x264 and suggested bitrate for DVD encoding

[Selur]

@hello_hello: do you know an decoder which has problems with mod2 ? (I only enforce mod4 for interlaced 4:2:0 content.)

[hello_hello]

@hello_hello: do you know an decoder which has problems with mod2 ? (I only enforce mod4 for interlaced 4:2:0 content.)

To be honest, no.
I kind of remember experiencing a mod2 oddness at some stage (long time ago) when playing video using this PC. The video would be filled out with a green bar or the last row of pixels would be repeated, but as you asked, I had a bit of a play to see if I could duplicate it again and couldn't. I'm still using the same video card but probably different drivers, although I dragged out an old pre-LAV version of MPC-HC (as that's what I would have been using) and mod2 played fine no matter what I did.

So aside from that one playback issue which maybe I imagined, there's DirectShow not always playing nice with mod2 widths, which in the end is the only reason I'm still a little cautious about it, and I think that's just a Windows API limitation and nothing which is a cause for worry in the real world. I've never had a problem playing mod2 h264 video using other devices.

Mind you even the DirectShow thing is confusing me now. I created a little video with a resolution of 1218x720 for testing and opened it with a DirectShow script in MPC-HC and it displayed perfectly. I tried the same thing with a 854x480 video and the result was the pic below. Is the mod2 problem resolution dependant? I'll have to play around with that some more at some stage, but it won't be for a few days.



Well here you go.... I managed to find one combination which produced some oddness with mod2. ffdshow's hardware decoder and the "system default" renderer for MPC-HC. Windows XP. So maybe I wasn't imagining it. It's like the edge of the video is being stretched to mod8 or something. Hopefully it's not too hard to see. I haven't tested other mods yet (out of time today) but maybe it's a DXVA thing? Whatever the cause..... I've still not seen it happen outside of PC playback.

The same pic (cropped differently) and the brightness bumped up a little for the second one.

[hello_hello]

I don't get the fixation with square pixels. I did that with X-Vid because it never handled aspect ratios correctly and mostly not at all. But with x264 the is no need for square pixels. I try to stick to the original which is NEVER more than 720 wide.

No fixation. There's a couple of standalone players in this house (a Bluray player and a media player in a TV) which ignore aspect ratios in MKV/MP4s, so rather than worry about playback problems, I resize to square pixels. Before then I used anamorphic encoding too.

I use Megui with anamorphic settings just like the original has though I do crop to the image. Nothing is lost that way. Nothing is added. I try to avoid resizing as that is an unneeded change. I have thought about no cropping as well but I wasn't satisfied with the results the last time I played around with it.

Try encoding a DVD anamorphically, then again by stretching the width to the correct aspect ratio with Spline36. It's of course a little dependant on the sharpness of the player's resizer, but the square pixel encode tends to look a bit sharper and I don't mind that. At least for PAL when it's 720x576 v 1024x576. The effect may be less for NTSC as there's less resizing.

[hello_hello]

For "standard" I meant "16:9" and "2,35:1". I know you want me to convince at any cost to resize "up" my videos but I don't like that solution.

I'm just not sure why. Resizing up tends to retain more picture detail than resizing down. Naturally it requires more bitrate for a given quality though.

And about the aspect ratio, honestly, I do not think worth doing a religion war for a pixel, also because the theme of this thread would be the bitrate.

Oh well..... the info you need to resize correctly is there, but you're free to resize however you like.

[Selur]

Resizing up tends to retain more picture detail than resizing down.

Resizing down you destroy infos, resizing up you normally doesn't. + then a lot depends on the resizer&postprocessing of your playback equipment.
Friend of mine always smoothed his content a bit too much, because the smoother content triggered some 'auto enhance magic' on his tv, until I visited him and disabled the enhancement on the tv. (first he was pissed since his old encoding didn't look as well as they did before, but he noticed that on all other devices his new encodes (with adjusted settings) looked way better -> especially tv really can screw with the viewing experience)

About the mod2 thing: you are right old dxva hardware decoders might not like it (some require mod8 and really old need mod16 and even older only work properly with some specific resolutions)

[jagabo]

Nevermind, I misread a post.

[Marco Bux]

No fixation. There's a couple of standalone players in this house (a Bluray player and a media player in a TV) which ignore aspect ratios in MKV/MP4s, so rather than worry about playback problems, I resize to square pixels. Before then I used anamorphic encoding too.

Thanks hello_hello,
you answered to my question before I did it
And you made me save a lot of test.

[Marco Bux]

Hi, guys!

About the resizing I would like to add a detail so as to clarify my point of view. Is little more than just an empirical finding...

My main target device is a full HD TV.

When you play a non full HD video in a HD TV it gets always resized up. So, a 720x304 (square pixel) video becomes 1920x810, more or less. Regardless of who makes the resizing operation (TV or player) it's a one-step job.

If you resize up an anamorphic video to preserve the original vertical size using square pixel you must stretch the horizontal size. For instance, a 2,35:1 video obtained from any anamorphic PAL DVD, once cropped can have about 428 horizontal lines, which multiplied by 2,35 makes more or less... mod4 (428 x 2,35) = 1004 vertical lines. In a full HD TV, a video so obtained is further resized to fit the 1920 horizontal resolution.

The risk is that the sum of these two operations can degrade the quality of the movie more then a single resizing job, despite the related video has a lower vertical resolution.

That's why, in my own experience, a 720x304 video seems to have at least the same quality than the same video with a "higher but stretched" resolution (and a higher bitrate, obviously).

