Blocks in dark areas

[santosx]

i'm converting downloaded movies to play them on a smartphone. the problem is that the display has an extreme contrast ratio (super amuled) and the blocking in dark areas becomes very well visible. turning down the gamma on conversion (xmedia recode) does help a bit, but not completely.

on brighter parts, like sky, walls etc, this blocking does not happen.

can i somehow set the conversion options to treat dark parts just like bright parts? im mostly using mpeg-4, xvid or h264

[jagabo]

I suspect the posterization artifacts are in your source. Turning down the black level may help. AviSynth has filters like gradfun2db and blockbuster that are designed these type or problems.

[santosx]

i also have it on BD rips of 9 gigs or more. gonna have a look at that prog, thanks.

[jagabo]

Maybe the problem is the black level of your monitor, not the files themselves.

[santosx]

real black is deep black on the monitor (no grey or shiny like on normal monitors when they are set to bright), but dark shades of whatever color that seem almost black on a normal monitor are not black on the amuled unlessthey realy are.

even on lowest brightness setting you see things that you normaly wouldnt on a regular screen. not a problem if there isnt any blocks (super amuled screen is deepest black and strongest colors existing atm afaik), but as the conversion at 1 to 1.5k bitrates tends to make stuff blocky in the (normaly invisible) dark areas, its not so great. i dont want to encode everything at 2.5k+ bitrates just so the dark parts dont become blocky. other stuff with plain surfaces with different shades of colors dont become blocky either when they arent dark.

so i suspected there must be some sort of setting controlling at which brightness level the compression algorythm becomes more aggressive. i dont want higher compression in darker areas if possible.

[jagabo]

You can try using no b frames. I think you're doing that already though (from another post).

[santosx]

yep, bframes arent supported, thats the main reason i need to convert most things.

[poisondeathray]

i also have it on BD rips of 9 gigs or more

Do you mean you used BD rip as a source, or it's in the BD rip that you used as a source? If it's already in your source before you encode, it's hard to fix . Filters (like gradfun2dbmod) that attempt to improve add noise and dithering which require lots of bitrate - something you said you didn't want to do

Setting lower deadzones (again expensive in bitrate terms to encode) , disable trellis, disable mb-tree (or increase qcomp), enabling weightp will all help, but they will require redistributing bitrate from other parts of the movie to improve the dark areas

yep, bframes arent supported, thats the main reason i need to convert most things.

I would bet money that you would actually get better results with b-frames if you were using x264; your earlier comments suggested that increasing bitrate improved it. This suggests your bitrate or settings (restrictions required by your device) aren't adequate enough i.e. compression isn't good enough

[jagabo]

Looks like he's using CBR too.

[poisondeathray]

Is that your ESP talking jagabo ? How do you know what he used ?

[santosx]

1)the 9 gigs BD rips are flawless, conversion adds the problem. you mean inter/intra luma quantization deadzones? inter is 21, and intra 11

what is qcomp? chroma qp offset maybe? its 0

enabling weightp is that "weighted pred. p-fames"? its set to smart analysis

what would be reasonable values? (im using xmedia recode btw)

2) i cant use b-frames cause they get skipped on the device. higher bitrates do help, but the rest of the image does not realy become better. raising the bitrate from 1k or so to 2.5k just because of the dark areas seems overkill.

[jagabo]

Is that your ESP talking jagabo ? How do you know what he used ?

A sample he posted in another thread.

[santosx]

the sample is from a about 1.4 gig source. a 2hour movie.

if you do look at it, there is a blur at 9 seconds into the clip. im trying to get rid of it but i cant (not without using another codec then h264 that is).

http://rapidshare.com/files/424691798/blurr1.avi

[poisondeathray]

1)the 9 gigs BD rips are flawless, conversion adds the problem. you mean inter/intra luma quantization deadzones? inter is 21, and intra 11

yes, reducing them will help, but if you use the same bitrate, the other sections will deteriorate.

