mjpeg to Divx5: why all these macroblocs? [Archive]

nalooti

28th June 2006, 16:22

Hi,

i'd really be grateful if someone can help me because these are my family's memories that are at risk!!!

My Canon digital photos camera (powershot s80) produces a very clean hi-res 1024x768 movie in 15fps, Mjpeg format. Files are huge but the quality is sublime on PC. I'd like to watch them on my standalone dvd player on TV screen but my player doesn't read hi-res (HD) and also it doesn't recognize Mjpeg, nor PCM audio (which is the original audio out of my camera).

So i decided to convert them all to Divx with mp3 audio...

And here comes my problem. I have many questions but the big one is why do i get big macroblocs whatever bitrate (i even tried 4Mbps Divx or 7Mbps Xvid!) i apply ?

I tried a commercial video converter (AVS) with very simple and straightforward GUI, doing two pass at 2000Kbps with a mono mp3 at 192Kbps. I resize with the Divx Pro 5.2 codec to 640x480. The result is a very degraded video (relative to the original mjpeg) no matter on PC or on my dvd player (which now at least can read them).

Then i tried VirtualDub to get a slighly better result with the same parameters but still with easily distinguishable macroblocs. The other problem with VirtualDub is the audio. It just can't find any mp3 or Lame mp3 driver. I searched on Internet and on doom9 for solutions. I installed LAME ACM, no way. Vdub doesn't propose me any bitrate unless i check "show all" at right and then it says compression not possible! So with virtual dub i can only get a Divx with the original PCM audio which is unreadable on my dvd player.

Even if i want to find a solution to my Vdub problem (because it is a very good freeware) my biggest concern is the quality and how to remove all these macroblocs ??? It seems like i'm missing a very big issue on Divx conversion but i searched throughout various sites and guides (digital/Divx digest, doom9, digitalFAQ, Nicky pages, etc.) and i found no big parameters that i could miss producing such a degraded video quality. They all explain different programs utilization without really focusing on codec's parameters.

I just don't understand how some guys can rip&convert DVDs to Divx with amazing quality!!! Maybe because the original is mpeg2 not mjpeg (does it matter ?), or maybe because it's not hi definition format ? Should i apply filters ? which one ?

thanks very much to help me
nalooti

Tentakulokans

28th June 2006, 17:45

nalooti

28th June 2006, 19:35

Hi nalooti

I don't have any experience with MJPEG so I'm afraid I can't help you about the video part of your problem.

But concerning the sound, if VDub doesn't display at once any choice in the audio compression formats list, that's probably because the original sound format is not compatible with the codec you choose.
To solve the problem, use the "conversion" entry in the VDub audio menu : you will then be able to change parameters of your audio source (sampling bitrate, precision and number of channels) and to find a format that your codec can handle.

Regards.

Hi Tentakulokans
thanks for taking your time to answer.

The original audio is PCM which is leaved as is by Vdub if i don't compress the audio. The problem is it is unreadable by my dvd player. However i agree, leaving it as is doesn't prove Vdub can or can't recognize it and if it can't , i understand that it can't compress it.
But, i touched nothing in "conversion", since it recognizes that it is mono and at 11024 Hz (case "no touch" already checked). Shoul i ask to convert at higher frequencies ?

More i really think Vdub can't find any mp3 encoders because when the case "show all format" is not checked it doesn't show any supported bitrate which is unusual. As i've read, one must not check that case; recognized codecs and available bitrate are shown without checking that box.

Regarding Video, i don't thing Mjpeg change anything. I think my problem is in Divx codec parameters, not the original format.

thanks
nalooti

nalooti

29th June 2006, 09:12

hi all,

i thought finding some video expert in this forum. My problem is simple and i think quite general for those having a digicam and taking movie with it and having to deal with mjpeg files.

