[FFmpeg-user] libx264 options through FFmpeg

[Thomas Worth]

On Thu, Jun 30, 2011 at 8:19 AM, Tim Nicholson <tim.nicholson at bbc.co.uk> wrote:
> On 30/06/11 15:30, Thomas Worth wrote:
>>
>> On Thu, Jun 30, 2011 at 3:22 AM, Tim Nicholson<tim.nicholson at bbc.co.uk>
>>  wrote:
>>>
>>> On 30/06/11 11:08, Tim Nicholson wrote:
>>>>
>>>> On 28/06/11 17:51, Thomas Worth wrote:
>>>>>
>>>>> On Tue, Jun 28, 2011 at 8:31 AM, Tim
>>>>> Nicholson<tim.nicholson at bbc.co.uk>  wrote:
>>>>>>
>>>>>> On 22/06/11 06:43, Thomas Worth wrote:
>>>>>>>
>>>>>>> While I've historically used a standalone x264 binary to do encoding
>>>>>>> by piping yuv420p from FFmpeg, I thought I'd try libx264 through
>>>>>>> FFmpeg since it's certainly more convenient.
>>>>>>>
>>>>>>> [....]
>>>>>>>
>>>>>>> If I can safely pass all my options via -x264opts then I'll just use
>>>>>>> that from now on and disregard FFmpeg's x264 interface.
>>>>>>
>>>>>> But what about options that require colon delimited parameters
>>>>>> themselves
>>>>>> such as "--sar 1:1"?
>>>>>
>>>>> If I use a forward slash (sar=16/9), libx264 doesn't complain but it
>>>>> also doesn't use the supplied ratio. It seems to default to "1/1"
>>>>> every time.
>>>>
>>>> I have tried sar="1:1" and it hasn't complained about that.
>>>>
>>>> Howver it doesn't want to accept a profile specification. Using:-
>>>>
>>>> ffmpeg -i $in_file -vcodec libx264 -pix_fmt yuv420p -s 1920x1080 -an \
>>>> -x264opts bitrate=35000:preset=veryslow:tune=$tune:\
>>>> [...]
>>>>
>>>> I get a:-
>>>> "[libx264 @ 0x12e0960] bad value for 'preset': 'veryslow'"
>>>>
>>>> error. replace "veryslow" with whatever you like from the legal list.
>>>>
>>>
>>> Actually its worse than that, it also doesn't accept any of the --tune
>>> parameters, or seem to handle options that don't have values, e.g --tff
>>
>> Yes, I had the same problems. What I found is that libx264 seems to
>> take all parameters through x264opts except the following:
>>
>> preset
>> profile
>> tune
>>
>> For some reason, it says "bad value for preset..." etc. But, and check
>> this out, if you supply any random value, you get the same error: "bad
>> value for 'giggity': 'goo'". So, it doesn't look like it even
>> recognizes it.
>>
>> I do this:
>>
>> ffmpeg -i file.mov -an -vcodec libx264 -preset medium -profile
>> baseline -tune film -x264opts $OPTS out.mp4
>>
>> That seems to be working.
>>
>
> Well so it does.... Thanks
>
>> I just saw your email about parameters that don't take values, and
>> you're correct. tff=1 or aud=1 or 8x8dct=0 is the way you turn them on
>> or off.
>>
>
> Or not quite as it happens.
>
> if you set :fake-interlaced=1: the x264 header showing the set parameters
> reports "interlaced=fake".
>
> However if you set tff=1 or bff=1 you get "interlaced=0" suggesting that
> these are not working.
>
> btw I see there is now a "bluray-compat" switch that saves having to
> explicitly specify a number of others, such as nal_hrd and b_pyramid.

Did you check libx264's output in the terminal during encoding? It
should show you a transcript of all of the settings passed. That's how
I was able to confirm the "param=1" trick. I'll go back and test it
and see if it's choking on options that use hyphens.

I noticed the bluray option as well. Is there documentation that shows
exactly what it sets?