[FFmpeg-user] Compressibility Check

dE . de.techno at gmail.com
Wed Mar 28 04:14:07 CEST 2012

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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