strange blurr

[santosx]

at about 9 seconds into the clip, the scene suddenly becomes blurry for a couple frames. i tried default settings as well as playing around with the settings, but the blurr remains. the source doesnt have the blurr, it just appears after conversion. and it happens always at that same spot. its h264/avi, no bframes, cabac

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

one moment its fine, then a blur, and fine again (see clip above or pics below)


[Attachment 3824 - Click to enlarge]
[Attachment 3823 - Click to enlarge]

[jagabo]

It happens at an I frame.

[santosx]

thats good to know? all i know is there is i and p frames and one frame is a still image and the other contains the changes in regard to the previous frame or so iirc. what does it mean for me that the blur is in an iframe?

[jagabo]

What I think is happening: the frame has too much detail to encode at the requested bitrate so the I frame is being encoded with a high quantizer (low detail) to keep its bitrate down. Then over the next few P frames the quality is cleaned up. Maybe if you switch to variable bitrate encoding instead of constant bitrate.

[santosx]

i always leave it at variable bitrate. i also tried setting the bitrate a good bit higher then the source (1700 instead of 1400), but it had no effect

[poisondeathray]

What I think is happening: the frame has too much detail to encode at the requested bitrate so the I frame is being encoded with a high quantizer (low detail) to keep its bitrate down. Then over the next few P frames the quality is cleaned up. Maybe if you switch to variable bitrate encoding instead of constant bitrate.

I agree this is what's happening. The low quality I-frame is bitrate starved . The --vbv-bufsize of 70 is too low so there is no leeway to adjust either even if VBR rate control was used

It's also a "mandatory" I-frame , because this --keyint was set at 250 (It occurs at 250). If he didn't force a max gop interval this wouldn't happen (P frame would have been placed and used a previous P frame as reference to code the difference, instead of requiring to encode an entire new IDR frame)

Unfortunately, I don't know what settings are compatible or not with your phone

[santosx]

ah, damn, almost 2am here, i understand that the buffsize should be higher, the rest appears kind of chinese to me

64
64
0.9

are the default settings. what would make more sense?


i got open gop off, gop length 250, min gop length 25. i dont see a max gop, so i suspect the "gop length" is the culprit you talk about. how would i change it or even disable it maybe?

[poisondeathray]

ah, damn, almost 2am here, i understand that the buffsize should be higher, the rest appears kind of chinese to me

64
64
0.9

are the default settings. what would make more sense?


i got open gop off, gop length 250, min gop length 25. i dont see a max gop, so i suspect the "gop length" is the culprit you talk about. how would i change it or even disable it maybe?

The max GOP length is specified by "--keyint" . It will still place IDR frames when deemed necessary (like a scenechange)

I don't use xmedia recode, but I would use 2pass VBR , --keyint infinite , --vbv-maxrate 1750 --vbv-bufsize 1750 for starters . If b-frames were compatible for your device it would help immensely for quality at a given bitrate

But some of the changes you make might break compatibility with your device - that's why they have presets - to ensure compatibility.

[santosx]

i suppose --keyint infite would translate to " GOP length 0" in my gui?

great, i will run more tests tomorrow. i will start with gop 0 and your vbr settings for the blur, and then try the deadzones for the blocks in dark areas (and then the other things if its still not good enough).

thanks for all the help from both off you. going to sleep for now.

[poisondeathray]

i suppose --keyint infite would translate to " GOP length 0" in my gui?

I don't know... I gave you the command line syntax. I have no idea what that GUI does

It might be your device cannot load those buffer values, if those were the ones you were given for the preset ?

Anyways you can experiment, good luck