severe pixel smearing on credits only

[IHATETYAN]

I'm using gordian knot and XVID and the only part of the movie that is having problems is the credits I have them set to reduction rate of 10% and to be encoded in grey scale. they smear horribly (letters sticking and blending together as they scroll upward) and return to normal for a second or so and then start the whole smearing thing all over again. I didnt have the problem when I left the default credit reduction rate of 20% so I think thats the culprit. is this known bug or error and is there a way around it. or a reduction rate below 20% that works correctly.

using keopis's latest stable build

[mf]

Originally posted by IHATETYAN
I'm using gordian knot and XVID and the only part of the movie that is having problems is the credits I have them set to reduction rate of 10% and to be encoded in grey scale. they smear horribly (letters sticking and blending together as they scroll upward) and return to normal for a second or so and then start the whole smearing thing all over again. I didnt have the problem when I left the default credit reduction rate of 20% so I think thats the culprit. is this known bug or error and is there a way around it. or a reduction rate below 20% that works correctly.

using keopis's latest stable build
I think your problem (just guessing here) is that it's not 10% reduction rate, but 10% of total rate. Try 90% instead.

[IHATETYAN]

I know its 10% of total rate. thats where i want it to be. 90% would use too much bitrate. I'm trying to save it for main part of the movie.

[manono]

Hi-

is this known bug or error...

Neither. It's using half the bitrate of the default. If you don't like how 10% looks, then reset it to 20%. You're saving, what, 10 MB or so when using 10%? That's not enough to appreciably improve the main movie.

[mf]

Originally posted by IHATETYAN
I know its 10% of total rate. thats where i want it to be. 90% would use too much bitrate. I'm trying to save it for main part of the movie.
Well 10% of total rate is just going to show these kind of artifacts. This is XviD, not RV9.

[Danzel]

If you are using Trellis, then i recomend you disable it for your credits.

When I was compressing some credits to hit tiny sizes, i had trouble when trellis was enabled.

However it is possible you are trying to go too far.

Danzel.

[Koepi]

10% of bitrate doesn't mean it should be like 70 mb of 700 - it means that the credits get i.e. 90kbps while the main movie gets 900kbps. This is very seldom a bitrate to achieve. I recommend not to go below 30%, it's usually not getting any smaller than with quant31 %)

Regards
Koepi

[vijv]

i had the same problem at 20% when encoding lotr:ttt. The credits looked fine for a while but after a few minutes it completed blurred out. Sure it is not a bug?

[Prettz]

If the credits are just scrolling against a solid color background I'd say your best bet would be to encode them as a seperate two-pass clip with GMC enabled. I've done this for several movies and the result has always been *stunning* quality at obscenely small file sizes. So far it's worked like a charm for b&w scrolling credits with MPEG quant and even with color scrolling credits with H.263 quant.

edit: forgot, when I did b&w credits with MPEG quant, I turned motion search precision down to 5. This made them look very nice, where for some reason with a setting of 6 they looked bad.

[IHATETYAN]

Originally posted by Koepi
10% of bitrate doesn't mean it should be like 70 mb of 700 - it means that the credits get i.e. 90kbps while the main movie gets 900kbps. This is very seldom a bitrate to achieve. I recommend not to go below 30%, it's usually not getting any smaller than with quant31 %)

Regards
Koepi

but isnt the default value @ 20%????

i'm 2 lazy to split it up so I'll try @ 15

could the VHQ setting have something to do with this I until now never used anything above 2 but this time I tried 3??? just a thought

or maybe that i'm using ogg audio??

I'm new to this forum and only do straightforward encodes so i dont do custom matrices and stuff so I got no clue what trellis even is, someone clue me in please. i'd like to get a little more advanced.

[Danzel]

Your using Ogg Audio wouldnt be influencing this at all.

Using VHQ of 3 instead of 2 wouldnt cause this (afaik), it should look better infact ;)

Trellis RD is uh... well im not sure what it is, hopefully someone will come to my rescue and explain it.

Its selectable under the debug tab and makes my encodes look better :o, but when i encode my credits (which i do seperately) i disable trellis, as i have got some weird blocking and smudging when i encode credits at ultra-low bitrate while using it.

You are probally just (still) trying to squish your credits to much, but i guess only encoding them will tell.

Danzel.

