[FFmpeg-user] Multiple outputs worse performance than multiple instances

[Henk D. Schoneveld]

On Oct 22, 2013, at 9:33 AM, littlebat <dashing.meng at gmail.com> wrote:

> On Mon, 21 Oct 2013 14:36:47 +0200
> Carl Lindqvist <lulebo at gmail.com> wrote:
> 
>> Sorry for the previous top post. Gmail is giving me a headache..
>> 
>> I did a small typo/brain fart, what I meant to say was:
>> 
>> Everything works perfectly, but cpu usage on the very fast server (16
>> cores) is quite bad. I can set -preset slow and get the same fps
>> encoding speed, but with higher cpu usage.
If you do a simple test on 1 file, just change threads 1, threads 2 …. threads 0, and note what each added core adds, you'll discover that every additional core adds LESS.
Your original multiple instances AFAIK will be the optimum you'll get out your CPU-cores.
Breaking up the source file to get 1 single core to encode 1 piece and then catting them together will be maximum encoding speed you'll get. 
Henk
>> 
> Don't know more about multiple threads decoding or encoding, But I
> think you need understand some things:
> 
> 1, CPU usage is low, if there are some other bottle neck? e.g., disk IO?
> 
> 2, What kinds of codecs support multiple threads decoding or encoding?
> 
> 3, If a codecs support multiple threads decoding or encoding, if these
> threads can occupy all the CPUs' usage?
> 
> Just a clue. If we can't issue enough commands at same time to occupy
> all the CPU cores, and how to use the multiple decoding and encoding
> ability of ffmpeg to achieve this goal, I am also interest in this
> question :)
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