MJPEG to DiVX?

[Enrico Ng]

I've got two questions about DiVX?

Is it a good idea to convert MJPEG to DiVX, I thought I read somewhere that this wasnt good practice.

also, I have some DiVX movies and I dont understand how they encode them. for example, I have the Matrix, its 578MB, 640x304 (at 23.97fps for somereason) and two hours.
when I encode my own videos (704x480@29.97) I have to raise the data rate to 2000 to get decent video that isnt choppy and grainy and the size ends up twice as big.

my matrix video is on average 72kb/sec my own turns out around 162kb/sec.
matrix is pretty much crystal clear, but mine is still alittle grainy.
is there another way to encode in DiVX.

[Sciascia]

I don't know too much about DiVX (I believe it is just the Microsoft MPEG4 codec with encoding enabled), but I do know that anytime you encode from one from of cmpression to another, you are going to get some artifacting. It is just an inherent trait in "compresion". Anytime you use comression, you are eliminationg "unneeded" info, then the next compressor has less data to work with. I would assume that the other video you speak of was captured directly to DiVX, since the quality is so good. I know that an MPEG4 file size is about a 10th of an MJPEG when directly captured. I also think that the 23.97 fps is the standard for film and some encoders (I believe BBMPEG) use it for their MPEG2 encoding. That would help to explain the file size and also make it easier to capture directly to 640x480 using software compression (given a screaming proc and HD array).

[Railie]

This is not a good idea to convert MJPEG to DiVX(or other MPEG). Much better is capturing to YUY2 or RGB. Good loseless codec for capturing is HuffYUV.

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Sorry for my poor ENGLISH

[Enrico Ng]

oh, this kinda sucks.
I CAN capture YUV or RGB up to 704x480, but then I can only get about 15min before my Hd is filled.
I also CAN capture MJPEG, but then it isnt as good when going to DiVX
I also CAN capture RGB or YUV at 352x480 and encode to DiVX directly, but I cant at 704x480 with out dropping tons of frames.
I guess I just need tons of HD space or settle for a lower quality

[gibverse]

Enrico,
First off, MJPEG->DivX will always have really poor results.

If you have a fast enough CPU, you may be able to capture in realtime to divx, and not need to worry about hard disk issues. On my PII-400 I can do 352x240 at 30fps in realtime usually with no problem. But I really suggest you don't try it, it really puts a load on my box, and crashes are frequent.

And don't forget to adjust the bitrate in the Divx codec properties. That can help reduce file size. I found that capturing with VirtualDub/AviIO is much better than Ulead for Divx as well.

Hope that helps,
John

[Dr Mordrid]

Now you know why I have that 120 gig RAID stuffed into my box

Dr. Mordrid

[Enrico Ng]

so I guess the question is which is better?

352x240@29.97 RGB to DiVX realtime
or
704x480@29.97 MJPEG to 352x240 DiVX

[Dr Mordrid]

RGB or YUY2 to 352x240 realtime would seem the most logical to me. Then you're not transcoding from MJPeg to DivX.

Dr. Mordrid

[Enrico Ng]

Is going from MJPEG to DiVX really worse that 352x480 instead of 704x480->352x480

I just want to know how much of a difference there is between MJPEG and RGB or YUY

eventhough capturing at 704x480 and going down to 352x240 will make it clearer, will it be clearer than captureing using RGB instead of MJPEG and going to DiVX.
740z480MJPEG->352x240DiVX
or
352x240RGB->352x240DiVX

[This message has been edited by Enrico Ng (edited 30 June 2000).]

[Dr Mordrid]

Video editing 101: the fewer format conversions the better. Raw video to DivX would fit this. U pick if RGB or YUY2 looks better to you.

Dr. Mordrid

[Enrico Ng]

oh, I figured 704x480 has 4 times more "info" that 352x240, but I didnt know MJPEG->DiVX would make more of a diff.