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

[Dave Stevens]

I see there's more discussion but apart from the specifics of this 
instance it's a general rule that there will always be files that get 
larger for a compression attempt. If this were not so one could 
repeatedly compress a file to any arbitrary degree.

Dave




On Friday 25/06/2021 at 1:12 pm, iburman at compuscience.com wrote:
>
>>
>> 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
>
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email 
> ffmpeg-user-request at ffmpeg.org
> with subject "unsubscribe".
>
>
> _______________________________________________
> ffmpeg-user mailing list
> ffmpeg-user at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
> To unsubscribe, visit link above, or email
> ffmpeg-user-request at ffmpeg.org with subject "unsubscribe".