what is qcomp? chroma qp offset maybe? its 0

qcomp is quantizer curve compression factor , not chroma qp offset

enabling weightp is that "weighted pred. p-fames"? its set to smart analysis

that's fine

what would be reasonable values? (im using xmedia recode btw)

I'm not familiar with xmedia recode , but if it is using x264 the settings should be the same.

mbtree has the most negative impact on p-frames before an I with fades, disabling it will help at the expense of lowering quality on other parts. If you don't want to disable it, increasing qcomp will weaken the mbtree effect

I cannot suggest exact settings , because every source is different. I can only give suggestions for you to try out

You can look at more explanation of the settings here
http://mewiki.project357.com/wiki/X264_Settings

You probably are limited to using lower quality profiles by your device

[santosx]

thanks i will try the deadzones first, if that substracts bitrate from the other areas it sounds like its exactly what i need.

whats your favorite encoder btw (or most recommended by you)? is xmedia most likely good or should i get better results with something else?

[poisondeathray]

I think xmediarecode is just a GUI . It's probably using x264 as the back end when you are encoding h264

what is your device and what program are you using to encode ?

[santosx]

You probably are limited to using lower quality profiles by your device

not sure what profiles you refer to, the highest quality i tried so far was mpeg-4 iso with about 6k bitrate. runs fine and looks great.

is it "Profile: main/baseline/high" what you mean? i got that set to main.

[santosx]

the device is samsung wave gt s8500.

the prog i use is xmedia recode 2.2.7.2. it has tons of presets for mobile devices, but when not choosing one of those presets a lot of other options become availabe. i use avi mostly now because the phone only supports ac3 5.1 and not aac5.1. and it does not like mp4 with ac3 5.1, but it works fine with avi containing ac3 5.1 (ac3 5.1 in order to use the virtual 5.1 feature of the phone).

[poisondeathray]

I'm referring to x264 settings. Most mobile devices cannot handle the higher quality settings/features (not enough CPU power). One example, you cannot use b-frames for your device, so that can drastically impair compression. I looked at your sample, and it has low vbv-bufsize values and it's essentially CBR. With such a low buffer (70), it cannot adapt to changing scenes, explosions etc...

It's a very inefficient encode = you need a higher bitrate for a give level of "quality" to compensate. If your device was compatible with better settings, you could use lower bitrate and still get better quality . Your only option might be to use high bitrate to compensate - I have no idea what your phone supports so I can't help you much

[santosx]

s8500 is the model (samsung wave gt s8500).

low vbv buffsize values? i did not set those, i left them at default settings. is that a hint that the default values in xmedia arent very good?

cbr as in constant bitrate? i never use that. maybe the sample i uploaded was a 2 pass, but it shouldnt be cbr. could it be that my codecs are messed up somehow? i tried tons of encoders including format factory. i uninstalled them again though and installed cccp in the hope it would reset things.

PS what prog do you use to see eg the buffsize values. i use mediainfo which doesnt seem to give that much in detail info.

[santosx]

PS, in the sample you downloaded, at about 9 seconds playtime, the image becomes blurry for a couple frames. i have been trying to fix that for hours but i always appears at the same spot. only on h264 though. the source doesnt have it.

and "ahhhhh", now i get it, the buffsize values are so small that they actualy degrade the variable bitrate to a more less constant bitrate?

[poisondeathray]

Maybe you should post about that in the other thread, they are slightly different topics. Jagabo addressed it there, and I agree with his observation

I don't know what vbv values are compatible with your phone. But it's important. Your encode is basically a CBR encode. There is hardly variation in the bitrate distribution (the explosion should get a lot, but it doesn't so it looks like crap). It's a very inefficient encode (wasted bitrate)

[santosx]

what would be a standard setting for the buffer?buffersize 64, maximum bitrate 64, initial buffer 0.9, bitrate variance 1.0, quantizer comression 0.6, lookahead 40 are the default settings on that tab. i dont have a tool that shows me this information on downloaded movies, so i would have to make a blind guess.

maybe 256,256 for the first 2 values?

edit: the answer is on https://forum.videohelp.com/threads/326984-strange-blurr?p=2024887#post2024887

getting complex now