Producing Pal DVD from mpeg2 hd content

[Trevor Andrew]

Hi

So given that file size is not an option.

If I use Video Studio to render at 4000

Would Variable produce a better overall quality than Constant.?

Constant has to win as Variable will encode every frame below 4000. The variable average being lower than 4000.

Afaik Constant will encode every frame at 4000 the average being 4000.

Retired people have plenty of time, and can manage more than 5 minutes¡K¡K¡K¡K¡K

[GeorgeW]

The CBR should look better overall because all frames are using the "MAX", vs the VBR encode at 4000 where only some frames would use the "MAX"

Regards,
George

[daniel]

I was discussing 2-vs-1 pass VBR. CBR is superior in every way.

Quality is the best you can have since VBR will not go higher (in VS)
and size is of course bitrate times seconds so superior too.

VBR is used only to reduce size (again, as implemented in VS, if you don't use the undocumented Advanced mode). If you don't need a smaller size, don't bother.

2nd-pass is an attempt to optimize the extra compression by trying probably both to reduce the size further (succeeds most of the time), or to use another algorithm for better results in a given GOP for the same size or anyway not higher than max keeping the whole around average (no idea if it succeeds but sometimes it uses more bits).

[GeorgeW]

I was discussing 2-vs-1 pass VBR. CBR is superior in every way.

Quality is the best you can have since VBR will not go higher (in VS)
and size is of course bitrate times seconds so superior too.

VBR is used only to reduce size (again, as implemented in VS, if you don't use the undocumented Advanced mode). If you don't need a smaller size, don't bother.

2nd-pass is an attempt to optimize the extra compression by trying probably both to reduce the size further (succeeds most of the time), or to use another algorithm for better results in a given GOP for the same size or anyway not higher than max keeping the whole around average (no idea if it succeeds but sometimes it uses more bits).

That's where I'm having a problem that you're saying two-pass gives better compression -- 2-pass or 10-pass -- if the encoder obeys the AVERAGE bitrate setting, then the resulting file size should be the same vs. single-pass (give or take a few bytes). Like you said -- filesize is bitrate x seconds -- in the case of VBR, it's AVERAGE-BITRATE x Seconds -- so maybe VS is altering the avg-bitrate during a multiple-pass encode

Regards,
George

[GeorgeW]

Forgot to mention -- to me, the purpose of VBR is not smaller file sizes. It's to be able to generate better quality when forced to use a certain bitrate (say 4mbps).

So instead of using CBR 4mbps, try VBR with Min (3mbps), Avg (4mbps), and Max (5mbps)

But Ulead does not allow you to specify all 3 variable -- you enter a bitrate that is the MAX (so people tend to think using VBR automatically means smaller file sizes -- but it's only because you cannot specify the AVG and MIN).

NOTE: You can alter some settings to open up the ADVANCED settings in some Ulead software, but that's a different story...

Regards,
George

[etech6355]

I just viewed a Blu-Ray Disc HD Movie and the VBR bit-rates range from 1000kbs - 27000kbs. Interesting to watch how the pro's do this. Must take a very long time to encode these movies.

I think it's hard to compare VBR versus CBR because it depends on the quality of the source material and the profile level of encoding. The ulead encoder doesn't swing above/below the average very much for VBR. I think this is because of the mpeg2 profile level it's choosen to encode at (also easier to edit at a later date).
Many of my encodes are above 9000kbs, I can't notice any difference between CBR & VBR at such a high bit-rate.

I did give 5 minute videos to a retired persons to evaluate. This didn't work at all......
They all fell asleep after 2 minutes

[etech6355]

Forgot to mention -- to me, the purpose of VBR is not smaller file sizes. It's to be able to generate better quality when forced to use a certain bitrate (say 4mbps).

But that usually results in a smaller file size correct?
That's my understanding of it. My Panasonic Dvd Recorder really swings the bit-rates around when in the 2 hour mode of recording, 3600kbs -6500kbs. That is the SD mode.
If I record in the HQ mode which is the 1 hour mode it seems to stay at about 9100kbs. Doesn't seem to matter trying to encode VBR if your running close to the maximum bit-rate.

