AMV size

The Wired Knight · Post by **The Wired Knight** » Thu Oct 03, 2002 7:23 pm

WTF???!!! I just rendered my AMV to see how it was going at 720x480 and it's at perfect quality but the file size is only 82 megs. I'm encoding in Mpeg 2 with NTSC quality and wav sound compression. What the hell is going on? Why is the file size so low?

Zarxrax · Post by **Zarxrax** » Thu Oct 03, 2002 7:26 pm

Wow, thats really interesting. I had no idea that multiple colorspace conversions could degrade the image like that. But I'm with RadicalEd, I really wouldn't need to do more than one colorspace conversion. Anyways, could you explain why that happens? The way I always sort of understood it was that in yuy2 mode, it used 1 quarter resolution for the chominace data, so basically you were geting 1 out of ever block of 4 chrominance pixels. Thus, all 4 of the pixels chominance in that block would be the same. Now if you converted that to rgb, since all 4 are the same, it would simply still copy them all the same, exactly like the yuy2 vid looked. Now if you were to convert that back to yuy2, it chooses the one pixel again, and converts the other 3 so they are the same... but since they are already the same then nothing would happen. Is my idea of this flawed? (Well I guess it must be, so rather, where is it flawed?)

RadicalEd0 · Post by **RadicalEd0** » Thu Oct 03, 2002 7:28 pm

......
how long is the video? because if its 4 minutes and you're using uncompressed wav that means you've got exactly 1388 kbps video bitrate using mpeg-2 at 720 x 480 resolution. Which should look a little bit like utter crap. er.. what resolution wav and how long is the video?

RadicalEd0 · Post by **RadicalEd0** » Thu Oct 03, 2002 7:36 pm

@zarxrax
well it works out like this.. chrominace is stored at 1/2 the res of luminace. When the conversion to rgb occurs, all the chrominace/luminace data is essentially lost, and when it is re-compressed, it re-samples it at 1/2, which would theoretically look like 1/4th compared to the original. Thus, essentially, the loss and bleeding gets exponentially worse every time you convert from rgb back to yuv. Thats a rough explanation to say the least.

The Wired Knight · Post by **The Wired Knight** » Thu Oct 03, 2002 7:39 pm

48 kHz wav file. And the video is 3:36 in length. and the quality is pretty damn good, I can send it to you if you want but I just don't get it. The quality is amazing and the file size is pretty much nill.

RadicalEd0 · Post by **RadicalEd0** » Thu Oct 03, 2002 7:45 pm

48 khz 2 channel uncompressed wav
3:36
your video bitrate should be exactly 1574 kbps
thats 4.66 bpp
uh...
erm...
there must not be a lot of action in the video

The Wired Knight · Post by **The Wired Knight** » Thu Oct 03, 2002 8:40 pm

Well granted there are a number of still shots but they only last for maybe five frames a piece. Included with teh wav of the audio track I've also got some of the series original audio in there. The video is pretty fast moving and hass 200+ scenes used in it. I can't figure out what in blazes is going on with this file size. I can send it to you if you want and you can tell me. Either way, whatever is going on, I'm not complaining.

Hitori · Post by **Hitori** » Thu Oct 03, 2002 9:36 pm

The Wired Knight - What kind of codec are you using?

I use the vob files in premiere now. Also edited in and exported with HuffYUV in YUY2 at 720x480.

RadicalEd0 · Post by **RadicalEd0** » Thu Oct 03, 2002 9:44 pm

hes using mpeg-2
I'll gladly download it if you can host it somewhere or wait I'll IM you and see if we can connect n you could send it to me

RadicalEd0 · Post by **RadicalEd0** » Thu Oct 03, 2002 9:47 pm

just kidding your not on aim.. uh, well try to IM me it when you read this