How to achieve the maximum bit rate in variable bit rate mode ?

[Sxn]

How to achieve that?

[jagabo]

Find a video with lots of static scenes and a very busy scene and encode with variable bitrate.

2pass.avi

Bitrate Viewer graph (one second intervals):

[Sxn]

Hey guys, my media player (321) is not able to play .wmv files. What codec should i install?

[Sxn]

This what i'm getting.. if i convert it in variable bitrate mode.

[jagabo]

My sample video? Using what software? What settings? You really need to be clearer about what you are doing. Nobody here can read your mind. But, in general, don't expect an encoder to hit your average bitrate when encoding a very short, highly unusual, video like the one I posted. Also, don't expect tools to report statistics about such files properly either. And lastly, don't expect a second generation encoding using an AVC encoder, encoding an Xvid AVI file, to work really well.

[Sxn]

A bitrate cap is a ceiling that you cannot go above (i.e a maximum). You generally never want to use it, because it can impair quality (unless you set it very very high), or you need to have a sufficient buffer to buffer the peaks

I want to use this bitrate cap. can anyone suggest how?

[jagabo]

vbv-maxrate

[Sxn]

Sorry, didn't get u there.

I'm using Xvid4psp.

[jagabo]

vbv-maxrate is the x264 argument that sets the bitrate cap. You also have to set the vbv-bufsize. From the x264 docs:

--vbv-maxrate <integer> Max local bitrate (kbit/s) [0]
--vbv-bufsize <integer> Enable CBR and set size of the VBV buffer (kbit) [0]

I don't think Xvid4psp supports these settings. Try MeGUI.

[poisondeathray]

The cap doesn't necessarily mean you will achieve those rates, it limits the maximum rate so you don't go above a certain value. If you set --vbv-maxrate 50000 and --vbv-bufsize 50000, it doesnt mean you will achieve that instantaneous bitrate. It's an upper limit and denotes how much is allocated to the buffer, not the video. Your actual peaks might be a lot less or a lot more depending on your settings

Also you might go above briefly, because the vbv buffer is just a buffer. The model is like is a pool that data enters, and data leaves as it's decompressed for display. Locally you can get peaks above the maxrate value, as long as the pool is sufficient to buffer it. Buffered peaks are good, because devices choke on it otherwise

If you want higher bitrate peaks for some sections, this means less bitrate for other frames = lower quality. This is a balancing act. If that higher bitrate is used on an important IDR frame, it might be good, but it can also lower the quailty of other sections. Using mb-tree in newer builds will give much larger variance (higher peaks), but some sections will be much lower like fades. Also raising qcomp in older builds will have a similar effect on variance. (sections like action scenes get more allocation, and static scenes get less)

If you are using a set bitrate, always use 2pass. ABR will always give you worse quality

[Sxn]

K.. got it.

Can anyone provide some guides for basics of the video tuts? Like which parameter is for what ..

[poisondeathray]

Unfortunately there are no good guides. x264 is very actively developed, and a guide that is put out a month ago would already be obsolete because of new features/switches. This means if you are using a version a even a month old, some commands will be slightly different. Many of the GUI's have are no longer actively developed

This is pretty recent and well maintained to reflect new changes commited to newer build. You can dig through the history tab to see commands that relate to your specific x264 version
http://mewiki.project357.com/wiki/X264_Settings

The new presets system makes x264 much more easy to use from the command line

The basic choice of rate control is CRF vs. 2-pass. If you need a set size, use 2-pass, otherwise use CRF. It's faster, and gives similiar quality if the end result had been the same bitrate using 2-pass. Lower CRF values give you higher average bitrate, higher CRF values give you lower bitrate.

[Sxn]

Quite a big page !
One good thing is it has a hell lotta info... 8)

Thanks.