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

[Cqr]

> On 25 Jun 2021, at 21:51, Dave Stevens <geek at uniserve.com> wrote:
> 
> 
> 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
> 

That holds for lossless compression, but is less applicable for the sort of schemes used in video compression where quality is often traded for size.

https://youtu.be/icruGcSsPp0 



> 
> 
> 
>> 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
>> 
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