Confusion about DivX-Encoding settings

[foxhunter]

Hi all,

i've bought a new multimedia harddrive and now i started to tranfer all of my Videos taken with a miniDV-Camcorder to this harddrive. I want to use DivX, but i'm a little bit confused about the settings.

If i run the Encoder with the profile "Home Theater" i can select any Quantizer i want, the result is always the same. I've taken a one minute sample to try the different settings of the encoder.
All the files taken with the profile are in a size of about 4.8 Mps. If i change it to 'unrestricted, i'm able to select the Quantizer. But even if i'm using Q4, the file is bigger, the rate is higher, but the quality is not as good as with profile. Is that usual for the DivX-Encoder?

And another question: How about the option for changing the method of encoding (on second tab). I tested it with the several options, but the quality looks quite the same. May i leave it in the fastest option?

And how about the B-Frames? Another guy told me, that i have to switch them off for a Media Player.

The last question: My camcorder (NV-GS150) always records in interlaced mode. Do i have to use the deinterlace filter of VirtualDub, or are there any kind of filter in the settings of the DivX-Codec?

Many thanks

A video beginner from germany.

[foxhunter]

Hi guys,

any ideas so far?

I just played around with several options and i think i will leave the Home Theater profile enabled. Is anybody able to explain me the different Quality-Settings of the codec? It looks like they aren't active if a profile is used. If i'm using the fastest option i get the same video quality as if i'm using the extreme quality option. But the encoding took 4 times more.

I've set up a deshaker filter in Virtual dub. The effects are stunning, it looks like a steady cam. One problem of course is the sharpness.

I figure out, which is the correct workflow for getting the most out of the videos.

I would use the deinterlacing filter, the deshaking filter and a sharpness filter.

Which one of the deinterlacing and sharpness filters should i use? Which settings?

In which order should the filters be applied?

Thanks in advance

UWe

[jman98]

I can't believe no one has responded to this post. There are better people out there than me to answer this, but what little I can tell you may be better than nothing.

I don't encode to Divx a lot, but when I do, I use Dr. Divx. I use the quality setting that is just below Insane. I don't remember the name - is that Extreme? Insane takes a very long time to encode and I don't think it's really any better than the option just below it.

I don't think that's correct what you were told about needing to turn off B frames for playback on media players.

I can't help you with the fliters question. I don't do this very often, but when I do need to do it I use AviSynth. I've got a script I wrote some time ago that I use when I need to do this, but I don't remember which AviSynth filters I used. If nobody else responds and you want to know what filters I used, send me a private message and I'll reply some hours later when I'm at home and can look at my script.

[foxhunter]

Hi,

thanks for your response.

Is Dr. Divx compatible to DivX 7 (6.8.5) ? I have read, that it is not.

I got an answer in a german board. It depends on the high rate of my videos. If i'm using Home Theater, the average bitrate is about 4.8000 kbps, with that it doesn't matter, which speed i use.

This guy also told me, that the filters of VirtualDub are somewhat outdated and i have to use other filters.

Greetings Uwe

[jagabo]

Divx profiles set limits on the encoding. With Home Theater you are limited to 720x576 25 fps, 720x480 30 fps, or lower frame sizes and frame rates. If you try to go higher you will get an error. It also limits bitrate peaks to something like 4000 kbps. If your requested constant quantizer encode will go over that bitrate limit a higher quantizer will be used (for that frame or short group of frames) to keep the bitrate within the profile. You are limited to single B frames in this profile. The unrestricted profile allows the bitrate to go as high as necessary for the selected quantizer. It also allows for bigger frame sizes and more B frames.

The Codec Performance -> Encoding Mode controls how wide a motion search the codec will perform. The wider the search the better the compression (at least in theory) but the longer it takes. Going higher than "Better Quality" rarely increases compression by anything significant but can take much longer to encode.

B frames allow for more compression by letting the quality suffer for a short period of time (1 or 2 frames). On the theory that you won't notice these very short reductions in quality as they will be cleaned up with an I or P frame shortly.

I recommend you use Xvid instead of Divx. Compression is significantly better with Xvid's adaptive quantization enabled.

[foxhunter]

Hi,

thanks for your reply.

I have forgotten to tell you, that the compression and size of the files don't matter. So i would better use high quality instead of high compression.

The problem is, that higher rates (e.g. unrestricted, Q2 generates nearly 9000 kpbs) aren't running smooth on my drive.

[jagabo]

In this context, when I say you get better compression I mean you get the same quality with a smaller file size or better quality with the same file size.

Divx with the Fastest encode mode will generate much bigger files than Divx with the Insane encode mode, but quality will be the same.

