What's best for low bitrate - MPEG1 or MPEG2?

[slolsby]

I have some low quality VHS material that I wish to burn to DVD, but I need to be able to get about 8 hours worth on one disc. For this amount of data, the encoding rate is only going to be around 1000-1100kbs/s, so, given I am using a picture size of 352x288 (the source is PAL), which is better for this sort of encoding - MPEG1 or MPEG2? I've done a few short tests using CBR, and the MPEG1 looks marginally better, but there's not much in it. At these low bitrates, is there any advantage to using VBR?

Thanks

[oddyseus]

Mpeg1 is the best regarding low bitrates. Mpeg2 encoders show their potentials at much higher bitrates. Encode a vhs material at 352x288 and 1150 kbs and it would be much much better in quality than mpeg2.

At 1150kbs (vcd video bitrate) there is no need for vbr, actually I don't recall if vcd accepts vbr at all. Most probably the bitrate would stick to the max all the time.

[bb]

I guess this "MPEG-1 is better than MPEG-2 for lower bitrates" is nothing but a myth. Proof: MPEG-2 is nothing but a superset of MPEG-1.

If someone really wants to create a VCD nowadays (why should you do that?), you need to use MPEG-1, and CBR audio, as it is fixed in the standard.

But slolsby wasn't talking about VCD, but DVD. 352x288 is a DVD compliant resolution for PAL DVDs. Regarding the bitrate distribution VBR is superior to CBR at the same average bitrate. Set a low min. bitrate like 300 kbps, and don't go too high with the max. bitrate - maybe 2500 kbps. The average bitrate is what you calculate according to the lenght of the material you are going to encode. Using a good encoder like TMPGEnc or CCE in conjunction with multipass (2-pass only for TMPGEnc) you should get reasonable results.

bb

[oddyseus]

I respectfully disagree here bb.

Fitting 8 hours of video at 192kbs audio gives u average bitrate of video max 1080kbs without considering muxing overhead. A bitrate that is lower than vcd's standard of 1150.

So at this low bitrate, video is much more efficiently encoded with mpeg1 and cbr than it is with mpeg2 (cbr or vbr).

[JoeShrubbery]

How so oddyseus?
If mpeg2 is a superset of mpeg1 (as mpeg4 is a superset of mpeg2) then mpeg2 has all the compression techniques and more than mpeg1 available to it. I believe the mpeg1 encoders easily available are better tuned out of the box for lower bitrates, but with the right tweaking (say, by using a quantization matrix tuned for lower bitrates) mpeg2 should be just as good if not better in those situations. The problem is, of course, most mpeg2 encoders are tuned for high bitrate situations out of the box, and depending on your encoder you might not have the flexibility to tweak it enough away from the defaults. Ultimately, in order to see whether mpeg1 or mpeg2 is gonna give you better results, you have to test it yourself and come to your own conclusion based on the software at hand and your own knowhow concerning tweakable settings. Just make sure you're playback platform can play your resulting content fine before spending hours on end encoding all this stuff if you play around somewhat :'>

[Sulik]

MPEG-1 is more efficient than MPEG2 at low bitrates, and there is a simple reason for it: MPEG-2 has more header information (more overhead) in the frame (sequence_display_extension, picture_display_extension, etc).
At high bitrates, this overhead is small and doesn't make much difference, but at low bitrates (<1.5Mbps), it starts showing up.

However, the difference is quite small unless you go to really low bitrates (<500Kbps), where every extra bit per second can make a difference.

[Richard Iredale]

Quoting from the "Bible" (Jim Taylor's 'DVD Demystified', page 521):

"If you want to pack a large amount of video on a disk, don't try to encode to MPEG2 under 2Mbps. Use MPEG1 between 1 and 1.86Mbps; it will look better. You could also use "half D1" resolution....Before encoding the video, use heavy digital video noise reduction....

He goes on to give a few more tricks to use when using such low bitrates. I have not tried such low bitrates; it would be interesting to compare MPEG1 to MPEG2 at these levels.