AVStoDVD - Quantizer..?

[VenusAndMars]

Hi, while using AVStoDVD to make a DVD out of .avi-files I get this error message from HCenc 0.25:

very low Qantizer, bad Q estimation, please reconsider settings

What is Quantizer? And where and by what criteria do I set it?

Thank you.

[_MrC_]

Quantization is basically a smart mpeg2/4 encoding strategy to allocate bitrate where it is more needed.

HCenc works using quantization factors. Release 0.24 has introduced the possibility to perform 1-pass VBR encoding, having a quick first predictive step and then the effective encoding pass. If the prediction step gives a low quantization factor (probably due to a high target bitrate), the HCenc will throw out a warning message. For target bitrates less then 6500 kbps, just ignore it (that's my experience).



Bye

[manono]

Yeah, the bitrate is way too high for the other settings and you probably won't be able to achieve the size you want. I think you can probably get rid of the message by switching to a high-bitrate quantization matrix, one such as the included Fox Home Entertainment (aka Fox 1) Matrix.

[VenusAndMars]

Thanks to _MrC_ and manono! I have made DVD-files of AVStoDVD's output, and can see no picture deterioration, so it's probably OK to go ahead and put IMGBurn to it.
If I had indeed needed to change quantization factor(s): where would I do it?

[manono]

If I had indeed needed to change quantization factor(s): where would I do it?

You wouldn't. You'd adjust the bitrate instead. If you're asking where to change the quantization matrix, it's in the ... Matrix Tab.

[VenusAndMars]

Thx manono

[Ze Tomes]

Greetings, and special Greetings MrC. It's been a long time

I have the same message as VenusAndMars and it wouldn't be a problem if the resulting video wouldn't had a sort of fading effect present, like a subtle ghost. I changend the matrix to Fox 1 as Manono suggested, yet, the message persists. I don't know if somehow the resulting video will have the same problem or if there is indeed a conection between the message and the sort of ghostly image. I have to wait for the the result of the edition

Thanks

[Goodluck Jonathan]

Greetings, and special Greetings MrC. It's been a long time

I have the same message as VenusAndMars and it wouldn't be a problem if the resulting video wouldn't had a sort of fading effect present, like a subtle...etc.

[Attachment 12754 - Click to enlarge]

Great input Ze Tomes; the quest goes on!

[Ze Tomes]

The result was identical to the first test, the message keeps apearing. I don't know if it's my interpretation, because everything's almost flawless in the edited video, except for the very subtle shading effect on movement specially on 3/4, medium and close-up shots. Could it be the source video or another encoder I should use?

Thanks

[_MrC_]

Do not mind: HCenc is designed to work best with low bitrates (that, as rule of thumb, correspond to high quantizer values) so it complains if the predicted q value is low, so that the encoding is becoming more CBR than VBR. BTW the output is usually very good indeed. Simply ignore that warning message.



Bye

[manono]

Could it be the source video...?

You can't tell? You don't know how to examine the frames yourself? If not, upload a 10 second piece from the source either here, Sendspace, or MediaFire, a section with steady movement, and we'll have a look. Maybe it's field-blended or has some other peculiarity that prevents it from looking good without some special filtering.

[_MrC_]

Simply ignore that warning message

and focus elsewhere the troubleshooting (...some words have remained in my keyboard...).

As manono suggested, a short portion of source file, together with AVStoDVD project log file to quick get the encoding options you used, would be very useful.



Bye

[Ze Tomes]

Okidoqui, let me edit it. Cheers

[Ze Tomes]

By the way which software should I use to cut a piece of the original video file not interfering with its original properties?

[poisondeathray]

By the way which software should I use to cut a piece of the original video file not interfering with its original properties?

According to the log input file is a MKV, 1280x720, but 23.976 VFR . If it's truly VFR (variable framerate) , it can give you problems, it's not compatible with DVD (CFR only) . VFR=>CFR conversion can use blends or duplicates depending on how it was done. This might explain your "ghosts". Use mkvextract and extract the timecodes to check if it is truly VFR

To cut a piece of video you could use either mkvtoolnix (split & cut tab, use timecodes) , or avidemux (set video & audio to "copy", mark in/out on keyframes, format to mkv)

Another reason for ghosts is you're using PAL dvd (25 FPS), but the source is 23.976 FPS. And ConvertFPS() was used for the conversion

[poisondeathray]

Just to explain - ConvertFPS() does a blend conversion for the 23.976p=>25p to smooth everything over - that's likely why you're getting blurry ghosts

Portugal is a 50Hz (PAL) region, but most modern PAL spec DVD players can play NTSC discs as well, so one option might be to make a NTSC DVD instead - this would have no ghosts. However, if the source is VFR, you might still have to use convertfps, but 23.976 instead of 25 - in this regard you might still get ghosts depending on how variable the source frame rate was

The other option is to use AssumeFPS() instead, this will do typical 23.976=>25p "PAL speedup" (i.e. every frame will be the same like the original, no ghosts), but the audio has to be sped up as well, so duration of video is shorter by the same fraction

[Ze Tomes]

I wasn't able to extract the timecodes (the timecodes file wasn't present while viewing the video file on mkextract, perhaps I delete it while editing it previously - could it be the reason for the ghosts, the absense of this information on the mkv file?) nevertheless I used MediaInfo for the same purpose. I think it's trully a VFR.

I'm using avidemux and it sent me a message: H.264 detected (if the file is using B-frames as reference it can lead to a crash or stuttering.) I chose not to use the safe mode. It said also that the index was not up to date. I Rebuild frame as it was suggested, piece of the video cut and uploaded after.

I hadn't any problem with conversions since I've been massacrating MrC with my neverending questions. The results have been perfect since, flawless and perfectly fluid like water (salve salve AVSTODVD and MrC!) This video is an exception, i never had this kind of subtle ghost tracking.

Thank you guys for the patience (manono, poisondeathray), indeed I learn a lot around this great forum with your major help.