Come on, please drop me a line or two

thanks
nalooti

GodofaGap

29th June 2006, 10:39

The original audio is PCM which is leaved as is by Vdub if i don't compress the audio. The problem is it is unreadable by my dvd player. However i agree, leaving it as is doesn't prove Vdub can or can't recognize it and if it can't , i understand that it can't compress it.
It is not about if VirtualDub can recognise it, but
mono and at 11024 Hz
is not a valid format for mp3 compression. Hence, Lame doesn't show any compression options unless you check "show all formats" (which you only should use to see what formats a compressor support, not to try bypass incompatibilities). Go to the audio conversion menu and resample to 22050 Hz (perhaps it will accept 11025 too, I don't know).

I think my problem is in Divx codec parameters, not the original format.
So don't you think it would be useful to tell us what settings you use?

Perhaps you could upload a sample clip (preferably of the source) to rapidshare or savefile.com so people might have a better idea what they are dealing with.

i thought finding some video expert in this forum. My problem is simple and i think quite general for those having a digicam and taking movie with it and having to deal with mjpeg files.
A little more patience and self-experimenting on your side would be appreciated. :)

nalooti

29th June 2006, 11:59

It is not about if VirtualDub can recognise it, but

is not a valid format for mp3 compression. Hence, Lame doesn't show any compression options unless you check "show all formats" (which you only should use to see what formats a compressor support, not to try bypass incompatibilities). Go to the audio conversion menu and resample to 22050 Hz (perhaps it will accept 11025 too, I don't know).

So don't you think it would be useful to tell us what settings you use?

Perhaps you could upload a sample clip (preferably of the source) to rapidshare or savefile.com so people might have a better idea what they are dealing with.

A little more patience and self-experimenting on your side would be appreciated. :)

Ok i'll try to resample to 22050 Hz and let you know the result. I'd grately appreciate if i'm not constrained to process audio and video separately since it takes so much time.

Regarding codec setting, frankly i don't set any parameter i don't know. All parameters are set to default. I do it in two pass at 2000kbps and resize to 640x480 in codec itself rather than in video tool (e.g. Vdub). The codec is in Home theater profile and i use standard compression. EVERYTHING else is untouched and by default!
I've read lots of guides on divx conversion. Some speak of divx4 which has more parameters to control but i think you agree with me that in Divx5.2 Pro there are far less control.

Regarding patience and self-experimenting on my side, again i agree with you that i'm in this forum since few days and i must be patient. But please believe me i'm working on this since few months and i did various tests with different tools and posted questions on various forums without any solution.
I could write two more pages explaining what did i do but i'm affraid people doesn't like and read long messages so i started with few and simple questions but willing to answer every question you have.
In the following days i'll prepare a sample short video clip with my canon s80 camera and hope to be able to share it with you.

Again thank you, this time for YOUR patience :)
regards
nalooti

Jacquers

29th June 2006, 15:27

Try the DivX 6 codec - it has made a couple of improvements over v 5. And if you need an easier, but still free tool, try Dr. DivX 2 0SS.

xyloy

29th June 2006, 18:46

If you do not want macroblocks, try a codec like XviD v1.2 (http://www.koepi.org/xvid.shtml) with a one passe constant quantizer encoding type(quantizer value=4).
http://membres.lycos.fr/xcomcmdr/XviD1(CQ).png
http://membres.lycos.fr/xcomcmdr/XviD2(Profile)(new).png
http://membres.lycos.fr/xcomcmdr/XviD3(ZoneOptions).png
http://membres.lycos.fr/xcomcmdr/XviD4(AdvancedOptions).png
For 15 FPS, 150 should be better for file-seeking issues instead of 250
http://membres.lycos.fr/xcomcmdr/XviD4(TrellisQuantization).png

or x264 (http://x264.nl/) with --crf 18 --ref 8 --mixed-refs --no-fast-pskip --bframes 3 --b-pyramid --b-rdo --bime --weightb --direct auto --subme 7 --trellis 2 --analyse all --8x8dct --me umh --progress --no-dct-decimate --no-psnr --output "C:\OutputVideoFile.mp4" "C:\AviSynthInputScript.avs" (thoses paths are only examples)

