[FFmpeg-user] Compressed file is larger than original...

[iburman at compuscience.com]

>try a larger value for -crf

OK. The initial value was crf 18 and I now used crf=27 with a better result.
I also took my original video, uploaded and downloaded it to youtube to see
what youtube accomplishes, and here are the results:

Original file:  18MB
CRF=18:  25 MB
CRF=27:   11.5 MB
Youtube:  8.6MB

I extracted stream info with ffprobe and here are some values. I'm not sure
if these ones are the relevant ones; if more are required please let me
know:

ORIGINAL:
r_frame_rate=60/1
avg_frame_rate=56724480/945439 ~ 60/1
bit_rate=2376739
nb_frames=3693
------------------
COMPRESSED  CRF 18
r_frame_rate=60/1
avg_frame_rate=60/1
bit_rate=3233826
nb_frames=3694
------------------
COMPRESSED CRF 27
r_frame_rate=60/1
avg_frame_rate=60/1
bit_rate=1408499
nb_frames=3694
-------------------
Youtube:
r_frame_rate=30/1
avg_frame_rate=30/1
bit_rate=1011745
nb_frames=1847
------------------------------

What seems significant to me here is that YouTube reduced the frame rate and
consequently the number of frames to half. The quality of the video still
seems reasonably to what I need it for, so is there a command in ffmpeg
where I can reduce the frame rate and accomplish the same as YouTube?

Thanks


-----Original Message-----
From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of Michael Koch
Sent: Friday, June 25, 2021 10:07 PM
To: ffmpeg-user at ffmpeg.org
Subject: Re: [FFmpeg-user] Compressed file is larger than original...

Am 25.06.2021 um 20:40 schrieb iburman at compuscience.com:
> I'm trying to reduce the size of an mp4 file to adjust it for 
> streaming. The video is about one minute long and I used the sample 
> command shown in https://trac.ffmpeg.org/wiki/Encode/YouTube.
>
>   
>
> The original file size is ~18MB while the compressed file ended up at
25MB.
> While would the compressed file be larger?
>
>   
>
> Below is the ffmpeg output:
>
>   
>
> ffmpeg -i HBR_TT747.mp4 -c:v libx264 -preset slow -crf 18 -c:a copy 
> -pix_fmt yuv420p HBR_TT747_Compressed.mp4

try a larger value for -crf

Michael

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