Proper MPEG2 conversion bitrate / resolution for old footage

[Granddad]

Hello,

I would be very grateful for your help with a confusing issue.

I have a Sony Digital8 camcorder, and I was shooting DV for a number of years. I usually transfer the footage to a PC, split the resulting AVI file into clips, then encode them to MPEG2 using TMPGEnc at a constant bit rate of 8000 kbps and author a DVD. The video from one Sony D8 tape (60 min in SP mode) more than fits onto a standard single-layer DVD.

Now I am finally ready to undertake a long-due project and start converting my old analog videos to the digital format, in order to show my grandchildren what their parents were like . These archive videos were taken in Hi8 format by my previous-generation Sony Hi8 camcorder. I verified that these tapes play nicely in my Digital8 unit (as they should), which generates DV that I upload to the computer. Thus, analog->digital conversion is handled by the camcorder automatically, and I am left with an about 24.6 Gb AVI file of DV for a standard Sony 120-min Hi8 tape. I would like to preserve this footage with the minimum loss of quality.

My question is: how to choose an MPEG2 conversion bitrate for the footage that was thusly digitized from a Hi8 tape? If I stick to the 8000 kbps CBR, the whole set of resulting files will obviously not fit on a single DVD. - And for a variety of reasons, including my desire to have one-to-one correspondence between archival tape numbers and future DVD numbers, I would much prefer to have them together on one disk - if it does not involve loss of quality. The calculated bitrate to encode 120 min on a 4.37 Gb DVD would be around 5600 kbps.

I reason that since my Hi8 original had lower resolution than a DV format (something like 510 horizontal lines??), the process of converting Hi8 to DV just extrapolated the data in each frame to achieve DV format size, so if I choose the 8000 kbps CBR as the highest possible rate I would just preserve conversion artefacts, while going down to some (which?) rate would just bring a resolution back to quality similar to the Hi8 original.

The analogy I am making is the following: If someone had blown up a digital image 4x by extrapolating one pixel in both horizontal and vertical directions, then reducing a size again would bring quality on par with the original.

Or should I just encode the AVI clips to MPEG2 in "half-resolution" (352x480), instead of 720x480 ?

Is my thinking wrong? I was not able to find any reliable data on the subject. My goal is to maintain the best quality without artificially improving what cannot become better that the source.

Thanks in advance!

[cowgoo]

You should check out http://www.digitalfaq.com , it has alot of info that you'll find useful

[GMaq]

Grandad,
I am probably not qualified to answer any of your questions on the DV side of things but I have done quite a bit of Hi-8 to MPEG-2 direct capture, If you go the 352x480 route you will not lose any noticeable quality from your source, At 4000kbps (352x480)you are getting the same bits per pixel allocation as you do at 8000kbps at 720x480. My only concern is this, I have done many hours of captures using 352x480 as long as it stays on a DVD it looks terrific. In the last year or so I've been converting a lot of this footage to MPEG-4 for iPod, I have noticed that there is a large difference in sharpness in the converted files whose source was 720x480 vs. the 352x480. So even if at the present time you aren't concerned about other formats, perhaps your Grandchildren will be. I think a good usable middle suggestion would be 720x480@ 6500kbpsVBR with MP2 Audio @ 192kbps, It may not quite fit in all cases depending on the source footage but it will still give very good quality @720x480 and preserve that quality for other formats. Just a suggestion, best of luck

[redwudz]

I may have missed it if you mentioned what format you were using for DVD audio. If it's PCM from DV, you can shrink that quite a bit by using AC3 or Mpeg 1, layer 2 audio. I use ffmpeggui to convert to AC3 as it's more DVD compatible, and that helps give me more room on the DVD for a higher video bitrate.

The second thought is: Try a representative 5 - 10 minute clip and encode that at different settings and bitrates. That will tell you what you need and what you will be happy with. To complete the comparisons, burn them to a DVD RW and test them out on your standalone DVD player and TV, the bigger the better, to see how they look compared to your older DV to DVD encodes at 8000kbps. You may find that a slightly lower bitrate or even 1/2 D1 will work fine.