--crf is the one-pass constant quality mode. x264 should give you a smaller file than XviD. If not, try --crf 24 or 26. ;)

jggimi

29th June 2006, 19:20

nalooti, the original poster, wants to be able to play the output on his standalone player. A constant quality encoding will likely exceed the player's maximum bitrate.
DivX can do constant quality encoding, too. This thread is in the DivX Encoding forum, and recommendations to use other codecs are taken in the spirit given, per http://forum.doom9.org/announcement.php?f=56 which had expired, and is now renewed. ;)

BigDid

29th June 2006, 19:46

[... and recommendations to use other codecs are taken in the spirit given, per http://forum.doom9.org/announcement.php?f=56 which had expired, and is now renewed. ;)

Jggimi :goodpost:

This forum is just so huge :) , I remember having looked (overlooked) this sticky and I am glad to have a reminder on it.

Others stickys like this one could, for the benefit of all, be popped up once a while, run a contest between mods? :D

Did

nalooti

29th June 2006, 21:47

hi again and thanks to all for your time and patience; you'll need a little bit more to download my samples :)

please use the following link:

http://www.savefile.com/projects.php?pid=306760

or

http://www.savefile.com/projects/306760

you'll find two original mjpeg and the corresponding converted divx files (4 files in total).

originals are at 15fps, 1024x768, mjpeg video, PCM audio just out of my canon s80 digicam.

I converted them to 640x480 in order to view them on my standalone dvd player with mp3 mono at 192 Kbps audio.

Following are my codec parameters (for 2 converted files):
Divx certified Home Theater(for compatibility), 2000 kbps, standard compression, 2-pass (the 2nd time i override the 1st resulting file i.e. i don't change the file name when doing 2nd pass), resizing in the codec to 640x480 bilinear. These are all parameters i can control under this mode. And the 2 converted files are with the above parameters

I also tried slow compression in this mode with the same result.

Then i changed mode to a profile non guaranteed to play in Divx certified standalone dvd players. I tried GMC, Quarter Pixel and bidirectional encoding with almost the same results and macroblocks!
I always did it in 2 pass, never in 1 pass.
All other parameters remained untouched. I didn't post any of these results because there is no improvments.

Regarding the post suggesting Xvid, i must say that i already tested it in 2 pass as high as 7Mbps with the same macroblocks. Anyway, the difference between Divx and Xvid apart from free versus commercial angle, is just a question of taste IMHO. While here, i'm struggling with a huge mistake i still can't find.

But I'm sure with experts like you, i shouldn't be far from the real solution.

many thanks
nalooti

GodofaGap

30th June 2006, 09:25

nalooti

30th June 2006, 21:59

Sorry, but looking at your samples I can't say I see the horrible blocking you are talking about. For an encode at avg quant 9 this looks rather ok. In full screen mode it looks unsharp, but that's expected when downsizing to 640x480...

Perhaps you should do an constant q encode at q 3 or q 4 and see if it suits you better. I don't remember the DivX 5.2 interface that well anymore (it's quite old) but it should be possible to do this (perhaps you need to select unconstrained profile.)

Although, seeing that q 9 already results in 1500 kbps those files will probably be way out profile specification and won't play on you SAP. You might have to do some denoising to try and bring the bitrate down or downsize even more.

hi GodofaGap

first of all thanks very much for mp3 problem. After upscaling at 22050 Hz Vdub now give a file with lame mp3 encoded audio. But i think i have to upscale more (44.1Khz or 48 Khz) to be able to read it in my dvd player (i didn't yet tested it).

Second, i agree macroblocks are less visible in this sample maybe be cause i had more light for poroper filming ? i have another where they're horrible (i can't send it, it's too long and contains some people i don't know if i'm authorized to do so).

