Need help with the x264 "--zones" function

[djesteban]

Hi,

I am encoding a clip with x264 using the following presets:
Preset: Slow
Tuning: Film
Profile: High
The target bitrate is : 15000 (kbit/s)

Now, I want to use the --zones function in order to increase the bitrate on certain parts of the footage, but I am having trouble understanding how the function works.

Here's two scenarios of what I would like to achieve with --zones:

1- I want to double my target bitrate from frame 1000 to 2000: --zones 1000,2000,<options?>

2- I want to specify manually a new value for the target bitrate (let's say 20000 kbit/s) from frame 1000 to 2000: --zones 1000,2000,<options?>

Would really appreciate help with this one, thanks!! :)

[Blue_MiSfit]

From x264.exe --fullhelp

--zones <zone0>/<zone1>/... Tweak the bitrate of regions of the video
Each zone is of the form
<start frame>,<end frame>,<option>
where <option> is either
q=<integer> (force QP)
or b=<float> (bitrate multiplier)


So, in your example, --zones 1000,2000,b=1.33 would do what you want.... I think :devil:

Cheers,
Derek

[djesteban]

From x264.exe --fullhelp

--zones <zone0>/<zone1>/... Tweak the bitrate of regions of the video
Each zone is of the form
<start frame>,<end frame>,<option>
where <option> is either
q=<integer> (force QP)
or b=<float> (bitrate multiplier)


So, in your example, --zones 1000,2000,b=1.33 would do what you want.... I think :devil:

Cheers,
Derek
Would that be for scenario 1 or 2? If I understand 1.33 is multiplied by my original bitrate, is that it? But that gives around 20000 kbit/s right? Is that how it works? So if I want to double my original value, I would put b=2, is that it? It's a simple multiply? Just want to make sure :}

[J_Darnley]

> bitrate multiplier

[LoRd_MuldeR]

Would that be for scenario 1 or 2? If I understand 1.33 is multiplied by my original bitrate, is that it? But that gives around 20000 kbit/s right? Is that how it works? So if I want to double my original value, I would put b=2, is that it? It's a simple multiply? Just want to make sure :}

Bitrate multiplier applies to the target bitrate. x264 doesn't even know the bitrate of the original source in many cases (think of Avisynth input or "raw" input from stdin).

So the "b=<float>" option actually handles both cases. As you know what target bitrate you have specified, you can handle scenario 1 as well as scenario 2.

[djesteban]

Bitrate multiplier applies to the target bitrate. x264 doesn't even know the bitrate of the original source in many cases (think of Avisynth input or "raw" input from stdin).

So the "b=<float>" option actually handles both cases. As you know what target bitrate you have specified, you can handle scenario 1 as well as scenario 2.

Thanks a bunch LoRd_MuldeR!