Xvid at Q2 generates smaller files than Divx at Q2 (both using the unrestricted profile) but both look the same. Divx with the Home Theater profile will generate smaller files than Divx with the Unrestricted profile if the bitrate would exceed the Home Theater limit.

Most computers should have not problem playing Divx/Xvid at 9000 kbps. Many set-top Divx/DVD players will.

[foxhunter]

Oh thanks, there was a misunderstanding.

I want to use the videos for easier playback on a Multimedia Harddrive, directly connected to a Flatscreen TV.

I tried several settings with higher rates, but the videos won't run smooth. They only do that at lower rates. The rates of HT are ok, i think these are rates with the highest compatibility?

[jagabo]

The Home Theater profile exists exactly because of the problem you are having.

[foxhunter]

yepp, that's what i thought.

What does this mean if i want to give XVid a chance? There isn't a Home Theater profile. Which settings should i use?

Is it a try and error?

[jagabo]

Xvid has profiles just like Divx, including Home Theater. Unfortunately, Xvid's constant quantizer encoding is a true constant quantizer. The profiles don't limit the bitrate when using constant quantizer encoding.

Using a quantizer of 2 may be overkill. Using 3 results in a little lower quality if you examine enlarged still frames but you won't really see this at normal playback speeds. That will usually keep your bitrate low enough for most stand alone players.

[foxhunter]

Hi,

thanks for that.

I will play around with this.

How about the settings for B-Frames there? Another guy told me, to deactivate the B-VOPs in the profile tab to make it more compatible. What about the pixel apect ratio? My files are in size 720x576 (PAL). Should i leave the settings at 1:1 or should i select 4:3 (as it is)?

Sorry about so many newbie questions...

[foxhunter]

Hi again,

i've just created some testfiles to check the quality.

I've created some screenshots of the same frame to see the differencies. Just decide by yourself. The most differencies can be seen in front on the brown floor and on the white wall of the building in the back.

Screenshot from original AVI

DivX with Home Theater profile

XVid with Quantizer 5


I've selected Q5 in XVid, because this ends up in the same rate than the DivX-File (and a similar size). But in my opinion, the quality of the XVid is better than DivX.

I only have to check, if my media player is able to play higher rates (like Q4 or Q3)

Thanks for your help !

[jman98]

How about the settings for B-Frames there? Another guy told me, to deactivate the B-VOPs in the profile tab to make it more compatible. What about the pixel apect ratio? My files are in size 720x576 (PAL). Should i leave the settings at 1:1 or should i select 4:3 (as it is)?

I found a source that says that Divx never uses more than 1 B-VOP and this no problem for playback, but Xvid may use 2 and that can be a problem for playback on Media Tek chips. So I think if you set B-VOP to 1 or 0 (if you wish) you will be fine, but again, I am not sure that it has to be 0 for playback to be OK.

I've only seen Divx/Xvid encodes at 1:1 pixel aspect ratio, so I think not using that could be a bad idea. But I am only guessing here.

[jagabo]

Divx's Home Theater profile uses only one B frame. Higher profiles allow two B frames. Home Theater certified players can play Divx with one B frame but aren't guaranteed to play two. Most current models do though.

Using no B frames will get you larger files in constant quality mode, overall less quality in bitrate mode.

[foxhunter]

Thanks for the infos

I will create several files with different settings to see which one fits best to my MP

[foxhunter]

Hi guys.

I've done some testing.

As far as i can see, the DivX/Xvid - Files will not be played correctly if there is a bitrate higher than 7000 kbps. That means, that Quantizer 3 won't work.

DivX with Q4 produces a bitrate of around 7000, which runs. Q4 in Xvid generates a bitrate of around 5.500 wich works also.

Q3 in Xvid generates slightly 10 Mbit, doesn't run smoothly, audio is interrupted.

I've generated some MPEG1 testfiles in 720x576 (like the source). There all bitrates up to 9000 kbps are running.

Any ideas? Should i use the outdated MPEG1 if i possibly want to use the files for later editing/cutting?

I know, this is usually not a good idea, but i want to have best quality within the possibility to play the videos on my media player without errors,.

Thanks
Uwe

[guns1inger]

1. Exactly what is your media player. So far you have been pretty vague on this point. The more details you can provide, the better.

2. What, if anything, does the manual say about supported formats ? What you want to use has no bearing on the matter. You can only use what is supported by the player.

3. If you must use mpeg, use mpeg-2 at those bitrates, not mpeg-1. The quality will be better.

4. If you want to edit the files later, go back to the original tapes and re-capture the footage. Using some lossy compression now will only make the quality lower when you come to editing.

