I-only capture using ATI MMC 7.7

[videopete]

I am performing an I-frame only capture using MMC7.7 VBR 15MB/sec (max), 98 motion quality. I do this because my computer cannot handle proper capture to MPEG-2 using the proper GOP structure - long story. I then use TMPGEnc 2.5.x to properly encode it (and reduce the filesize I might add) using 8.5MB/sec GOP structure 1-3-2 etc. I personally do not see any quality loss in the final product compared to the source.

My question is: During the encode phase only, is 8.5Mb a proper video bitrate to use for my purpose (capturing Hi8mm home videos) for archival purposes. If I can, I would like to use a lower bitrate WITHOUT LOSING ANY VIDEO QUALITY so that I can fit more on a std DVD-R (I currently can fit approx. 80minutes of video the way I'm doing it now). I read in another post that anything over 4.5Mb/sec is a waste of space for my 352x480 resolution that I'm capturing/encoding in. If this is true, and I can truly use 4.5Mb, then I would surely almost double my capacity!!

Thanks.

[videopete]

Can anyone point me in the right direction here???
I can't believe that no one has an answer to this?

[gadgetguy]

Check this site for info on bitrates.
http://www.mediachance.com/dvdlab/tutorial/bitrate.html
What will work best will depend on too many factors for a direct answer.

[ronnylov]

If you use 2-pass VBR you can probably decrease the average bitrate to 6 mbit/s without any big notacibly loss of quality (if you encode to 704x480 resolution). What you can try to get better quality is to use PicVideo MJPEG codec at your initial capture because I think you can get better quality with that compared to I-frame only MPEG2. Use a quality setting of 18 or better in picvideo mjpeg. You may also get better results with 704x480 resolution because Hi8 can be better than 352x480 resolution.

With 352x480 resolution I think you can drop the average bitrate to 4 mbit/s and still get very good quality for archival purpose.

I suggest you do some testing with different settings and make your own decistion of what to use.

Personally for archival purpose I capture analogue home video video in huffyuv format (704x576 resolution 25 fps PAL) and make one conversion to DVD encoded at 8 Mbit/s CBR video and PCM audio 48 kHz stereo. I make another conversion of the original huffyuv capture to DV-format and store it on DVD-R as avi files (20 minutes per disc). As backup I also store it on DV tape...

This way I can easier edit my captures in the future and reencode from a better format when new technologies arrives. The DVD copy is for handy viewing on my standalone DVD-player.

[videopete]

Thanks for your help - I will give these a try!

[videopete]

I did some further testing. It seems that if Hardware Accelleration is turned on to the MAX on the video card, the stuttering problem shows itself in the captured video.

When I decreased the hardware accelleration to the minimal level required to run the ATI MMC TV app - the stuttering seemed to disappear even at 15Mbit/sec video rate.

On another note, for some reason though, 4Mbit/sec mpeg2 capture at 352x480 res. produces an extremely poor quaility video for me when most guides suggest that no more than 4-5Mbit/sec is needed at this resolution??? Interesting? 8Mbit/sec mpeg2 capture at 352x480 seems to produce excellent results....not sure why the high video bit rate is needed in my case but it is working fine....I will do some more fine tuning to get the BEST settings for this card....

Thanks to all who responded for all your help.

[Sulik]

I-frame only captures require a MUCH higher bitrate than IBBP for the same level of quality (hence your doubling of the bitrate).

[videopete]

I should have explained myself more clearly.
When I performed my 4Mbit/sec video bitrate, I was not using I-frame only capture - I know I-frame only capture requires an extremely high bit rate...I was attempting 1-4-2 true MPEG2 capture which was giving me the terrible output....I need to go up to 8Mbit/sec at 352x480 using 1-4-2 gop structure to get decent results.