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custom transcode profile??


Dam0
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sorry for the NOOB question.

 

im looking into setting up emby to play with, and was wondering if i can enter my own ffmpeg encode string for transcoding to myself when im connecting from an external ip?

 

ive searched this forum, and the wiki, and can only find where says to set max bitrate, but ive found that low bitrate encodes might require other settings to have an enjoyable playback experience.

 

many thanks in advance,

Dam0

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Hi, welcome. We don't currently offer this level of control. Can you give some examples of how you would improve the command lines for low bitrates? Thanks.

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this is what i have used in the past, its not black magic, but the result i think is not a bad compromise.

 

 

-r 25 -c:v libx264 -x264-params deblock=-3 -crf 23.0 -maxrate 650k -bufsize 2500k -subq 7 -vf cropdetect -vf gradfun=3.5:8 -s 720x405 -c:a aac -ac 1 -strict -2

 

i do realise it not hd, but watchable and quiet friendly with bandwidth.

 

D.

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-crf is a quality setting

-maxrate 650k -bufsize 2500k forces the bitrate to lower because -crf or 23 will usually result in larger bitrate then i can sustain at upload 

 

  • -subq 6 (FFmpeg)

    1: Fastest, but extremely low quality. Should be avoided except on first pass encoding.

    2-5: Progressively better and slower, 5 serves as a good medium for higher speed encoding.

    6-7: 6 is the default. Activates rate-distortion optimization for partition decision. This can considerably improve efficiency, though it has a notable speed cost. 6 activates it in I/P frames, and subme7 activates it in B frames.

    8-9: Activates rate-distortion refinement, which uses RDO to refine both motion vectors and intra prediction modes. Slower than subme 6, but again, more efficient.

    An extremely important encoding parameter which determines what algorithms are used for both subpixel motion searching and partition decision.
-vf cropdetect - self explanitory
-vf gradfun=3.5:8 Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit color depth. Interpolate the gradients that should go where the bands are, and dither them.
 
-s 720x405 - resize the video image
 
-c:a aac -ac 1 - set audio to mono and using aac
 
im not sure of the commands that emby currently utilises.
 
i hope this is clear, as i just copy/paste some of the descriptions
 
D.
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Not sure all those options are actually being used by ffmpeg
 
I am pretty sure that
 
-subq 6
-x264-params deblock=-3
 
are nulled by the crf
 
-vf cropdetect
is used to find the amount of cropping required to remove black space around the actual video the values it produces must then be used in a crop as is it does nothing.
 
-vf gradfun=3.5:8
 
I have never used so I don't know
 
specifying the framerate @ 25 is not going to look good on all videos better to just leave it at the original.
 
Cutting down the aac to mono wont do a whole lot the saving will be very small if you wanted to do it it would be better to specify a bitrate of 64k 
 
so you would basically get the same video from
 
 -c:v libx264  -crf 23.0 -maxrate 650k -bufsize 2500k  -vf gradfun=3.5:8 -s 720x405 -c:a aac -ac 1 -strict -2

So really the options that are already there will out do that command line everyday of the week imho

Edited by DrWatson
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