Then, i understood nothing of your suggestions :)

what is that:
> Perhaps you should do an constant q encode at q 3 or q 4

what should i do ?

regards
nalooti

Blue_MiSfit

2nd July 2006, 09:31

nalooti

3rd July 2006, 10:16

I downloaded your first sample, and got it down to under 3 megs with XviD using the following AviSynth Script:

loadplugin("...\removegrainsse3.dll")

directshowsource("d:\sample1.avi")

removegrain(mode=2)
fft3dgpu(sigma=2)

lanczosresize(640,480)

I used some pretty standard XviD settings. 2 pass mode targeting 3000kbps, using the Home Theater NTSC profiles to enable the VBV buffer, thereby limiting the maximum bitrate to ~4800kbit. I used all the quality enhancing features I could, and only 1 bvop. The results were pretty darned good. When I queue the source and the result, and loop it up, I have a hard time telling the difference between the two, except for a little blurring in the trees - probably a result of fft3dgpu(sigma=2) and/or the downsampling.

All in all not bad. I had to give it 3000kbps to keep from dropping frames. Those trees were making huge bitrate spikes, so I filtered the hell out of them, and threw a lot of bitrate at it. I think your camera takes really nice MJPEG video. Almost HD resolution, if only it could capture that at 24 fps!!! I bet that fills up your memory card rather quickly though. How long can your camera keep this up? I would imagine 30 seconds max or so??

Anyway... That was fun. Thanks for some new material to play with :D

~MiSfit

Hi Blue_MiSfit, and thanks for all your time spent for my problem:)

First, i must say i know nothing about avisynth but since almost everyone who knows about video encoding use it, i always wanted to learn it also but unfortunately i found no straightforward guide to teach me how to do it. I know there is one in doom9 but frankly i'm not at ease with that kind of explanation.
I'm looking for a kind of recipe to begin, then an explanation step by step of what i'm doing, and also a maximum of automation since i have lots of family video to convert and i can't spend too much time for each except for the 1st one just to understand the way. Can you point me to a good guide please ?

Since i started this thread and thanks to our experts here, i can now do this conversion with far better results. I'll write what i did very soon.

Regarding my digicam, this is a compact Canon s80 with few movie modes. The two best modes are 640x480 at 30fps and the hd 1024x768 at 15fps. These two modes fill a 1GB SD memory card in almost 7 minutes. Yes i'd prefer having the hd mode at 25 or 30 fps also but that would fill the memory twice faster i guess. However Canon should have provided that mode anyway because memory cards have bigger and bigger capacities these days. All in all this is a very good camera, specially having a wide angle which is not so common in this category and at the same time small enough to put in in my pocket anywhere i go. Lastly, i agree that the hd movie mode is really sublime, that's why i was so frustrated not being able to compress it without too much loss. Hopefully i'm in the right way to do it.

thanks to all

jggimi

3rd July 2006, 15:14

To learn AviSynth scripting:
Click on www.avisynth.org
Click on the "Learn to Script" link on the left side of the page.

nalooti

4th July 2006, 10:38

Hi all,

Thanks to GodofaGap's suggestion and also some experimenting i finaly did it with Divx 5.2 Pro by encoding my movies in 1pass quality based encoding with quantizer 4. Also i tested them on my standalone player and it reads them all.

I'm very satisfied but not at 100% and this is why.

1/ I had to disable Divx certified profiles and even if my player can read them, it's not guaranteed other players can do it also. And since i'm preparing these family movies for other family members with other players brands, i'm not sure this is the right way to go.

2/ I still don't understand why 2pass encoding at 2000kbps doesn't give me good results. I'm googling hard to satisfy my curiosity and in every guide and forum i found, people seem to agree that 1pass quality based encoding is the easy way to go (specially for real-time capture) but not the best one. They almost unanimously suggest 2pass encoding for better quality and size.

3/ Beside satisfying my curiosity, i really want to control the bitrate i am using!!!

In about 2 weeks i'm going to visit my families and hopefuly not empty handed. I want to bring them a piece of these memories, so here are again few questions:

A/ What's the recipe to encode in Divx certified profile (Home Theater) in 2 pass ??? what are the settings ???

B/ Is it possible to encode in quality based and still have some control on the bitrate and file size ?

