[FFmpeg-user] libx264 - unknown decoder,

[Lou]

On Sun, Jun 26, 2011 at 04:02:43AM +0100, Sw at g wrote:
>
>
> On 06/26/2011 03:45 AM, Lou wrote:
>> On Sun, Jun 26, 2011 at 03:28:48AM +0100, Sw at g wrote:
>>> Hi all,
>>>
>>> I am recording a webcam using ffmpeg (ideally to replace mencoder) on
>>> archlinux (the latest package has been updated on 7th of June) and when
>>> running the following command I run into the "Unknown decoder 'libx264'"
>>>
>>> But as you can see from the error ffmpeg has been build with the
>>> --enable-libx264 options.
>>>
>>> Any suggestions?
>>>
>>> Looking forward for your reply,
>>>
>>> Regards,
>>>
>>> $ ffmpeg -f video4linux2 -vcodec libx264 -b 3000k -r 15 -crf 16 -pix_fmt
>>> yuv420p -i /dev/video0 out.avi
>>> ffmpeg version git-N-30610-g1929807, Copyright (c) 2000-2011 the FFmpeg
>>> developers
>>>    built on Jun  7 2011 19:14:56 with gcc 4.6.0 20110513 (prerelease)
>>>    configuration: --enable-gpl --enable-libx264 --enable-x11grab
>>>    libavutil    51.  6. 1 / 51.  6. 1
>>>    libavcodec   53.  6. 1 / 53.  6. 1
>>>    libavformat  53.  2. 0 / 53.  2. 0
>>>    libavdevice  53.  1. 1 / 53.  1. 1
>>>    libavfilter   2. 14. 0 /  2. 14. 0
>>>    libswscale    0. 14. 1 /  0. 14. 1
>>>    libpostproc  51.  2. 0 / 51.  2. 0
>>> Unknown decoder 'libx264'
>> You're applying '-vcodec libx264' as an input option, and your input is
>> being decoded, so FFmpeg is expecting a decoder called libx264 but there
>> is no such thing.
>>
>> If you want to encode with libx264 then use it as an output option (after
>> -i foo).
>
> Many thanks for your reply,
>
> I tried like your suggested:
> ffmpeg -f video4linux2 -b 3000k -r 15 -crf 16 -pix_fmt yuv420p -i -vcodec libx264 /dev/video0 out.avi

With this command you're telling FFmpeg that your input is named "-vcodec".

> but that give me an error:
> [video4linux2 @ 0x9fab8e0] Cannot open video device -vcodec : No such file or directory
>
> So I tried:
> ffmpeg -f video4linux2 -b 3000k -r 15 -crf 16 -pix_fmt yuv420p -i /dev/video0 out.mkv -vcodec libx264
>
> that work without error, but when I check mediainfo -f out.mkv then I can see the "Codec : V_MPEG4/ISO/ASP" so obviously ffmpeg hasn't encode with libx264.
>
> What would the command be exactly?

I'm not sure what you want, but you can start with something like:

ffmpeg -f video4linux2 -r 15 -i /dev/video0 -vcodec libx264 -preset medium \
-crf 26 -threads 0 output.mkv

If the quality is too crappy then decrease the crf value until it looks
good enough to you.