[GeorgeW]

Forgot to mention -- to me, the purpose of VBR is not smaller file sizes. It's to be able to generate better quality when forced to use a certain bitrate (say 4mbps).

But that usually results in a smaller file size correct?
That's my understanding of it. My Panasonic Dvd Recorder really swings the bit-rates around when in the 2 hour mode of recording, 3600kbs -6500kbs. That is the SD mode.
If I record in the HQ mode which is the 1 hour mode it seems to stay at about 9100kbs. Doesn't seem to matter trying to encode VBR if your running close to the maximum bit-rate.

No, not if you use the same AVERAGE bitrate as the CBR Bitrate. The point is that you do your calculations, and find out you have to encode at 4mbps to fit your material.

Your 2-hour mode (on DVD5) would need roughly 4.8mbps video bitrate (assuming compressed audio at ~224kbps). So it jumps between the bitrates you mentioned, but maintains the AVG bitrate of around 4.8mbps.

You can generate a file roughly the same size as CBR 4mbps by using VBR Min (3mbps), AVG (4mbps), and MAX (5mbps). But the VBR encode should give you better quality because it will go up to 5mbps on the "complex" parts, down to 3mbps on the "less complex" parts, and attempt to maintain the stated AVERAGE bitrate of 4mbps.

The reason it's smaller in Ulead is because Ulead does not allow you to specify all 3 variables (Min/Avg/Max).

Regards,
George

[toni1]

I was imagining that when making two pass the first pass is just a monitoring step to see in which part of the video will be delt with, while in one pass every GOP or goupes of GOP is delt with one after the other;
That is probably not the way int works upon comments I am reading

[GeorgeW]

I was imagining that when making two pass the first pass is just a monitoring step to see in which part of the video will be delt with, while in one pass every GOP or goupes of GOP is delt with one after the other;
That is probably not the way int works upon comments I am reading

Essentially, that is how multi-pass works -- analyze the video stream (taking "notes" on which scenes need more bits, and which can use less bits), and then eventually use the "notes" to render the file. And all along try to maintain the specified AVERAGE bitrate. Again, if your encoder allows entry of all 3 settings, then CBR 4mbps vs AVERAGE-VBR 4mbps should produce roughly the same size file. Other software that allows entry of only one bitrate treats that as the AVERAGE bitrate. Ulead treats it as the MAXIMUM bitrate (with the AVERAGE being less).

Regards,
George

[harry_hariz]

so u mean when captured as LFF editing also must be like that format?

can instead editng in LFF but when rendered to mpg 1 0r 2 i changed taht to frame based for best viewing on tv?

[etech6355]

so u mean when captured as LFF editing also must be like that format?
can instead editng in LFF but when rendered to mpg 1 0r 2 i changed taht to frame based for best viewing on tv?

If your original recording was field based LFF and you render to frame_based it will look like poo poo on your TV.
Producing a frame_based video for your TV will lose the true motion that was originally recorded.

You keep the format the same from start to finish. It's so Simple that people look into it to much and make/cause a problem with the fielding.

[harry_hariz]

oooo....if icaptured as LFF, then edit also in LFF n finally convert to mpg also LFF format?

what the difference if i set it as frma based from LFF souce video?

[Trevor Andrew]

Hi Harry

As a Guide:-

Your target audience determines what Field Type you use.

If your audience is the internet then use Frame Based (for computer screens)

If your audience is the standard TV then use a Field Order

There are two orders Upper and Lower.

The order is determined by the SOURCE of your video.

If its Digital (a digital camcorder etc) then Lower Field is normally used

If its Analogue (a VHS tape recorder etc) then Upper field is used.

Using the incorrect order will create poor video.

[etech6355]

As a guide I never change the fielding of the original source video.
No need for me to do this.

When viewing on computer screens the software player de-interlaces & blends the fields to display on the computer screen correctly.
If sending over the internet you create a wmv file, wmv conversion will de-interlace the video. The hd-wmv encoder has a smoothness setting that helps somewhat with the de-interlacing.

If creating a divx file the divx encoder de-interlaces the video.