[FFmpeg-user] ffmpeg low bitrate with with qulaity

Ted Park kumowoon1025 at gmail.com
Wed Apr 8 10:51:49 EEST 2020


> So, as a first step, just try reducing your 5 Mb/s to 2 Mb/s and see
> what happens.
> Secondly, encoding is basically a trade-off between encoding speed,
> resulting size (file size or bit rate), and quality. Up to certain
> limits, you can sacrifice one for the other. E.g. you can get a higher
> compression rate out of some codecs by putting more CPU/GPU (or more
> time, if you're no realtime) into encoding.

Yeah, you just need to try different settings and decide what is acceptable for yourself,
results vary wildly depending on the nature of the media as well.
This might be a prejudice I have, but imo until gpu’s started coming with 
dedicated blocks for encoding or decoding, they were faster for sure,
but didn’t compress as well while maintaining quality. That’s just how I remember it,
and the difference is practically gone, or surpassed by GPU onboard encoders with 
the newer rendering focused models, but I still tend to lean towards multiple passes 
on CPU’s for predictable results.

>> yadif_cuda=mode=0:-1:0,scale_npp=1920:1080 -r 25 -b:v 6M -bf 2 -g 150 -c:a
>> aac -b:a 128k -ar 48000 -strict -2 -f flv
> I don't see how you achieve 5 Mb/s is you encode with "-b:v 6M" and "-b:a
> 128k", that's more than 6.1 Mb/s.

I think because it’s a single pass encode, and the encoder simply didn’t find the need for 
the extra (target) bitrate by the time it was finished, it has a gop of 6 seconds, so.

Ted Park

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