Do Movie Maker or Virtualdub re-encode DV-AVI when saving? Quality concern?

[sdineen]

I see after editing out my dead space from my imported home movies (ends of tapes), either program "saves" the DV-AVI again. I just had a dumb question if this was impacting quality? I believe DV-AVI is what they call "loss-less" correct, and that is not the case?

[poisondeathray]

only if used in "direct stream copy mode". This means no effects, etc...

[sdineen]

Rocking! I'll make sure to tap that setting. I really appreciate it!

[sdineen]

Okay, and as a follow up, it has to Save (e.g. dub) what's edited. It has to run the entire file again. I guess I was hoping wondering if it couldn't just cut off the tails/deadspace, save, and that's it, without seemingly reprocessing the remaining video.

[edDV]

The older versions of WMM converted 720x480 YCbCr DV into 640x480 square pixel RGB whenever fitering or effects were employed. Then it was converted back to 720x480 YCbCr when exported to "DV-AVI". This process is lossy. I haven't tested recent versions of WMM to see if this is still happening.

Virtualdub will convert everything to RGB on import regardless of filtering. With AVISynth, you can maintain YCbCr and use YCbCr filters.

Programs like Vegas or Premiere will maintain the 720x480 raster but also matrix to RGB during effects or filtering. Premiere Pro can be set to a YCrCr process path usually in uncompressed real time modes. Default is RGB.

PS: I should say that when in DV or HDV project modes, Premiere and Vegas do not process when just doing cuts. They simply copy source frames to output.

[Gavino]

I was hoping wondering if it couldn't just cut off the tails/deadspace, save, and that's it, without seemingly reprocessing the remaining video.

That's exactly what VirtualDub will do, if you select the Direct Stream Copy option (for both video and audio).

[sdineen]

edDV, when you say "Virtualdub will convert everything to RGB on import regardless of filtering. With AVISynth, you can maintain YCbCr and use YCbCr filters. " I assume you mean if I'm importing that way? I used WinDV to get the files initially transferred. If I should use AVISynth, please let me know. Again, although it would be nice to edit, short term I'm just trying to cut off 1:30 of dead space (and 18GB) off of some of these files/tapes.

Gavino, when you say exactly what it should do, it still seems to be processing (virtual dub that is) when I "Save as AVI" because when I just cut out 1:30 of my last tape, and made sure to tag both A/V for direct stream (and missed this first time, thank you), it still is processing with dialog box stating "processing at 100-120 frames per second (varies), estimated time 5 minutes." Is Save as AVI not the correct choice? Is this just how it works, and it's not actually re-processing (with Loss) the avi?

[Gavino]

... it still is processing with dialog box stating "processing at 100-120 frames per second (varies), estimated time 5 minutes." Is Save as AVI not the correct choice? Is this just how it works, and it's not actually re-processing (with Loss) the avi?

You are doing it correctly. Bear in mind that it still has to read through the entire input file, parsing its contents to know which frames to leave out, and write the corresponding output file - that takes time. But it does not need to do any other processing (such as decompression or recompression), saving as much time as possible, and is a lossless process (apart from the bits you deleted, of course ).

[jagabo]

Gavino is correct. In Direct Stream Copy Mode VirtualDub does not convert to RGB. It doesn't even decompress the frames. It just passes compressed frames from the source to the destination. The status box message is telling you fast it's dealing with the video.

[sdineen]

That is terrific news and just what I needed. Thank you both! I've skinned down 60GB of blank vid already!