How about?

[poisondeathray]

If you resize up an anamorphic video to preserve the original vertical size using square pixel you must stretch the horizontal size. For instance, a 2,35:1 video obtained from any anamorphic PAL DVD, once cropped can have about 428 horizontal lines, which multiplied by 2,35 makes more or less... mod4 (428 x 2,35) = 1004 vertical lines. In a full HD TV, a video so obtained is further resized to fit the 1920 horizontal resolution.

The risk is that the sum of these two operations can degrade the quality of the movie more then a single resizing job, despite the related video has a lower vertical resolution.

That's why, in my own experience, a 720x304 video seems to have at least the same quality than the same video with a "higher but stretched" resolution (and a higher bitrate, obviously).

How about?

Scaling down will always yield lower quality, except in the scenario of inadequate/low bitrates .

Loss of ~40% vertical resolution will be more important than resizing twice . And what makes you think it's actually scaled twice?

It's easy to test and prove

[jagabo]

The risk is that the sum of these two operations can degrade the quality of the movie more then a single resizing job, despite the related video has a lower vertical resolution.

That's not the way it usually works. Most players that support non-square-pixel video resize to the target frame size in a single step. The source is decompressed to a frame buffer that's the size of the video then the graphics renderer upscales to the targe size. All the players I have do that. So it's your resizing to square pixel resolution first that is causing two scaling operations.

You can easily verify this using a test pattern of alternating, single pixel thick, black and white lines. The Belle Nuit test pattern has patches with such lines. An anamorphic encoding will be displayed on the HDTV as obvious alternating black and white lines. Downscaling or upscaling by a small amount to square pixel resolution before encoding screws up the lines. Then the TV upscales those screwed up lines screwing them up even more.

Convert the attached 720x480 16:9 anamorphic video to square pixel. Then compare the two with full screen playback.

[hello_hello]

About the mod2 thing: you are right old dxva hardware decoders might not like it (some require mod8 and really old need mod16 and even older only work properly with some specific resolutions)

I'm still not sure it's a hardware decoder issue as such, because it doesn't happen with every renderer. Decoding with ffdshow's DXVA decoder each time.....

I choose the system default renderer in MPC-HC's options and the last row of pixels is repeated as per my previous pic. MPC-HC's File/Properties menu shows Video Size: 864x480 (AR 427:240). Keep in mind it's really 854x480 with square pixels.
Switch to the overlay mixer and I get a black bar down one side. MPC-HC now reports Video Size: 864x484
Switch to VMR9 and we're back to Video Size 854x480 and it displays as it should.

As a quick test I found an old version of MPC-HC (pre LAV filters) which supports DXVA on XP and it's exhibiting the same oddness, so I guess it's not ffdshow's fault. It's over my head...

As is the DirectShow thing..... why would some mod2 video display fine and some not so fine?

[ndjamena]

@hello_hello: do you know an decoder which has problems with mod2 ? (I only enforce mod4 for interlaced 4:2:0 content.)

I'm currently encoding Astro Boy with a resolution of 698x572 (MOD2 x MOD4) and VLC is adding a green bar on the right edge as I play it. As far as I'm aware VLC relies solely on internal codecs so I'm not sure why there would be a problem.

(If I switch to Windows GDI output the green bar goes black)

[Selur]

As is the DirectShow thing..... why would some mod2 video display fine and some not so fine?

Some of the older DirectShow Filters are really picky when it comes to mod2, but ffdshow should normally work fine. Renderfilters also are sometime picky regarding mod. (Never really bothered looking further into it, since all my systems play fine using madvr.)

[ndjamena]

Nevermind. Switching to OpenGL rendering fixed it.

[hello_hello]

Some of the older DirectShow Filters are really picky when it comes to mod2, but ffdshow should normally work fine. Renderfilters also are sometime picky regarding mod. (Never really bothered looking further into it, since all my systems play fine using madvr.)

I think I'll just try to forget about it and go back to a newer renderer myself, although that's the reason I still have a little mod2 width paranoia. Aside from the PC (Windows), I've never had a mod2 playback problem I can recall, and no problem with mod4, mod8 or mod16 at all.

Nevermind. Switching to OpenGL rendering fixed it.

You did make me feel better though..... knowing it's not just me.

[Marco Bux]

Friend of mine always smoothed his content a bit too much, because the smoother content triggered some 'auto enhance magic' on his tv, until I visited him and disabled the enhancement on the tv. (first he was pissed since his old encoding didn't look as well as they did before, but he noticed that on all other devices his new encodes (with adjusted settings) looked way better -> especially tv really can screw with the viewing experience)

In some cases I noticed an excessive smoothing, expecially when CRF18 returns a bitrate <= 1200 Kbps. It seems it not depends on the resolution because it happens only with some movie.

I use AviDemux 2.6.8.v2. Is there some setting I can use to reduce smoothing in these cases?

Thanks!

[Selur]

@Marco Bux: If your bit rate in x264 seems to low for the content it's normally due to the content being really dark. (the bit rate info doesn't say much without frame resolution and frame rate ) Changing adaptive quantization and psychovisual settings or using lower values for dead zone normally should help with that.

[jagabo]

Try using --aq-mode=2 --aq-strength=1.8. Adjust the latter to 1.5 to 2.0 to get what you want.

http://mewiki.project357.com/wiki/X264_Settings#aq-mode

Or lowering qcomp may help.

http://mewiki.project357.com/wiki/X264_Settings#qcomp