C/ While encoding, my CPU is at 60-70%. The fan begin to spin faster and louder. My Speed Fan application shows an increase in temperature of the CPU (above 50° celcius). Is there any danger to leave the system in this state for a long time ? how long ? (this is because i use Vdub in job control where i put dozen of files to encode sequentially)

thanks
nalooti

GodofaGap

4th July 2006, 11:11

Hi, glad you made at least some progress. :)

1/ I had to disable Divx certified profiles and even if my player can read them, it's not guaranteed other players can do it also. And since i'm preparing these family movies for other family members with other players brands, i'm not sure this is the right way to go.
The latest version of DivX (6.2 IIRC) has a quality based mode that respects the certified profiles.

2/ I still don't understand why 2pass encoding at 2000kbps doesn't give me good results. I'm googling hard to satisfy my curiosity and in every guide and forum i found, people seem to agree that 1pass quality based encoding is the easy way to go (specially for real-time capture) but not the best one. They almost unanimously suggest 2pass encoding for better quality and size.
1-pass quality based (QB) mode is the best method (quality wise) of encoding. A 2 pass encode is basically trying to achieve the same bit rate distribtution as a 1 pass QB encode. The difference is that for 2 pass you can specify a bitrate and for a 1-pass QB encode you cannot.

2000 kbps is just too low for this video I think. You can compare the it with the bitrate you got from the file you created with QB mode. (check in VirtualDubs file information).

C/ While encoding, my CPU is at 60-70%. The fan begin to spin faster and louder. My Speed Fan application shows an increase in temperature of the CPU (above 50° celcius). Is there any danger to leave the system in this state for a long time ? how long ? (this is because i use Vdub in job control where i put dozen of files to encode sequentially)
If your cooling fan is working properly there shouldn't be a problem.

xyloy

4th July 2006, 11:14

1/ I had to disable Divx certified profiles and even if my player can read them, it's not guaranteed other players can do it also. And since i'm preparing these family movies for other family members with other players brands, i'm not sure this is the right way to go.
Sorry, I don't find how to it with DivX 5.2(perhaps newer versions can do it), but with XviD you can encode at a constant quantizer of 4 and with the Home Theatre Profile activated, wich enables the use of VBV(just like with DivX) to ensure that it will be playable on any standalone DivX-certified player.
The VBV limits the bitrate to a certain amount(among other things). Beyond this amount of bitrate, most standalone DivX-certified players have a hard time decoding the file(or even won't). ;)
edit: The Home Theatre Player also disables the use of QPEL, GMC, Packed Bitstream, and CQMs. The last think to check in order to ensure that the file will be playable by a standalone DivX player is to set the number of Max B-VOPs on 1.
2/ I still don't understand why 2pass encoding at 2000kbps doesn't give me good results. I'm googling hard to satisfy my curiosity and in every guide and forum i found, people seem to agree that 1pass quality based encoding is the easy way to go (specially for real-time capture) but not the best one. They almost unanimously suggest 2pass encoding for better quality and size.
2pass is only better if you have to respect a certain filesize(or bitrate)

C/ While encoding, my CPU is at 60-70%. The fan begin to spin faster and louder. My Speed Fan application shows an increase in temperature of the CPU (above 50° celcius). Is there any danger to leave the system in this state for a long time ? how long ? (this is because i use Vdub in job control where i put dozen of files to encode sequentially)
Usually, desktop computers (not portable or mini PCs) support this kind of situations very well.
For example, with Folding at Home running day & night, my PC's CPU is at 56 ° C all the time. And it is like that for more than a year. ;)
In fact, keeping the same temperature will provide longer life time to a PC(instead of turning it off(low temperature) and on(higher temperature) all the time).
But that's just a little difference in lifetime(at least for a PC), and of course not everyone can bare to sleep with the sound of a fan. :P

check

4th July 2006, 11:40

Hi, this is an offtopic suggestion, but if you are aiming to produce a file that can be read by a DVD player, have you considered encoding to MPEG2 (ie, the codec DVDs use) instead?

nalooti

4th July 2006, 14:23

2000 kbps is just too low for this video I think. You can compare the it with the bitrate you got from the file you created with QB mode. (check in VirtualDubs file information).
problem.

ok i'll do and let you know.

