Is HuffyUV a truly "lossless" codec?

Kearly · Post by **Kearly** » Tue Oct 12, 2004 11:42 pm

HuffyUV is considered a lossless codec. In my many AMV exports from premiere, I've consistently exported with HuffyUV. I then take my HuffyUV file, which supposedly is perfect quality, and process it further in Virtual dub (I use XVID compression).

But even before processing in Virtualdub, I've looked at my HuffyUV files. The quality looks good, theres no splotchyness or major video problems. However, the video seems a little dark, and the colors somehow don't quite jump off the screen quite the same way.

Maybe its just my imagination, but I have never truly "felt" that HuffyUV has given me a perfect looking video. I would use "uncompressed" before sending the processing to Vdub, I have the Memory. Unfortunately, uncompressed is not an available export option.

Zarxrax · Post by **Zarxrax** » Tue Oct 12, 2004 11:51 pm

Huffyuv is lossless, but you may be noticing lost color data due to RGB<=>YUV conversions. DVDs are natively YV12, but footage has to be edited in RGB... then it must be converted back to YV12 yet again for xvid.

AMVfreak · Post by **AMVfreak** » Tue Oct 12, 2004 11:55 pm

I would use "uncompressed" before sending the processing to Vdub, I have the Memory. Unfortunately, uncompressed is not an available export option.

Premiere can export uncompressed

Kearly · Post by **Kearly** » Wed Oct 13, 2004 2:37 am

Zarxrax wrote:Huffyuv is lossless, but you may be noticing lost color data due to RGB<=>YUV conversions. DVDs are natively YV12, but footage has to be edited in RGB... then it must be converted back to YV12 yet again for xvid.

Thank you Zarxrax.

It sounds like the color is lost when the YV12 is converted to RGB in avisynth. Is the loss of color recovered from moving back to YV12? Or is it lost no matter what?

Actually, my big question is, how do I convert back to YV12 at all? Is it done in the "virtual dub stage" or do I have to make the YV12 conversion in premiere, after editing but before exporting in HuffyUV?

I did not see any color conversion options in XVID or in virtualdub's filters, but I did see something like it in HuffyUV: a "convert to YUY2" option. Its not YV12, but its as close as I've been able to figure out so far.

How do you execute the conversion? And does the conversion recover the lost color?

AbsoluteDestiny · Post by **AbsoluteDestiny** » Wed Oct 13, 2004 2:57 am

Xvid will convert anything it gets to YV12. It's not optional, it's mandatory.

There is no way to regain the information that you have lost with a colourspace conversion.

AbsoluteDestiny · Post by **AbsoluteDestiny** » Wed Oct 13, 2004 3:01 am

Oh also, remember that when you are watching a DVD etc you are watching it being played back in direct show, probably using hardware assisted decompression and gamma control due to the overlay layer. This will give a different representation of the brightness and colours of the source than looking at the Video for Windows image with huffyuv.

Most of the colorspace conversion losses are not actually noticable, I'm guessing you are noticing the difference in the original image versus the way the image is presented when played via directshow on your video card.

Scintilla · Post by **Scintilla** » Wed Oct 13, 2004 3:18 am

Kearly wrote:It sounds like the color is lost when the YV12 is converted to RGB in avisynth.

Or in Premiere itself, if you don't throw any conversions into your script.

Kearly wrote:Is the loss of color recovered from moving back to YV12?

As AD said, no.

Kearly wrote:I did not see any color conversion options in XVID or in virtualdub's filters, but I did see something like it in HuffyUV: a "convert to YUY2" option. Its not YV12, but its as close as I've been able to figure out so far.

How do you execute the conversion? And does the conversion recover the lost color?

"Convert to YUY2" just means that the HuffYUV file you save will be in YUY2 instead of RGB, which means that exporting from Premiere in that mode will be very slightly lossy. Personally, I do it anyway, because I enjoy the smaller filesizes, and all the postprocessing filters I use work in YUV space anyway. (Though nowadays some, like deen, require YV12, which means another conversion... but oh well.)

kearlywi · Post by **kearlywi** » Wed Oct 13, 2004 2:45 pm

Thanks AD, scintilla.

I guess I'm a little dissapointed in the answer, but then again its good to know I wasn't making a huge mistake when I was processing my previous AMV's.