[Libav-user] How to set bit_rate for MPEG4/2

[Harald Schlangmann]

One new observation:

When setting rc_min_rate and rc_max_rate to bit_rate, the bitrate for the video written matches the definition. 
The odd thing is it kind of takes forever now. It seems the system requires lots of iterations to enforce the bit_rate range… 
Please understand “forever” as a factor 10 or so. Too much to be used.

Does this add a hint on what is wrong? 

Greetings Harald

-
Harald Schlangmann
Antwerpener Str. 52, 50672 Köln, Germany
+49 151 2265 4439
Harry at gps-laptimer.de
www.gps-laptimer.de

On 20.04.2014, at 17:25, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Harald Schlangmann <harry at ...> writes:
> 
>> Looks I’m doing something fundamentally wrong here.
> 
> Did you test with ffmpeg (the application)?
> I am not convinced that single pass encoding can 
> generally guarantee a target bitrate.
> 
>> Any hint on how to influence result file size for mpeg4?
> 
>> The only other fields I initialize for AVCodecContext 
>> are width, height, time_base, pix_fmt,  
> 
> At least constant quantiser vs. bitrate can (and must) 
> be set.
> 
> Carl Eugen
> 
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