Is the "lossless" FFV1 codec a fake? (IMPORTANT)

[Stears555]

Hello Guys!

Do you think that FFV1 "lossless" video codec is a real lossless video codec? I have serious doubts.

At first I used Xmedia recode (and later other 3 transcoders) to transform AVCHD MTS (progressive segmneted frame) camcorder files into FFV1 MKV format. I tried 4:2:0 planar 12bpp and all avaiable other higher FFv1 options. They had the same results ((

The png photos were taken by Potplayer from the video-frame: 810 th.
The original camcorder file (179 M.byte only) is located here: http://dictaphone.atw.hu/00097.MTS

Photos:
Seach the difference in the red square! (please, download and enlarge them in a photo viewer application)

Original MTS file: (frame: 810)
http://dictaphone.atw.hu/mts.png

The FFV1 file: (frame 810)
http://dictaphone.atw.hu/ffv1.png


I red an article, which proposed the unecessary color palette conversion as the cause of quality losses. But it is not beliveable: http://forum.doom9.org/archive/index.php/t-72709.html

Have you got any idea or suggestion about this "lossless" quality problem? The huffyuv didn't produced that quality problem.

Thank you for your reply!

[poisondeathray]

yes FFV1 itself is 100% definitely lossless in the same colorspace/model, but you might have some other problems - eg. maybe problem with xmediarecode (it's implementation of FFV1, or preprocessing of the video) , or problem with method of capturing screenshots with potplayer

Your screenshots show too much loss of detail in the shadows. You probably inadvertently used wrong lossy codec or one of the other problems above

[jagabo]

I agree. This is a codec (decoding the original video), handling, or filter issue, not an FFV1 issue.

I opened your MTS PNG file in VirtualDub and saved as FFV1 YV12 with

 ImageSource("1.png", start=0, end=10).ConvertToYV12()

Then I opened that image again and the FFV1 YV12 AVI file with:

v1=ImageSource("1.png", start=0, end=10).ConvertToYV12()
v2=AviSource("1.avi")
sub = v1.subtract(v2) 
substrong = sub.levels(112,1,144,0,255) 
StackVertical(StackHorizontal(v1.subtitle("png"),v2.subtitle("ffv1")),StackHorizontal(sub.subtitle("Difference"),substrong.subtitle("Difference amplified 8x")))

This script subtracts one video from the other and shows the differences and the differences amplified by 8x. You can see that there are no differences, even with 8x amplification:



Those flat gray expanses at the bottom left and right indicate the two videos are identical.

Then I compared your two PNG files using the same technique.

v1=ImageSource("1.png", start=0, end=10).ConvertToYV12()
v2=ImageSource("2.png", start=0, end=10).ConvertToYV12()
sub = v1.subtract(v2) 
substrong = sub.levels(112,1,144,0,255) 
StackVertical(StackHorizontal(v1.subtitle("png"),v2.subtitle("ffv1")),StackHorizontal(sub.subtitle("Difference"),substrong.subtitle("Difference amplified 8x")))

Here are the differences amplified by 8x (just the lower right quadrant):

[Stears555]

Ok, but what is the same colospace? (I know 4:2:0) AVCHD is YV12, but what is the perfect 4:2:0 PLANAR in FFV1 conversion? 12bit/sec? (12bpp) AVCHD is also a 12bpp video, isn't it?

[jagabo]

YV12 is 4:2:0 planar, 12 bit/pixel. AVC is usually 4:2:0 12 bit/pixel but can be other formats. Also keep in mind that the format used internally is not necessarily the same thing the decoder provides to the program requesting frames.

[Stears555]

YV12 is 4:2:0 planar, 12 bit/pixel. AVC is usually 4:2:0 12 bit/pixel but can be other formats. Also keep in mind that the format used internally is not necessarily the same thing the decoder provides to the program requesting frames.

Do you think that most transcoders are wrong? Forexample the Xmedia recode?

[jagabo]

I don't know what Xmedia Recode is doing. But the sample image you posted indicates something is screwing up your FFV1 encodings. And what you're seeing is far worse than a colorspace conversion.

[jagabo]

I used VirtualDub to convert your MTS file to AVI with FFV1, then remuxed the FFV1 video into an MKV with mmg. Here's a portion from the area of your screen caps. On my computer it looks like your original mts.png image, not the ffv1.png.