be keen to hear from you (even a pointer to the best FCP discussion boards). Now ... back to Google Advanced Search .....