[foxhunter]

Hi,

that's why i'm asking about the possible choices

I wouldn't do a lot of DivX-Testing if the player wouldn't support this.

The Media Player supports MPEG-1, DivX 3/4/5/6, XVid. It doesn't support MPEG-2 or the playback of the source out of the Camcorder (AVI, DVCodec).

I'm not a video professional. The only editing will be cutting out scenes to built a new video. No effects, no exactly cutting of frames neccessary.

Greetings

[jagabo]

Even noisy, shakey handheld, interlaced camcorder footage only requires about 4000 kbps when I encode with Xvid at target quantizer 3. Are you using some strange Xvid settings? Really short GOPs? No B frames? The Real Time quality preset?

[foxhunter]

Hi,

i'm using the 'unrestricted' profile and i've set the Quantizer to '3'

This results in an XVID-AVI with around 7000 kbps. Does this depend on the content of the source? The sample is a one minute AVI with some quick movement scenes.

[jagabo]

Yes, when using Target Quantizer mode the size of the video will depend on the source. A perfectly still shot with no noise will compress down to almost nothing. Noisy, shaky, handheld, interlaced camcorder video will require lots of bitrate.

Selecting the unrestricted profile doesn't set all the other important options in the codec. You need to go through the dialogs and set all the options individually. Some settings to check:

Profile @ Level -> More:
Set Quantization Type to H.263.
Enable Adaptive Quantization.
Enable Interlaced Encoding if your video is interlaced
Disable Quarter Pixel.
Disable Global Motion Compensation
Enable B-VOPs, set Max Consecutive BVOPs to 1
Enable Packed bitstream

Quality Preset -> More
Motion Search Precision: 6 - Ultra High
VHQ mode: 4 - Wide Search
Enable Use VHQ for bframes
Enable Use Chroma Motion
Set Maximum I-frame interval to somewhere between 100 and 300.

[foxhunter]

Hi,

thanks for your recommended settings.

I will give them a try.

Another idea was rising. Keep the original AVI, save it to a compressed archive (for editing later) and create a copy with a codec that could be played directly on the harddisk. This would prevent me from using an ultra high bitrate.

But i tried several compressors (winzip, winrar etc.) and the compression is not more than 10-15%.....

[jagabo]

Video files are already compressed with ZIP/RAR like algorithms. The final step of MJPEG, DV, Divx/Xvid, and h.264 encoding is a huffman entropy encoding.

[foxhunter]

Hi, thanks for your quick response.

i'm thinking of your qoute about the average bitrate of a video.

Let's say, i have a full video, mixed with 'quiet' and 'action' scenes. If i use a Quantizer setting, the video might be in a special bitrate (let's say 4.000 kbps in average).

Does that mean, the action scenes will have a much more higher bitrate and the quiet scenes a lower one? That means, the action scenes won't run smooth on my screen.

Or am i completely wrong?

[jagabo]

Let's say, i have a full video, mixed with 'quiet' and 'action' scenes. If i use a Quantizer setting, the video might be in a special bitrate (let's say 4.000 kbps in average).

Does that mean, the action scenes will have a much more higher bitrate and the quiet scenes a lower one? That means, the action scenes won't run smooth on my screen.

Yes. That is why Divx limits peak bitrates when using the Home Theater profile. Xvid doesn't do this unless you use 2-pass encoding.

[foxhunter]

Thanks, this would be the main problem.

So i have to decide wether i use the Home Theater profile in DivX or i reduce the Quantizer in XVid to a lower value than possible.

I think i will create a DivX-File vor viewing and a MPEG2-File for archiving. This is better than keeping the huge DV-Files.

[jagabo]

Or use 2-pass encoding with Xvid or Divx. Both will limit the max bitrate when doing 2-pass encoding with the Home Theater profile.

[foxhunter]

Hi all,

i'm already testing....

Another question came up:

I know that i have to deinterlace the videos, if i want to show them on a PC-Monitor
or with a overhead projector. But how about newer Flatscreen-(HD)-TV?
I have read, that they usually have a deinterlacer on board. I'm using a Philips 42" LCD-TV,
but i don't find anything about that in the technical specifications.

Do you know anything about this? If this is true, i don't need an additional filter in VirtualDub.

[jagabo]

It depends on how you get your video to the HDTV. If it's via a traditionally interlaced cable (s-video, composite, SCART) the TV will deinterlace it. From a DVD player (playing standard movie DVD), either the DVD player or TV will deinterlace. From a computer via DVI/HDMI, the computer will have to deinterlace.

As I understand it you are an external drive with video output, probably composite or s-video. It may not support interlaced Divx/Xvid properly. Most set-top Divx/DVD players don't do well with interlaced Divx/Xvid.