I just wanted to make few points in the meantime about your statement above.

The only difference i see in my case comparing to those who rip&convert DVDs into Divx with very good results with as low as 800 to 1000kbps is that in my case the original resolution is 1024x768. Maybe Divx codec is confused with this kind of resolution which can be seen as HD! Maybe i should enable HD profile in the codec. Problem is my standalone player & TV aren't HD :)

More, i don't know if i told you but encoding at 2000kbps gives me a resulting file at less bitrate (although above 1500Kbps). I suppose 2000kbps is a limit, not the mean bitrate.

May i take a general rule like saying: since Divx compresses at 1/4 bitrate (as an example) of the original with the same quality, i sould take any original bitrate, divide it by 4 and give it to the codec and theoretically i'll be fine ?
I know i'm too simplistic; i hear you laughin :)

nalooti

4th July 2006, 14:39

Sorry, I don't find how to it with DivX 5.2(perhaps newer versions can do it), but with XviD you can encode at a constant quantizer of 4 and with the Home Theatre Profile activated, wich enables the use of VBV(just like with DivX) to ensure that it will be playable on any standalone DivX-certified player.
The VBV limits the bitrate to a certain amount(aong othet things). Beyond this amount of bitrate, most standalone DivX-certified players have a hard time decoding the file(or even won't). ;)

Living near Bordeaux! good old vine heu?

I'll certainly give a try to Xvid (i did it previously and if i remember i was at almost 7Mbps!) but Divx players are just more common although Xvid is supported in most of them too.
The point is i want to first finish the work i started as is and also i don't think the difference between them is so enormeous so i have to succeed with Divx first.

And i know you're more familiar with Xvid and still you do your best to help me. Just be sure that your suggestions are not going to a deaf ear :)
thanks

nalooti

4th July 2006, 14:55

Hi, this is an offtopic suggestion, but if you are aiming to produce a file that can be read by a DVD player, have you considered encoding to MPEG2 (ie, the codec DVDs use) instead?

Hi check

thanks for your suggestion. Yes i've considered mpeg2 also. But i prefer do it with a standalone DVD recorder directly via a firewire/S-video camera when i'll have one :) Actually i have lots of Hi-8 films that i must digitize and the easy way is to go directly with a recorder rather than capturing on PC via a special card. These machines are just here for this kind of job and they give a pretty good results too without having to set manually every parameters which can be complex. I could then encode in Divx/Xvid the resulting mpeg2 files just as people do it with DVDs. And that would be my second backup.

However in this case, from mjpeg files out of my digicam right to my PC with a copy via USB port, i just see no point converting them in mpeg2 with the same quality as in Divx but with much larger sizes, specially that my standalone player is Divx compatible :)

nalooti

4th July 2006, 17:28

Hi, glad you made at least some progress. :)

The latest version of DivX (6.2 IIRC) has a quality based mode that respects the certified profiles.

.

Hi,
what is the version 6.2 IIRC ?
according to the following link:
http://www.divx-digest.com/articles/divx6_setup_print.html

1-pass quality-based option is only available when the "Unconstrained" profile is selected!!

GodofaGap

5th July 2006, 10:14

Yes it is possible with version 6.2. Information there is outdated.

http://img95.imageshack.us/img95/6205/divxconfigwindow1kp.th.png (http://img95.imageshack.us/my.php?image=divxconfigwindow1kp.png)

The only difference i see in my case comparing to those who rip&convert DVDs into Divx with very good results with as low as 800 to 1000kbps is that in my case the original resolution is 1024x768. Maybe Divx codec is confused with this kind of resolution which can be seen as HD! Maybe i should enable HD profile in the codec. Problem is my standalone player & TV aren't HD
Your source is 10x times more noisy than those clean DVDs. Noise is random and therefor difficult to compress, that's why it takes a lot more bits. Has nothing to do with the original resolution.

