[FFmpeg-user] Compressibility Check

[Brendan Brewster]

On Tue, Mar 27, 2012 at 10:14 PM, dE . <de.techno at gmail.com> wrote:

> On 03/27/12 21:34, Brendan Brewster wrote:
>
>> On Mon, Mar 26, 2012 at 11:53 PM, dE .<de.techno at gmail.com>  wrote:
>>
>>  On 03/27/12 04:52, Brendan Brewster wrote:
>>>
>>>  Hi,
>>>>
>>>> I am trying to implement a compressibility check via ffmpeg to determine
>>>> an
>>>> appropriate resolution for the full encode.
>>>>
>>>>  Can you please be more clear about what you're trying to do? What do
>>> you
>>> mean by 'compressibility'. Changing resolution is just one of changing
>>> compression level.
>>>
>>>  The idea is to take some percentage of the input, say 5%, at various
>> points
>> throughout and encode this with the default (input) resolution and
>> bitrate.
>> I have a specific file size to meet, such as DVD5, and therefore know the
>> bitrate cap in order to fit my output onto the destination media (given a
>> certain audio bitrate). I can then determine the number of bits per pixel
>> for the default encode and prepare ratios with regard to lesser
>> resolutions
>> with the enforced bitrate. We choose a lower resolution if the ratio is
>> poor. This is what I mean by a compressibility check. Similar
>> functionality
>> was implemented by the legacy Gordian Knot as well as within Tuxrip.
>>
>> I would just like to speed up my analysis by avoiding the majority of the
>> seek time incurred especially in passes that pinpoint points later in the
>> input video stream. I was really hoping that there might be a way to
>> achieve the same end via one pass.
>>
>> Thanks,
>> Brendan
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>>
>
> From what I understand, you're asking for CBR, but that can be done using
> a combination of -maxrate and -minrate. That will reduce on the quality not
> resolution. This way you can keep the resolution constant.
>
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>

I appreciate your response but no, I'm not looking for guidance on
achieving CBR. My intent is to pick an appropriate resolution for the given
bitrate. I have no issues staying within my target output size during the
full encode no matter the resolution. All I'm trying to do is optimize my
current solution for the initial analysis prior to the actual full encode.

Maybe someone else has some thoughts for me :)

Thanks,
Brendan