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

[Dave Stevens]

On Friday 25/06/2021 at 2:45 pm, Cqr  wrote:
>
>
>>
>> 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

ontologist is great! thanks!

d
>
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>
>>
>>
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>>>
>>> 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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>>>
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>>
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