[FFmpeg-user] Fast encoding

[Steve Boyer]

On Wed, Aug 12, 2015 at 11:03 PM, Robin Lery <robinlery at gmail.com> wrote:
> I know about presets but faster presets lose the video quality. Are there
> any hardware requirements I need to consider? Or are there any settings
> that I need to tweak? And lastly where do I place the -threads flag to
> encode video (before input or after input), I saw topics on thread but they
> were confusing.

It's my experience that CRF more directly affects the quality, and
presets more influence filesize and encoding speed; a preset of slow
will be ABOUT the same quality as veryfast but the bitrate between the
two would be drastically different (in my opinion and eyes). A
comparison I found a while back is at
http://mmmash.blogspot.com/2013/02/x264-settings-comparison-part-2-presets.html.
There IS a noticable difference of the HD screen caps between the
original and the ultrafast preset, but between original and veryfast,
I don't see much of a difference.

I've used -threads=1 successfully after input, before output file name.

>
> This is the command I am using now:
>
> ffmpeg -i input.mp4 \
>             -codec:v libx264 -tune zerolatency -profile:v main -preset
> medium -crf 23 -maxrate 1000k -bufsize 10000k -s hd720 -codec:a libfdk_aac
> -pix_fmt yuv420p -movflags +faststart -threads 4 highoutput.mp4 \
>             -codec:v libx264 -tune zerolatency -profile:v main -preset
> medium -crf 23 -maxrate 500k -bufsize 5000k -s hd480 -codec:a libfdk_aac
> -pix_fmt yuv420p -movflags +faststart -threads 4 lowoutput.mp4
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