More, i don't know if i told you but encoding at 2000kbps gives me a resulting file at less bitrate (although above 1500Kbps). I suppose 2000kbps is a limit, not the mean bitrate.

On a normal lenght file (say 5 minutes or longer) this really shouldn't happen. If you ask 2000 kbps you should get 2000 kbps. It is possible that a codec get saturated and can't use any more bits, but the bitrate in your case should be much higher than that. OF course on very short samnples a codec will also have difficulty achieving the target bitrate.

smok3

5th July 2006, 13:15

yes, you have to understand that non-delta codec (like mjpeg) will not have as many problems with noisy sources as delta ones (mpeg2, xvid, divx, ect...)

nalooti

5th July 2006, 14:17

Yes it is possible with version 6.2. Information there is outdated.

thanks very much for the screenshot.I'll install it asap.

Your source is 10x times more noisy than those clean DVDs. Noise is random and therefor difficult to compress, that's why it takes a lot more bits. Has nothing to do with the original resolution.

It is quite possible because my digicam isn't a professional camera and usually Canon is not as good as others regarding noise reduction specially in photos but i suppose it's the same in movies.

Regarding my conversions, i can now confirm my problem as you said before was simply not enough bandwidth and this is how i found it.

First, after converting with 1-pass QB Q=4, the file info gave me almost 2700 Kbps. So i converted again the same file this time in 2-pass with 3000Kbps and i got the same quality as before.

I can now understand why quality depends on each content. And the numbers weredifferent with each piece of content So my conclusion is: following are 2 methods for divx converting:

1/ 1-pass QB
pros: get the desired quality
cons: no control on bitrate/file size

2/ 2-pass (or 1-pass)
pros: control on bitrate/file size
cons: no control on the desired quality

Unfortunately (now i understand why), there isn't any in-between. You have to test it yourself with small samples and compromise between quality and size.

For now, the exact size doesn't matter for me. So i go for QB.

Is it right to say that 1-pass QB mode is like a kind of CBR and 1or 2-pass a kind of VBR ?

If any analogy with sound encoding (Lame mp3/Winamp) can be made here, i'd say that VBR is only good if you want smaller sizes (although the question is how much smaller and if it's worth it). Because, beside compatibility problems with VBR encoding, in LAME for example, VBR is based on a psychoacoustic algorithm that is entirely subjective and can misinterpret the signal.

Anyway, i'd like to thank everyone here who answered to my questions. I have learnt a lot and that was thanks to all of you.

Now, i have to make work my Lame ACM with Vdub in order to encode in higher sound quality and if i believe google stories this isn't as straightforward as it should be.

thank you all
nalooti

xyloy

5th July 2006, 14:23

Is it right to say that 1-pass QB mode is like a kind of CBR and 1or 2-pass a kind of VBR ?
Quality(or Constant Quantizer) is VBR. Each image needs a different amount of bitrate to reach a certain quantizer(because each image may or may not be as detailled/noisy as another one)

GodofaGap

5th July 2006, 15:43

Is it right to say that 1-pass QB mode is like a kind of CBR and 1or 2-pass a kind of VBR ?

QB mode is VBR. 1-pass bitrate is CBR (or ABR).

If any analogy with sound encoding (Lame mp3/Winamp) can be made here, i'd say that VBR is only good if you want smaller sizes (although the question is how much smaller and if it's worth it). Because, beside compatibility problems with VBR encoding, in LAME for example, VBR is based on a psychoacoustic algorithm that is entirely subjective and can misinterpret the signal.
CBR mode uses the same psycho-acoustic model, it would sound pretty crappy if it didnt. Also, due to the bitrate reservoir even CBR is not really CBR with MP3. :)

In Lame the VBR mode is always better quality than CBR, unless you use the maximum bitrate.

In general, with a normal functioning codec, VBR is constant quality with unpredictable filesize and CBR is predictable file size with not constant quality.