[IHATETYAN]

it finally dawned on me...i took a look at the avi file b4 running it through ogg mux and it infact didnt smudge as much but did have some artifacts so ogg mux did seem to make it worse but I think you guys are right about the bitrate just being pushed 2 far and its introducing the artifacts. Some I'm gonna keep upping it til i hit a level with no or minimal artifacts trying to squeeze every bit possible into the main movie. I still wanna know what trellis does...anyone?

[Prettz]

Originally posted by IHATETYAN
it finally dawned on me...i took a look at the avi file b4 running it through ogg mux and it infact didnt smudge as much but did have some artifacts so ogg mux did seem to make it worse but I think you guys are right about the bitrate just being pushed 2 far and its introducing the artifacts. Some I'm gonna keep upping it til i hit a level with no or minimal artifacts trying to squeeze every bit possible into the main movie. I still wanna know what trellis does...anyone?
Trellis is a Rate-Distortion algorithm for when you are using H.263 quantization, and from what I understand it does something to the effect of removing very small unnoticeable details to save bits.

I would really like to know if my earlier suggestion of doing your credits in a seperate two-pass with GMC works for you.

[mf]

Originally posted by Prettz
Trellis is a Rate-Distortion algorithm for when you are using H.263 quantization, and from what I understand it does something to the effect of removing very small unnoticeable details to save bits.
But ONLY if the detail removing (dropping of DCT coefficients) will result in higher quality than just keeping them and scaling them down.



afaik

[BoNz1]

I haven't seen GMC deal with credits any better. What I do with them is a little the same as what you do though Prettz. I think it a lot better to just cut the credits and 2-pass them. I use a bilinearresize() and use about 2 or even 3 bframes and crank up the threshold to like 20 or 25 or so. Usually, I can get the credits down to about 300kbps or even less sometimes around 200kbps and it still looks good, hardly any artifacts even when using like 704x304 res. As you might imagine this saves a ton of bitrate if the credits are like 9 min or so like they sometimes are.

[Prettz]

Originally posted by BoNz1
I haven't seen GMC deal with credits any better. What I do with them is a little the same as what you do though Prettz. I think it a lot better to just cut the credits and 2-pass them. I use a bilinearresize() and use about 2 or even 3 bframes and crank up the threshold to like 20 or 25 or so. Usually, I can get the credits down to about 300kbps or even less sometimes around 200kbps and it still looks good, hardly any artifacts even when using like 704x304 res. As you might imagine this saves a ton of bitrate if the credits are like 9 min or so like they sometimes are.
You have to play around with other settings (like motion search precision in my case) in order to get it to look right. I was able to get 4 minutes of color credits at 640x272 down to 8MB (200-240kbps), but the catch is that it had NO artifacts. Honestly it looked just like the DVD source. The GMC cleans up all the artifacts so that there's no blocking and no trails left behind by the text. It's just so cool that I feel obligated to get everyone else to try it too :D

[mf]

Originally posted by Prettz
You have to play around with other settings (like motion search precision in my case) in order to get it to look right. I was able to get 4 minutes of color credits at 640x272 down to 8MB (200-240kbps), but the catch is that it had NO artifacts. Honestly it looked just like the DVD source. The GMC cleans up all the artifacts so that there's no blocking and no trails left behind by the text. It's just so cool that I feel obligated to get everyone else to try it too :D
Afaik sysKin once encoded matrix credits at sub-100kbps :D. The trick is to use lots of consecutive B-frames because the motion is so linear that even after something like 24 frames there is still picture to motion-reference from.

[Prettz]

Originally posted by mf
Afaik sysKin once encoded matrix credits at sub-100kbps :D. The trick is to use lots of consecutive B-frames because the motion is so linear that even after something like 24 frames there is still picture to motion-reference from.
That is rather impressive. How many consecutive b-frames did he use (is that 24 the number?), and did the results have many artifacts?

[IHATETYAN]

Originally posted by Prettz
Trellis is a Rate-Distortion algorithm for when you are using H.263 quantization, and from what I understand it does something to the effect of removing very small unnoticeable details to save bits.

I would really like to know if my earlier suggestion of doing your credits in a seperate two-pass with GMC works for you.

I'm gonna try it out tomorrow after I upgrade my processors.

[mikeson]

mf is right. sysKin once wrote outstanding suggestion about credits encoding. The trick was to use 5 b-frames and treshold of 90. Try it and you'll be surprised.