[FFmpeg-user] libx264 options through FFmpeg

[Thomas Worth]

On Thu, Jun 30, 2011 at 8:51 AM, Thomas Worth <dev at rarevision.com> wrote:
> On Thu, Jun 30, 2011 at 8:39 AM, Thomas Worth <dev at rarevision.com> wrote:
>> 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.
>
> Sorry, I misread what you wrote. Disregard that. I tried this just
> now, and yep, I can't get libx264 to say it's encoding as interlaced,
> either. It just says "interlaced=0" as you mentioned. Perhaps there is
> some other check that x264 is doing to ensure the input is actually
> interlaced, or perhaps it's influenced by the preset or tune
> parameter. You should be warned about this, if that is the case as you
> are when you try to encode interlaced with the baseline profile
> (baseline doesn't support interlaced, apparently).

Ok, here's what you have to do. You have to pass ffmpeg the +ildct flag:

ffmpeg -i input.mov -an -flags +ildct -vcodec libx264 -preset medium
-profile main -x264opts $OPTS output.mov

Now it says "interlaced=tff"