mpeg4 back to raw avi?

[mk_lai]

I have several videos that I captured into raw avi. Since the avi file sizes are so big, I decided to convert it to mpeg4 format using QuickTime Pro (for ease of emailing the videos) and then deleted the original avi files. However, several of my relatives indicated that they would like the files on either CD or DVD.

As such, I tried to convert the mpeg4 to VCD, SVCD, and DVD format but found that the quality of the videos to be very poor. For the videos that I still have the original avi, the quality was fine. I also used QuickTime Pro to convert the mpeg4 back to avi but the quality was only slightly better but not as good as the ones that I have the original avi.

My question is, is there a way to somehow improve the quality of the videos or a way to convert the mpeg4 back to the original avi format? That is, is mpeg4 considered a no-loss conversion?

Sorry for the long post. Thanks in advance for any assistance.

[edDV]

" That is, is mpeg4 considered a no-loss conversion? "

MPeg anything is a lossy conversion with MPeg4 (wmv, divx, xvid nero, apple, ...) being the highest compressed and hence most lossy.

Use MPeg4 where high compression is needed but keep the original if the material is important.

[mk_lai]

Dang. This is probably a redundant question but is there any way for me to improve the avi conversion? So that it is as close as possible to the original product.

If not, can you recommend some no-loss formats for future reference?

Thanks.

[celtic_druid]

The quality of MPEG4 can be pretty decent (high quality matrix, low fixed quant), just that Apples MPEG4 implimentation is crap for a start. But as said it will never be lossless.

Check out some lossless video codecs like huffyuv, VLBE, MILK, ffv1, snow, etc.

[edDV]

Describe your capture method and source for this "raw avi" (i.e. source, capture device, sample rate, etc.)

DV format, 13.5GB/hr makes a good general light compression archive format (4:1:1, 13.5 MHz sample rate, 720x480, 5 to 1 compression). Good enough for the broadcasters of the world for general use.

Better is DV50 27GB/hr (DVCPro50) 3 to 1 compression and 4:2:2

A bit better yet is 10Bit Digital Betacam tape 2 to 1 compression and 4:2:2

Lower is MPeg2 at 8Mbps for DVD ~ 15 to 1 compression

[spectroelectro]

You're almost certainly talking about Type 1 or Type 2 AVI, 720 x 480 at 3.5 megabytes/sec. That's the standard output from a digital camcorder or a typical video capture card.

If you want good quality results, you should work directly from your AVI file and ignore the MPEG-4. Alas, MPEG-4 generates video artifacts which look much uglier than MPEG-2. They also persist at much higher bitrates. Beyond a certain bitrate (for full D1, around 6000 kbits/sec) MPEG-2 becomes transparent and exhibits no visible artifacts. MPEG-4 typically exhibits annoying video compression artifacts even at very high bitrates, and the artifacts become downright ugly at low bitrates.

If you need to work from the MPEG-4, you're going to have do some serious video filtering to reduce the compression artifacts. That means smoothing and deblocking. First you'll have to convert the divx mpeg-4 file to a Type 1 or 2 DV file, which you can do with VirtualDub, and then you'll have to run smoothing and deblocking filters on the DV file and finally encode it into DVD format, which is easy enough to do with TMPGenc or Quenc or Canopus Procoder or CCE Express or Mainconcept MPEG-2 encoders.