[libav-tools] libx264 option -x264-params

Torsten Römer dode at luniks.net
Wed Aug 7 12:32:21 CEST 2013


Am 07.08.2013 09:59, schrieb Luca Barbato:
> On 05/08/13 14:04, Torsten Römer wrote:
>> Am 05.08.2013 13:21, schrieb Luca Barbato:
>>> On 05/08/13 12:57, Luca Barbato wrote:
>>>> On 29/07/13 20:47, Torsten Römer wrote:
>>>>> I would like to use the libx264 option --blueray_compat, and since
>>>>> it is
>>>>> not available as private option in libav, I tried to use
>>>>> -x264-params as
>>>>> described in the documentation, but this option is unrecognized,
>>>>> even in
>>>>> the current 9.8 release that I just downloaded and built. What am I
>>>>> missing?
>>>> I'll add it, in the master branch you can use the x264-params to pass
>>>> the x264 raw params (see documentation).
>>> To make it clearer -x264-params "bluray_compat=1" works as intended on
>>> libav git.
>>>
>>> lu
>> Nice, cheers!
> Kieran pointed out bluray-compat=1 force-cfr=1 is the correct setting.
>
> I added a shortcut -bluray-compat" to also set the encoder as cfr so you
> can produce correct bluray bitstream with ease (assuming you are feeding
> the encoder correctly).
>
> lu

Very nice the shortcut, it will be very useful also for applications 
like kdenlive (MLT?), where I think it may not be possible to pass raw 
parameters with the -x264-params parameter.

It is just that libx264 now gives the following warning:

[libx264 @ 0x331d8e0] NAL HRD parameters require VBV parameters

I think two more libx264 parameters need to be set, --vbv-maxrate and 
--vbv-bufsize as suggested here: 
http://mewiki.project357.com/wiki/X264_Encoding_Suggestions#Blu-ray_Encoding

I added them to my local copy of libavcodec/libx264.c, set the suggested 
values and indeed the warning goes away.

Torsten

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