Pushing the mpeg-2 envelope

farss wrote on 5/26/2005, 3:23 AM
Assuming my video contains only stills with only straight cuts just how low can one push the bitrate, I'm assuming one could use a very long GOP with an I frame only at the start of a new still.
Thing is I don't think the MC encoder is smart enough to let me pull this off. I suppose I could encode each still to a separate file and stitch it all together but that might get a bit tedious.
Also I'd probably want to use mp3 audio which DVDA will not let me do but I seem to recall reading is within the DVD spec.
I'm trying to get say 10 hours of audio with a few stills onto a DVD that'll play in a DVD player.
Anyone know if this is doable?
Bob.

Comments

Chienworks wrote on 5/26/2005, 4:27 AM
I wish the MPEG encoder would allow arbitrary frame rates. I do this sort of thing with WMV and get absolutely miniscule files by choosing a frame rate of something like 0.25 (four seconds per frame) and bitrates in the 40Kbps range. That gives the encoder 20Kbytes for each frame which results in a pretty sharp picture. Sadly, the Main Concept encoder only allows 23.976 to 30.000 and a minimum bitrate of 192Kbps. I remember testing some other cheap NLE years ago and being able to pick any frame rate and bitrates as low as 20Kbps for MPEG. I would think that most DVD players would handle this sort of thing and simply duplicate the current frame 29.97 (or 25, or whatever) times per second until the next media frame arrives.

Does anyone have any experience with alternate MPEG encoders that allow more flexibility?
farss wrote on 5/26/2005, 5:19 AM
I wasn't thinking of dropping the frame rate, I suspect that might be quite a strain for the DVD player / TV. I've been able to fit over 3 hours of video onto a DVD at 3 MB.sec with very little loss of quality. But that was well shot with a 2/3" camera, not even a cut. Only time things looked nasty was during the fade ups and downs at the ends.

So I figure if I can that low with motion I should be able to go to an average of 0.5Mb/sec but still a high peak rate to handle the cuts if I'm only handling still stills.

The other bridge I'm going to have to cross is mastering DL, sigh...

Bob.
apit34356 wrote on 5/26/2005, 6:26 AM
Farss, have you tried to encode the fade in/outs as a small file,(high bit rate), then merge them together using any mpeg editor or just use tmpgenc.
Chienworks wrote on 5/26/2005, 7:27 AM
On doing some quick calculations i figure that 10 hours of AC3 audio at the default 192Kbps would only need about 840MB. This leaves about 3.5 or so GB available for video and that should allow an average bitrate of 0.8Mbps. You could probably get away with 3Mbps peaks. There may be a little artifacting when the image changes, but hopefully it will be minimal. A very short crossfade may help mask it, but then that would also demand more bits. It's probably worth a few DVD-RW experiments to see how it looks.

Dual layer would let you use about 1.8Mbps and that should look spiffy.
farss wrote on 5/26/2005, 8:07 AM
It was a football match, not worth the effort!
apit34356 wrote on 5/26/2005, 10:04 AM
farss, "It was a football match, not worth the effort!" i thought those were fighting in the sports world of "soccer/football".
cacher wrote on 5/26/2005, 2:45 PM
Before I bought my DVD burner I used to do a lot of VCD slideshows. The quality was astounding, since (believe it or not) a VCD can display a 704x480 still image. Using this method I could cram in excess of 1000 image stills onto a VCD. I don't know if it will work the same on a DVD but maybe I can give it a try on the weekend.
Here's the way I used to do it: http://www.vcdeasy.org/modules.php?name=_Guides&id=SimpleStills