AQA - "conservative" w\ Dqant "I frames" good combo for low bitrate 1080p?

[Furiousflea]

Hi there as title, I'm just getting to grips with Expression Encoder 2 and with the right settings VC1 isn't half bad except it can take a long time for the encodes. Anyway, I've been doing a few rips of my HD DVDs and have some quite good results at around 8mbit for 1080p sources (1920x800 when black bars cropped).

I hadn't tried encoding with Adaptive Quantization on until yesterday and I found the results very good even though I only set the "good" preset in Expression Encoder. The only problem was that I think as a result of AQA being set on (conservative mode used) I noticed that when there were large areas of black\dark that banding\sligh blocking was visible. I was wondering if it would be a good idea to use AQA conservative mode with Dqant set to "I frames" to combat this....Or am I barking up the wrong tree?

I intend to do some 720p encodes also of films about 3 hours long using these settings. I know that using the "better" preset might be the ideal option, as when I used that before I didn't get any banding\slight blocking on similar source\bitrate but turning on AQA\Dqant has a much lower penalty in encoding time.

This is for clean video sources with little grain to be seen...

Just curious on opinions on this, Ben Waggoner said in a previous thread that Dqant "I frames" should only really be used for CGI but maybe with AQA on for lower bit rates (<10mbit for 1080p for example) it might be a good idea?

Many thanks for any advice on this :) Rob

[benwaggoner]

For most film/video content at lower bitrates, I-Frame DQuant isn't a good fit. The EEv2 implementation is very big-hungry, reducing the bits available to other frames and higher detail parts of I-frames. That could be the source of your blocking/banding

Conservative Adaptive Deadzone is gnerally safe to use; it often helps and only very rarely hurts.

Overlap should also be on if you're seeing any blocking.

Is this 1-pass CBR or 2-pass VBR? If 1-pass CBR, make sure you have Scene Change Detection on as well.

[Furiousflea]

Thanks Mr Waggoner.

So...

Adaptive Deadzone - Conservative - good nearly always
Dqant - Not good except for very high bitrates

Overlap - I'm unsure of this one...

I thought this would only really be of use for very low bitrates like in a couple of threads where the nutters are trying to squeeze every ounce of juice out of a codec for low bitrate test samples at 720p\1mbit encodes...

Would this still have a place in 1080p encodes at around 6-7mbit? I'm abit unsure, could this possibly save blocking but give me a generally blurrier image or doesn't it work like that. I would have thought it would be more appropriate for extremly low bit rate stuff but not so useful on 1080p encodes....

Correct me if I'm wrong, I don't mind a slight blurring instead of blocking, obviously that's nicer on the eyese for scenes where blocking would normally happen in high motion, just need to know if it will be applied throughout the encode thus causing blurring throoughtout where it isn't an issue.

I suppose I'm asking if it is working like a general purpose filter or an "intelligent" optimisation?

Thsnks for your help with all my elementary quesions. :o

[benwaggoner]

Adaptive Deadzone - Conservative - good nearly always
Correct.

Dqant - Not good except for very high bitrates
For film/video. It can be useful for animation, particularly I-frame DQuant for low-motion animation or graphics where the very high quality I-frame gets a whole lot of references forward.

Overlap - I'm unsure of this one...

I thought this would only really be of use for very low bitrates like in a couple of threads where the nutters are trying to squeeze every ounce of juice out of a codec for low bitrate test samples at 720p\1mbit encodes...

Would this still have a place in 1080p encodes at around 6-7mbit? I'm abit unsure, could this possibly save blocking but give me a generally blurrier image or doesn't it work like that. I would have thought it would be more appropriate for extremly low bit rate stuff but not so useful on 1080p encodes....

Correct me if I'm wrong, I don't mind a slight blurring instead of blocking, obviously that's nicer on the eyese for scenes where blocking would normally happen in high motion, just need to know if it will be applied throughout the encode thus causing blurring throoughtout where it isn't an issue.

I suppose I'm asking if it is working like a general purpose filter or an "intelligent" optimisation?

Well, you should give it a shot yourself with your own content. 6-8 Mbps generally is helped by Overlap. Generally overlap is helpful whenever you're bitrate contrainted more than resolution constrained; net detail retention is better at a littler higher resoution with overlap on than at a little lower resolution with it off. So, you'll generally have it off until you've got a high enough bitrate with your content and frame size that you're not seeing blocking.

[benwaggoner]

Adaptive Deadzone - Conservative - good nearly always
Correct.

Dqant - Not good except for very high bitrates
For film/video. It can be useful for animation, particularly I-frame DQuant for low-motion animation or graphics where the very high quality I-frame gets a whole lot of references forward.

Overlap - I'm unsure of this one...

I thought this would only really be of use for very low bitrates like in a couple of threads where the nutters are trying to squeeze every ounce of juice out of a codec for low bitrate test samples at 720p\1mbit encodes...

Would this still have a place in 1080p encodes at around 6-7mbit? I'm abit unsure, could this possibly save blocking but give me a generally blurrier image or doesn't it work like that. I would have thought it would be more appropriate for extremly low bit rate stuff but not so useful on 1080p encodes....

Correct me if I'm wrong, I don't mind a slight blurring instead of blocking, obviously that's nicer on the eyese for scenes where blocking would normally happen in high motion, just need to know if it will be applied throughout the encode thus causing blurring throoughtout where it isn't an issue.

I suppose I'm asking if it is working like a general purpose filter or an "intelligent" optimisation?

Well, you should give it a shot yourself with your own content. 6-8 Mbps generally is helped by Overlap. Generally overlap is helpful whenever you're bitrate contrainted more than resolution constrained; net detail retention is better at a littler higher resoution with overlap on than at a little lower resolution with it off. So, you'll generally have it off until you've got a high enough bitrate with your content and frame size that you're not seeing blocking.

[Furiousflea]

That's pretty much what I was hoping, thanks for explaining it to me...

No more questions from me for a while :o

Cheers for your time :thanks: