Into deep: 4:4:4, 10 bit, relevant for amvs?

[Bauzi]

Hey there,

I polish my digital video technique basics for an exam and I came across 10bit video signals and 4:2:2 and 4:4:4. They have their benefits, but are they relevant for amvs?

So 10bits instead of a 8bit color depth give me more detailed greyscales (I guess that's the biggest advantage for the human eye). That could be interessting if you plan to make an amv with a lot of b&w scenes. Can/do codecs like x.264 or XviD compress with a 10bit colour depth?

4:4:4 instead of 4:2:2 gives me better chroma values. That could be usefull for colour correction and chroma keying, but... heck do DVDs, Blurays or downloaded material even come with 4:4:4 ? Are there even sources that we get into our hands that have 4:4:4 ?

I hope you can make those things clear for me. Thanks in advice.

[Zarxrax]

Pretty much all distribution formats (DVD, blu-ray, x264) are 4:2:0 (chroma is sampled at 1/4 of its full resolution). 4:4:4 is pretty much just limited to your editing software.

Also, 10-bit video is not really available on DVDs or x264 or anything. It does give you a nice increase in color depth, but you can't output it to anything useful, unfortunately. However, that doesn't mean it can't be helpful to edit with it, because you have less rounding errors if you do.

[NeoQuixotic]

This is generally not really relevant to AMVs since we are starting out with 4:2:0 sources. You can get 4:2:2 and higher from very expensive video cameras or if the source was creative digitally to begin with. Also, many cameras output 4:2:2 from their HDMI and/or SDI/HD-SDI connection since it is the raw signal from the sensor before getting compressed into whatever codec the camera uses. By using a field recorder like the nanoFlash or Ki Pro, you can capture this higher quality signal. But this does us no good since we only have access to DVDs, Blu-rays, and web video, which all are 4:2:0. You can't really convert it back up, but working in 32-bit color modes in Vegas/Premiere/After Effects can help, mainly when adding effects. I know that Funimation gets many things on Digitial Betacam and HDCAM, which are capable of 4:2:2 and 10 bit. So unless you want to intercept shipments of raw material between studios or raid some studio, I wouldn't worry about it too much.

I recently listened to this podcast and they talked about chroma subsampling among other interesting things.
http://twit.tv/htg8

[Bauzi]

Thank you very much guys. I love usefull info =)

[Qyot27]

There are some test sequences available in RGB48 (like CrowdRun/ParkRun, which is distributed as an SGI sequence), which you could then convert to 16bpc 4:4:4, but the process to do so hasn't really been hammered out well enough yet. Kept giving me corrupted frames when I tried.

As far as I know, DVD and Blu-ray only support up to 8bpc, even though H.264 can use higher bpc values and colorspaces (although x264 hasn't implemented them yet; 4:2:2 was a SoC project, but I don't think it went too far). As far as 4:2:2 goes, I'm not sure if that's allowed per DVD and Blu-ray - although from the way it looks HCenc is be able to output 4:2:2, and eventually could do 4:4:4. Of course, HCenc is an MPEG-2 encoder, but if retaining the YUV colorspace is important to you, then that's better than not having it freely for H.264.

[Bauzi]

Does Lagarith and HuffYUV work in 4:2:0 too? Than I would switch to Pro Res 4222 for working.

[Qyot27]

Lagarith supports 4:2:0 (YV12) and 4:2:2 (YUY2). Standard HuffYUV supports 4:2:2 (YUY2) but not 4:2:0 (YV12) - to use YV12-mode HuffYUV you have to use ffvhuff, either through ffdshow's VFW interface, ffmpeg, or other libavcodec-based encoders (mencoder, Avidemux, VLC, etc.). Using YV12-mode and adaptive Huffman tables makes it fall much closer to Lagarith, filesize-wise, than it does standard HuffYUV, and it decodes a lot faster than either one of them.

FFV1, on the other hand, supports 4:4:4, 4:2:2, YV12/4:2:0, 4:1:1, 4:1:0, and RGB32 (which are all the ones listed in ffdshow's Configuration dialog; it may support even more colorspaces than that) - like ffvhuff, it's only available in libavcodec-based solutions. It gives similar size ratios as Lagarith, for reference. FFV1 also supports 16bpc, but I never got it to work right with the CrowdRun sequence, although that was last August/September - it may have gotten completely fixed by now. It may also have 10bpc and 12bpc support, but I'm not entirely sure on that point (nor do I know, if it does support them, if it works as well as the default 8bpc mode does). That thread seems to hint that it does.

[Bauzi]

I see. Thank you very much.

I have another question: You talk about YV12 mode in Lagarith. There is also the RGB mode. Can RGB even run in 4:2:2/4:4:4 ? I didn't got that answer out of my course.

[Qyot27]

4:2:2/4:4:4/etc refer strictly to YUV. 4:4:4 is essentially the YUV equivalent of RGB24, but that's not really a good comparison because the way YUV is handled is fundamentally different, so 4:2:2 and 4:2:0 don't - to my knowledge - have RGB-based analogs.

[a1ic3]

I would like to inform bauzi that the distribution format 4:2:0 is used by DVD. But I really wonder whether Blu-ray makes use of this. From my knowledge Blu-ray makes use of 4:2:2 and not 4:2:0. Regarding 10 bit video it is certainly superior to 8-bit because it will provide a much better picture quality. But the problem is that you cannot extract a 10-bit video on a DVD. If you try to extract then it will be extracted as an 8 bit and clarity will be less.